{"gene":"C3AR1","run_date":"2026-06-09T22:02:45","timeline":{"discoveries":[{"year":1996,"finding":"Human C3aR was cloned from differentiated U-937 cells; it encodes a 482-residue GPCR with seven transmembrane helices and an unusually large second extracellular loop (~175 residues). Transfected HEK-293 cells specifically bound iodinated C3a, and CHO cells co-transfected with C3aR and Gα-16 showed increased phosphoinositide hydrolysis in response to C3a, demonstrating functional G protein coupling.","method":"Expression cloning, radioligand binding assay, phosphoinositide hydrolysis assay in transfected cells","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — receptor cloning with functional reconstitution (binding + signaling) in two independent transfected cell systems","pmids":["8765043"],"is_preprint":false},{"year":1999,"finding":"Agonist-stimulated C3aR undergoes rapid (t½ ~15 s), dose-dependent, reversible phosphorylation on serine and threonine residues (not tyrosine), mediated by GRK2, GRK3, GRK5, and GRK6. Overexpression of each GRK enhanced C3a-induced C3aR phosphorylation 1.5–1.9-fold, while antibody-mediated inhibition of endogenous GRK2/3 blocked phosphorylation. The same phosphorylation was detected on endogenously expressed C3aR in HMC-1 mast cells.","method":"Metabolic radiolabeling/phosphorylation assay, GRK overexpression in COS-7 cells, antibody-mediated GRK inhibition, phosphoamino acid analysis","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 1 / Strong — in vitro phosphorylation assay with mutagenesis-equivalent GRK overexpression/inhibition experiments, confirmed in primary mast cells","pmids":["10508278"],"is_preprint":false},{"year":2003,"finding":"The C3a–C3aR axis retains hematopoietic stem/progenitor cells (HSPCs) in bone marrow by increasing their responsiveness to SDF-1. C3aR-/- mice and C3-/- mice showed significantly enhanced G-CSF-induced HSPC mobilization. Chimeric mouse experiments demonstrated that C3aR deficiency on graft-derived (hematopoietic) cells—not host stromal cells—was responsible for the increased mobilization.","method":"C3aR-/- and C3-/- mouse mobilization studies, bone marrow chimeras, G-CSF treatment, C3aR antagonist SB290157","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout replicated with pharmacological antagonist and reciprocal chimeric mouse experiments","pmids":["14604969"],"is_preprint":false},{"year":2007,"finding":"C3aR signaling on dendritic cells (DCs) upregulates surface MHC and costimulatory molecule expression and is required for efficient T-cell priming against alloantigen. DCs lacking C3aR or treated with C3aR antagonist showed defective allostimulation and impaired skin allograft rejection. The alternative complement pathway (factor B-dependent, C4-independent) was identified as the relevant source of C3a.","method":"C3aR-/- bone marrow-derived DC allostimulation assays, skin allograft model, complement-deficient DC experiments (factor B-/-, C4-/-)","journal":"Blood","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic knockout plus pharmacological inhibition plus in vivo transplant model with defined pathway dissection","pmids":["18056835"],"is_preprint":false},{"year":2008,"finding":"C3aR agonist treatment in neonatal rat cerebellum decreased the thickness of the external granule cell layer (EGL) and increased the internal granule cell layer (IGL), consistent with accelerated granule cell migration. Video-microscopy of cultured granule neurons confirmed a direct role for C3aR in cell motility.","method":"In vivo sub-dural injection of C3aR agonist/antagonist, histological analysis of cerebellar cortical layers, live video-microscopy of cultured neurons","journal":"Molecular immunology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo and in vitro orthogonal approaches in single study, single lab","pmids":["18635264"],"is_preprint":false},{"year":2009,"finding":"C3aR on hematopoietic stem/progenitor cells promotes engraftment by augmenting MMP-9 secretion and cell adhesion to stroma. C3aR-/- HSPCs transplanted into lethally irradiated recipients showed 5–7 day delayed platelet/leukocyte recovery and reduced CFU-spleen. Blockade of C3aR on human cord blood CD34+ cells with SB290157 also impaired engraftment in NOD/SCID mice. Although C3a-enhanced SDF-1 responsiveness persisted in C3aR-/- cells (C3aR-independent effect), C3aR-/- cells secreted less MMP-9 and showed impaired stromal adhesion.","method":"C3aR-/- HSPC transplantation into irradiated mice, CFU assays, MMP-9 secretion assay, adhesion assay, human cord blood NOD/SCID xenograft with C3aR antagonist","journal":"Leukemia","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (KO mouse transplantation, pharmacological blockade, human cell model) converging on same mechanistic conclusion","pmids":["19357704"],"is_preprint":false},{"year":2012,"finding":"Absence of C3aR (and C5aR) signaling in CD4+ T cells leads to cessation of PI3Kγ/Akt/mTOR signaling, increased PKA activity, initiation of autoinductive TGF-β1 signaling, and differentiation into Foxp3+ induced regulatory T cells. Endogenous TGF-β1 suppressed C3aR/C5aR signaling by preventing C3a/C5a production and upregulating C5L2. The resulting iTreg cells showed enhanced stability and suppressed autoimmune disease.","method":"C3aR/C5aR-deficient mice, pharmacological antagonism, signaling pathway analysis (PI3Kγ, Akt, mTOR, PKA), Foxp3 reporter assays, autoimmune disease models, human iTreg induction","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic and pharmacological approaches with defined signaling pathway dissection, validated in human cells","pmids":["23263555"],"is_preprint":false},{"year":2013,"finding":"The VGF-derived neuropeptide TLQP-21 acts as a ligand for rodent C3AR1. Unbiased transcriptome sequencing of responsive CHO-K1 cells combined with defined receptor antagonists and siRNA knockdown identified C3AR1 as the GPCR mediating TLQP-21 signaling. TLQP-21 activity was pertussis toxin-sensitive (consistent with Gi coupling of C3AR1) and the peptide directed migration of mouse RAW264.7 macrophages through C3aR1.","method":"Transcriptome sequencing, receptor antagonist pharmacology, siRNA knockdown, pertussis toxin sensitivity assay, cell migration assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — unbiased genomic screen plus orthogonal validation (antagonists + siRNA + functional assays) converging on same target","pmids":["23940034"],"is_preprint":false},{"year":2014,"finding":"TLQP-21 is intrinsically disordered and adopts an α-helical conformation (disorder-to-order transition) upon binding cells expressing C3aR1. The C-terminus of TLQP-21 constitutes the functional hot spot: mutations in the last four amino acids progressively reduce bioactivity, and a single R21A mutation or C-terminal amidation abolishes function completely. Human TLQP-21 (S20A variant) activates human C3aR1 with lower potency than the rodent sequence.","method":"NMR/structural biology of TLQP-21, site-directed mutagenesis of TLQP-21, cell-based functional assays","journal":"Structure (London, England : 1993)","confidence":"High","confidence_rationale":"Tier 1 / Strong — structural characterization combined with systematic mutagenesis and functional validation defining binding mechanism","pmids":["25456411"],"is_preprint":false},{"year":2014,"finding":"C3aR signaling protects myeloid and lymphoid cells against Listeria monocytogenes-induced apoptosis. C3aR-/- mice showed increased bacterial burden and mortality, with increased Fas expression, higher caspase-3 activity, and reduced Bcl-2 expression in splenocytes, without defects in macrophage function or cytokine/chemokine responses.","method":"C3aR-/- mouse infection model, TUNEL staining, caspase-3 activity assay, Bcl-2/Fas expression, bacterial burden measurement","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse model with multiple orthogonal readouts (survival, bacterial burden, apoptosis markers) identifying specific molecular mechanism","pmids":["24981453"],"is_preprint":false},{"year":2016,"finding":"C3aR on neutrophils drives NETosis following LPS-induced complement C3a upregulation, which induces coagulation and N2 pro-tumorigenic polarization in intestinal tumorigenesis.","method":"Mouse model of spontaneous intestinal tumorigenesis, C3aR expression analysis on neutrophils, NET formation assay, coagulation assays","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo model with mechanistic pathway analysis, single lab","pmids":["26996437"],"is_preprint":false},{"year":2016,"finding":"TLQP-21 opposes obesity via C3aR1-mediated enhancement of adrenergic-induced lipolysis. TLQP-21 does not possess intrinsic lipolytic activity but potentiates β-adrenergic receptor-induced lipolysis through a mechanism requiring Ca2+ mobilization and ERK activation of hormone-sensitive lipase (HSL). Chronic peripheral TLQP-21 treatment decreased body weight/fat mass in diet-induced obese mice in a β-adrenergic and C3aR1-dependent manner.","method":"C3aR1 KO mice, β-AR-deficient mice, 3T3-L1 and primary adipocyte in vitro assays, in vivo lipolysis experiments, pharmacological approaches","journal":"Molecular metabolism","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO plus pharmacological validation plus defined signaling intermediates (Ca2+, ERK, HSL) in multiple orthogonal models","pmids":["28123945"],"is_preprint":false},{"year":2017,"finding":"C3aR1 is strongly expressed in the brain (predominantly on microglia), lung, intestinal lamina propria, and visceral adipose tissue; most macrophage and eosinophil populations are C3aR-positive. Notably, bone marrow neutrophils, mast cells, and all circulating lymphoid cells were C3aR-negative in mice, as determined by a reporter knock-in mouse.","method":"Floxed tdTomato-C3aR reporter knock-in mouse, flow cytometry, immunohistochemistry across multiple tissues","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct genetic reporter system providing high-resolution cell-type specific localization data across tissues","pmids":["28626064"],"is_preprint":false},{"year":2017,"finding":"C3aR1 activation by C3a promotes intestinal stem cell expansion and organoid formation via Wnt-signaling. C3-/- and C3aR1-/- mice showed significantly limited intestinal organoid formation; exogenous C3a rescued organoid growth from C3-/- mice but not from C3aR1-/- mice. C3 is expressed in Lgr5+ intestinal stem cells and C3aR1 on various intestinal cells.","method":"C3-/- and C3aR1-/- mouse intestinal organoid assays, Lgr5.egfp reporter mice, C3aR1 deficiency rescue experiments, ischemia/reperfusion injury model","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal KO rescue experiments with defined Wnt-signaling pathway linkage","pmids":["28928734"],"is_preprint":false},{"year":2017,"finding":"C3aR and C5aR1 activation potentiates glucose-induced insulin secretion from human and mouse islets, increases intracellular calcium and ATP generation, and protects islets against apoptosis induced by pro-apoptotic cytokines or palmitate. Conditioned media from glucose-stimulated islets activates C3aR-driven β-arrestin recruitment.","method":"Radioimmunoassay for insulin, intracellular calcium measurement, ATP assay, β-arrestin recruitment assay, apoptosis assay in human and mouse islets","journal":"Cellular and molecular life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal functional readouts in primary human and mouse islets, single lab","pmids":["28921001"],"is_preprint":false},{"year":2018,"finding":"C3a/C3aR signaling in platelets regulates platelet adhesion, spreading, Ca2+ influx, and thrombus formation by activating the small GTPase Rap1b. C3aR-/- mice showed altered bleeding time and reduced thrombosis; reconstitution of C3aR-/- mice with C3aR+/+ platelets rescued thrombosis phenotype, demonstrating the platelet-specific mechanism. C3aR-/- mice were less prone to experimental stroke and myocardial infarction.","method":"C3aR-/- mice, platelet depletion/reconstitution experiments, intravital microscopy, in vitro platelet function tests, nano-LC-MS/MS for Rap1b identification, in vivo disease models","journal":"Circulation","confidence":"High","confidence_rationale":"Tier 2 / Strong — platelet-specific reconstitution experiment isolates mechanism, combined with MS identification of Rap1b and multiple in vitro/in vivo assays","pmids":["29802205"],"is_preprint":false},{"year":2018,"finding":"C3a-C3aR signaling promotes development of thoracic aortic dissection by upregulating MMP2 expression in smooth muscle cells. C3aR knockout inhibited BAPN-induced TAD formation; recombinant C3a stimulation enhanced MMP2 expression in mechanically stretched smooth muscle cells; MMP2-knockdown mice showed reduced TAD formation.","method":"C3aR-/- mice in BAPN model, C3aR antagonist treatment, recombinant C3a stimulation of SMCs, MMP2 KD via AAV-shRNA in vivo, histology","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, pharmacological antagonism, cell-based mechanistic experiment, and downstream effector KD all converging on MMP2 mechanism","pmids":["29367209"],"is_preprint":false},{"year":2018,"finding":"C3aR1 deletion in PS19 tauopathy mice rescues tau pathology and attenuates neuroinflammation, synaptic deficits, and neurodegeneration. Mechanistically, STAT3 was identified as a direct downstream target of C3-C3aR signaling that functionally mediates tau pathogenesis. C3aR deletion inactivates a transcription factor network that drives disease-associated microglia and neurotoxic astrocyte signatures.","method":"C3ar1-/- PS19 mice, RNA sequencing, cell-type-specific transcriptomic analysis, histological assessment of tau pathology, synaptic and neurodegenerative markers","journal":"Neuron","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO in disease model with transcriptome-wide analysis and identification of specific downstream effector (STAT3)","pmids":["30415998"],"is_preprint":false},{"year":2019,"finding":"C3aR1 controls BM neutrophil mobilization after spinal cord injury by acting as a physiological antagonist of CXCR2-driven neutrophil mobilization. C3aR1 engages PTEN (a negative regulator of PI3K/AKT) to restrain CXCR2-driven neutrophil egress from bone marrow. C3aR1-/- mice showed exaggerated neutrophil mobilization and worse SCI outcomes.","method":"C3aR1-/- mice in SCI model, PTEN/PI3K/AKT signaling analysis, pharmacological CXCR2 antagonism, human SCI correlation data","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined signaling mechanism (C3aR1→PTEN→PI3K/AKT axis) plus pharmacological validation","pmids":["31045582"],"is_preprint":false},{"year":2019,"finding":"VEGFR2 survival and mitotic signaling in endothelial cells requires concurrent C3aR1/C5aR1 and IL-6R-gp130 co-signaling. C3aR1/C5aR1 blockade abolished VEGFR2 auto-phosphorylation and downstream Src, ERK, AKT, mTOR, and STAT3 activation, as well as EC cell cycle entry. VEGF-A augmented production of C3a/C5a/IL-6 via a p-Tyk2/p-STAT3 mechanism. The four receptors (VEGFR2, C3aR1, C5aR1, IL-6R) were found to be physically interactive by co-IP, confocal microscopy, ligand pulldown, and BRET assays.","method":"Co-immunoprecipitation, confocal microscopy, BRET assay, ligand pulldown, C3aR1/C5aR1 blockade, signaling pathway analysis, in vivo retinal angiogenesis","journal":"Journal of cell science","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (Co-IP, BRET, confocal, functional signaling) demonstrating physical interaction and functional co-dependence","pmids":["30765465"],"is_preprint":false},{"year":2019,"finding":"Autocrine C3aR1 signaling in B2 cells is required for antibody production and class switch recombination (CSR). C3ar1-deficient mice immunized with OVA produced IgM but no other isotypes. CD40 upregulation, IL-6 production, BAFF/APRIL-driven growth, AID/Bcl-6 expression, and CD21 production all depended on B2 cell-intrinsic C3aR1/C5aR1 signaling. B2 cells themselves produced factor I and C3 to generate the autocrine signal.","method":"C3ar1-/- mice, μMT recipients of WT/C3ar1-/- B2 cells, C3-/- recipients with WT bone marrow, OVA/HEL immunization, adoptive transfer experiments","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal adoptive transfer experiments in multiple genetic backgrounds with defined functional readouts","pmids":["31217324"],"is_preprint":false},{"year":2019,"finding":"Recipient C3aR1 signaling promotes alloreactive CD8+ T cell expansion and differentiation by two mechanisms: (1) T cell-intrinsic C3aR1 drives CD8+ T cell proliferation, mTOR activation, and T-bet expression; (2) host C3aR1 amplifies APC costimulatory molecule expression and innate cytokine production to indirectly facilitate CD8+ T cell expansion.","method":"C3ar1-/- mice cardiac allograft model, reciprocal adoptive transfer of WT/C3ar1-/- CD8+ T cells, pharmacological C3aR1 blockade, mTOR and T-bet signaling analysis","journal":"American journal of transplantation","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal adoptive transfers distinguish T cell-intrinsic vs host mechanisms with defined signaling pathway readouts","pmids":["30565852"],"is_preprint":false},{"year":2019,"finding":"C3aR signaling inhibits NK cell infiltration into the tumor microenvironment. C3aR directly interacts with LFA-1 on activated NK cells, inducing a high-affinity LFA-1 conformation that decreases NK cell migration into tumors. Blocking C3aR signaling increased NK cell infiltration and led to tumor regression.","method":"C3aR-LFA-1 interaction studies, C3aR blockade in mouse tumor models, NK cell migration assays, LFA-1 conformation analysis","journal":"Cancer immunology research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct receptor interaction demonstrated with functional consequence in vivo, single lab","pmids":["34819308"],"is_preprint":false},{"year":2020,"finding":"C3aR on microglia mediates white matter injury after chronic cerebral hypoperfusion. Genetic deletion of C3ar1 significantly inhibited aberrant microglial activation and reversed white matter injury, and C3aR antagonist SB290157 decreased microglial adherence to myelin and attenuated white matter injury and cognitive deficits in rats.","method":"C3aR-/- mice in bilateral carotid artery occlusion model, SB290157 pharmacological treatment in rats, CLARITY imaging, immunohistochemistry, behavioral testing","journal":"Theranostics","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO replicated with pharmacological antagonism, multiple behavioral and histological readouts","pmids":["31903107"],"is_preprint":false},{"year":2020,"finding":"C3a-C3aR signaling in cancer-associated fibroblasts (CAFs) facilitates breast cancer lung metastasis by augmenting pro-metastatic cytokine secretion and extracellular matrix component expression via PI3K-AKT signaling activation.","method":"Genetic and pharmacological C3aR blockade in mouse breast cancer models, ex vivo cytokine/ECM assays, PI3K-AKT signaling analysis","journal":"Journal of experimental & clinical cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic and pharmacological approaches with defined pathway (PI3K-AKT), single lab","pmids":["31931851"],"is_preprint":false},{"year":2020,"finding":"The C3-C3aR pathway mediates microglia-astrocyte interaction following status epilepticus. In C3-/- and C3aR-/- mice, microglia-astrocyte interaction was significantly reduced in response to kainic acid-induced status epilepticus, and C3-/- mice showed less neurodegeneration, identifying C3aR-dependent glial crosstalk as a contributor to KA-induced neurodegeneration.","method":"C3-/- and C3aR-/- mice in kainic acid status epilepticus model, microglial ablation, immunohistochemistry, spatial interaction analysis","journal":"Glia","confidence":"High","confidence_rationale":"Tier 2 / Strong — two independent genetic KO lines (C3-/- and C3aR-/-) with microglial ablation experiment converging on same glial communication mechanism","pmids":["33314324"],"is_preprint":false},{"year":2020,"finding":"C3aR depletion in microglia reverses HIF-1α-induced metabolic impairment in Alzheimer's disease context. C3ar1-null microglia had lower HIF-1α expression, were resistant to hypoxia mimetic-induced metabolic changes and lipid droplet accumulation, and showed improved receptor recycling and Aβ phagocytosis. Crossing C3ar1-KO with APP-KI mice rescued dysregulated lipid profiles and improved microglial phagocytic and clustering abilities, identifying a C3aR/HIF-1α signaling axis governing microglial metabolic homeostasis.","method":"C3ar1 KO × APP-KI mice, primary microglial cultures, HIF-1α expression analysis, lipid droplet/metabolism assays, phagocytosis assays, synaptic/cognitive functional tests","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO in disease model combined with primary cell mechanistic studies identifying C3aR/HIF-1α axis with multiple orthogonal readouts","pmids":["37317973"],"is_preprint":false},{"year":2021,"finding":"Complement C3aR (but not C5aR1 or C5aR2) deficiency mirrors C3 deficiency in reducing sarcoma growth. C3aR deficiency was associated with reduced tumor-associated macrophage accumulation, a shift to MHC II-dependent antigen presentation pathway in macrophages, and increased T cell activation and response to anti-PD-1 therapy, identifying the lectin pathway → C3aR axis as a key mediator of macrophage-driven immunosuppression in sarcomas.","method":"C3aR-/-, C3-/-, MBL1/2-/-, C4-/-, C5aR1-/-, C5aR2-/- mice in sarcoma models, transcriptional profiling of tumor-infiltrating macrophages, anti-PD-1 combination therapy","journal":"Nature cancer","confidence":"High","confidence_rationale":"Tier 2 / Strong — systematic comparison of multiple complement KO lines with transcriptional profiling and therapeutic intervention in vivo","pmids":["34505065"],"is_preprint":false},{"year":2021,"finding":"C3aR-/- mice display increased innate (unconditioned) anxiety, independent of C3a (the canonical ligand), suggesting an alternative ligand mediates this phenotype. This is mechanistically distinct from C3-/- mice which show increased conditioned fear via iC3b/CR3 signaling, demonstrating that C3 and C3aR control dissociable emotional behaviors through different signaling mechanisms.","method":"C3aR-/- and C3-/- mice, anxiety and fear conditioning behavioral assays","journal":"Brain, behavior, and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — clean genetic KO behavioral dissection but single lab with purely behavioral readouts; alternative ligand hypothesis not confirmed","pmids":["34543680"],"is_preprint":false},{"year":2021,"finding":"The reported C3aR antagonist SB290157 is actually a potent C3aR agonist in transfected cells and a partial C5aR2 agonist (β-arrestin recruitment) in both transfected cells and primary human and mouse macrophages, where SB290157 dampens C5a-induced ERK signaling via C5aR2 agonism. SB290157 acts as an antagonist in primary human macrophages for C3aR, but as an agonist in transfected cells, demonstrating cell context-dependent pharmacology.","method":"β-arrestin recruitment assays, ERK signaling assays, primary macrophage studies, C3aR/C5aR1/C5aR2 transfected cell models","journal":"Frontiers in pharmacology","confidence":"High","confidence_rationale":"Tier 1 / Strong — systematic pharmacological characterization across three receptors in multiple cell systems revealing mechanistic off-target effects of a widely used tool compound","pmids":["33551801"],"is_preprint":false},{"year":2022,"finding":"IL-1R/NF-κB signaling in astrocytes drives C3 release, which activates microglial C3aR, triggering hyperactivation of the microglial APT2/DHHC7 palmitoylation cycle, STAT3 translocation, and proinflammatory cytokine expression, leading to abnormal synaptic pruning in the prefrontal cortex in depression. C3aR blockade inhibited this cascade.","method":"LPS and chronic stress mouse models, C3aR antagonist treatment, proteomic analysis, APT2/DHHC7 palmitoylation cycle assay, STAT3 translocation assay, synaptic density analysis","journal":"Cell & bioscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological C3aR blockade with defined molecular mechanism (palmitoylation cycle, STAT3), single lab","pmids":["35715851"],"is_preprint":false},{"year":2022,"finding":"C3aR signaling inhibits NK cell infiltration into tumors through direct physical interaction between C3aR and LFA-1, inducing high-affinity LFA-1 conformation and reduced NK cell migration. Blocking C3aR increased NK-cell TME infiltration and caused tumor regression in mouse models.","method":"C3aR-LFA-1 co-localization/interaction, LFA-1 conformation assay, C3aR blockade in tumor mouse models, NK cell migration assays","journal":"Cancer immunology research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct protein-protein interaction demonstrated with functional consequence, single lab","pmids":["34819308"],"is_preprint":false},{"year":2022,"finding":"C3aR on dorsal root ganglion (DRG) macrophages mediates paclitaxel-induced peripheral neuropathic pain by upregulating TRPV4 on DRG neurons and promoting DRG macrophage expansion. C3aR1-/- mice showed less mechanical allodynia, reduced TRPV4 expression, and less macrophage expansion. C3aR1 antagonist in TRPV4 KO mice provided additional protection, indicating C3aR1 acts upstream of TRPV4.","method":"C3aR1-/- mice, C3aR1 antagonist treatment, TRPV4 KO mice, DRG macrophage expansion analysis, TRPV4 expression, neuron excitability measurement, intraepidermal nerve fiber density","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, pharmacological antagonism, and epistasis experiment (C3aR1 antagonist in TRPV4 KO) defining pathway order","pmids":["37861348"],"is_preprint":false},{"year":2022,"finding":"C3aR contributes to renal interstitial fibrosis by promoting NLRP3 inflammasome assembly in renal tubular epithelial cells. C3aR-/- mice showed attenuated renal fibrosis and reduced NLRP3 inflammasome activation after UUO. NLRP3 inhibition (MCC950) did not affect C3aR expression, placing C3aR upstream of the NLRP3 inflammasome.","method":"C3aR-/- mice in UUO model, MCC950 NLRP3 inhibitor, Western blot, immunohistochemistry, renal function assays","journal":"Life sciences","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO plus pharmacological epistasis defining C3aR upstream of NLRP3, single lab","pmids":["36041502"],"is_preprint":false},{"year":2023,"finding":"C3a-bound C3aR and apo-C3aR structures were determined. The structures reveal: (1) a conserved recognition pattern for anaphylatoxin binding that differs from chemokine receptors; (2) unique pocket topologies of C3aR mediating ligand selectivity; and (3) a common activation mechanism for C3aR and C5aR1. Mutagenesis validated key contact residues.","method":"Cryo-EM/X-ray crystallography of C3a-bound C3aR, apo-C3aR, and C5a-bound C5aR1; site-directed mutagenesis","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 / Strong — atomic-resolution structures of ligand-bound receptor combined with mutagenesis validation, providing definitive mechanistic insight","pmids":["37169960"],"is_preprint":false},{"year":2023,"finding":"C3aR1 preferentially couples to Gi/o/z proteins and recruits β-arrestins to cause receptor internalization. Compared to C3a63-77, TLQP-21 exhibits biased agonism toward Gi/o-mediated signaling over β-arrestin recruitment/internalization. SB290157 is a potent C3aR1 agonist that antagonizes ligand-stimulated calcium flux through potent β-arrestin-mediated receptor internalization. Signaling bias has functional consequences for calcium influx, lipolysis in adipocytes, phagocytosis in microglia, and mast cell degranulation.","method":"BRET-based G protein coupling assays, β-arrestin recruitment assays, receptor internalization assays, calcium flux measurements, adipocyte lipolysis, microglial phagocytosis, mast cell degranulation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal signaling assays (BRET, calcium, functional cell assays) systematically characterizing G protein coupling, β-arrestin bias, and functional consequences","pmids":["38072064"],"is_preprint":false},{"year":2023,"finding":"C3aR1 on macrophages is critical for rapid capture of pathogenic fungi (Histoplasma capsulatum, Candida albicans, Coccidioides posadasii) but is dispensable for phagocytosis of bacteria and latex beads. C3aR1 localizes to the early phagosome during H. capsulatum infection and coordinates formation of actin-rich membrane protrusions that promote fungal capture. The ER membrane complex (EMC) promotes surface expression of C3aR, thus enabling this function.","method":"Genome-scale CRISPR-Cas9 screen, C3aR KO validation, phagocytosis assays with bacteria/beads/fungi, phagosomal localization imaging, actin protrusion analysis, EMC-C3aR epistasis","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Strong — unbiased CRISPR screen with mechanistic validation (subcellular localization, actin dynamics, upstream regulator EMC) across multiple fungal pathogens","pmids":["36174103"],"is_preprint":false},{"year":2023,"finding":"C3a/C3aR activation promotes EMT in renal tubular epithelial cells synergistically with TGF-β via ERK-mediated NLRP3 inflammasome assembly. C3aR inhibition attenuated EMT and NLRP3 activation; ERK inhibition blocked NLRP3 activation but not C3aR expression, placing ERK downstream of C3aR and upstream of NLRP3 in a C3aR→ERK→NLRP3→EMT pathway.","method":"C3aR antagonist, NLRP3 inhibitor MCC950, ERK inhibitor PD98059 in TCMK-1 cells; C3aR-/- mice in UUO model; Western blot, immunofluorescence, ELISA","journal":"Journal of translational medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological epistasis defining pathway order (C3aR→ERK→NLRP3), validated in vivo in C3aR KO mice, single lab","pmids":["38082306"],"is_preprint":false},{"year":2023,"finding":"C3aR in astrocytes mediates chronic post-thoracotomy pain by inducing neurotoxic A1 astrocyte polarization, while also influencing M1 microglial activation. Intrathecal AAV-mediated knockdown of C3aR specifically in astrocytes (GFAP promoter) inhibited LPS-induced A1 activation, decreased M1 microglia, and alleviated chronic pain. C3aR downregulation also increased anti-inflammatory A2 astrocyte numbers.","method":"Rat thoracotomy pain model, AAV2/9-rC3ar1 shRNA-GFAP intrathecal injection, single-cell RNA sequencing, RT-PCR, Western blot, immunofluorescence, behavioral pain assessment","journal":"Biochimica et biophysica acta. Molecular basis of disease","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — cell-type-specific in vivo KD with defined astrocyte polarization mechanism, single lab","pmids":["36871753"],"is_preprint":false},{"year":2023,"finding":"Renin cleaves C3 into C3a which activates C3aR on renal tubular epithelial cells, impairing PPARα/CPT-1α-mediated mitochondrial fatty acid oxidation and inducing a profibrotic phenotype. C3aR antagonist SB290157 restored mitochondrial FAO and alleviated tubulointerstitial fibrosis in 2K1C hypertensive rats.","method":"In vitro renin-C3 cleavage assay (ELISA), HK2 cell C3a/C3aR antagonist experiments, 2K1C rat model, PPARα/CPT-1α pathway analysis, Western blot","journal":"Frontiers in bioscience","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined biochemical mechanism (renin cleaves C3→C3a→C3aR→PPARα/CPT-1α impairment) with in vitro and in vivo validation, single lab","pmids":["37919077"],"is_preprint":false},{"year":2023,"finding":"In NPM1-mutated AML cells, C3AR stimulation with C3a activates ERK1/2 and promotes AML cell survival. Anti-C3AR antibodies efficiently elicit NK cell-mediated killing of primary AML cells ex vivo.","method":"Flow cytometry, scRNA sequencing, C3a stimulation/ERK1/2 phosphorylation assay, NK cell cytotoxicity assay, xenotransplantation into immunodeficient mice","journal":"Blood advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct signaling assay (C3a→ERK1/2) plus functional NK killing assay, single lab","pmids":["36383712"],"is_preprint":false},{"year":2024,"finding":"C3aR activation exacerbates early brain injury after subarachnoid hemorrhage via the C3aR→ERK→P2X7→NLRP3 inflammasome signaling axis. C3a promotes ATP efflux through ERK1/2 phosphorylation, which activates P2X7 receptor, which in turn activates the NLRP3 inflammasome. C3aR inhibition (SB290157) reduced inflammasome activation, neuroinflammation, and improved outcomes in SAH mice.","method":"ERK inhibitor, P2X7R antagonist (JNJ-55308942), C3aR inhibitor (SB290157) in BV-2 cells and SAH mouse model; Western blot, ELISA, behavioral analysis, ATP release assay","journal":"Inflammation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — pharmacological epistasis defining pathway order with multiple signaling inhibitors in vitro and in vivo, single lab","pmids":["39528767"],"is_preprint":false},{"year":2024,"finding":"Adipocyte-specific C3aR1 knockout in male mice enhances white adipose tissue thermogenesis and increases respiration, whereas female adipocyte-specific C3aR1-KO mice display decreased brown fat thermogenesis and cold intolerance, revealing sexual dimorphism in the adipsin/C3a/C3aR1 axis. Female mice express lower levels of Adipsin in thermogenic adipocytes and lower C3aR1 in subcutaneous adipose tissue than males.","method":"Adipocyte-specific C3aR1-KO mice (male and female), Adipsin/Cfd-KO mice, energy expenditure measurement, cold tolerance test, adipose thermogenesis assessment","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type-specific conditional KO in both sexes with rigorous metabolic phenotyping revealing sex-dependent mechanism","pmids":["38713526"],"is_preprint":false},{"year":2024,"finding":"In a membranous nephropathy glomerulus-on-a-chip model, C3aR activation on podocytes (not membrane attack complex formation) is the critical mechanism of complement-mediated albumin permselectivity loss. C3AR gene silencing or C3aR antagonism reduced oxidative stress and prevented albumin leakage, whereas MAC inhibition did not. C3aR antagonist prevented proteinuria in a mouse MN model.","method":"Glomerulus-on-a-chip with primary human podocytes, C3AR siRNA knockdown, C3aR antagonist, MAC inhibitor, in vivo mouse MN model with C3aR antagonist","journal":"JCI insight","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — organ-on-chip reconstitution with genetic (siRNA) and pharmacological inhibition plus in vivo validation, demonstrating specificity over alternative mechanism (MAC)","pmids":["38227377"],"is_preprint":false},{"year":2024,"finding":"In glioma, NFAT1 in tumor-associated macrophages transcriptionally upregulates C3 and increases C3a secretion; C3a binds C3aR and promotes M2-like macrophage polarization by activating TIM-3. C3a/C3aR also activates the Ca2+-NFAT1 pathway forming a positive feedback loop for M2 polarization, which promotes mesenchymal glioma stem cell transition.","method":"Nfat1-/- mice glioma model, C3 transcriptional activity assay, TIM-3 pathway analysis, Ca2+-NFAT1 signaling assay, C3aR inhibitor in vitro and in vivo","journal":"Cancer immunology research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined NFAT1→C3→C3aR→TIM-3→NFAT1 feedback loop mechanism with in vitro and in vivo validation, single lab","pmids":["38289255"],"is_preprint":false},{"year":2024,"finding":"C3aR modulates susceptibility to depressive-like behaviors through mPFC glutamatergic neuronal excitability. C3aR deletion or intra-mPFC antagonism confers resilience; C3aR-null mPFCGlu neurons display hyperexcitability upon LPS treatment, which is anti-depressant. C3aR expression in mPFC neurons makes KO mice susceptible when C3aR is reintroduced, identifying C3aR as a direct modulator of glutamatergic neuronal excitability.","method":"C3aR KO mice, intra-mPFC C3aR antagonism, viral C3aR re-expression in KO mPFC neurons, mPFCGlu neuron-specific excitability assays (electrophysiology), LPS depression model","journal":"Progress in neurobiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO, pharmacological antagonism, viral rescue, and electrophysiology converging on specific mechanism (C3aR→mPFCGlu excitability)","pmids":["38641040"],"is_preprint":false},{"year":2024,"finding":"Astrocyte-derived C3, induced via TLR2/NF-κB signaling by α-synuclein PFFs, signals to dopaminergic neurons via C3aR to influence neuronal apoptosis and α-synuclein pathology potentially through GSK3β modulation. Overexpression of C3 exacerbated, and downregulation of C3 protected against, motor dysfunction and dopaminergic neuron loss in PFF-injected mice.","method":"AAV-mediated C3 overexpression/knockdown in PFF-injected mice, TLR2/NF-κB inhibitor treatment in primary astrocytes, astrocyte-neuron co-culture C3/C3aR pathway analysis, GSK3β signaling","journal":"Brain, behavior, and immunity","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — defined astrocyte-neuron communication pathway with mechanistic intermediates (TLR2/NF-κB→C3→C3aR→GSK3β), single lab","pmids":["39288893"],"is_preprint":false}],"current_model":"C3AR1 is a Gi/o/z-coupled GPCR with a uniquely large second extracellular loop that binds C3a (and the VGF-derived peptide TLQP-21 as a biased agonist) to trigger intracellular signaling including PI3Kγ/Akt/mTOR, ERK, calcium mobilization, and STAT3 activation; upon ligand binding, C3aR undergoes GRK2/3/5/6-mediated serine/threonine phosphorylation and β-arrestin-mediated internalization, with ligand identity determining the balance between Gi/o signaling and β-arrestin recruitment; the receptor mediates diverse context-dependent functions including hematopoietic stem cell retention in bone marrow (via MMP-9 secretion and stromal adhesion), Treg induction (via suppression of PI3Kγ/Akt/mTOR and activation of PKA/TGF-β1 autocrine signaling), platelet-dependent thrombus formation (via Rap1b activation), neutrophil mobilization (via PTEN/PI3K-AKT antagonism of CXCR2), B cell class switch recombination (autocrine), dendritic cell allostimulation, adipocyte lipolysis enhancement (via Ca2+/ERK/HSL axis potentiating β-adrenergic signaling), microglial phagocytosis and metabolic regulation (via HIF-1α), and podocyte injury in membranous nephropathy; structurally, cryo-EM reveals that C3a engages a receptor pocket topology distinct from chemokine receptors and that the VEGFR2, C3aR1, C5aR1, and IL-6R form a physically interactive signaling platform required for RTK growth signaling."},"narrative":{"mechanistic_narrative":"C3AR1 encodes a seven-transmembrane G protein-coupled receptor with an unusually large second extracellular loop (~175 residues) that binds the complement anaphylatoxin C3a to trigger intracellular signaling [PMID:8765043]. The receptor preferentially couples to Gi/o/z proteins and recruits β-arrestins to drive internalization, with ligand identity tuning the balance between G protein signaling and β-arrestin recruitment; the VGF-derived neuropeptide TLQP-21 is a biased agonist favoring Gi/o-mediated signaling over arrestin engagement [PMID:38072064, PMID:23940034]. Upon agonist binding, C3aR is rapidly phosphorylated on serine/threonine residues by GRK2/3/5/6, initiating desensitization and internalization [PMID:10508278]. Cryo-EM structures of C3a-bound and apo-C3aR define a unique pocket topology that confers anaphylatoxin selectivity distinct from chemokine receptors and reveal an activation mechanism shared with C5aR1 [PMID:37169960]. Downstream, C3aR signals through PI3Kγ/Akt/mTOR, ERK, calcium mobilization, and STAT3 to produce strongly context-dependent outputs across many cell types [PMID:23263555, PMID:38072064, PMID:30415998]. In hematopoiesis it retains stem/progenitor cells in bone marrow and promotes engraftment via MMP-9 secretion and stromal adhesion [PMID:14604969, PMID:19357704], and it restrains CXCR2-driven neutrophil mobilization through a PTEN/PI3K-AKT axis [PMID:31045582]. In adaptive immunity, loss of C3aR signaling drives Foxp3+ regulatory T cell differentiation by suppressing PI3Kγ/Akt/mTOR and engaging autocrine TGF-β1 [PMID:23263555], while autocrine C3aR signaling in B cells is required for class switch recombination [PMID:31217324] and recipient C3aR amplifies alloreactive CD8+ T cell expansion [PMID:30565852]. In platelets C3aR activates Rap1b to promote thrombus formation [PMID:29802205], and in adipocytes it potentiates β-adrenergic lipolysis via a Ca2+/ERK/HSL axis with sexually dimorphic effects on adipose thermogenesis [PMID:28123945, PMID:38713526]. In the nervous system C3aR is expressed predominantly on microglia [PMID:28626064] and governs microglial metabolic homeostasis and Aβ phagocytosis through a HIF-1α axis [PMID:37317973], tau pathology via STAT3 [PMID:30415998], and neuronal excitability and emotional behavior [PMID:38641040]. Across cancer and fibrotic disease the receptor recurrently drives ERK→NLRP3 inflammasome and PI3K-AKT programs and macrophage immunosuppression [PMID:38082306, PMID:31931851, PMID:34505065], and on podocytes it mediates complement-driven albumin permselectivity loss in membranous nephropathy independent of the membrane attack complex [PMID:38227377]. C3aR also functions within a physically interactive VEGFR2–C3aR1–C5aR1–IL-6R signaling platform required for receptor tyrosine kinase growth signaling [PMID:30765465].","teleology":[{"year":1996,"claim":"Established the molecular identity of the C3a receptor as a functional GPCR, answering whether C3a signals through a defined seven-transmembrane receptor.","evidence":"Expression cloning from U-937 cells with radioligand binding and phosphoinositide hydrolysis in transfected HEK-293/CHO cells","pmids":["8765043"],"confidence":"High","gaps":["G protein coupling shown only with co-transfected Gα-16, not native G proteins","Function of the large second extracellular loop undefined"]},{"year":1999,"claim":"Defined how agonist-bound C3aR is desensitized, identifying GRK-mediated serine/threonine phosphorylation as the regulatory mechanism.","evidence":"Phosphorylation/radiolabeling assays with GRK2/3/5/6 overexpression and antibody inhibition in COS-7 and primary mast cells","pmids":["10508278"],"confidence":"High","gaps":["Specific phosphoacceptor residues not mapped","Link to β-arrestin recruitment not directly established here"]},{"year":2003,"claim":"Demonstrated a physiological role in hematopoiesis, showing C3aR retains stem/progenitor cells in bone marrow by enhancing SDF-1 responsiveness.","evidence":"C3aR-/- and C3-/- mouse mobilization studies with bone marrow chimeras and SB290157 antagonist","pmids":["14604969"],"confidence":"High","gaps":["Molecular link between C3aR and SDF-1/CXCR4 responsiveness undefined","SB290157 later shown to have agonist activity"]},{"year":2009,"claim":"Resolved the engraftment mechanism distinct from mobilization, attributing it to C3aR-driven MMP-9 secretion and stromal adhesion.","evidence":"C3aR-/- HSPC transplantation, CFU assays, MMP-9/adhesion assays, human cord blood NOD/SCID xenografts","pmids":["19357704"],"confidence":"High","gaps":["Signaling pathway from C3aR to MMP-9 induction not mapped","C3a-enhanced SDF-1 response found C3aR-independent, complicating the model"]},{"year":2013,"claim":"Identified a second, non-complement ligand class by showing the VGF peptide TLQP-21 is a C3aR1 agonist, broadening receptor pharmacology.","evidence":"Transcriptome screen of CHO-K1 cells with antagonist pharmacology, siRNA, pertussis toxin sensitivity, and macrophage migration","pmids":["23940034"],"confidence":"High","gaps":["Demonstrated for rodent receptor; human potency lower","Whether TLQP-21 and C3a share the same binding pocket not addressed"]},{"year":2014,"claim":"Defined the structural basis of TLQP-21 binding, showing a disorder-to-order transition and a C-terminal hot spot governing activity.","evidence":"NMR/structural analysis with systematic TLQP-21 mutagenesis and cell-based functional assays","pmids":["25456411"],"confidence":"High","gaps":["Receptor-side contacts not yet resolved at this stage","Human variant has reduced potency"]},{"year":2012,"claim":"Established C3aR as a brake on regulatory T cell induction, linking its signaling to PI3Kγ/Akt/mTOR suppression and autocrine TGF-β1.","evidence":"C3aR/C5aR-deficient mice, pharmacological antagonism, signaling dissection, Foxp3 reporters, human iTreg induction","pmids":["23263555"],"confidence":"High","gaps":["Relative contributions of C3aR vs C5aR not fully separated","Mechanism of C3a production in T cell microenvironment incomplete"]},{"year":2014,"claim":"Extended C3aR function to cell survival, showing it protects immune cells against Listeria-induced apoptosis via Bcl-2/Fas/caspase-3 control.","evidence":"C3aR-/- mouse infection model with TUNEL, caspase-3 activity, and Bcl-2/Fas expression","pmids":["24981453"],"confidence":"High","gaps":["Direct signaling pathway from C3aR to apoptotic machinery not mapped"]},{"year":2018,"claim":"Defined a platelet-specific effector, identifying Rap1b activation as the mechanism by which C3aR promotes thrombosis.","evidence":"C3aR-/- mice with platelet reconstitution, intravital microscopy, nano-LC-MS/MS identification of Rap1b, stroke/MI models","pmids":["29802205"],"confidence":"High","gaps":["Coupling between C3aR and Rap1b activation not biochemically reconstituted"]},{"year":2016,"claim":"Revealed a metabolic role, showing C3aR1 potentiates β-adrenergic lipolysis through Ca2+/ERK/HSL rather than acting as an intrinsic lipolytic signal.","evidence":"C3aR1-KO and β-AR-deficient mice, 3T3-L1/primary adipocyte assays, in vivo obesity experiments","pmids":["28123945"],"confidence":"High","gaps":["Molecular point of crosstalk with β-adrenergic receptor unresolved"]},{"year":2017,"claim":"Mapped the cellular expression landscape of C3aR1, establishing microglia, macrophages, and adipose as principal sites and excluding circulating lymphoid cells.","evidence":"tdTomato-C3aR reporter knock-in mouse with flow cytometry and immunohistochemistry across tissues","pmids":["28626064"],"confidence":"High","gaps":["Reporter expression in mouse may not fully reflect human distribution","Inducible expression under disease conditions not captured"]},{"year":2019,"claim":"Placed C3aR1 within a physical RTK co-signaling platform required for VEGFR2-driven endothelial growth signaling.","evidence":"Co-IP, BRET, confocal, ligand pulldown, C3aR1/C5aR1 blockade, and in vivo retinal angiogenesis","pmids":["30765465"],"confidence":"High","gaps":["Stoichiometry and architecture of the four-receptor complex undefined","Whether the platform forms in non-endothelial cells unknown"]},{"year":2019,"claim":"Established cell-intrinsic and autocrine roles in adaptive immunity, showing C3aR1 is required for B cell class switch recombination and amplifies alloreactive CD8+ T cell responses.","evidence":"C3ar1-/- mice with reciprocal adoptive transfer into μMT and C3-/- recipients; cardiac allograft and CD8 expansion analysis with mTOR/T-bet readouts","pmids":["31217324","30565852"],"confidence":"High","gaps":["Source and regulation of autocrine C3a/C3 in lymphocytes incompletely defined"]},{"year":2018,"claim":"Showed C3aR drives tissue remodeling and fibrotic disease via MMP and inflammasome effectors in vascular and renal pathology.","evidence":"C3aR-/- mice and effector knockdown in BAPN aortic dissection (MMP2) and UUO renal fibrosis (NLRP3) models","pmids":["29367209","36041502","38082306"],"confidence":"High","gaps":["Multiple effector pathways (MMP2, ERK→NLRP3) not unified into a single mechanism","Some renal findings are single-lab Medium confidence"]},{"year":2018,"claim":"Established C3aR as a central driver of neuroinflammatory and neurodegenerative pathology, identifying STAT3 and HIF-1α as key microglial effectors.","evidence":"C3ar1-/- crosses with PS19 tauopathy and APP-KI mice, RNA-seq, primary microglia metabolic/phagocytosis assays, and multiple injury models","pmids":["30415998","37317973","31903107","33314324"],"confidence":"High","gaps":["Ligand(s) driving CNS C3aR signaling in some contexts unconfirmed","How STAT3 and HIF-1α arms relate mechanistically unclear"]},{"year":2021,"claim":"Demonstrated a tumor-immunosuppressive role, showing C3aR shapes macrophage polarization, antigen presentation, and checkpoint therapy responsiveness.","evidence":"Systematic complement KO comparison in sarcoma with macrophage transcriptional profiling and anti-PD-1 combination; tumor models in breast cancer and glioma","pmids":["34505065","31931851","38289255"],"confidence":"High","gaps":["Generalizability of the lectin-pathway→C3aR axis across tumor types untested","Some downstream loops (NFAT1, TIM-3) are single-lab Medium confidence"]},{"year":2021,"claim":"Exposed the off-target pharmacology of the widely used compound SB290157, reframing it as a context-dependent C3aR agonist and partial C5aR2 agonist.","evidence":"β-arrestin and ERK assays across C3aR/C5aR1/C5aR2 transfected cells and primary human/mouse macrophages","pmids":["33551801"],"confidence":"High","gaps":["Reinterpretation of prior SB290157 studies needed","Determinants of cell-context switch between agonism and antagonism unresolved"]},{"year":2023,"claim":"Provided the definitive structural and signaling framework, resolving the C3a-bound receptor and systematically characterizing Gi/o/z coupling and β-arrestin bias.","evidence":"Cryo-EM/crystallography of C3a-C3aR and apo-C3aR with mutagenesis; BRET G protein and β-arrestin assays with functional readouts in adipocytes, microglia, and mast cells","pmids":["37169960","38072064"],"confidence":"High","gaps":["Structure of TLQP-21-bound receptor not determined","Structural basis of biased agonism not directly visualized"]},{"year":2024,"claim":"Refined disease relevance by isolating podocyte C3aR as the critical complement effector in membranous nephropathy and revealing sex-dependent adipose function.","evidence":"Glomerulus-on-a-chip with siRNA/antagonist and in vivo MN model; adipocyte-specific C3aR1-KO in both sexes with metabolic phenotyping","pmids":["38227377","38713526"],"confidence":"High","gaps":["Molecular basis of sexual dimorphism in adipose C3aR signaling incomplete","Podocyte oxidative-stress mechanism downstream of C3aR not fully mapped"]},{"year":2023,"claim":"Identified a non-immune-classical role in innate immunity, showing C3aR1 enables macrophage capture of fungal pathogens via phagosomal localization and actin protrusions.","evidence":"Genome-scale CRISPR screen with C3aR KO validation, phagocytosis assays across fungi/bacteria/beads, phagosomal imaging, and EMC epistasis","pmids":["36174103"],"confidence":"High","gaps":["Whether a defined ligand drives this capture function unknown","Selectivity for fungi over bacteria mechanistically unexplained"]},{"year":null,"claim":"How a single receptor with one structural framework produces such divergent, cell-type-specific outputs—and the identity of the non-C3a ligand(s) implicated in CNS and behavioral phenotypes—remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["Alternative ligand driving C3a-independent anxiety phenotype unidentified","No unifying model linking Gi/o vs β-arrestin bias to specific tissue outcomes","Structural basis of biased agonism by TLQP-21 vs C3a not determined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,34,35]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[29,35]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0,12,19]},{"term_id":"GO:0031410","term_label":"cytoplasmic vesicle","supporting_discovery_ids":[36]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[2,6,20,27]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,18,35]},{"term_id":"R-HSA-8953897","term_label":"Cellular responses to stimuli","supporting_discovery_ids":[26,37,41]}],"complexes":["VEGFR2–C3aR1–C5aR1–IL-6R signaling platform"],"partners":["C3A","TLQP-21","GRK2","GRK3","GRK5","GRK6","VEGFR2","LFA-1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"Q16581","full_name":"C3a anaphylatoxin chemotactic receptor","aliases":[],"length_aa":482,"mass_kda":53.9,"function":"Receptor for the chemotactic and inflammatory peptide anaphylatoxin C3a, stimulating chemotaxis, granule enzyme release and superoxide anion production (PubMed:12871936, PubMed:37852260, PubMed:8702752). Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of downstream effectors, such as adenylate cyclase (PubMed:37852260). C3AR1 is coupled to G(i)/G(o) (GNAI1 or GNAO1) G alpha proteins and mediates inhibition of adenylate cyclase (PubMed:37852260)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q16581/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/C3AR1","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/C3AR1","total_profiled":1310},"omim":[{"mim_id":"605246","title":"COMPLEMENT COMPONENT 3a RECEPTOR 1; C3AR1","url":"https://www.omim.org/entry/605246"},{"mim_id":"601665","title":"OBESITY","url":"https://www.omim.org/entry/601665"},{"mim_id":"600807","title":"ASTHMA, SUSCEPTIBILITY TO","url":"https://www.omim.org/entry/600807"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in many","driving_tissues":[{"tissue":"lymphoid tissue","ntpm":37.8}],"url":"https://www.proteinatlas.org/search/C3AR1"},"hgnc":{"alias_symbol":["C3AR","AZ3B"],"prev_symbol":[]},"alphafold":{"accession":"Q16581","domains":[{"cath_id":"1.20.1070.10","chopping":"20-177_328-458","consensus_level":"medium","plddt":89.8178,"start":20,"end":458}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16581","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q16581-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q16581-F1-predicted_aligned_error_v6.png","plddt_mean":68.81},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=C3AR1","jax_strain_url":"https://www.jax.org/strain/search?query=C3AR1"},"sequence":{"accession":"Q16581","fasta_url":"https://rest.uniprot.org/uniprotkb/Q16581.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q16581/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q16581"}},"corpus_meta":[{"pmid":"30415998","id":"PMC_30415998","title":"Complement C3aR Inactivation Attenuates Tau Pathology and Reverses an Immune Network Deregulated in Tauopathy Models and Alzheimer's Disease.","date":"2018","source":"Neuron","url":"https://pubmed.ncbi.nlm.nih.gov/30415998","citation_count":406,"is_preprint":false},{"pmid":"23263555","id":"PMC_23263555","title":"Absence of signaling into CD4⁺ cells via C3aR and C5aR enables autoinductive TGF-β1 signaling and induction of Foxp3⁺ regulatory T cells.","date":"2012","source":"Nature immunology","url":"https://pubmed.ncbi.nlm.nih.gov/23263555","citation_count":257,"is_preprint":false},{"pmid":"26996437","id":"PMC_26996437","title":"Coagulation induced by C3aR-dependent NETosis drives protumorigenic neutrophils during small intestinal tumorigenesis.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/26996437","citation_count":214,"is_preprint":false},{"pmid":"31903107","id":"PMC_31903107","title":"Microglia exacerbate white matter injury via complement C3/C3aR pathway after hypoperfusion.","date":"2020","source":"Theranostics","url":"https://pubmed.ncbi.nlm.nih.gov/31903107","citation_count":172,"is_preprint":false},{"pmid":"14604969","id":"PMC_14604969","title":"Mobilization studies in mice deficient in either C3 or C3a receptor (C3aR) reveal a novel role for complement in retention of hematopoietic stem/progenitor cells in bone marrow.","date":"2003","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/14604969","citation_count":147,"is_preprint":false},{"pmid":"18056835","id":"PMC_18056835","title":"Local production and activation of complement up-regulates the allostimulatory function of dendritic cells through C3a-C3aR interaction.","date":"2007","source":"Blood","url":"https://pubmed.ncbi.nlm.nih.gov/18056835","citation_count":142,"is_preprint":false},{"pmid":"8765043","id":"PMC_8765043","title":"Expression cloning of the human C3a anaphylatoxin receptor (C3aR) from differentiated U-937 cells.","date":"1996","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/8765043","citation_count":130,"is_preprint":false},{"pmid":"33314324","id":"PMC_33314324","title":"The complement C3-C3aR pathway mediates microglia-astrocyte interaction following status epilepticus.","date":"2020","source":"Glia","url":"https://pubmed.ncbi.nlm.nih.gov/33314324","citation_count":127,"is_preprint":false},{"pmid":"23118029","id":"PMC_23118029","title":"C5aR and C3aR antagonists each inhibit diet-induced obesity, metabolic dysfunction, and adipocyte and macrophage signaling.","date":"2012","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/23118029","citation_count":120,"is_preprint":false},{"pmid":"36792546","id":"PMC_36792546","title":"Helicobacter pylori-derived outer membrane vesicles contribute to Alzheimer's disease pathogenesis via C3-C3aR signalling.","date":"2023","source":"Journal of extracellular vesicles","url":"https://pubmed.ncbi.nlm.nih.gov/36792546","citation_count":116,"is_preprint":false},{"pmid":"29802205","id":"PMC_29802205","title":"Functional Relevance of the Anaphylatoxin Receptor C3aR for Platelet Function and Arterial Thrombus Formation Marks an Intersection Point Between Innate Immunity and Thrombosis.","date":"2018","source":"Circulation","url":"https://pubmed.ncbi.nlm.nih.gov/29802205","citation_count":94,"is_preprint":false},{"pmid":"23940034","id":"PMC_23940034","title":"Identification of the C3a receptor (C3AR1) as the target of the VGF-derived peptide TLQP-21 in rodent cells.","date":"2013","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/23940034","citation_count":83,"is_preprint":false},{"pmid":"31924226","id":"PMC_31924226","title":"VGF-derived peptide TLQP-21 modulates microglial function through C3aR1 signaling pathways and reduces neuropathology in 5xFAD mice.","date":"2020","source":"Molecular neurodegeneration","url":"https://pubmed.ncbi.nlm.nih.gov/31924226","citation_count":77,"is_preprint":false},{"pmid":"28626064","id":"PMC_28626064","title":"Monitoring C3aR Expression Using a Floxed tdTomato-C3aR Reporter Knock-in Mouse.","date":"2017","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/28626064","citation_count":74,"is_preprint":false},{"pmid":"26956419","id":"PMC_26956419","title":"Contribution of the anaphylatoxin receptors, C3aR and C5aR, to the pathogenesis of pulmonary fibrosis.","date":"2016","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/26956419","citation_count":73,"is_preprint":false},{"pmid":"31379815","id":"PMC_31379815","title":"The Complement Receptors C3aR and C5aR Are a New Class of Immune Checkpoint Receptor in Cancer Immunotherapy.","date":"2019","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/31379815","citation_count":71,"is_preprint":false},{"pmid":"31045582","id":"PMC_31045582","title":"Complement receptor C3aR1 controls neutrophil mobilization following spinal cord injury through physiological antagonism of CXCR2.","date":"2019","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/31045582","citation_count":70,"is_preprint":false},{"pmid":"34505065","id":"PMC_34505065","title":"Complement activation promoted by the lectin pathway mediates C3aR-dependent sarcoma progression and immunosuppression.","date":"2021","source":"Nature cancer","url":"https://pubmed.ncbi.nlm.nih.gov/34505065","citation_count":61,"is_preprint":false},{"pmid":"35715851","id":"PMC_35715851","title":"IL-1R/C3aR signaling regulates synaptic pruning in the prefrontal cortex of depression.","date":"2022","source":"Cell & bioscience","url":"https://pubmed.ncbi.nlm.nih.gov/35715851","citation_count":61,"is_preprint":false},{"pmid":"19357704","id":"PMC_19357704","title":"Defective engraftment of C3aR-/- hematopoietic stem progenitor cells shows a novel role of the C3a-C3aR axis in bone marrow homing.","date":"2009","source":"Leukemia","url":"https://pubmed.ncbi.nlm.nih.gov/19357704","citation_count":61,"is_preprint":false},{"pmid":"31931851","id":"PMC_31931851","title":"C3a-C3aR signaling promotes breast cancer lung metastasis via modulating carcinoma associated fibroblasts.","date":"2020","source":"Journal of experimental & clinical cancer research : CR","url":"https://pubmed.ncbi.nlm.nih.gov/31931851","citation_count":58,"is_preprint":false},{"pmid":"37317973","id":"PMC_37317973","title":"Complement C3aR depletion reverses HIF-1α-induced metabolic impairment and enhances microglial response to Aβ pathology.","date":"2023","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/37317973","citation_count":56,"is_preprint":false},{"pmid":"18635264","id":"PMC_18635264","title":"Role of complement anaphylatoxin receptors (C3aR, C5aR) in the development of the rat cerebellum.","date":"2008","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/18635264","citation_count":55,"is_preprint":false},{"pmid":"37169960","id":"PMC_37169960","title":"Revealing the signaling of complement receptors C3aR and C5aR1 by anaphylatoxins.","date":"2023","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/37169960","citation_count":53,"is_preprint":false},{"pmid":"25456411","id":"PMC_25456411","title":"The TLQP-21 peptide activates the G-protein-coupled receptor C3aR1 via a folding-upon-binding mechanism.","date":"2014","source":"Structure (London, England : 1993)","url":"https://pubmed.ncbi.nlm.nih.gov/25456411","citation_count":50,"is_preprint":false},{"pmid":"15940127","id":"PMC_15940127","title":"Expression of the anaphylatoxin receptors C3aR and C5aR is increased in fatal asthma.","date":"2005","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/15940127","citation_count":50,"is_preprint":false},{"pmid":"29367209","id":"PMC_29367209","title":"The Complement C3a-C3aR Axis Promotes Development of Thoracic Aortic Dissection via Regulation of MMP2 Expression.","date":"2018","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/29367209","citation_count":46,"is_preprint":false},{"pmid":"10508278","id":"PMC_10508278","title":"Ligand-induced phosphorylation of anaphylatoxin receptors C3aR and C5aR is mediated by \"G protein-coupled receptor kinases.","date":"1999","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/10508278","citation_count":42,"is_preprint":false},{"pmid":"34439277","id":"PMC_34439277","title":"Pan-Cancer Analysis of Immune Complement Signature C3/C5/C3AR1/C5AR1 in Association with Tumor Immune Evasion and Therapy Resistance.","date":"2021","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/34439277","citation_count":40,"is_preprint":false},{"pmid":"19900981","id":"PMC_19900981","title":"C3aR inhibition reduces neurodegeneration in experimental lupus.","date":"2009","source":"Lupus","url":"https://pubmed.ncbi.nlm.nih.gov/19900981","citation_count":39,"is_preprint":false},{"pmid":"28921001","id":"PMC_28921001","title":"C3aR and C5aR1 act as key regulators of human and mouse β-cell function.","date":"2017","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/28921001","citation_count":38,"is_preprint":false},{"pmid":"37087484","id":"PMC_37087484","title":"Cntnap4 partial deficiency exacerbates α-synuclein pathology through astrocyte-microglia C3-C3aR pathway.","date":"2023","source":"Cell death & disease","url":"https://pubmed.ncbi.nlm.nih.gov/37087484","citation_count":38,"is_preprint":false},{"pmid":"28123945","id":"PMC_28123945","title":"The neuropeptide TLQP-21 opposes obesity via C3aR1-mediated enhancement of adrenergic-induced lipolysis.","date":"2016","source":"Molecular metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/28123945","citation_count":37,"is_preprint":false},{"pmid":"24981453","id":"PMC_24981453","title":"The receptor for the complement C3a anaphylatoxin (C3aR) provides host protection against Listeria monocytogenes-induced apoptosis.","date":"2014","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/24981453","citation_count":34,"is_preprint":false},{"pmid":"31865842","id":"PMC_31865842","title":"Endothelial progenitor cell transplantation alleviated ischemic brain injury via inhibiting C3/C3aR pathway in mice.","date":"2019","source":"Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/31865842","citation_count":33,"is_preprint":false},{"pmid":"26394814","id":"PMC_26394814","title":"Complement anaphylatoxin receptors C3aR and C5aR are required in the pathogenesis of experimental autoimmune uveitis.","date":"2015","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/26394814","citation_count":33,"is_preprint":false},{"pmid":"34921829","id":"PMC_34921829","title":"C3/C3aR inhibition alleviates GMH-IVH-induced hydrocephalus by preventing microglia-astrocyte interactions in neonatal rats.","date":"2021","source":"Neuropharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/34921829","citation_count":31,"is_preprint":false},{"pmid":"33551801","id":"PMC_33551801","title":"The \"C3aR Antagonist\" SB290157 is a Partial C5aR2 Agonist.","date":"2021","source":"Frontiers in pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/33551801","citation_count":31,"is_preprint":false},{"pmid":"32762445","id":"PMC_32762445","title":"Protective Role of C3aR (C3a Anaphylatoxin Receptor) Against Atherosclerosis in Atherosclerosis-Prone Mice.","date":"2020","source":"Arteriosclerosis, thrombosis, and vascular biology","url":"https://pubmed.ncbi.nlm.nih.gov/32762445","citation_count":28,"is_preprint":false},{"pmid":"38289255","id":"PMC_38289255","title":"An NFAT1-C3a-C3aR Positive Feedback Loop in Tumor-Associated Macrophages Promotes a Glioma Stem Cell Malignant Phenotype.","date":"2024","source":"Cancer immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/38289255","citation_count":27,"is_preprint":false},{"pmid":"31217324","id":"PMC_31217324","title":"Follicular B2 Cell Activation and Class Switch Recombination Depend on Autocrine C3ar1/C5ar1 Signaling in B2 Cells.","date":"2019","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/31217324","citation_count":27,"is_preprint":false},{"pmid":"30565852","id":"PMC_30565852","title":"Absence of recipient C3aR1 signaling limits expansion and differentiation of alloreactive CD8+ T cell immunity and prolongs murine cardiac allograft survival.","date":"2019","source":"American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons","url":"https://pubmed.ncbi.nlm.nih.gov/30565852","citation_count":27,"is_preprint":false},{"pmid":"28928734","id":"PMC_28928734","title":"C3a Enhances the Formation of Intestinal Organoids through C3aR1.","date":"2017","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/28928734","citation_count":27,"is_preprint":false},{"pmid":"38713438","id":"PMC_38713438","title":"Transcriptome Analysis Reveals Dynamic Microglial-Induced A1 Astrocyte Reactivity via C3/C3aR/NF-κB Signaling After Ischemic Stroke.","date":"2024","source":"Molecular neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/38713438","citation_count":26,"is_preprint":false},{"pmid":"30294325","id":"PMC_30294325","title":"Anaphylatoxin Receptors C3aR and C5aR1 Are Important Factors That Influence the Impact of Ethanol on the Adipose Secretome.","date":"2018","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/30294325","citation_count":25,"is_preprint":false},{"pmid":"23638016","id":"PMC_23638016","title":"The complement anaphylatoxin C3a receptor (C3aR) contributes to the inflammatory response in dextran sulfate sodium (DSS)-induced colitis in mice.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23638016","citation_count":25,"is_preprint":false},{"pmid":"31274379","id":"PMC_31274379","title":"Distinct roles of the anaphylatoxin receptors C3aR, C5aR1 and C5aR2 in experimental meningococcal infections.","date":"2019","source":"Virulence","url":"https://pubmed.ncbi.nlm.nih.gov/31274379","citation_count":24,"is_preprint":false},{"pmid":"39288893","id":"PMC_39288893","title":"Astrocyte-neuron communication through the complement C3-C3aR pathway in Parkinson's disease.","date":"2024","source":"Brain, behavior, and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/39288893","citation_count":23,"is_preprint":false},{"pmid":"34819308","id":"PMC_34819308","title":"C3aR Signaling Inhibits NK-cell Infiltration into the Tumor Microenvironment in Mouse Models.","date":"2021","source":"Cancer immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/34819308","citation_count":23,"is_preprint":false},{"pmid":"36341694","id":"PMC_36341694","title":"Astrocyte-microglia interaction through C3/C3aR pathway modulates neuropathic pain in rats model of chronic constriction injury.","date":"2022","source":"Molecular pain","url":"https://pubmed.ncbi.nlm.nih.gov/36341694","citation_count":23,"is_preprint":false},{"pmid":"34543680","id":"PMC_34543680","title":"Complement C3 and C3aR mediate different aspects of emotional behaviours; relevance to risk for psychiatric disorder.","date":"2021","source":"Brain, behavior, and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/34543680","citation_count":23,"is_preprint":false},{"pmid":"36762625","id":"PMC_36762625","title":"Microglia refine developing retinal astrocytic and vascular networks through the complement C3/C3aR axis.","date":"2023","source":"Development (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/36762625","citation_count":22,"is_preprint":false},{"pmid":"32898628","id":"PMC_32898628","title":"Aristolochic acid I promotes the invasion and migration of hepatocellular carcinoma cells by activating the C3a/C3aR complement system.","date":"2020","source":"Toxicology letters","url":"https://pubmed.ncbi.nlm.nih.gov/32898628","citation_count":22,"is_preprint":false},{"pmid":"35745148","id":"PMC_35745148","title":"Gypenoside XVII, an Active Ingredient from Gynostemma Pentaphyllum, Inhibits C3aR-Associated Synaptic Pruning in Stressed Mice.","date":"2022","source":"Nutrients","url":"https://pubmed.ncbi.nlm.nih.gov/35745148","citation_count":21,"is_preprint":false},{"pmid":"38072064","id":"PMC_38072064","title":"Functional profiling of the G protein-coupled receptor C3aR1 reveals ligand-mediated biased agonism.","date":"2023","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/38072064","citation_count":20,"is_preprint":false},{"pmid":"31048001","id":"PMC_31048001","title":"Aristolochic acid I aggravates renal injury by activating the C3a/C3aR complement system.","date":"2019","source":"Toxicology letters","url":"https://pubmed.ncbi.nlm.nih.gov/31048001","citation_count":20,"is_preprint":false},{"pmid":"30765465","id":"PMC_30765465","title":"VEGFR2 survival and mitotic signaling depends on joint activation of associated C3ar1/C5ar1 and IL-6R-gp130.","date":"2019","source":"Journal of cell science","url":"https://pubmed.ncbi.nlm.nih.gov/30765465","citation_count":19,"is_preprint":false},{"pmid":"35597971","id":"PMC_35597971","title":"C3aR costimulation enhances the antitumor efficacy of CAR-T cell therapy through Th17 expansion and memory T cell induction.","date":"2022","source":"Journal of hematology & oncology","url":"https://pubmed.ncbi.nlm.nih.gov/35597971","citation_count":19,"is_preprint":false},{"pmid":"38227377","id":"PMC_38227377","title":"C3aR-initiated signaling is a critical mechanism of podocyte injury in membranous nephropathy.","date":"2024","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/38227377","citation_count":18,"is_preprint":false},{"pmid":"35837068","id":"PMC_35837068","title":"The complement C3a-C3aR and C5a-C5aR pathways promote viability and inflammation of human retinal pigment epithelium cells by targeting NF-κB signaling.","date":"2022","source":"Experimental and therapeutic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/35837068","citation_count":18,"is_preprint":false},{"pmid":"34950700","id":"PMC_34950700","title":"Identification and Validation of CYBB, CD86, and C3AR1 as the Key Genes Related to Macrophage Infiltration of Gastric Cancer.","date":"2021","source":"Frontiers in molecular biosciences","url":"https://pubmed.ncbi.nlm.nih.gov/34950700","citation_count":18,"is_preprint":false},{"pmid":"38713526","id":"PMC_38713526","title":"Adipsin and adipocyte-derived C3aR1 regulate thermogenic fat in a sex-dependent fashion.","date":"2024","source":"JCI insight","url":"https://pubmed.ncbi.nlm.nih.gov/38713526","citation_count":16,"is_preprint":false},{"pmid":"38778507","id":"PMC_38778507","title":"Complement C3aR signaling: Immune and metabolic modulation and its impact on Alzheimer's disease.","date":"2024","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/38778507","citation_count":16,"is_preprint":false},{"pmid":"37174113","id":"PMC_37174113","title":"Complement Activation and Up-Regulated Expression of Anaphylatoxin C3a/C3aR in Glioblastoma: Deciphering the Links with TGF-β and VEGF.","date":"2023","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/37174113","citation_count":16,"is_preprint":false},{"pmid":"35386704","id":"PMC_35386704","title":"Complement C3a Enhances the Phagocytic Activity of B Cells Through C3aR in a Fish.","date":"2022","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/35386704","citation_count":16,"is_preprint":false},{"pmid":"33176600","id":"PMC_33176600","title":"Down-Regulation of C3aR/C5aR Inhibits Cell Proliferation and EMT in Hepatocellular Carcinoma.","date":"2020","source":"Technology in cancer research & treatment","url":"https://pubmed.ncbi.nlm.nih.gov/33176600","citation_count":15,"is_preprint":false},{"pmid":"36871753","id":"PMC_36871753","title":"C3aR in astrocytes mediates post-thoracotomy pain by inducing A1 astrocytes in male rats.","date":"2023","source":"Biochimica et biophysica acta. Molecular basis of disease","url":"https://pubmed.ncbi.nlm.nih.gov/36871753","citation_count":15,"is_preprint":false},{"pmid":"34403734","id":"PMC_34403734","title":"Dissociable effects of complement C3 and C3aR on survival and morphology of adult born hippocampal neurons, pattern separation, and cognitive flexibility in male mice.","date":"2021","source":"Brain, behavior, and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/34403734","citation_count":15,"is_preprint":false},{"pmid":"36754188","id":"PMC_36754188","title":"Echinacea purpurea (L.) Moench extract suppresses inflammation by inhibition of C3a/C3aR signaling pathway in TNBS-induced ulcerative colitis rats.","date":"2023","source":"Journal of ethnopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/36754188","citation_count":15,"is_preprint":false},{"pmid":"35503088","id":"PMC_35503088","title":"C-reactive protein inhibits C3a/C3aR-dependent podocyte autophagy in favor of diabetic kidney disease.","date":"2022","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/35503088","citation_count":14,"is_preprint":false},{"pmid":"31272467","id":"PMC_31272467","title":"C3aR signaling and gliosis in response to neurodevelopmental damage in the cerebellum.","date":"2019","source":"Journal of neuroinflammation","url":"https://pubmed.ncbi.nlm.nih.gov/31272467","citation_count":14,"is_preprint":false},{"pmid":"24743347","id":"PMC_24743347","title":"Downregulation of complement C3 and C3aR expression in subcutaneous adipose tissue in obese women.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24743347","citation_count":14,"is_preprint":false},{"pmid":"30612786","id":"PMC_30612786","title":"Expression of complement C3, C5, C3aR and C5aR1 genes in resting and activated CD4+ T cells.","date":"2018","source":"Immunobiology","url":"https://pubmed.ncbi.nlm.nih.gov/30612786","citation_count":14,"is_preprint":false},{"pmid":"39528767","id":"PMC_39528767","title":"Complement Molecule C3a Exacerbates Early Brain Injury After Subarachnoid Hemorrhage by Inducing Neuroinflammation Through the C3aR-ERK-P2X7-NLRP3 Inflammasome Signaling Axis.","date":"2024","source":"Inflammation","url":"https://pubmed.ncbi.nlm.nih.gov/39528767","citation_count":14,"is_preprint":false},{"pmid":"36041502","id":"PMC_36041502","title":"C3aR contributes to unilateral ureteral obstruction-induced renal interstitial fibrosis via the activation of the NLRP3 inflammasome.","date":"2022","source":"Life sciences","url":"https://pubmed.ncbi.nlm.nih.gov/36041502","citation_count":14,"is_preprint":false},{"pmid":"22151392","id":"PMC_22151392","title":"Participation of complement 3a receptor (C3aR) in the sensitization phase of Th2 mediated allergic contact dermatitis.","date":"2012","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/22151392","citation_count":14,"is_preprint":false},{"pmid":"35258803","id":"PMC_35258803","title":"Complement C3a Receptor (C3aR) Mediates Vascular Dysfunction, Hippocampal Pathology, and Cognitive Impairment in a Mouse Model of VCID.","date":"2022","source":"Translational stroke research","url":"https://pubmed.ncbi.nlm.nih.gov/35258803","citation_count":13,"is_preprint":false},{"pmid":"22901903","id":"PMC_22901903","title":"Decreased expression of complement 3a receptor (C3aR) in human placentas from severe preeclamptic pregnancies.","date":"2012","source":"European journal of obstetrics, gynecology, and reproductive biology","url":"https://pubmed.ncbi.nlm.nih.gov/22901903","citation_count":13,"is_preprint":false},{"pmid":"40801798","id":"PMC_40801798","title":"CD81+ senescent-like fibroblasts exaggerate inflammation and activate neutrophils via C3/C3aR1 axis in periodontitis.","date":"2025","source":"eLife","url":"https://pubmed.ncbi.nlm.nih.gov/40801798","citation_count":12,"is_preprint":false},{"pmid":"35925892","id":"PMC_35925892","title":"C3aR plays both sides in regulating resistance to bacterial infections.","date":"2022","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/35925892","citation_count":12,"is_preprint":false},{"pmid":"37861348","id":"PMC_37861348","title":"Complement Receptor C3aR1 Contributes to Paclitaxel-Induced Peripheral Neuropathic Pain in Mice and Rats.","date":"2023","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/37861348","citation_count":12,"is_preprint":false},{"pmid":"39801259","id":"PMC_39801259","title":"C3/C3aR Bridges Spinal Astrocyte-Microglia Crosstalk and Accelerates Neuroinflammation in Morphine-Tolerant Rats.","date":"2025","source":"CNS neuroscience & therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/39801259","citation_count":12,"is_preprint":false},{"pmid":"39218048","id":"PMC_39218048","title":"Complement 3a induces the synapse loss via C3aR in mitochondria-dependent NLRP3 activating mechanisms during the development and progression of Alzheimer's disease.","date":"2024","source":"Neuroscience and biobehavioral reviews","url":"https://pubmed.ncbi.nlm.nih.gov/39218048","citation_count":11,"is_preprint":false},{"pmid":"31908021","id":"PMC_31908021","title":"RTK signaling requires C3ar1/C5ar1 and IL-6R joint signaling to repress dominant PTEN, SOCS1/3 and PHLPP restraint.","date":"2019","source":"FASEB journal : official publication of the Federation of American Societies for Experimental Biology","url":"https://pubmed.ncbi.nlm.nih.gov/31908021","citation_count":11,"is_preprint":false},{"pmid":"38866102","id":"PMC_38866102","title":"Microglia aggravate white matter injury via C3/C3aR pathway after experimental subarachnoid hemorrhage.","date":"2024","source":"Experimental neurology","url":"https://pubmed.ncbi.nlm.nih.gov/38866102","citation_count":11,"is_preprint":false},{"pmid":"38082306","id":"PMC_38082306","title":"C3a/C3aR synergies with TGF-β to promote epithelial-mesenchymal transition of renal tubular epithelial cells via the activation of the NLRP3 inflammasome.","date":"2023","source":"Journal of translational medicine","url":"https://pubmed.ncbi.nlm.nih.gov/38082306","citation_count":11,"is_preprint":false},{"pmid":"28797008","id":"PMC_28797008","title":"Resveratrol Attenuates Adriamycin-Induced Focal Segmental Glomerulosclerosis through C3aR/C5aR- Sphingosine Kinase 1 Pathway.","date":"2017","source":"Pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/28797008","citation_count":11,"is_preprint":false},{"pmid":"33748161","id":"PMC_33748161","title":"C3AR1 mRNA as a Potential Therapeutic Target Associates With Clinical Outcomes and Tumor Microenvironment in Osteosarcoma.","date":"2021","source":"Frontiers in medicine","url":"https://pubmed.ncbi.nlm.nih.gov/33748161","citation_count":11,"is_preprint":false},{"pmid":"29315316","id":"PMC_29315316","title":"The C3aR promotes macrophage infiltration and regulates ANCA production but does not affect glomerular injury in experimental anti-myeloperoxidase glomerulonephritis.","date":"2018","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/29315316","citation_count":11,"is_preprint":false},{"pmid":"17459702","id":"PMC_17459702","title":"Discovery of new C3aR ligands. Part 2: amino-piperidine derivatives.","date":"2007","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/17459702","citation_count":11,"is_preprint":false},{"pmid":"38641040","id":"PMC_38641040","title":"C3aR in the medial prefrontal cortex modulates the susceptibility to LPS-induced depressive-like behaviors through glutamatergic neuronal excitability.","date":"2024","source":"Progress in neurobiology","url":"https://pubmed.ncbi.nlm.nih.gov/38641040","citation_count":10,"is_preprint":false},{"pmid":"36174103","id":"PMC_36174103","title":"Genome-scale CRISPR screening reveals that C3aR signaling is critical for rapid capture of fungi by macrophages.","date":"2022","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/36174103","citation_count":10,"is_preprint":false},{"pmid":"33194030","id":"PMC_33194030","title":"Blockade of C3a/C3aR axis alleviates severe acute pancreatitis-induced intestinal barrier injury.","date":"2020","source":"American journal of translational research","url":"https://pubmed.ncbi.nlm.nih.gov/33194030","citation_count":10,"is_preprint":false},{"pmid":"28576690","id":"PMC_28576690","title":"Complement component C3aR constitutes a novel regulator for chick eye morphogenesis.","date":"2017","source":"Developmental biology","url":"https://pubmed.ncbi.nlm.nih.gov/28576690","citation_count":9,"is_preprint":false},{"pmid":"36383712","id":"PMC_36383712","title":"The complement receptor C3AR constitutes a novel therapeutic target in NPM1-mutated AML.","date":"2023","source":"Blood advances","url":"https://pubmed.ncbi.nlm.nih.gov/36383712","citation_count":8,"is_preprint":false},{"pmid":"36521939","id":"PMC_36521939","title":"Molecular signatures of intrarenal complement receptors C3AR1 and C5AR1 correlate with renal outcome in human lupus nephritis.","date":"2022","source":"Lupus science & medicine","url":"https://pubmed.ncbi.nlm.nih.gov/36521939","citation_count":8,"is_preprint":false},{"pmid":"33446393","id":"PMC_33446393","title":"Autoantibodies against C5aR1, C3aR1, CXCR3, and CXCR4 are decreased in primary Sjogren's syndrome.","date":"2021","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33446393","citation_count":8,"is_preprint":false},{"pmid":"37919077","id":"PMC_37919077","title":"C3aR Antagonist Alleviates C3a Induced Tubular Profibrotic Phenotype Transition via Restoring PPARα/CPT-1α Mediated Mitochondrial Fatty Acid Oxidation in Renin-Dependent Hypertension.","date":"2023","source":"Frontiers in bioscience (Landmark edition)","url":"https://pubmed.ncbi.nlm.nih.gov/37919077","citation_count":8,"is_preprint":false},{"pmid":"10952089","id":"PMC_10952089","title":"A novel computational method for predicting the transmembrane structure of G-protein coupled receptors: application to human C5aR and C3aR.","date":"2000","source":"Receptors & channels","url":"https://pubmed.ncbi.nlm.nih.gov/10952089","citation_count":8,"is_preprint":false},{"pmid":"27551680","id":"PMC_27551680","title":"Whole-exome sequencing of a patient with severe and complex hemostatic abnormalities reveals a possible contributing frameshift mutation in C3AR1.","date":"2016","source":"Cold Spring Harbor molecular case studies","url":"https://pubmed.ncbi.nlm.nih.gov/27551680","citation_count":8,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":54032,"output_tokens":13328,"usd":0.181008,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":25105,"output_tokens":6353,"usd":0.142175,"stage2_stop_reason":"end_turn"},"total_usd":0.323183,"stage1_batch_id":"msgbatch_0179Z2pxRYBsXi2xADneafRw","stage2_batch_id":"msgbatch_01LaY9ZaVdgjWArcZo9eqQE5","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1996,\n      \"finding\": \"Human C3aR was cloned from differentiated U-937 cells; it encodes a 482-residue GPCR with seven transmembrane helices and an unusually large second extracellular loop (~175 residues). Transfected HEK-293 cells specifically bound iodinated C3a, and CHO cells co-transfected with C3aR and Gα-16 showed increased phosphoinositide hydrolysis in response to C3a, demonstrating functional G protein coupling.\",\n      \"method\": \"Expression cloning, radioligand binding assay, phosphoinositide hydrolysis assay in transfected cells\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — receptor cloning with functional reconstitution (binding + signaling) in two independent transfected cell systems\",\n      \"pmids\": [\"8765043\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"Agonist-stimulated C3aR undergoes rapid (t½ ~15 s), dose-dependent, reversible phosphorylation on serine and threonine residues (not tyrosine), mediated by GRK2, GRK3, GRK5, and GRK6. Overexpression of each GRK enhanced C3a-induced C3aR phosphorylation 1.5–1.9-fold, while antibody-mediated inhibition of endogenous GRK2/3 blocked phosphorylation. The same phosphorylation was detected on endogenously expressed C3aR in HMC-1 mast cells.\",\n      \"method\": \"Metabolic radiolabeling/phosphorylation assay, GRK overexpression in COS-7 cells, antibody-mediated GRK inhibition, phosphoamino acid analysis\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — in vitro phosphorylation assay with mutagenesis-equivalent GRK overexpression/inhibition experiments, confirmed in primary mast cells\",\n      \"pmids\": [\"10508278\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The C3a–C3aR axis retains hematopoietic stem/progenitor cells (HSPCs) in bone marrow by increasing their responsiveness to SDF-1. C3aR-/- mice and C3-/- mice showed significantly enhanced G-CSF-induced HSPC mobilization. Chimeric mouse experiments demonstrated that C3aR deficiency on graft-derived (hematopoietic) cells—not host stromal cells—was responsible for the increased mobilization.\",\n      \"method\": \"C3aR-/- and C3-/- mouse mobilization studies, bone marrow chimeras, G-CSF treatment, C3aR antagonist SB290157\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout replicated with pharmacological antagonist and reciprocal chimeric mouse experiments\",\n      \"pmids\": [\"14604969\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"C3aR signaling on dendritic cells (DCs) upregulates surface MHC and costimulatory molecule expression and is required for efficient T-cell priming against alloantigen. DCs lacking C3aR or treated with C3aR antagonist showed defective allostimulation and impaired skin allograft rejection. The alternative complement pathway (factor B-dependent, C4-independent) was identified as the relevant source of C3a.\",\n      \"method\": \"C3aR-/- bone marrow-derived DC allostimulation assays, skin allograft model, complement-deficient DC experiments (factor B-/-, C4-/-)\",\n      \"journal\": \"Blood\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic knockout plus pharmacological inhibition plus in vivo transplant model with defined pathway dissection\",\n      \"pmids\": [\"18056835\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"C3aR agonist treatment in neonatal rat cerebellum decreased the thickness of the external granule cell layer (EGL) and increased the internal granule cell layer (IGL), consistent with accelerated granule cell migration. Video-microscopy of cultured granule neurons confirmed a direct role for C3aR in cell motility.\",\n      \"method\": \"In vivo sub-dural injection of C3aR agonist/antagonist, histological analysis of cerebellar cortical layers, live video-microscopy of cultured neurons\",\n      \"journal\": \"Molecular immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo and in vitro orthogonal approaches in single study, single lab\",\n      \"pmids\": [\"18635264\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"C3aR on hematopoietic stem/progenitor cells promotes engraftment by augmenting MMP-9 secretion and cell adhesion to stroma. C3aR-/- HSPCs transplanted into lethally irradiated recipients showed 5–7 day delayed platelet/leukocyte recovery and reduced CFU-spleen. Blockade of C3aR on human cord blood CD34+ cells with SB290157 also impaired engraftment in NOD/SCID mice. Although C3a-enhanced SDF-1 responsiveness persisted in C3aR-/- cells (C3aR-independent effect), C3aR-/- cells secreted less MMP-9 and showed impaired stromal adhesion.\",\n      \"method\": \"C3aR-/- HSPC transplantation into irradiated mice, CFU assays, MMP-9 secretion assay, adhesion assay, human cord blood NOD/SCID xenograft with C3aR antagonist\",\n      \"journal\": \"Leukemia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (KO mouse transplantation, pharmacological blockade, human cell model) converging on same mechanistic conclusion\",\n      \"pmids\": [\"19357704\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Absence of C3aR (and C5aR) signaling in CD4+ T cells leads to cessation of PI3Kγ/Akt/mTOR signaling, increased PKA activity, initiation of autoinductive TGF-β1 signaling, and differentiation into Foxp3+ induced regulatory T cells. Endogenous TGF-β1 suppressed C3aR/C5aR signaling by preventing C3a/C5a production and upregulating C5L2. The resulting iTreg cells showed enhanced stability and suppressed autoimmune disease.\",\n      \"method\": \"C3aR/C5aR-deficient mice, pharmacological antagonism, signaling pathway analysis (PI3Kγ, Akt, mTOR, PKA), Foxp3 reporter assays, autoimmune disease models, human iTreg induction\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic and pharmacological approaches with defined signaling pathway dissection, validated in human cells\",\n      \"pmids\": [\"23263555\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"The VGF-derived neuropeptide TLQP-21 acts as a ligand for rodent C3AR1. Unbiased transcriptome sequencing of responsive CHO-K1 cells combined with defined receptor antagonists and siRNA knockdown identified C3AR1 as the GPCR mediating TLQP-21 signaling. TLQP-21 activity was pertussis toxin-sensitive (consistent with Gi coupling of C3AR1) and the peptide directed migration of mouse RAW264.7 macrophages through C3aR1.\",\n      \"method\": \"Transcriptome sequencing, receptor antagonist pharmacology, siRNA knockdown, pertussis toxin sensitivity assay, cell migration assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — unbiased genomic screen plus orthogonal validation (antagonists + siRNA + functional assays) converging on same target\",\n      \"pmids\": [\"23940034\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"TLQP-21 is intrinsically disordered and adopts an α-helical conformation (disorder-to-order transition) upon binding cells expressing C3aR1. The C-terminus of TLQP-21 constitutes the functional hot spot: mutations in the last four amino acids progressively reduce bioactivity, and a single R21A mutation or C-terminal amidation abolishes function completely. Human TLQP-21 (S20A variant) activates human C3aR1 with lower potency than the rodent sequence.\",\n      \"method\": \"NMR/structural biology of TLQP-21, site-directed mutagenesis of TLQP-21, cell-based functional assays\",\n      \"journal\": \"Structure (London, England : 1993)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — structural characterization combined with systematic mutagenesis and functional validation defining binding mechanism\",\n      \"pmids\": [\"25456411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"C3aR signaling protects myeloid and lymphoid cells against Listeria monocytogenes-induced apoptosis. C3aR-/- mice showed increased bacterial burden and mortality, with increased Fas expression, higher caspase-3 activity, and reduced Bcl-2 expression in splenocytes, without defects in macrophage function or cytokine/chemokine responses.\",\n      \"method\": \"C3aR-/- mouse infection model, TUNEL staining, caspase-3 activity assay, Bcl-2/Fas expression, bacterial burden measurement\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse model with multiple orthogonal readouts (survival, bacterial burden, apoptosis markers) identifying specific molecular mechanism\",\n      \"pmids\": [\"24981453\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"C3aR on neutrophils drives NETosis following LPS-induced complement C3a upregulation, which induces coagulation and N2 pro-tumorigenic polarization in intestinal tumorigenesis.\",\n      \"method\": \"Mouse model of spontaneous intestinal tumorigenesis, C3aR expression analysis on neutrophils, NET formation assay, coagulation assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo model with mechanistic pathway analysis, single lab\",\n      \"pmids\": [\"26996437\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"TLQP-21 opposes obesity via C3aR1-mediated enhancement of adrenergic-induced lipolysis. TLQP-21 does not possess intrinsic lipolytic activity but potentiates β-adrenergic receptor-induced lipolysis through a mechanism requiring Ca2+ mobilization and ERK activation of hormone-sensitive lipase (HSL). Chronic peripheral TLQP-21 treatment decreased body weight/fat mass in diet-induced obese mice in a β-adrenergic and C3aR1-dependent manner.\",\n      \"method\": \"C3aR1 KO mice, β-AR-deficient mice, 3T3-L1 and primary adipocyte in vitro assays, in vivo lipolysis experiments, pharmacological approaches\",\n      \"journal\": \"Molecular metabolism\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO plus pharmacological validation plus defined signaling intermediates (Ca2+, ERK, HSL) in multiple orthogonal models\",\n      \"pmids\": [\"28123945\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"C3aR1 is strongly expressed in the brain (predominantly on microglia), lung, intestinal lamina propria, and visceral adipose tissue; most macrophage and eosinophil populations are C3aR-positive. Notably, bone marrow neutrophils, mast cells, and all circulating lymphoid cells were C3aR-negative in mice, as determined by a reporter knock-in mouse.\",\n      \"method\": \"Floxed tdTomato-C3aR reporter knock-in mouse, flow cytometry, immunohistochemistry across multiple tissues\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct genetic reporter system providing high-resolution cell-type specific localization data across tissues\",\n      \"pmids\": [\"28626064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"C3aR1 activation by C3a promotes intestinal stem cell expansion and organoid formation via Wnt-signaling. C3-/- and C3aR1-/- mice showed significantly limited intestinal organoid formation; exogenous C3a rescued organoid growth from C3-/- mice but not from C3aR1-/- mice. C3 is expressed in Lgr5+ intestinal stem cells and C3aR1 on various intestinal cells.\",\n      \"method\": \"C3-/- and C3aR1-/- mouse intestinal organoid assays, Lgr5.egfp reporter mice, C3aR1 deficiency rescue experiments, ischemia/reperfusion injury model\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal KO rescue experiments with defined Wnt-signaling pathway linkage\",\n      \"pmids\": [\"28928734\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"C3aR and C5aR1 activation potentiates glucose-induced insulin secretion from human and mouse islets, increases intracellular calcium and ATP generation, and protects islets against apoptosis induced by pro-apoptotic cytokines or palmitate. Conditioned media from glucose-stimulated islets activates C3aR-driven β-arrestin recruitment.\",\n      \"method\": \"Radioimmunoassay for insulin, intracellular calcium measurement, ATP assay, β-arrestin recruitment assay, apoptosis assay in human and mouse islets\",\n      \"journal\": \"Cellular and molecular life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal functional readouts in primary human and mouse islets, single lab\",\n      \"pmids\": [\"28921001\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"C3a/C3aR signaling in platelets regulates platelet adhesion, spreading, Ca2+ influx, and thrombus formation by activating the small GTPase Rap1b. C3aR-/- mice showed altered bleeding time and reduced thrombosis; reconstitution of C3aR-/- mice with C3aR+/+ platelets rescued thrombosis phenotype, demonstrating the platelet-specific mechanism. C3aR-/- mice were less prone to experimental stroke and myocardial infarction.\",\n      \"method\": \"C3aR-/- mice, platelet depletion/reconstitution experiments, intravital microscopy, in vitro platelet function tests, nano-LC-MS/MS for Rap1b identification, in vivo disease models\",\n      \"journal\": \"Circulation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — platelet-specific reconstitution experiment isolates mechanism, combined with MS identification of Rap1b and multiple in vitro/in vivo assays\",\n      \"pmids\": [\"29802205\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"C3a-C3aR signaling promotes development of thoracic aortic dissection by upregulating MMP2 expression in smooth muscle cells. C3aR knockout inhibited BAPN-induced TAD formation; recombinant C3a stimulation enhanced MMP2 expression in mechanically stretched smooth muscle cells; MMP2-knockdown mice showed reduced TAD formation.\",\n      \"method\": \"C3aR-/- mice in BAPN model, C3aR antagonist treatment, recombinant C3a stimulation of SMCs, MMP2 KD via AAV-shRNA in vivo, histology\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, pharmacological antagonism, cell-based mechanistic experiment, and downstream effector KD all converging on MMP2 mechanism\",\n      \"pmids\": [\"29367209\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"C3aR1 deletion in PS19 tauopathy mice rescues tau pathology and attenuates neuroinflammation, synaptic deficits, and neurodegeneration. Mechanistically, STAT3 was identified as a direct downstream target of C3-C3aR signaling that functionally mediates tau pathogenesis. C3aR deletion inactivates a transcription factor network that drives disease-associated microglia and neurotoxic astrocyte signatures.\",\n      \"method\": \"C3ar1-/- PS19 mice, RNA sequencing, cell-type-specific transcriptomic analysis, histological assessment of tau pathology, synaptic and neurodegenerative markers\",\n      \"journal\": \"Neuron\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO in disease model with transcriptome-wide analysis and identification of specific downstream effector (STAT3)\",\n      \"pmids\": [\"30415998\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"C3aR1 controls BM neutrophil mobilization after spinal cord injury by acting as a physiological antagonist of CXCR2-driven neutrophil mobilization. C3aR1 engages PTEN (a negative regulator of PI3K/AKT) to restrain CXCR2-driven neutrophil egress from bone marrow. C3aR1-/- mice showed exaggerated neutrophil mobilization and worse SCI outcomes.\",\n      \"method\": \"C3aR1-/- mice in SCI model, PTEN/PI3K/AKT signaling analysis, pharmacological CXCR2 antagonism, human SCI correlation data\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined signaling mechanism (C3aR1→PTEN→PI3K/AKT axis) plus pharmacological validation\",\n      \"pmids\": [\"31045582\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"VEGFR2 survival and mitotic signaling in endothelial cells requires concurrent C3aR1/C5aR1 and IL-6R-gp130 co-signaling. C3aR1/C5aR1 blockade abolished VEGFR2 auto-phosphorylation and downstream Src, ERK, AKT, mTOR, and STAT3 activation, as well as EC cell cycle entry. VEGF-A augmented production of C3a/C5a/IL-6 via a p-Tyk2/p-STAT3 mechanism. The four receptors (VEGFR2, C3aR1, C5aR1, IL-6R) were found to be physically interactive by co-IP, confocal microscopy, ligand pulldown, and BRET assays.\",\n      \"method\": \"Co-immunoprecipitation, confocal microscopy, BRET assay, ligand pulldown, C3aR1/C5aR1 blockade, signaling pathway analysis, in vivo retinal angiogenesis\",\n      \"journal\": \"Journal of cell science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (Co-IP, BRET, confocal, functional signaling) demonstrating physical interaction and functional co-dependence\",\n      \"pmids\": [\"30765465\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Autocrine C3aR1 signaling in B2 cells is required for antibody production and class switch recombination (CSR). C3ar1-deficient mice immunized with OVA produced IgM but no other isotypes. CD40 upregulation, IL-6 production, BAFF/APRIL-driven growth, AID/Bcl-6 expression, and CD21 production all depended on B2 cell-intrinsic C3aR1/C5aR1 signaling. B2 cells themselves produced factor I and C3 to generate the autocrine signal.\",\n      \"method\": \"C3ar1-/- mice, μMT recipients of WT/C3ar1-/- B2 cells, C3-/- recipients with WT bone marrow, OVA/HEL immunization, adoptive transfer experiments\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal adoptive transfer experiments in multiple genetic backgrounds with defined functional readouts\",\n      \"pmids\": [\"31217324\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Recipient C3aR1 signaling promotes alloreactive CD8+ T cell expansion and differentiation by two mechanisms: (1) T cell-intrinsic C3aR1 drives CD8+ T cell proliferation, mTOR activation, and T-bet expression; (2) host C3aR1 amplifies APC costimulatory molecule expression and innate cytokine production to indirectly facilitate CD8+ T cell expansion.\",\n      \"method\": \"C3ar1-/- mice cardiac allograft model, reciprocal adoptive transfer of WT/C3ar1-/- CD8+ T cells, pharmacological C3aR1 blockade, mTOR and T-bet signaling analysis\",\n      \"journal\": \"American journal of transplantation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal adoptive transfers distinguish T cell-intrinsic vs host mechanisms with defined signaling pathway readouts\",\n      \"pmids\": [\"30565852\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"C3aR signaling inhibits NK cell infiltration into the tumor microenvironment. C3aR directly interacts with LFA-1 on activated NK cells, inducing a high-affinity LFA-1 conformation that decreases NK cell migration into tumors. Blocking C3aR signaling increased NK cell infiltration and led to tumor regression.\",\n      \"method\": \"C3aR-LFA-1 interaction studies, C3aR blockade in mouse tumor models, NK cell migration assays, LFA-1 conformation analysis\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct receptor interaction demonstrated with functional consequence in vivo, single lab\",\n      \"pmids\": [\"34819308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C3aR on microglia mediates white matter injury after chronic cerebral hypoperfusion. Genetic deletion of C3ar1 significantly inhibited aberrant microglial activation and reversed white matter injury, and C3aR antagonist SB290157 decreased microglial adherence to myelin and attenuated white matter injury and cognitive deficits in rats.\",\n      \"method\": \"C3aR-/- mice in bilateral carotid artery occlusion model, SB290157 pharmacological treatment in rats, CLARITY imaging, immunohistochemistry, behavioral testing\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO replicated with pharmacological antagonism, multiple behavioral and histological readouts\",\n      \"pmids\": [\"31903107\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C3a-C3aR signaling in cancer-associated fibroblasts (CAFs) facilitates breast cancer lung metastasis by augmenting pro-metastatic cytokine secretion and extracellular matrix component expression via PI3K-AKT signaling activation.\",\n      \"method\": \"Genetic and pharmacological C3aR blockade in mouse breast cancer models, ex vivo cytokine/ECM assays, PI3K-AKT signaling analysis\",\n      \"journal\": \"Journal of experimental & clinical cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic and pharmacological approaches with defined pathway (PI3K-AKT), single lab\",\n      \"pmids\": [\"31931851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"The C3-C3aR pathway mediates microglia-astrocyte interaction following status epilepticus. In C3-/- and C3aR-/- mice, microglia-astrocyte interaction was significantly reduced in response to kainic acid-induced status epilepticus, and C3-/- mice showed less neurodegeneration, identifying C3aR-dependent glial crosstalk as a contributor to KA-induced neurodegeneration.\",\n      \"method\": \"C3-/- and C3aR-/- mice in kainic acid status epilepticus model, microglial ablation, immunohistochemistry, spatial interaction analysis\",\n      \"journal\": \"Glia\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two independent genetic KO lines (C3-/- and C3aR-/-) with microglial ablation experiment converging on same glial communication mechanism\",\n      \"pmids\": [\"33314324\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"C3aR depletion in microglia reverses HIF-1α-induced metabolic impairment in Alzheimer's disease context. C3ar1-null microglia had lower HIF-1α expression, were resistant to hypoxia mimetic-induced metabolic changes and lipid droplet accumulation, and showed improved receptor recycling and Aβ phagocytosis. Crossing C3ar1-KO with APP-KI mice rescued dysregulated lipid profiles and improved microglial phagocytic and clustering abilities, identifying a C3aR/HIF-1α signaling axis governing microglial metabolic homeostasis.\",\n      \"method\": \"C3ar1 KO × APP-KI mice, primary microglial cultures, HIF-1α expression analysis, lipid droplet/metabolism assays, phagocytosis assays, synaptic/cognitive functional tests\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO in disease model combined with primary cell mechanistic studies identifying C3aR/HIF-1α axis with multiple orthogonal readouts\",\n      \"pmids\": [\"37317973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Complement C3aR (but not C5aR1 or C5aR2) deficiency mirrors C3 deficiency in reducing sarcoma growth. C3aR deficiency was associated with reduced tumor-associated macrophage accumulation, a shift to MHC II-dependent antigen presentation pathway in macrophages, and increased T cell activation and response to anti-PD-1 therapy, identifying the lectin pathway → C3aR axis as a key mediator of macrophage-driven immunosuppression in sarcomas.\",\n      \"method\": \"C3aR-/-, C3-/-, MBL1/2-/-, C4-/-, C5aR1-/-, C5aR2-/- mice in sarcoma models, transcriptional profiling of tumor-infiltrating macrophages, anti-PD-1 combination therapy\",\n      \"journal\": \"Nature cancer\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — systematic comparison of multiple complement KO lines with transcriptional profiling and therapeutic intervention in vivo\",\n      \"pmids\": [\"34505065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"C3aR-/- mice display increased innate (unconditioned) anxiety, independent of C3a (the canonical ligand), suggesting an alternative ligand mediates this phenotype. This is mechanistically distinct from C3-/- mice which show increased conditioned fear via iC3b/CR3 signaling, demonstrating that C3 and C3aR control dissociable emotional behaviors through different signaling mechanisms.\",\n      \"method\": \"C3aR-/- and C3-/- mice, anxiety and fear conditioning behavioral assays\",\n      \"journal\": \"Brain, behavior, and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — clean genetic KO behavioral dissection but single lab with purely behavioral readouts; alternative ligand hypothesis not confirmed\",\n      \"pmids\": [\"34543680\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"The reported C3aR antagonist SB290157 is actually a potent C3aR agonist in transfected cells and a partial C5aR2 agonist (β-arrestin recruitment) in both transfected cells and primary human and mouse macrophages, where SB290157 dampens C5a-induced ERK signaling via C5aR2 agonism. SB290157 acts as an antagonist in primary human macrophages for C3aR, but as an agonist in transfected cells, demonstrating cell context-dependent pharmacology.\",\n      \"method\": \"β-arrestin recruitment assays, ERK signaling assays, primary macrophage studies, C3aR/C5aR1/C5aR2 transfected cell models\",\n      \"journal\": \"Frontiers in pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — systematic pharmacological characterization across three receptors in multiple cell systems revealing mechanistic off-target effects of a widely used tool compound\",\n      \"pmids\": [\"33551801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"IL-1R/NF-κB signaling in astrocytes drives C3 release, which activates microglial C3aR, triggering hyperactivation of the microglial APT2/DHHC7 palmitoylation cycle, STAT3 translocation, and proinflammatory cytokine expression, leading to abnormal synaptic pruning in the prefrontal cortex in depression. C3aR blockade inhibited this cascade.\",\n      \"method\": \"LPS and chronic stress mouse models, C3aR antagonist treatment, proteomic analysis, APT2/DHHC7 palmitoylation cycle assay, STAT3 translocation assay, synaptic density analysis\",\n      \"journal\": \"Cell & bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological C3aR blockade with defined molecular mechanism (palmitoylation cycle, STAT3), single lab\",\n      \"pmids\": [\"35715851\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"C3aR signaling inhibits NK cell infiltration into tumors through direct physical interaction between C3aR and LFA-1, inducing high-affinity LFA-1 conformation and reduced NK cell migration. Blocking C3aR increased NK-cell TME infiltration and caused tumor regression in mouse models.\",\n      \"method\": \"C3aR-LFA-1 co-localization/interaction, LFA-1 conformation assay, C3aR blockade in tumor mouse models, NK cell migration assays\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct protein-protein interaction demonstrated with functional consequence, single lab\",\n      \"pmids\": [\"34819308\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"C3aR on dorsal root ganglion (DRG) macrophages mediates paclitaxel-induced peripheral neuropathic pain by upregulating TRPV4 on DRG neurons and promoting DRG macrophage expansion. C3aR1-/- mice showed less mechanical allodynia, reduced TRPV4 expression, and less macrophage expansion. C3aR1 antagonist in TRPV4 KO mice provided additional protection, indicating C3aR1 acts upstream of TRPV4.\",\n      \"method\": \"C3aR1-/- mice, C3aR1 antagonist treatment, TRPV4 KO mice, DRG macrophage expansion analysis, TRPV4 expression, neuron excitability measurement, intraepidermal nerve fiber density\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, pharmacological antagonism, and epistasis experiment (C3aR1 antagonist in TRPV4 KO) defining pathway order\",\n      \"pmids\": [\"37861348\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"C3aR contributes to renal interstitial fibrosis by promoting NLRP3 inflammasome assembly in renal tubular epithelial cells. C3aR-/- mice showed attenuated renal fibrosis and reduced NLRP3 inflammasome activation after UUO. NLRP3 inhibition (MCC950) did not affect C3aR expression, placing C3aR upstream of the NLRP3 inflammasome.\",\n      \"method\": \"C3aR-/- mice in UUO model, MCC950 NLRP3 inhibitor, Western blot, immunohistochemistry, renal function assays\",\n      \"journal\": \"Life sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO plus pharmacological epistasis defining C3aR upstream of NLRP3, single lab\",\n      \"pmids\": [\"36041502\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"C3a-bound C3aR and apo-C3aR structures were determined. The structures reveal: (1) a conserved recognition pattern for anaphylatoxin binding that differs from chemokine receptors; (2) unique pocket topologies of C3aR mediating ligand selectivity; and (3) a common activation mechanism for C3aR and C5aR1. Mutagenesis validated key contact residues.\",\n      \"method\": \"Cryo-EM/X-ray crystallography of C3a-bound C3aR, apo-C3aR, and C5a-bound C5aR1; site-directed mutagenesis\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — atomic-resolution structures of ligand-bound receptor combined with mutagenesis validation, providing definitive mechanistic insight\",\n      \"pmids\": [\"37169960\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"C3aR1 preferentially couples to Gi/o/z proteins and recruits β-arrestins to cause receptor internalization. Compared to C3a63-77, TLQP-21 exhibits biased agonism toward Gi/o-mediated signaling over β-arrestin recruitment/internalization. SB290157 is a potent C3aR1 agonist that antagonizes ligand-stimulated calcium flux through potent β-arrestin-mediated receptor internalization. Signaling bias has functional consequences for calcium influx, lipolysis in adipocytes, phagocytosis in microglia, and mast cell degranulation.\",\n      \"method\": \"BRET-based G protein coupling assays, β-arrestin recruitment assays, receptor internalization assays, calcium flux measurements, adipocyte lipolysis, microglial phagocytosis, mast cell degranulation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal signaling assays (BRET, calcium, functional cell assays) systematically characterizing G protein coupling, β-arrestin bias, and functional consequences\",\n      \"pmids\": [\"38072064\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"C3aR1 on macrophages is critical for rapid capture of pathogenic fungi (Histoplasma capsulatum, Candida albicans, Coccidioides posadasii) but is dispensable for phagocytosis of bacteria and latex beads. C3aR1 localizes to the early phagosome during H. capsulatum infection and coordinates formation of actin-rich membrane protrusions that promote fungal capture. The ER membrane complex (EMC) promotes surface expression of C3aR, thus enabling this function.\",\n      \"method\": \"Genome-scale CRISPR-Cas9 screen, C3aR KO validation, phagocytosis assays with bacteria/beads/fungi, phagosomal localization imaging, actin protrusion analysis, EMC-C3aR epistasis\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — unbiased CRISPR screen with mechanistic validation (subcellular localization, actin dynamics, upstream regulator EMC) across multiple fungal pathogens\",\n      \"pmids\": [\"36174103\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"C3a/C3aR activation promotes EMT in renal tubular epithelial cells synergistically with TGF-β via ERK-mediated NLRP3 inflammasome assembly. C3aR inhibition attenuated EMT and NLRP3 activation; ERK inhibition blocked NLRP3 activation but not C3aR expression, placing ERK downstream of C3aR and upstream of NLRP3 in a C3aR→ERK→NLRP3→EMT pathway.\",\n      \"method\": \"C3aR antagonist, NLRP3 inhibitor MCC950, ERK inhibitor PD98059 in TCMK-1 cells; C3aR-/- mice in UUO model; Western blot, immunofluorescence, ELISA\",\n      \"journal\": \"Journal of translational medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological epistasis defining pathway order (C3aR→ERK→NLRP3), validated in vivo in C3aR KO mice, single lab\",\n      \"pmids\": [\"38082306\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"C3aR in astrocytes mediates chronic post-thoracotomy pain by inducing neurotoxic A1 astrocyte polarization, while also influencing M1 microglial activation. Intrathecal AAV-mediated knockdown of C3aR specifically in astrocytes (GFAP promoter) inhibited LPS-induced A1 activation, decreased M1 microglia, and alleviated chronic pain. C3aR downregulation also increased anti-inflammatory A2 astrocyte numbers.\",\n      \"method\": \"Rat thoracotomy pain model, AAV2/9-rC3ar1 shRNA-GFAP intrathecal injection, single-cell RNA sequencing, RT-PCR, Western blot, immunofluorescence, behavioral pain assessment\",\n      \"journal\": \"Biochimica et biophysica acta. Molecular basis of disease\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — cell-type-specific in vivo KD with defined astrocyte polarization mechanism, single lab\",\n      \"pmids\": [\"36871753\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Renin cleaves C3 into C3a which activates C3aR on renal tubular epithelial cells, impairing PPARα/CPT-1α-mediated mitochondrial fatty acid oxidation and inducing a profibrotic phenotype. C3aR antagonist SB290157 restored mitochondrial FAO and alleviated tubulointerstitial fibrosis in 2K1C hypertensive rats.\",\n      \"method\": \"In vitro renin-C3 cleavage assay (ELISA), HK2 cell C3a/C3aR antagonist experiments, 2K1C rat model, PPARα/CPT-1α pathway analysis, Western blot\",\n      \"journal\": \"Frontiers in bioscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined biochemical mechanism (renin cleaves C3→C3a→C3aR→PPARα/CPT-1α impairment) with in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"37919077\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"In NPM1-mutated AML cells, C3AR stimulation with C3a activates ERK1/2 and promotes AML cell survival. Anti-C3AR antibodies efficiently elicit NK cell-mediated killing of primary AML cells ex vivo.\",\n      \"method\": \"Flow cytometry, scRNA sequencing, C3a stimulation/ERK1/2 phosphorylation assay, NK cell cytotoxicity assay, xenotransplantation into immunodeficient mice\",\n      \"journal\": \"Blood advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct signaling assay (C3a→ERK1/2) plus functional NK killing assay, single lab\",\n      \"pmids\": [\"36383712\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"C3aR activation exacerbates early brain injury after subarachnoid hemorrhage via the C3aR→ERK→P2X7→NLRP3 inflammasome signaling axis. C3a promotes ATP efflux through ERK1/2 phosphorylation, which activates P2X7 receptor, which in turn activates the NLRP3 inflammasome. C3aR inhibition (SB290157) reduced inflammasome activation, neuroinflammation, and improved outcomes in SAH mice.\",\n      \"method\": \"ERK inhibitor, P2X7R antagonist (JNJ-55308942), C3aR inhibitor (SB290157) in BV-2 cells and SAH mouse model; Western blot, ELISA, behavioral analysis, ATP release assay\",\n      \"journal\": \"Inflammation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — pharmacological epistasis defining pathway order with multiple signaling inhibitors in vitro and in vivo, single lab\",\n      \"pmids\": [\"39528767\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Adipocyte-specific C3aR1 knockout in male mice enhances white adipose tissue thermogenesis and increases respiration, whereas female adipocyte-specific C3aR1-KO mice display decreased brown fat thermogenesis and cold intolerance, revealing sexual dimorphism in the adipsin/C3a/C3aR1 axis. Female mice express lower levels of Adipsin in thermogenic adipocytes and lower C3aR1 in subcutaneous adipose tissue than males.\",\n      \"method\": \"Adipocyte-specific C3aR1-KO mice (male and female), Adipsin/Cfd-KO mice, energy expenditure measurement, cold tolerance test, adipose thermogenesis assessment\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type-specific conditional KO in both sexes with rigorous metabolic phenotyping revealing sex-dependent mechanism\",\n      \"pmids\": [\"38713526\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In a membranous nephropathy glomerulus-on-a-chip model, C3aR activation on podocytes (not membrane attack complex formation) is the critical mechanism of complement-mediated albumin permselectivity loss. C3AR gene silencing or C3aR antagonism reduced oxidative stress and prevented albumin leakage, whereas MAC inhibition did not. C3aR antagonist prevented proteinuria in a mouse MN model.\",\n      \"method\": \"Glomerulus-on-a-chip with primary human podocytes, C3AR siRNA knockdown, C3aR antagonist, MAC inhibitor, in vivo mouse MN model with C3aR antagonist\",\n      \"journal\": \"JCI insight\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — organ-on-chip reconstitution with genetic (siRNA) and pharmacological inhibition plus in vivo validation, demonstrating specificity over alternative mechanism (MAC)\",\n      \"pmids\": [\"38227377\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"In glioma, NFAT1 in tumor-associated macrophages transcriptionally upregulates C3 and increases C3a secretion; C3a binds C3aR and promotes M2-like macrophage polarization by activating TIM-3. C3a/C3aR also activates the Ca2+-NFAT1 pathway forming a positive feedback loop for M2 polarization, which promotes mesenchymal glioma stem cell transition.\",\n      \"method\": \"Nfat1-/- mice glioma model, C3 transcriptional activity assay, TIM-3 pathway analysis, Ca2+-NFAT1 signaling assay, C3aR inhibitor in vitro and in vivo\",\n      \"journal\": \"Cancer immunology research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined NFAT1→C3→C3aR→TIM-3→NFAT1 feedback loop mechanism with in vitro and in vivo validation, single lab\",\n      \"pmids\": [\"38289255\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"C3aR modulates susceptibility to depressive-like behaviors through mPFC glutamatergic neuronal excitability. C3aR deletion or intra-mPFC antagonism confers resilience; C3aR-null mPFCGlu neurons display hyperexcitability upon LPS treatment, which is anti-depressant. C3aR expression in mPFC neurons makes KO mice susceptible when C3aR is reintroduced, identifying C3aR as a direct modulator of glutamatergic neuronal excitability.\",\n      \"method\": \"C3aR KO mice, intra-mPFC C3aR antagonism, viral C3aR re-expression in KO mPFC neurons, mPFCGlu neuron-specific excitability assays (electrophysiology), LPS depression model\",\n      \"journal\": \"Progress in neurobiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO, pharmacological antagonism, viral rescue, and electrophysiology converging on specific mechanism (C3aR→mPFCGlu excitability)\",\n      \"pmids\": [\"38641040\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Astrocyte-derived C3, induced via TLR2/NF-κB signaling by α-synuclein PFFs, signals to dopaminergic neurons via C3aR to influence neuronal apoptosis and α-synuclein pathology potentially through GSK3β modulation. Overexpression of C3 exacerbated, and downregulation of C3 protected against, motor dysfunction and dopaminergic neuron loss in PFF-injected mice.\",\n      \"method\": \"AAV-mediated C3 overexpression/knockdown in PFF-injected mice, TLR2/NF-κB inhibitor treatment in primary astrocytes, astrocyte-neuron co-culture C3/C3aR pathway analysis, GSK3β signaling\",\n      \"journal\": \"Brain, behavior, and immunity\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — defined astrocyte-neuron communication pathway with mechanistic intermediates (TLR2/NF-κB→C3→C3aR→GSK3β), single lab\",\n      \"pmids\": [\"39288893\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"C3AR1 is a Gi/o/z-coupled GPCR with a uniquely large second extracellular loop that binds C3a (and the VGF-derived peptide TLQP-21 as a biased agonist) to trigger intracellular signaling including PI3Kγ/Akt/mTOR, ERK, calcium mobilization, and STAT3 activation; upon ligand binding, C3aR undergoes GRK2/3/5/6-mediated serine/threonine phosphorylation and β-arrestin-mediated internalization, with ligand identity determining the balance between Gi/o signaling and β-arrestin recruitment; the receptor mediates diverse context-dependent functions including hematopoietic stem cell retention in bone marrow (via MMP-9 secretion and stromal adhesion), Treg induction (via suppression of PI3Kγ/Akt/mTOR and activation of PKA/TGF-β1 autocrine signaling), platelet-dependent thrombus formation (via Rap1b activation), neutrophil mobilization (via PTEN/PI3K-AKT antagonism of CXCR2), B cell class switch recombination (autocrine), dendritic cell allostimulation, adipocyte lipolysis enhancement (via Ca2+/ERK/HSL axis potentiating β-adrenergic signaling), microglial phagocytosis and metabolic regulation (via HIF-1α), and podocyte injury in membranous nephropathy; structurally, cryo-EM reveals that C3a engages a receptor pocket topology distinct from chemokine receptors and that the VEGFR2, C3aR1, C5aR1, and IL-6R form a physically interactive signaling platform required for RTK growth signaling.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"C3AR1 encodes a seven-transmembrane G protein-coupled receptor with an unusually large second extracellular loop (~175 residues) that binds the complement anaphylatoxin C3a to trigger intracellular signaling [#0]. The receptor preferentially couples to Gi/o/z proteins and recruits \\u03b2-arrestins to drive internalization, with ligand identity tuning the balance between G protein signaling and \\u03b2-arrestin recruitment; the VGF-derived neuropeptide TLQP-21 is a biased agonist favoring Gi/o-mediated signaling over arrestin engagement [#35, #7]. Upon agonist binding, C3aR is rapidly phosphorylated on serine/threonine residues by GRK2/3/5/6, initiating desensitization and internalization [#1]. Cryo-EM structures of C3a-bound and apo-C3aR define a unique pocket topology that confers anaphylatoxin selectivity distinct from chemokine receptors and reveal an activation mechanism shared with C5aR1 [#34]. Downstream, C3aR signals through PI3K\\u03b3/Akt/mTOR, ERK, calcium mobilization, and STAT3 to produce strongly context-dependent outputs across many cell types [#6, #35, #17]. In hematopoiesis it retains stem/progenitor cells in bone marrow and promotes engraftment via MMP-9 secretion and stromal adhesion [#2, #5], and it restrains CXCR2-driven neutrophil mobilization through a PTEN/PI3K-AKT axis [#18]. In adaptive immunity, loss of C3aR signaling drives Foxp3+ regulatory T cell differentiation by suppressing PI3K\\u03b3/Akt/mTOR and engaging autocrine TGF-\\u03b21 [#6], while autocrine C3aR signaling in B cells is required for class switch recombination [#20] and recipient C3aR amplifies alloreactive CD8+ T cell expansion [#21]. In platelets C3aR activates Rap1b to promote thrombus formation [#15], and in adipocytes it potentiates \\u03b2-adrenergic lipolysis via a Ca2+/ERK/HSL axis with sexually dimorphic effects on adipose thermogenesis [#11, #42]. In the nervous system C3aR is expressed predominantly on microglia [#12] and governs microglial metabolic homeostasis and A\\u03b2 phagocytosis through a HIF-1\\u03b1 axis [#26], tau pathology via STAT3 [#17], and neuronal excitability and emotional behavior [#45]. Across cancer and fibrotic disease the receptor recurrently drives ERK\\u2192NLRP3 inflammasome and PI3K-AKT programs and macrophage immunosuppression [#37, #24, #27], and on podocytes it mediates complement-driven albumin permselectivity loss in membranous nephropathy independent of the membrane attack complex [#43]. C3aR also functions within a physically interactive VEGFR2\\u2013C3aR1\\u2013C5aR1\\u2013IL-6R signaling platform required for receptor tyrosine kinase growth signaling [#19].\",\n  \"teleology\": [\n    {\n      \"year\": 1996,\n      \"claim\": \"Established the molecular identity of the C3a receptor as a functional GPCR, answering whether C3a signals through a defined seven-transmembrane receptor.\",\n      \"evidence\": \"Expression cloning from U-937 cells with radioligand binding and phosphoinositide hydrolysis in transfected HEK-293/CHO cells\",\n      \"pmids\": [\"8765043\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"G protein coupling shown only with co-transfected G\\u03b1-16, not native G proteins\", \"Function of the large second extracellular loop undefined\"]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Defined how agonist-bound C3aR is desensitized, identifying GRK-mediated serine/threonine phosphorylation as the regulatory mechanism.\",\n      \"evidence\": \"Phosphorylation/radiolabeling assays with GRK2/3/5/6 overexpression and antibody inhibition in COS-7 and primary mast cells\",\n      \"pmids\": [\"10508278\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific phosphoacceptor residues not mapped\", \"Link to \\u03b2-arrestin recruitment not directly established here\"]\n    },\n    {\n      \"year\": 2003,\n      \"claim\": \"Demonstrated a physiological role in hematopoiesis, showing C3aR retains stem/progenitor cells in bone marrow by enhancing SDF-1 responsiveness.\",\n      \"evidence\": \"C3aR-/- and C3-/- mouse mobilization studies with bone marrow chimeras and SB290157 antagonist\",\n      \"pmids\": [\"14604969\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link between C3aR and SDF-1/CXCR4 responsiveness undefined\", \"SB290157 later shown to have agonist activity\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Resolved the engraftment mechanism distinct from mobilization, attributing it to C3aR-driven MMP-9 secretion and stromal adhesion.\",\n      \"evidence\": \"C3aR-/- HSPC transplantation, CFU assays, MMP-9/adhesion assays, human cord blood NOD/SCID xenografts\",\n      \"pmids\": [\"19357704\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signaling pathway from C3aR to MMP-9 induction not mapped\", \"C3a-enhanced SDF-1 response found C3aR-independent, complicating the model\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Identified a second, non-complement ligand class by showing the VGF peptide TLQP-21 is a C3aR1 agonist, broadening receptor pharmacology.\",\n      \"evidence\": \"Transcriptome screen of CHO-K1 cells with antagonist pharmacology, siRNA, pertussis toxin sensitivity, and macrophage migration\",\n      \"pmids\": [\"23940034\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Demonstrated for rodent receptor; human potency lower\", \"Whether TLQP-21 and C3a share the same binding pocket not addressed\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Defined the structural basis of TLQP-21 binding, showing a disorder-to-order transition and a C-terminal hot spot governing activity.\",\n      \"evidence\": \"NMR/structural analysis with systematic TLQP-21 mutagenesis and cell-based functional assays\",\n      \"pmids\": [\"25456411\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Receptor-side contacts not yet resolved at this stage\", \"Human variant has reduced potency\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Established C3aR as a brake on regulatory T cell induction, linking its signaling to PI3K\\u03b3/Akt/mTOR suppression and autocrine TGF-\\u03b21.\",\n      \"evidence\": \"C3aR/C5aR-deficient mice, pharmacological antagonism, signaling dissection, Foxp3 reporters, human iTreg induction\",\n      \"pmids\": [\"23263555\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of C3aR vs C5aR not fully separated\", \"Mechanism of C3a production in T cell microenvironment incomplete\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Extended C3aR function to cell survival, showing it protects immune cells against Listeria-induced apoptosis via Bcl-2/Fas/caspase-3 control.\",\n      \"evidence\": \"C3aR-/- mouse infection model with TUNEL, caspase-3 activity, and Bcl-2/Fas expression\",\n      \"pmids\": [\"24981453\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct signaling pathway from C3aR to apoptotic machinery not mapped\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Defined a platelet-specific effector, identifying Rap1b activation as the mechanism by which C3aR promotes thrombosis.\",\n      \"evidence\": \"C3aR-/- mice with platelet reconstitution, intravital microscopy, nano-LC-MS/MS identification of Rap1b, stroke/MI models\",\n      \"pmids\": [\"29802205\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Coupling between C3aR and Rap1b activation not biochemically reconstituted\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Revealed a metabolic role, showing C3aR1 potentiates \\u03b2-adrenergic lipolysis through Ca2+/ERK/HSL rather than acting as an intrinsic lipolytic signal.\",\n      \"evidence\": \"C3aR1-KO and \\u03b2-AR-deficient mice, 3T3-L1/primary adipocyte assays, in vivo obesity experiments\",\n      \"pmids\": [\"28123945\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular point of crosstalk with \\u03b2-adrenergic receptor unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Mapped the cellular expression landscape of C3aR1, establishing microglia, macrophages, and adipose as principal sites and excluding circulating lymphoid cells.\",\n      \"evidence\": \"tdTomato-C3aR reporter knock-in mouse with flow cytometry and immunohistochemistry across tissues\",\n      \"pmids\": [\"28626064\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reporter expression in mouse may not fully reflect human distribution\", \"Inducible expression under disease conditions not captured\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Placed C3aR1 within a physical RTK co-signaling platform required for VEGFR2-driven endothelial growth signaling.\",\n      \"evidence\": \"Co-IP, BRET, confocal, ligand pulldown, C3aR1/C5aR1 blockade, and in vivo retinal angiogenesis\",\n      \"pmids\": [\"30765465\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry and architecture of the four-receptor complex undefined\", \"Whether the platform forms in non-endothelial cells unknown\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Established cell-intrinsic and autocrine roles in adaptive immunity, showing C3aR1 is required for B cell class switch recombination and amplifies alloreactive CD8+ T cell responses.\",\n      \"evidence\": \"C3ar1-/- mice with reciprocal adoptive transfer into \\u03bcMT and C3-/- recipients; cardiac allograft and CD8 expansion analysis with mTOR/T-bet readouts\",\n      \"pmids\": [\"31217324\", \"30565852\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Source and regulation of autocrine C3a/C3 in lymphocytes incompletely defined\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Showed C3aR drives tissue remodeling and fibrotic disease via MMP and inflammasome effectors in vascular and renal pathology.\",\n      \"evidence\": \"C3aR-/- mice and effector knockdown in BAPN aortic dissection (MMP2) and UUO renal fibrosis (NLRP3) models\",\n      \"pmids\": [\"29367209\", \"36041502\", \"38082306\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Multiple effector pathways (MMP2, ERK\\u2192NLRP3) not unified into a single mechanism\", \"Some renal findings are single-lab Medium confidence\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Established C3aR as a central driver of neuroinflammatory and neurodegenerative pathology, identifying STAT3 and HIF-1\\u03b1 as key microglial effectors.\",\n      \"evidence\": \"C3ar1-/- crosses with PS19 tauopathy and APP-KI mice, RNA-seq, primary microglia metabolic/phagocytosis assays, and multiple injury models\",\n      \"pmids\": [\"30415998\", \"37317973\", \"31903107\", \"33314324\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Ligand(s) driving CNS C3aR signaling in some contexts unconfirmed\", \"How STAT3 and HIF-1\\u03b1 arms relate mechanistically unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Demonstrated a tumor-immunosuppressive role, showing C3aR shapes macrophage polarization, antigen presentation, and checkpoint therapy responsiveness.\",\n      \"evidence\": \"Systematic complement KO comparison in sarcoma with macrophage transcriptional profiling and anti-PD-1 combination; tumor models in breast cancer and glioma\",\n      \"pmids\": [\"34505065\", \"31931851\", \"38289255\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Generalizability of the lectin-pathway\\u2192C3aR axis across tumor types untested\", \"Some downstream loops (NFAT1, TIM-3) are single-lab Medium confidence\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Exposed the off-target pharmacology of the widely used compound SB290157, reframing it as a context-dependent C3aR agonist and partial C5aR2 agonist.\",\n      \"evidence\": \"\\u03b2-arrestin and ERK assays across C3aR/C5aR1/C5aR2 transfected cells and primary human/mouse macrophages\",\n      \"pmids\": [\"33551801\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Reinterpretation of prior SB290157 studies needed\", \"Determinants of cell-context switch between agonism and antagonism unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Provided the definitive structural and signaling framework, resolving the C3a-bound receptor and systematically characterizing Gi/o/z coupling and \\u03b2-arrestin bias.\",\n      \"evidence\": \"Cryo-EM/crystallography of C3a-C3aR and apo-C3aR with mutagenesis; BRET G protein and \\u03b2-arrestin assays with functional readouts in adipocytes, microglia, and mast cells\",\n      \"pmids\": [\"37169960\", \"38072064\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of TLQP-21-bound receptor not determined\", \"Structural basis of biased agonism not directly visualized\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Refined disease relevance by isolating podocyte C3aR as the critical complement effector in membranous nephropathy and revealing sex-dependent adipose function.\",\n      \"evidence\": \"Glomerulus-on-a-chip with siRNA/antagonist and in vivo MN model; adipocyte-specific C3aR1-KO in both sexes with metabolic phenotyping\",\n      \"pmids\": [\"38227377\", \"38713526\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of sexual dimorphism in adipose C3aR signaling incomplete\", \"Podocyte oxidative-stress mechanism downstream of C3aR not fully mapped\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identified a non-immune-classical role in innate immunity, showing C3aR1 enables macrophage capture of fungal pathogens via phagosomal localization and actin protrusions.\",\n      \"evidence\": \"Genome-scale CRISPR screen with C3aR KO validation, phagocytosis assays across fungi/bacteria/beads, phagosomal imaging, and EMC epistasis\",\n      \"pmids\": [\"36174103\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether a defined ligand drives this capture function unknown\", \"Selectivity for fungi over bacteria mechanistically unexplained\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How a single receptor with one structural framework produces such divergent, cell-type-specific outputs\\u2014and the identity of the non-C3a ligand(s) implicated in CNS and behavioral phenotypes\\u2014remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Alternative ligand driving C3a-independent anxiety phenotype unidentified\", \"No unifying model linking Gi/o vs \\u03b2-arrestin bias to specific tissue outcomes\", \"Structural basis of biased agonism by TLQP-21 vs C3a not determined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 34, 35]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0004930\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [29, 35]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0, 12, 19]},\n      {\"term_id\": \"GO:0031410\", \"supporting_discovery_ids\": [36]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [2, 6, 20, 27]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 18, 35]},\n      {\"term_id\": \"R-HSA-8953897\", \"supporting_discovery_ids\": [26, 37, 41]}\n    ],\n    \"complexes\": [\n      \"VEGFR2\\u2013C3aR1\\u2013C5aR1\\u2013IL-6R signaling platform\"\n    ],\n    \"partners\": [\n      \"C3a\",\n      \"TLQP-21\",\n      \"GRK2\",\n      \"GRK3\",\n      \"GRK5\",\n      \"GRK6\",\n      \"VEGFR2\",\n      \"LFA-1\"\n    ],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":11,"faith_total":11,"faith_pct":100.0}}