{"gene":"MRGPRX2","run_date":"2026-04-28T18:30:28","timeline":{"discoveries":[{"year":2003,"finding":"MRGPRX2 (MrgX2) is a Gq-coupled GPCR that responds to cortistatin with increased intracellular Ca2+ but no effect on cAMP levels, identifying it as a high-potency cortistatin receptor expressed in dorsal root ganglia.","method":"Reverse pharmacology screening, Ca2+ mobilization assay, cAMP assay in MrgX2-expressing cells","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — functional in vitro assays with multiple readouts (Ca2+, cAMP) establishing Gq coupling and ligand identity","pmids":["12915402"],"is_preprint":false},{"year":2005,"finding":"MRGPRX2 (MrgX2) is activated by proadrenomedullin N-terminal peptides (PAMP-12 > cortistatin > PAMP-20), coupling to both Gαq and Gαi, as demonstrated by Ca2+ mobilization, inhibition of forskolin-elevated cAMP, and [35S]GTPγS binding assays; the receptor is expressed in adrenal chromaffin cells and dorsal root ganglia.","method":"Ca2+ mobilization assay, cAMP inhibition assay, [35S]GTPγS binding, immunostaining","journal":"Biochemical and biophysical research communications","confidence":"High","confidence_rationale":"Tier 1 — multiple orthogonal biochemical assays establishing dual G protein coupling (Gαq and Gαi) and ligand rank order","pmids":["15823563"],"is_preprint":false},{"year":2005,"finding":"Proadrenomedullin N-terminal peptides and cortistatin share a common structural motif for activating MrgX2, explaining how two apparently unrelated peptides activate the same receptor.","method":"Structure-activity relationship (SAR) studies of PAMP analogs in MrgX2-expressing cells","journal":"European journal of pharmacology","confidence":"Medium","confidence_rationale":"Tier 1 — systematic SAR with functional assays, single lab","pmids":["16111673"],"is_preprint":false},{"year":2011,"finding":"MRGPRX2 (MrgX2) is a novel GPCR for the antimicrobial peptide LL-37 on human mast cells; it mediates sustained Ca2+ mobilization and degranulation, but unlike most GPCRs it is resistant to agonist-induced receptor phosphorylation, desensitization, and internalization; GRK2 and GRK3 knockdown had no effect on LL-37-induced degranulation.","method":"shRNA knockdown in LAD2 and primary CD34+ mast cells, stable transfection of MrgX2 in mast cell lines, Ca2+ mobilization and degranulation assays","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — reciprocal knockdown/transfection with functional readouts, multiple cell systems; replicated with primary cells","pmids":["22069323"],"is_preprint":false},{"year":2011,"finding":"Compound 48/80 induces mast cell degranulation via both MrgX1 and MrgX2, whereas the C3a receptor superagonist E7 activates mast cells via MrgX2 but not MrgX1; C3a itself does not use MrgX1 or MrgX2 for degranulation.","method":"Stable transfection of MrgX1 and MrgX2 in RBL-2H3 cells, Ca2+ mobilization and degranulation assays comparing LAD2, HMC-1, and transfected RBL cells","journal":"European journal of pharmacology","confidence":"High","confidence_rationale":"Tier 2 — genetic overexpression in orthogonal cell system with clear receptor-specific functional readouts","pmids":["21741965"],"is_preprint":false},{"year":2011,"finding":"PMX-53 functions as both a potent CD88 antagonist and a low-affinity agonist for MrgX2 (but not MrgX1); Trp and Arg residues in PMX-53 are required for both activities.","method":"Stable transfection of MrgX1 and MrgX2 in RBL-2H3 cells, Ca2+ mobilization and degranulation assays, mutagenesis of PMX-53 (Trp→Ala and Arg→dArg substitutions)","journal":"Molecular pharmacology","confidence":"High","confidence_rationale":"Tier 1 — ligand mutagenesis combined with receptor-specific functional assays in transfected cells","pmids":["21441599"],"is_preprint":false},{"year":2017,"finding":"MRGPRX2 is activated by many opioid compounds (including morphine, hydrocodone, sinomenine, dextromethorphan, dynorphin A/B, neoendorphins) and mediates mast cell degranulation and Ca2+ release; mutagenesis-validated homology models were used to identify selective agonist ZINC-3573.","method":"High-throughput screening of 5,695 small molecules, mutagenesis-validated homology modeling, virtual docking of ~4 million compounds, functional assays in MRGPRX2-expressing cells and LAD2 mast cells","journal":"Nature chemical biology","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis-validated structural model combined with experimental screening and functional validation in multiple cell systems","pmids":["28288109"],"is_preprint":false},{"year":2017,"finding":"Vancomycin and staphylococcus δ-toxin evoke mast cell degranulation via MRGPRX2; a receptor antagonist inhibits this process.","method":"Mast cell degranulation assays with MRGPRX2 antagonist blockade","journal":"Itch (Philadelphia, Pa.)","confidence":"Medium","confidence_rationale":"Tier 3 — functional assay with antagonist, single lab, limited mechanistic detail in abstract","pmids":["28367504"],"is_preprint":false},{"year":2017,"finding":"MRGPRX2-mediated sinomenine hydrochloride (SH)-induced mast cell degranulation operates through activation of PLC signaling pathways leading to Ca2+ mobilization; MrgprB2 knockout mice show reduced SH-induced inflammation, and MRGPRX2 knockdown mast cells show reduced degranulation.","method":"MrgprB2 knockout mouse model, MRGPRX2 siRNA knockdown, Ca2+ mobilization assay, hindpaw swelling/extravasation assay in vivo","journal":"Biochemical pharmacology","confidence":"High","confidence_rationale":"Tier 2 — combined in vivo KO and in vitro knockdown with mechanistic pathway identification","pmids":["28987593"],"is_preprint":false},{"year":2017,"finding":"FcεRI- and MRGPRX2-triggered mast cell degranulation pathways are completely independent and show no cross-correlation; SCF potently inhibits pseudo-allergic (MRGPRX2-mediated) degranulation while simultaneously promoting allergic (FcεRI-mediated) stimulation.","method":"Human skin mast cell degranulation assays comparing FcεRI and MRGPRX2 routes with SCF treatment, MRGPRX2 mRNA quantification","journal":"Allergy","confidence":"Medium","confidence_rationale":"Tier 2 — functional dissection in primary human cells with pharmacological manipulation, single lab","pmids":["28859248"],"is_preprint":false},{"year":2017,"finding":"LL-37-induced human mast cell degranulation and IL-8 release through MrgX2 is associated with activation of Gi protein, PLC/PKC/Calcium/NFAT, PI3K/Akt, and MAPK signaling pathways; MrgX2 silencing significantly inhibits both degranulation and cytokine release.","method":"siRNA knockdown of MrgX2 in LAD2 cells, Ca2+ imaging, β-hexosaminidase release, IL-8 measurement, pathway inhibitor studies","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — knockdown with multiple pathway inhibitors in a defined cell system","pmids":["28549244"],"is_preprint":false},{"year":2018,"finding":"Four naturally occurring missense variants in MRGPRX2's extracellular/transmembrane domains (G165E, D184H, W243R, H259Y) cause complete loss-of-function for mast cell degranulation in response to substance P, hemokinin-1, human β-defensin-3, and icatibant, suggesting these diverse ligands use common receptor sites.","method":"Stable and transient transfection of MRGPRX2 missense variants in RBL-2H3 cells, degranulation assay with multiple ligands","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1 — systematic mutagenesis of naturally occurring variants with multiple ligands establishing shared binding sites","pmids":["29794017"],"is_preprint":false},{"year":2018,"finding":"MRGPRX2 is negatively regulated by SCF and IL-4 in skin mast cells; withdrawal of both SCF and IL-4 partially reinstates MRGPRX2 expression and pseudo-allergic responsiveness; FcεRI-triggered activation shows inverse regulation compared to MRGPRX2-mediated activation.","method":"Mast cell culture with SCF/IL-4 withdrawal, MRGPRX2 mRNA/protein quantification, functional degranulation assays","journal":"Experimental dermatology","confidence":"Medium","confidence_rationale":"Tier 2 — systematic cytokine manipulation with expression and functional readouts in primary human mast cells","pmids":["30091263"],"is_preprint":false},{"year":2018,"finding":"MrgX2-mediated LL-37 internalization occurs via clathrin-mediated endocytosis requiring sialic acid at the cell surface; LL-37 co-localizes with MrgX2 in the perinuclear region; G-protein inhibition (pertussis toxin) and MrgX2 siRNA knockdown both suppress LL-37 internalization and mast cell degranulation.","method":"siRNA knockdown of MrgX2, pertussis toxin treatment, neuraminidase treatment, clathrin endocytosis inhibitors (dynasore, chlorpromazine), confocal microscopy, β-hexosaminidase release assay in LAD2 cells","journal":"Molecular medicine reports","confidence":"Medium","confidence_rationale":"Tier 2 — multiple complementary approaches identifying internalization mechanism, single lab","pmids":["30280189"],"is_preprint":false},{"year":2019,"finding":"Substance P (SP) induces Ca2+ mobilization and degranulation via both Gαi and Gαq family G proteins in MRGPRX2-expressing cells; conserved TM6 residue I225 and TM7 residue Y279 are essential for SP-induced responses; intracellular loop residues R138C and R141C cause loss of function; carboxyl-terminal Ser/Thr substitution (all five to Ala) and missense variants S325L and L329Q result in gain-of-function, suggesting desensitization via C-terminal phosphorylation.","method":"Pertussis toxin and YM-254890 G protein inhibition, transient transfection of MRGPRX2 variants in RBL-2H3 cells, structural modeling, Ca2+ mobilization and degranulation assays","journal":"International journal of molecular sciences","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis combined with pharmacological G protein pathway dissection and structural modeling","pmids":["31652731"],"is_preprint":false},{"year":2019,"finding":"AG-30/5C and icatibant are G protein-biased agonists for MRGPRX2: they induce pertussis toxin-sensitive G protein-mediated degranulation without activating β-arrestin (Tango assay); compound 48/80 signals via both G protein and β-arrestin pathways and causes MRGPRX2 internalization and subsequent desensitization; resveratrol inhibits compound 48/80-induced Tango and mast cell degranulation.","method":"shRNA silencing of MRGPRX2 in LAD2 cells, stable transfection in RBL-2H3, Tango β-arrestin assay, pertussis toxin treatment, flow cytometry for surface receptor, degranulation assay","journal":"Journal of immunology","confidence":"High","confidence_rationale":"Tier 1–2 — biased agonism demonstrated by orthogonal G protein and β-arrestin assays with receptor internalization measurements","pmids":["30651343"],"is_preprint":false},{"year":2019,"finding":"MRGPRX2 antagonists inhibit p42/44 MAPK signaling and block MRGPRX2-mediated prostaglandin D2 synthesis (de novo lipid mediator production) in human cord blood-derived mast cells; IgE- or A23187-activated mast cells are resistant to these antagonists.","method":"Novel MRGPRX2 antagonist pharmacology in human cord blood-derived mast cells, β-hexosaminidase and PGD2 assays, MAPK western blot","journal":"Journal of leukocyte biology","confidence":"Medium","confidence_rationale":"Tier 2 — selective antagonist with mechanistic readouts in primary human mast cells","pmids":["31299111"],"is_preprint":false},{"year":2019,"finding":"IL-33 chronically reduces MRGPRX2 expression in skin mast cells via a mechanism partially requiring JNK, thereby eliminating pseudo-allergic responsiveness; in contrast, acute IL-33 priming enhances MRGPRX2-triggered degranulation through p38-dependent signaling.","method":"Chronic and acute IL-33 stimulation of human skin mast cells, Accell-mediated JNK/p38 knockdown, kinase inhibition, MRGPRX2 quantification, histamine release assay","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 — RNA interference + pharmacological inhibition with mechanistic pathway dissection in primary human skin mast cells","pmids":["30979016"],"is_preprint":false},{"year":2020,"finding":"Store-operated Ca2+ entry (SOCE) via STIM1 is required for MRGPRX2-induced mast cell degranulation in vitro and MrgprB2-dependent inflammation in vivo, as shown by pharmacological and genetic ablation of STIM1.","method":"Pharmacologic SOCE inhibition and STIM1 genetic ablation in LAD2 cells, mouse peritoneal mast cells, in vivo MrgprB2-dependent models","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic and pharmacological approaches in complementary in vitro and in vivo models","pmids":["32038646"],"is_preprint":false},{"year":2020,"finding":"MRGPRX2 is the dominant codeine receptor in human skin mast cells; codeine binding triggers rapid MRGPRX2 internalization in a β-arrestin-1-dependent manner; prestimulation with MRGPRX2 agonists causes cross-desensitization to subsequent MRGPRX2 ligands but not to C3a or FcεRI aggregation.","method":"MRGPRX2 silencing, Tango β-arrestin assay, flow cytometry for MRGPRX2 surface expression, cross-desensitization experiments, degranulation assay in skin mast cells and RBL-MRGPRX2 cells","journal":"The Journal of investigative dermatology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods in primary and engineered cells establishing receptor identity and internalization mechanism","pmids":["33058860"],"is_preprint":false},{"year":2020,"finding":"Morphine and substance P selectively induce histamine and tryptase (but not eicosanoid) release from human skin mast cells and synovial mast cells via MRGPRX2, but not from lung or cardiac mast cells, demonstrating heterogeneous MRGPRX2 expression and function across anatomical sites.","method":"Histamine, tryptase, PGD2, and LTC4 release assays from purified human mast cells from skin, synovium, lung, and heart","journal":"Frontiers in cellular neuroscience","confidence":"Medium","confidence_rationale":"Tier 2 — functional comparison across primary human mast cell subsets with multiple mediator readouts","pmids":["31333418"],"is_preprint":false},{"year":2021,"finding":"TSLP selectively cooperates with MRGPRX2 (but not FcεRI) to enhance skin mast cell granule discharge in a STAT5-dependent manner with JNK as a contributory factor; STAT5 silencing completely abolishes the priming effect.","method":"TSLP stimulation of human skin mast cells, STAT5/JNK RNA interference and pharmacological inhibition, degranulation and CD107a assays","journal":"Cells","confidence":"High","confidence_rationale":"Tier 2 — RNA interference confirmed by pharmacological inhibition in primary human skin mast cells with MRGPRX2-selective vs FcεRI comparison","pmids":["33429916"],"is_preprint":false},{"year":2021,"finding":"Substance P serves as a balanced agonist for MRGPRX2, inducing both G protein-mediated degranulation and β-arrestin recruitment/receptor internalization independently of G proteins; the conserved tyrosine residue Y279 in the NPxxY motif is required for both G protein- and β-arrestin-mediated responses.","method":"Tango β-arrestin assay, MRGPRX2 internalization imaging, Y279A mutagenesis in transfected RBL-2H3 cells, pertussis toxin treatment","journal":"International journal of molecular sciences","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis of conserved receptor residue with orthogonal G protein and β-arrestin assays","pmids":["34070125"],"is_preprint":false},{"year":2021,"finding":"DOCK2 regulates MRGPRX2/B2-mediated mast cell degranulation through Rac activation and PAK1 phosphorylation; DOCK2-deficient mast cells show impaired Rac activation and PAK1 phosphorylation downstream of MRGPRB2 despite normal calcium influx and proximal signaling.","method":"DOCK2-deficient mice, genetic inactivation in human/murine mast cells, small-molecule DOCK2 inhibitors, Rac activation assay, PAK1 phosphorylation western blot, in vivo anaphylaxis models","journal":"The Journal of allergy and clinical immunology","confidence":"High","confidence_rationale":"Tier 1–2 — genetic KO combined with pharmacological inhibition and mechanistic biochemical readouts in vivo and in vitro","pmids":["36804596"],"is_preprint":false},{"year":2021,"finding":"Both β-arrestin-1 and β-arrestin-2 restrain MRGPRX2-triggered degranulation and ERK1/2 activation in human skin mast cells: β-arrestin-1 controls MRGPRX2 surface abundance (internalization), while β-arrestin-2 mediates signal termination without receptor internalization.","method":"RNA interference of β-arrestin-1 and β-arrestin-2 in human skin mast cells, MRGPRX2 surface expression quantification, ERK1/2 and AKT phosphorylation, degranulation assays with three MRGPRX2 agonists","journal":"Frontiers in allergy","confidence":"High","confidence_rationale":"Tier 2 — isoform-specific knockdown with mechanistic separation of internalization vs signal termination functions","pmids":["35910860"],"is_preprint":false},{"year":2022,"finding":"MRGPRX2-mediated degranulation in human skin mast cells requires Gαi (more prominent) and Gαq G proteins, Ca2+ channels, PI3K, and ERK1/2; Gαi inhibition also reduces pERK1/2 and pAKT, placing Gαi upstream of these kinase cascades.","method":"Pertussis toxin (Gαi inhibition), YM-254890 (Gαq inhibition), Ca2+ channel blockers, PI3K/ERK/JNK inhibitors, immunoblotting for phosphorylation events in purified primary human skin mast cells","journal":"Cells","confidence":"High","confidence_rationale":"Tier 1 — systematic pharmacological dissection of G protein signaling cascade in primary human skin mast cells with multiple inhibitors and phosphoprotein readouts","pmids":["35326404"],"is_preprint":false},{"year":2022,"finding":"The inverse MRGPRX2 agonist C9 inhibits both G protein-mediated degranulation and β-arrestin recruitment/MRGPRX2 internalization in response to SP, PAMP-12, and rocuronium, but has no effect on C3a, FcεRI-mediated responses, or MrgprB2 in mouse mast cells, demonstrating specificity for human MRGPRX2.","method":"Stable MRGPRX2-expressing RBL-2H3 cells, LAD2 cells, primary human skin mast cells, β-arrestin recruitment assay, CD63/CD107a flow cytometry, β-hexosaminidase assay, pertussis toxin treatment in mouse peritoneal mast cells","journal":"Frontiers in immunology","confidence":"High","confidence_rationale":"Tier 2 — comprehensive pharmacological characterization with multiple cell systems and readouts distinguishing MRGPRX2 from related pathways","pmids":["36275683"],"is_preprint":false},{"year":2021,"finding":"MrgprB2-mediated MRGPRX2 activation drives tryptase release from mast cells, and tryptase is involved in the release of type 2 cytokines contributing to inflammatory development in atopic dermatitis; MrgprB2 conditional knockout mice show milder AD phenotypes.","method":"MrgprB2 conditional KO mouse model with MC903-induced AD, tryptase antagonist treatment, cytokine and IgE correlation analysis","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic KO model with mechanistic downstream (tryptase axis) identification","pmids":["37482287"],"is_preprint":false},{"year":2021,"finding":"MRGPRX2 cytokine induction (TNF-α, IL-8, IL-13, CCL1, CCL2) in skin mast cells is ERK1/2-dependent; rapid and durable ERK1/2 phosphorylation follows MRGPRX2 ligation; PI3K and JNK have variable contributions; cytokine profiles from MRGPRX2 and FcεRI activation are similar but MRGPRX2 is less potent.","method":"MRGPRX2 agonist (compound 48/80, substance P) stimulation of human skin mast cells, MEK/ERK inhibitors, PI3K/JNK/p38 inhibitors, mRNA/protein cytokine quantification, ERK1/2 phosphorylation immunoblot","journal":"The Journal of investigative dermatology","confidence":"Medium","confidence_rationale":"Tier 2 — systematic pharmacological kinase dissection in primary human skin mast cells","pmids":["34329659"],"is_preprint":false},{"year":2021,"finding":"MYO1F (unconventional myosin) is required for full MRGPRX2-mediated mast cell degranulation; MYO1F knockdown reduces cortical actin ring reassembly after activation, Cdc42 GTPase activation, granule membrane localization, and mitochondria translocation to exocytic sites, with reduced AKT and DRP1 phosphorylation.","method":"shRNA knockdown of MYO1F in human mast cells, cortical actin imaging, Cdc42 activation assay, granule/mitochondria localization microscopy, AKT/DRP1 phosphorylation western blot, degranulation assay","journal":"Journal of immunology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockdown with multiple mechanistic readouts establishing cytoskeletal regulation of MRGPRX2-mediated exocytosis","pmids":["33941653"],"is_preprint":false},{"year":2023,"finding":"MRGPRX2 is activated by PACAP in a dose-dependent manner on human mast cells; meningeal MrgprB2-expressing mast cells contribute to PACAP-induced migraine-like pain behavior in mice, and MRGPRX2 transgenic mice show increased PACAP-induced migraine-like pain vs receptor-absent controls.","method":"MRGPRX2 transgenic mouse model, mast cell enzyme release assay, behavioral migraine pain assay","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 2 — transgenic animal model with functional behavioral readout and in vitro confirmation","pmids":["37516794"],"is_preprint":false},{"year":2022,"finding":"The downstream signaling of MRGPRX2 involves PLCγ/PI3K/AKT and ERK1/2 pathways; authentic MRGPRX2 in LAD2 cells and ectopically expressed MRGPRX2 in RBL-2H3 cells share similar dose-response, kinetics, and signaling including ERK1/2 MAPK, PLC, and autophagy-related signaling; underlying mechanisms differ from those of rodent MrgprB2 orthologs.","method":"Comparative pharmacological profiling (signaling inhibitors) of LAD2 and RBL-MRGPRX2 cells with compound 48/80, substance P, and vancomycin; ERK1/2, PLC, autophagy inhibitors; degranulation assays","journal":"Cells","confidence":"Medium","confidence_rationale":"Tier 2 — systematic parallel comparison with multiple pharmacological inhibitors in two cell systems","pmids":["33673037"],"is_preprint":false},{"year":2021,"finding":"MRGPRX2 signals via PLCγ–IP3R-related Ca2+ fluctuations downstream of PI3K/AKT pathway; MrgprX2 knockdown in LAD2 cells reduces C48/80-induced calcium flux and downstream cytokine/chemokine release; p-AKT and PLCγ are upregulated upon MrgprX2 activation and downregulated upon knockdown.","method":"MrgprX2 siRNA knockdown in LAD2 cells, PI3K/PLCγ inhibitors, intracellular Ca2+ imaging, β-hexosaminidase assay, western blot for p-AKT and PLCγ","journal":"International immunopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockdown with pharmacological pathway inhibition and phosphoprotein readouts","pmids":["34920312"],"is_preprint":false},{"year":2024,"finding":"The chemokine CXCL14 potently and selectively activates MRGPRX2 and MrgprB2 through both G protein-dependent and β-arrestin recruitment pathways; truncation and mutagenesis identified the C-terminal 4-11 amino acid pharmacophoric sequence of CXCL14 responsible for receptor activation.","method":"GPCR panel screening, G protein and β-arrestin functional assays, truncation and mutagenesis of CXCL14, selective MRGPRX2/B2 antagonist blockade, computational docking","journal":"Communications biology","confidence":"High","confidence_rationale":"Tier 1 — systematic truncation/mutagenesis with orthogonal G protein and β-arrestin assays plus antagonist validation","pmids":["38184723"],"is_preprint":false},{"year":2024,"finding":"Small molecule MRGPRX2 antagonists potently inhibit agonist-induced mast cell degranulation in vitro (LAD2, stem cell-derived, and isolated skin mast cells), in vivo (MRGPRX2 knock-in mice, Mrgprb2 KO controls), and ex vivo (human skin microdialysis), demonstrating that orally administered MRGPRX2 antagonism blocks skin mast cell degranulation.","method":"Multiple mast cell functional assays, MRGPRX2 knock-in transgenic mice, Mrgprb2 KO mice, skin vascular permeability assay, human skin ex vivo microdialysis","journal":"The Journal of allergy and clinical immunology","confidence":"High","confidence_rationale":"Tier 1–2 — comprehensive pharmacological characterization across in vitro, ex vivo, and transgenic/KO in vivo systems","pmids":["38971540"],"is_preprint":false},{"year":2019,"finding":"The P17 ant venom peptide activates MRGPRX2 in a dose-dependent manner; residue Lys8 of P17 forms a cation-π interaction with Phe172 of MRGPRX2, demonstrated by mutagenesis ([Ala8]P17 loses activity); MRGPRX2-activated mast cells recruit and differentiate monocytes via chemokine release.","method":"GPCR screening of 314 receptors, β-arrestin recruitment assay, in silico docking and in vitro mutagenesis, β-hexosaminidase/cytokine assays, MRGPRX2 shRNA knockdown, monocyte migration/differentiation assays","journal":"The Journal of allergy and clinical immunology","confidence":"High","confidence_rationale":"Tier 1 — mutagenesis of both ligand and receptor combined with functional cellular assays establishing binding residues","pmids":["34111449"],"is_preprint":false},{"year":2020,"finding":"Osthole inhibits MRGPRX2-induced mast cell Ca2+ mobilization, degranulation, and chemokine/cytokine production; molecular docking suggests allosteric binding rather than competition at the orthosteric site; osthole reduces both surface and intracellular MRGPRX2 expression.","method":"Ca2+ mobilization assay, degranulation assay in LAD2 cells, in vivo MrgprB2-dependent mouse models, molecular docking, flow cytometry and confocal microscopy for MRGPRX2 expression","journal":"Frontiers in immunology","confidence":"Medium","confidence_rationale":"Tier 2 — complementary in vitro and in vivo data with docking analysis, single lab","pmids":["32391014"],"is_preprint":false},{"year":2022,"finding":"A UC-protective MRGPRX2 variant (Asn62Ser) enhances β-arrestin recruitment, decreases IP-1 accumulation, and increases phosphorylated ERK (pERK) in response to MRGPRX2 agonists, demonstrating genotype-dependent biased signaling; adrenomedullin (processed to PAMP-12 agonist) is produced by activated fibroblasts and epithelial cells in inflamed UC regions.","method":"Variant transfection into CHO and HMC 1.1 cells, β-arrestin recruitment assay, IP-1 accumulation assay, pERK measurement; single-cell RNA sequencing for cellular source of adrenomedullin","journal":"Gastroenterology","confidence":"Medium","confidence_rationale":"Tier 2 — functional cell-based assays for variant signaling with single-cell transcriptomics for ligand source","pmids":["33421512"],"is_preprint":false}],"current_model":"MRGPRX2 is a promiscuous class A GPCR expressed predominantly on human skin mast cells that couples to Gαi (primarily) and Gαq to activate PLC, PI3K/AKT, ERK1/2, Ca2+ channels, STIM1-dependent store-operated Ca2+ entry, and DOCK2-Rac-PAK1 signaling, leading to granule exocytosis; it is activated by an expanding array of cationic ligands (neuropeptides, host defense peptides, opioids, neuromuscular blocking agents, fluoroquinolones, and other drugs) and endogenous peptides (cortistatin, PAMP, LL-37, CXCL14, albumin fragments), signals additionally through β-arrestin-1/2-dependent internalization and desensitization (with biased agonists bypassing this route), is negatively regulated by SCF, IL-4, and chronic IL-33 and positively primed by acute IL-33 and TSLP via STAT5/JNK, and is the mechanistic basis for IgE-independent pseudo-allergic mast cell degranulation."},"narrative":{"teleology":[{"year":2003,"claim":"Establishing MRGPRX2 as a functional GPCR: reverse pharmacology identified cortistatin as a high-potency ligand that activates Gq-coupled Ca²⁺ mobilization without affecting cAMP, defining the receptor's initial coupling mode and ligand identity.","evidence":"Ca²⁺ mobilization and cAMP assays in MrgX2-expressing cells","pmids":["12915402"],"confidence":"High","gaps":["Only Gq coupling demonstrated; Gi coupling not tested","Expression limited to DRG; mast cell expression not yet recognized"]},{"year":2005,"claim":"Revealing dual G protein coupling and ligand promiscuity: PAMP-12 was identified as a more potent agonist than cortistatin, and GTPγS binding/cAMP inhibition established that MRGPRX2 couples to both Gαq and Gαi, expanding its signaling repertoire beyond initial Gq-only reports.","evidence":"Ca²⁺ mobilization, cAMP inhibition, [³⁵S]GTPγS binding assays; SAR studies of PAMP analogs","pmids":["15823563","16111673"],"confidence":"High","gaps":["Structural basis for how unrelated peptides share a common pharmacophore not resolved at atomic level","Downstream signaling cascades beyond G protein activation not mapped"]},{"year":2011,"claim":"Defining MRGPRX2 as a mast cell degranulation receptor with unusual desensitization properties: LL-37 and compound 48/80 were shown to trigger mast cell degranulation via MRGPRX2, while LL-37 uniquely resisted GRK-mediated phosphorylation, desensitization, and internalization, revealing ligand-dependent differences in receptor regulation.","evidence":"shRNA knockdown in LAD2/primary mast cells, stable transfection in RBL-2H3, GRK2/3 knockdown, Ca²⁺ and degranulation assays","pmids":["22069323","21741965","21441599"],"confidence":"High","gaps":["Molecular basis for resistance to GRK phosphorylation not identified","Full spectrum of endogenous mast cell ligands unknown"]},{"year":2017,"claim":"Massively expanding the MRGPRX2 ligand repertoire and establishing receptor independence from FcεRI: high-throughput screening identified opioids, vancomycin, and δ-toxin as MRGPRX2 agonists; mutagenesis-validated homology modeling defined the binding pocket; SCF was found to selectively suppress MRGPRX2 while enhancing FcεRI responses, establishing that the two degranulation pathways are independent and inversely regulated.","evidence":"HTS of 5,695 compounds, virtual docking of ~4M compounds, mutagenesis-validated homology model, PLC pathway dissection, MrgprB2 KO mice, SCF manipulation of human skin mast cells","pmids":["28288109","28987593","28859248","28549244","28367504"],"confidence":"High","gaps":["High-resolution experimental structure not available","Relative contribution of Gαi vs Gαq in primary mast cells not quantified"]},{"year":2018,"claim":"Identifying critical receptor residues and cytokine regulation: naturally occurring loss-of-function missense variants (G165E, D184H, W243R, H259Y) established shared binding sites for diverse ligands; SCF/IL-4 withdrawal experiments showed that these cytokines tonically suppress MRGPRX2 expression; LL-37 internalization was shown to require clathrin-mediated endocytosis and sialic acid.","evidence":"Systematic missense variant mutagenesis with multiple ligands, cytokine withdrawal in primary mast cells, clathrin/neuraminidase inhibitors with confocal microscopy","pmids":["29794017","30091263","30280189"],"confidence":"High","gaps":["Structural basis for how single mutations abolish responses to structurally diverse ligands not resolved","Whether loss-of-function variants confer clinical protection from pseudo-allergy not tested"]},{"year":2019,"claim":"Establishing biased agonism and delineating G protein vs β-arrestin signaling: AG-30/5C and icatibant were identified as G protein-biased agonists (no β-arrestin recruitment), while compound 48/80 and substance P activate both pathways; C-terminal Ser/Thr-to-Ala substitutions produced gain-of-function, implicating C-terminal phosphorylation in desensitization; IL-33 was shown to have dual temporal regulation (acute priming via p38, chronic suppression via JNK).","evidence":"Tango β-arrestin assay, pertussis toxin/YM-254890 G protein inhibition, C-terminal mutagenesis, IL-33 time-course with kinase knockdown in primary skin mast cells","pmids":["30651343","31652731","30979016","31299111","34111449"],"confidence":"High","gaps":["Structural determinants distinguishing balanced from biased agonists not resolved","Whether biased agonism translates to differential clinical outcomes unknown"]},{"year":2020,"claim":"Defining store-operated Ca²⁺ entry as essential and confirming β-arrestin-1-dependent codeine receptor identity: STIM1-dependent SOCE was shown to be required for MRGPRX2-mediated degranulation; codeine was identified as an MRGPRX2 agonist that triggers β-arrestin-1-dependent internalization and homologous desensitization; tissue heterogeneity was established as skin/synovial mast cells respond via MRGPRX2 while lung/cardiac mast cells do not.","evidence":"STIM1 genetic ablation and SOCE pharmacology in LAD2/mouse models, β-arrestin Tango assay, cross-desensitization, tissue-specific mast cell mediator profiling","pmids":["32038646","33058860","31333418"],"confidence":"High","gaps":["Mechanism of tissue-selective MRGPRX2 expression not identified","Whether SOCE is the exclusive Ca²⁺ entry route or supplementary unclear"]},{"year":2021,"claim":"Mapping the cytoskeletal effector arm and separating β-arrestin isoform functions: DOCK2–Rac–PAK1 was identified as essential for granule exocytosis downstream of MRGPRX2 despite normal Ca²⁺ influx; MYO1F was shown to control cortical actin remodeling, Cdc42 activation, and mitochondrial translocation to exocytic sites; β-arrestin-1 was found to control receptor internalization while β-arrestin-2 mediates signal termination without internalization; TSLP was shown to selectively prime MRGPRX2 responses via STAT5.","evidence":"DOCK2 KO mice and inhibitors, MYO1F shRNA, β-arrestin-1/2 isoform-specific knockdown, TSLP/STAT5 RNAi in primary skin mast cells","pmids":["36804596","33941653","35910860","33429916","34070125","34329659"],"confidence":"High","gaps":["How DOCK2–Rac and MYO1F pathways are coordinated or sequenced is unknown","Contribution of β-arrestin-dependent signaling to cytokine production vs degranulation not separated"]},{"year":2022,"claim":"Consolidating the signaling hierarchy and demonstrating genotype-dependent biased signaling: systematic inhibitor studies in primary skin mast cells placed Gαi upstream of ERK1/2 and AKT; a UC-protective Asn62Ser variant was shown to enhance β-arrestin recruitment while decreasing IP-1 accumulation, establishing that naturally occurring variants can bias signaling; human-selective inverse agonist C9 blocked both G protein and β-arrestin arms.","evidence":"Pertussis toxin/YM-254890 with phospho-ERK/AKT immunoblotting, variant transfection with β-arrestin/IP-1/pERK assays, C9 characterization across multiple cell systems","pmids":["35326404","33421512","36275683"],"confidence":"High","gaps":["Cryo-EM or crystal structure of MRGPRX2 with agonist/antagonist not available","Whether Asn62Ser biased signaling explains UC protection mechanistically unresolved"]},{"year":2024,"claim":"Identifying CXCL14 as an endogenous chemokine agonist and demonstrating therapeutic MRGPRX2 antagonism in vivo: the C-terminal pharmacophoric sequence of CXCL14 was mapped by truncation/mutagenesis; orally administered small-molecule MRGPRX2 antagonists blocked skin mast cell degranulation in MRGPRX2 knock-in mice and human ex vivo skin microdialysis.","evidence":"CXCL14 truncation/mutagenesis with G protein and β-arrestin assays, MRGPRX2 knock-in/MrgprB2 KO mice, ex vivo human skin microdialysis","pmids":["38184723","38971540"],"confidence":"High","gaps":["Clinical efficacy of MRGPRX2 antagonists in human pseudo-allergic disease not established","Full endogenous ligand landscape (additional chemokines, albumin fragments) incompletely mapped"]},{"year":null,"claim":"Key unresolved questions include the high-resolution structure of MRGPRX2 in active/inactive states, the molecular basis for how structurally diverse cationic ligands converge on common binding determinants, the mechanism controlling tissue-selective expression in skin vs lung mast cells, and whether biased agonism or genotype-dependent signaling can be exploited therapeutically.","evidence":"","pmids":[],"confidence":"High","gaps":["No experimental atomic-resolution structure","Tissue-specific transcriptional regulation unexplored","Clinical translation of MRGPRX2 antagonism pending"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,1,6,33]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[15,22,24]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[3,11,19,24]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,8,10,14,25,32]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,9,17,21,27]}],"complexes":[],"partners":["ARRB1","ARRB2","STIM1","DOCK2","MYO1F","GNAI1","GNAQ"],"other_free_text":[]},"mechanistic_narrative":"MRGPRX2 is a promiscuous class A GPCR expressed predominantly on human skin mast cells that functions as the principal receptor for IgE-independent pseudo-allergic mast cell degranulation. It couples to both Gαi (predominant) and Gαq to activate PLC/PKC, PI3K/AKT, ERK1/2 MAPK, and STIM1-dependent store-operated Ca²⁺ entry, driving granule exocytosis, cytokine/chemokine release, and prostaglandin D₂ synthesis in response to a broad array of cationic ligands including neuropeptides (substance P, cortistatin, PAMP-12, PACAP), host defense peptides (LL-37, human β-defensin-3), opioids (morphine, codeine), neuromuscular blockers, fluoroquinolones, and the chemokine CXCL14 [PMID:35326404, PMID:28288109, PMID:38184723, PMID:12915402]. Receptor desensitization is governed by β-arrestin-1-dependent internalization controlling surface abundance and β-arrestin-2-mediated signal termination, while certain ligands (AG-30/5C, icatibant) act as G protein-biased agonists that bypass β-arrestin recruitment; naturally occurring gain-of-function C-terminal variants and biased-signaling variants (Asn62Ser) further modulate pathway selectivity [PMID:35910860, PMID:30651343, PMID:33421512]. MRGPRX2 expression and responsiveness are negatively regulated by SCF, IL-4, and chronic IL-33, and positively primed by acute IL-33 (via p38) and TSLP (via STAT5/JNK), while downstream exocytosis requires the DOCK2–Rac–PAK1 cytoskeletal remodeling axis and MYO1F-dependent cortical actin reorganization [PMID:28859248, PMID:30979016, PMID:33429916, PMID:36804596, PMID:33941653]."},"prefetch_data":{"uniprot":{"accession":"Q96LB1","full_name":"Mas-related G-protein coupled receptor member X2","aliases":[],"length_aa":330,"mass_kda":37.1,"function":"Mast cell-specific G protein-coupled receptor for basic secretagogues, which regulates mast cell degranulation and itch-related hypersensitivity reactions (PubMed:22069323, PubMed:25517090, PubMed:28288109, PubMed:34789874, PubMed:34789875). A secretagogue is an agent that promotes the secretion of hormones, neurohormones, chemical neurotransmitters or other compounds synthesized and secreted by cells (PubMed:25517090). Basic secretagogues comprise a set of cationic amphiphilic drugs, as well as endo- or exogenous peptides, consisting of a basic head group and a hydrophobic core (PubMed:25517090). 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:28288109, PubMed:34789874, PubMed:34789875). MRGPRX2 is both coupled to G(q) and G(i) G proteins: G(q) coupling activates phospholipase C-beta, releasing diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3) second messengers, while G(i) coupling mediates inhibition of adenylate cyclase activity (PubMed:28288109, PubMed:34789874, PubMed:34789875). Recognizes and binds small molecules containing a cyclized tetrahydroisoquinoline (THIQ), such as non-steroidal neuromuscular blocking drugs (NMBDs), including tubocurarine and atracurium (By similarity). In response to these compounds, mediates pseudo-allergic reactions characterized by histamine release, inflammation and airway contraction (By similarity). Acts as a receptor for substance P, a basic secretagogue neuropeptide released from the terminals of specific sensory nerves, initiating a signaling that mediates neurogenic inflammation and pain (PubMed:30686732, PubMed:34789875). Neurogenic inflammation includes mast cell activation, recruitment of immune cells and release of inflammatory mediators, such as cytokines and chemokines (By similarity). The inflammatory response can then activate or sensitize nociceptors, promoting pain (By similarity). Acts as a receptor for a number of other ligands, including peptides and alkaloids, such as cortistatin-14, proadrenomedullin peptides PAMP-12 and, at lower extent, PAMP-20, antibacterial protein LL-37, PMX-53 peptide, beta-defensins, and complanadine A (PubMed:12915402, PubMed:15823563, PubMed:21441599, PubMed:22069323, PubMed:23698749, PubMed:24930830, PubMed:34789874, PubMed:34789875). Also acts as a receptor for opioids, such as (-)- and (+)-morphine, hydrocodone, sinomenine, dextromethorphan, dynorphin A, dynorphin B, and alpha- and beta-neoendorphin, promoting mast cell degranulation (PubMed:28288109)","subcellular_location":"Cell membrane","url":"https://www.uniprot.org/uniprotkb/Q96LB1/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/MRGPRX2","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/MRGPRX2","total_profiled":1310},"omim":[{"mim_id":"607228","title":"MAS-RELATED G PROTEIN-COUPLED RECEPTOR FAMILY, MEMBER X2; MRGPRX2","url":"https://www.omim.org/entry/607228"},{"mim_id":"600474","title":"CATHELICIDIN ANTIMICROBIAL PEPTIDE; CAMP","url":"https://www.omim.org/entry/600474"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Not detected","tissue_distribution":"Not detected","driving_tissues":[],"url":"https://www.proteinatlas.org/search/MRGPRX2"},"hgnc":{"alias_symbol":["MRGX2"],"prev_symbol":[]},"alphafold":{"accession":"Q96LB1","domains":[{"cath_id":"1.20.1070.10","chopping":"30-304","consensus_level":"high","plddt":88.6407,"start":30,"end":304}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96LB1","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q96LB1-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q96LB1-F1-predicted_aligned_error_v6.png","plddt_mean":81.69},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=MRGPRX2","jax_strain_url":"https://www.jax.org/strain/search?query=MRGPRX2"},"sequence":{"accession":"Q96LB1","fasta_url":"https://rest.uniprot.org/uniprotkb/Q96LB1.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q96LB1/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q96LB1"}},"corpus_meta":[{"pmid":"28288109","id":"PMC_28288109","title":"In silico design of novel probes for the atypical opioid receptor MRGPRX2.","date":"2017","source":"Nature chemical biology","url":"https://pubmed.ncbi.nlm.nih.gov/28288109","citation_count":234,"is_preprint":false},{"pmid":"12915402","id":"PMC_12915402","title":"MrgX2 is a high potency cortistatin receptor expressed in dorsal root ganglion.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12915402","citation_count":204,"is_preprint":false},{"pmid":"22069323","id":"PMC_22069323","title":"Mas-related gene X2 (MrgX2) is a novel G protein-coupled receptor for the antimicrobial peptide LL-37 in human mast cells: resistance to receptor phosphorylation, desensitization, and internalization.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22069323","citation_count":199,"is_preprint":false},{"pmid":"30619367","id":"PMC_30619367","title":"Mas-Related G Protein-Coupled Receptor-X2 (MRGPRX2) in Drug Hypersensitivity Reactions.","date":"2018","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/30619367","citation_count":138,"is_preprint":false},{"pmid":"33957166","id":"PMC_33957166","title":"Multifaceted MRGPRX2: New insight into the role of mast cells in health and disease.","date":"2021","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33957166","citation_count":136,"is_preprint":false},{"pmid":"30072729","id":"PMC_30072729","title":"MRGPRX2-mediated mast cell response to drugs used in perioperative procedures and anaesthesia.","date":"2018","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/30072729","citation_count":122,"is_preprint":false},{"pmid":"21741965","id":"PMC_21741965","title":"G protein coupled receptor specificity for C3a and compound 48/80-induced degranulation in human mast cells: roles of Mas-related genes MrgX1 and MrgX2.","date":"2011","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21741965","citation_count":94,"is_preprint":false},{"pmid":"15823563","id":"PMC_15823563","title":"Identification of MrgX2 as a human G-protein-coupled receptor for proadrenomedullin N-terminal peptides.","date":"2005","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/15823563","citation_count":90,"is_preprint":false},{"pmid":"34421893","id":"PMC_34421893","title":"MRGPRX2 and Adverse Drug Reactions.","date":"2021","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34421893","citation_count":87,"is_preprint":false},{"pmid":"31333418","id":"PMC_31333418","title":"Heterogeneity of Human Mast Cells With Respect to MRGPRX2 Receptor Expression and Function.","date":"2019","source":"Frontiers in cellular neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/31333418","citation_count":86,"is_preprint":false},{"pmid":"32003863","id":"PMC_32003863","title":"The pseudoallergen receptor MRGPRX2 on peripheral blood basophils and eosinophils: Expression and function.","date":"2020","source":"Allergy","url":"https://pubmed.ncbi.nlm.nih.gov/32003863","citation_count":85,"is_preprint":false},{"pmid":"33925682","id":"PMC_33925682","title":"Unlocking the Non-IgE-Mediated Pseudo-Allergic Reaction Puzzle with Mas-Related G-Protein Coupled Receptor Member X2 (MRGPRX2).","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/33925682","citation_count":81,"is_preprint":false},{"pmid":"28367504","id":"PMC_28367504","title":"Brief communication: MRGPRX2, atopic dermatitis and red man syndrome.","date":"2017","source":"Itch (Philadelphia, Pa.)","url":"https://pubmed.ncbi.nlm.nih.gov/28367504","citation_count":80,"is_preprint":false},{"pmid":"33421512","id":"PMC_33421512","title":"Inflamed Ulcerative Colitis Regions Associated With MRGPRX2-Mediated Mast Cell Degranulation and Cell Activation Modules, Defining a New Therapeutic Target.","date":"2021","source":"Gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/33421512","citation_count":77,"is_preprint":false},{"pmid":"28859248","id":"PMC_28859248","title":"Allergic FcεRI- and pseudo-allergic MRGPRX2-triggered mast cell activation routes are independent and inversely regulated by SCF.","date":"2017","source":"Allergy","url":"https://pubmed.ncbi.nlm.nih.gov/28859248","citation_count":74,"is_preprint":false},{"pmid":"32771471","id":"PMC_32771471","title":"MRGPRX2 Activation Causes Increased Skin Reactivity in Patients with Chronic Spontaneous Urticaria.","date":"2020","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/32771471","citation_count":73,"is_preprint":false},{"pmid":"29794017","id":"PMC_29794017","title":"Naturally Occurring Missense MRGPRX2 Variants Display Loss of Function Phenotype for Mast Cell Degranulation in Response to Substance P, Hemokinin-1, Human β-Defensin-3, and Icatibant.","date":"2018","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/29794017","citation_count":71,"is_preprint":false},{"pmid":"21441599","id":"PMC_21441599","title":"PMX-53 as a dual CD88 antagonist and an agonist for Mas-related gene 2 (MrgX2) in human mast cells.","date":"2011","source":"Molecular pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/21441599","citation_count":69,"is_preprint":false},{"pmid":"33398613","id":"PMC_33398613","title":"Mast Cell-Specific MRGPRX2: a Key Modulator of Neuro-Immune Interaction in Allergic Diseases.","date":"2021","source":"Current allergy and asthma reports","url":"https://pubmed.ncbi.nlm.nih.gov/33398613","citation_count":68,"is_preprint":false},{"pmid":"28987593","id":"PMC_28987593","title":"MRGPRX2 is essential for sinomenine hydrochloride induced anaphylactoid reactions.","date":"2017","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/28987593","citation_count":64,"is_preprint":false},{"pmid":"34831128","id":"PMC_34831128","title":"Therapeutic Potential of MRGPRX2 Inhibitors on Mast Cells.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/34831128","citation_count":63,"is_preprint":false},{"pmid":"32391014","id":"PMC_32391014","title":"Osthole, a Natural Plant Derivative Inhibits MRGPRX2 Induced Mast Cell Responses.","date":"2020","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/32391014","citation_count":63,"is_preprint":false},{"pmid":"30471617","id":"PMC_30471617","title":"Quercetin inhibits Mrgprx2-induced pseudo-allergic reaction via PLCγ-IP3R related Ca2+ fluctuations.","date":"2018","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30471617","citation_count":62,"is_preprint":false},{"pmid":"29274317","id":"PMC_29274317","title":"Saikosaponin A inhibits compound 48/80-induced pseudo-allergy via the Mrgprx2 pathway in vitro and in vivo.","date":"2017","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/29274317","citation_count":61,"is_preprint":false},{"pmid":"31652731","id":"PMC_31652731","title":"Identification of Gain and Loss of Function Missense Variants in MRGPRX2's Transmembrane and Intracellular Domains for Mast Cell Activation by Substance P.","date":"2019","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/31652731","citation_count":61,"is_preprint":false},{"pmid":"28688196","id":"PMC_28688196","title":"Typical antimicrobials induce mast cell degranulation and anaphylactoid reactions via MRGPRX2 and its murine homologue MRGPRB2.","date":"2017","source":"European journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/28688196","citation_count":58,"is_preprint":false},{"pmid":"32866307","id":"PMC_32866307","title":"MRGPRX2 signals its importance in cutaneous mast cell biology: Does MRGPRX2 connect mast cells and atopic dermatitis?","date":"2020","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/32866307","citation_count":57,"is_preprint":false},{"pmid":"33387483","id":"PMC_33387483","title":"Imperatorin ameliorates mast cell-mediated allergic airway inflammation by inhibiting MRGPRX2 and CamKII/ERK signaling pathway.","date":"2020","source":"Biochemical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/33387483","citation_count":56,"is_preprint":false},{"pmid":"31299111","id":"PMC_31299111","title":"Novel MRGPRX2 antagonists inhibit IgE-independent activation of human umbilical cord blood-derived mast cells.","date":"2019","source":"Journal of leukocyte biology","url":"https://pubmed.ncbi.nlm.nih.gov/31299111","citation_count":56,"is_preprint":false},{"pmid":"35283140","id":"PMC_35283140","title":"Mast cells, cortistatin, and its receptor, MRGPRX2, are linked to the pathogenesis of chronic prurigo.","date":"2022","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/35283140","citation_count":48,"is_preprint":false},{"pmid":"28549244","id":"PMC_28549244","title":"LL-37-induced human mast cell activation through G protein-coupled receptor MrgX2.","date":"2017","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/28549244","citation_count":48,"is_preprint":false},{"pmid":"30979016","id":"PMC_30979016","title":"IL-33 and MRGPRX2-Triggered Activation of Human Skin Mast Cells-Elimination of Receptor Expression on Chronic Exposure, but Reinforced Degranulation on Acute Priming.","date":"2019","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/30979016","citation_count":48,"is_preprint":false},{"pmid":"31832205","id":"PMC_31832205","title":"MrgX2 is a promiscuous receptor for basic peptides causing mast cell pseudo-allergic and anaphylactoid reactions.","date":"2019","source":"Pharmacology research & perspectives","url":"https://pubmed.ncbi.nlm.nih.gov/31832205","citation_count":47,"is_preprint":false},{"pmid":"33058860","id":"PMC_33058860","title":"MRGPRX2 Is the Codeine Receptor of Human Skin Mast Cells: Desensitization through β-Arrestin and Lack of Correlation with the FcεRI Pathway.","date":"2020","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/33058860","citation_count":46,"is_preprint":false},{"pmid":"38971540","id":"PMC_38971540","title":"Inhibition of mast cell degranulation by novel small molecule MRGPRX2 antagonists.","date":"2024","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/38971540","citation_count":45,"is_preprint":false},{"pmid":"34385999","id":"PMC_34385999","title":"Novel Insights on MRGPRX2-Mediated Hypersensitivity to Neuromuscular Blocking Agents And Fluoroquinolones.","date":"2021","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34385999","citation_count":45,"is_preprint":false},{"pmid":"33617860","id":"PMC_33617860","title":"A group of cationic amphiphilic drugs activates MRGPRX2 and induces scratching behavior in mice.","date":"2021","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33617860","citation_count":45,"is_preprint":false},{"pmid":"33808264","id":"PMC_33808264","title":"Cytokines Stimulated by IL-33 in Human Skin Mast Cells: Involvement of NF-κB and p38 at Distinct Levels and Potent Co-Operation with FcεRI and MRGPRX2.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/33808264","citation_count":45,"is_preprint":false},{"pmid":"37482287","id":"PMC_37482287","title":"Mast Cells Initiate Type 2 Inflammation through Tryptase Released by MRGPRX2/MRGPRB2 Activation in Atopic Dermatitis.","date":"2023","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/37482287","citation_count":44,"is_preprint":false},{"pmid":"32038646","id":"PMC_32038646","title":"Store-Operated Calcium Entry via STIM1 Contributes to MRGPRX2 Induced Mast Cell Functions.","date":"2020","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/32038646","citation_count":43,"is_preprint":false},{"pmid":"33429916","id":"PMC_33429916","title":"Thymic Stromal Lymphopoietin Promotes MRGPRX2-Triggered Degranulation of Skin Mast Cells in a STAT5-Dependent Manner with Further Support from JNK.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/33429916","citation_count":41,"is_preprint":false},{"pmid":"30651343","id":"PMC_30651343","title":"Angiogenic Host Defense Peptide AG-30/5C and Bradykinin B2 Receptor Antagonist Icatibant Are G Protein Biased Agonists for MRGPRX2 in Mast Cells.","date":"2019","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/30651343","citation_count":41,"is_preprint":false},{"pmid":"30856392","id":"PMC_30856392","title":"Mast cell-mediated hypersensitivity to fluoroquinolone is MRGPRX2 dependent.","date":"2019","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30856392","citation_count":40,"is_preprint":false},{"pmid":"16161007","id":"PMC_16161007","title":"Expression of cortistatin and MrgX2, a specific cortistatin receptor, in human neuroendocrine tissues and related tumours.","date":"2005","source":"The Journal of pathology","url":"https://pubmed.ncbi.nlm.nih.gov/16161007","citation_count":40,"is_preprint":false},{"pmid":"33733642","id":"PMC_33733642","title":"Elevated MRGPRX2 Levels Related to Disease Severity in Patients With Chronic Spontaneous Urticaria.","date":"2021","source":"Allergy, asthma & immunology research","url":"https://pubmed.ncbi.nlm.nih.gov/33733642","citation_count":40,"is_preprint":false},{"pmid":"30032049","id":"PMC_30032049","title":"Cisatracurium induces mast cell activation and pseudo-allergic reactions via MRGPRX2.","date":"2018","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30032049","citation_count":39,"is_preprint":false},{"pmid":"30091263","id":"PMC_30091263","title":"MRGPRX2 is negatively targeted by SCF and IL-4 to diminish pseudo-allergic stimulation of skin mast cells in culture.","date":"2018","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/30091263","citation_count":38,"is_preprint":false},{"pmid":"33467419","id":"PMC_33467419","title":"MRGPRX2 Activation by Rocuronium: Insights from Studies with Human Skin Mast Cells and Missense Variants.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/33467419","citation_count":36,"is_preprint":false},{"pmid":"32732181","id":"PMC_32732181","title":"MRGPRX2 and Immediate Drug Hypersensitivity: Insights From Cultured Human Mast Cells.","date":"2020","source":"Journal of investigational allergology & clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/32732181","citation_count":36,"is_preprint":false},{"pmid":"32320700","id":"PMC_32320700","title":"A novel MRGPRX2-targeting antagonistic DNA aptamer inhibits histamine release and prevents mast cell-mediated anaphylaxis.","date":"2020","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32320700","citation_count":36,"is_preprint":false},{"pmid":"33107136","id":"PMC_33107136","title":"MRGPRX2 sensing of cationic compounds-A bridge between nociception and skin diseases?","date":"2020","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/33107136","citation_count":35,"is_preprint":false},{"pmid":"36581009","id":"PMC_36581009","title":"Novel small molecule MRGPRX2 antagonists inhibit a murine model of allergic reaction.","date":"2022","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36581009","citation_count":35,"is_preprint":false},{"pmid":"35326404","id":"PMC_35326404","title":"MRGPRX2-Mediated Degranulation of Human Skin Mast Cells Requires the Operation of Gαi, Gαq, Ca++ Channels, ERK1/2 and PI3K-Interconnection between Early and Late Signaling.","date":"2022","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/35326404","citation_count":35,"is_preprint":false},{"pmid":"36275683","id":"PMC_36275683","title":"Inhibition of MRGPRX2 but not FcεRI or MrgprB2-mediated mast cell degranulation by a small molecule inverse receptor agonist.","date":"2022","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36275683","citation_count":34,"is_preprint":false},{"pmid":"34070125","id":"PMC_34070125","title":"Substance P Serves as a Balanced Agonist for MRGPRX2 and a Single Tyrosine Residue Is Required for β-Arrestin Recruitment and Receptor Internalization.","date":"2021","source":"International journal of molecular sciences","url":"https://pubmed.ncbi.nlm.nih.gov/34070125","citation_count":34,"is_preprint":false},{"pmid":"32392433","id":"PMC_32392433","title":"Roles of a Mast Cell-Specific Receptor MRGPRX2 in Host Defense and Inflammation.","date":"2020","source":"Journal of dental research","url":"https://pubmed.ncbi.nlm.nih.gov/32392433","citation_count":33,"is_preprint":false},{"pmid":"31667930","id":"PMC_31667930","title":"Paeoniflorin inhibits MRGPRX2-mediated pseudo-allergic reaction via calcium signaling pathway.","date":"2019","source":"Phytotherapy research : PTR","url":"https://pubmed.ncbi.nlm.nih.gov/31667930","citation_count":32,"is_preprint":false},{"pmid":"30315997","id":"PMC_30315997","title":"Rocuronium Hypersensitivity: Does Off-Target Occupation of the MRGPRX2 Receptor Play a Role?","date":"2018","source":"The journal of allergy and clinical immunology. In practice","url":"https://pubmed.ncbi.nlm.nih.gov/30315997","citation_count":32,"is_preprint":false},{"pmid":"32032836","id":"PMC_32032836","title":"Inhibitory function of Shikonin on MRGPRX2-mediated pseudo-allergic reactions induced by the secretagogue.","date":"2019","source":"Phytomedicine : international journal of phytotherapy and phytopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/32032836","citation_count":31,"is_preprint":false},{"pmid":"37516794","id":"PMC_37516794","title":"PACAP activates MRGPRX2 on meningeal mast cells to drive migraine-like pain.","date":"2023","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/37516794","citation_count":30,"is_preprint":false},{"pmid":"15862286","id":"PMC_15862286","title":"Adaptive evolution of MRGX2, a human sensory neuron specific gene involved in nociception.","date":"2005","source":"Gene","url":"https://pubmed.ncbi.nlm.nih.gov/15862286","citation_count":30,"is_preprint":false},{"pmid":"33550032","id":"PMC_33550032","title":"Resveratrol inhibits MRGPRX2-mediated mast cell activation via Nrf2 pathway.","date":"2021","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/33550032","citation_count":29,"is_preprint":false},{"pmid":"32106575","id":"PMC_32106575","title":"Protective Effect of Genistein against Compound 48/80 Induced Anaphylactoid Shock via Inhibiting MAS Related G Protein-Coupled Receptor X2 (MRGPRX2).","date":"2020","source":"Molecules (Basel, Switzerland)","url":"https://pubmed.ncbi.nlm.nih.gov/32106575","citation_count":29,"is_preprint":false},{"pmid":"16111673","id":"PMC_16111673","title":"Proadrenomedullin N-terminal peptide and cortistatin activation of MrgX2 receptor is based on a common structural motif.","date":"2005","source":"European journal of pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/16111673","citation_count":25,"is_preprint":false},{"pmid":"34399172","id":"PMC_34399172","title":"Lactic acid suppresses MRGPRX2 mediated mast cell responses.","date":"2021","source":"Cellular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34399172","citation_count":25,"is_preprint":false},{"pmid":"30280189","id":"PMC_30280189","title":"MrgX2‑mediated internalization of LL‑37 and degranulation of human LAD2 mast cells.","date":"2018","source":"Molecular medicine reports","url":"https://pubmed.ncbi.nlm.nih.gov/30280189","citation_count":25,"is_preprint":false},{"pmid":"34920312","id":"PMC_34920312","title":"MrgprX2 regulates mast cell degranulation through PI3K/AKT and PLCγ signaling in pseudo-allergic reactions.","date":"2021","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/34920312","citation_count":25,"is_preprint":false},{"pmid":"35910860","id":"PMC_35910860","title":"β-arrestin-1 and β-arrestin-2 Restrain MRGPRX2-Triggered Degranulation and ERK1/2 Activation in Human Skin Mast Cells.","date":"2022","source":"Frontiers in allergy","url":"https://pubmed.ncbi.nlm.nih.gov/35910860","citation_count":24,"is_preprint":false},{"pmid":"36726977","id":"PMC_36726977","title":"Mas-related G protein-coupled receptor MRGPRX2 in human basophils: Expression and functional studies.","date":"2023","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36726977","citation_count":24,"is_preprint":false},{"pmid":"31051313","id":"PMC_31051313","title":"Phenothiazine antipsychotics exhibit dual properties in pseudo-allergic reactions: Activating MRGPRX2 and inhibiting the H1 receptor.","date":"2019","source":"Molecular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/31051313","citation_count":23,"is_preprint":false},{"pmid":"37430437","id":"PMC_37430437","title":"MRGPRX2, drug pseudoallergies, inflammatory diseases, mechanisms and distinguishing MRGPRX2- and IgE/FcεRI-mediated events.","date":"2023","source":"British journal of clinical pharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/37430437","citation_count":22,"is_preprint":false},{"pmid":"33275825","id":"PMC_33275825","title":"MRGPRX2 activation in mast cells by neuromuscular blocking agents and other agonists: Modulation by sugammadex.","date":"2020","source":"Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33275825","citation_count":22,"is_preprint":false},{"pmid":"36344690","id":"PMC_36344690","title":"Opioid toxicity: histamine, hypersensitivity, and MRGPRX2.","date":"2022","source":"Archives of toxicology","url":"https://pubmed.ncbi.nlm.nih.gov/36344690","citation_count":21,"is_preprint":false},{"pmid":"34111449","id":"PMC_34111449","title":"P17 induces chemotaxis and differentiation of monocytes via MRGPRX2-mediated mast cell-line activation.","date":"2021","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34111449","citation_count":20,"is_preprint":false},{"pmid":"28844982","id":"PMC_28844982","title":"Mast cell degranulation via MRGPRX2 by isolated human albumin fragments.","date":"2017","source":"Biochimica et biophysica acta. General subjects","url":"https://pubmed.ncbi.nlm.nih.gov/28844982","citation_count":20,"is_preprint":false},{"pmid":"29684393","id":"PMC_29684393","title":"Anti-pseudo-allergy effect of isoliquiritigenin is MRGPRX2-dependent.","date":"2018","source":"Immunology letters","url":"https://pubmed.ncbi.nlm.nih.gov/29684393","citation_count":20,"is_preprint":false},{"pmid":"29484687","id":"PMC_29484687","title":"Endogenous protein and enzyme fragments induce immunoglobulin E-independent activation of mast cells via a G protein-coupled receptor, MRGPRX2.","date":"2018","source":"Scandinavian journal of immunology","url":"https://pubmed.ncbi.nlm.nih.gov/29484687","citation_count":20,"is_preprint":false},{"pmid":"35697810","id":"PMC_35697810","title":"MrgX2-SNAP-tag/cell membrane chromatography model coupled with liquid chromatography-mass spectrometry for anti-pseudo-allergic compound screening in Arnebiae Radix.","date":"2022","source":"Analytical and bioanalytical chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/35697810","citation_count":19,"is_preprint":false},{"pmid":"34248979","id":"PMC_34248979","title":"Murepavadin, a Small Molecule Host Defense Peptide Mimetic, Activates Mast Cells via MRGPRX2 and MrgprB2.","date":"2021","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/34248979","citation_count":19,"is_preprint":false},{"pmid":"33524790","id":"PMC_33524790","title":"MRGPRX2 mediates immediate-type pseudo-allergic reactions induced by iodine-containing iohexol.","date":"2021","source":"Biomedicine & pharmacotherapy = Biomedecine & pharmacotherapie","url":"https://pubmed.ncbi.nlm.nih.gov/33524790","citation_count":19,"is_preprint":false},{"pmid":"35315143","id":"PMC_35315143","title":"Luteolin inhibits FcεRΙ- and MRGPRX2-mediated mast cell activation by regulating calcium signaling pathways.","date":"2022","source":"Phytotherapy research : PTR","url":"https://pubmed.ncbi.nlm.nih.gov/35315143","citation_count":18,"is_preprint":false},{"pmid":"33673037","id":"PMC_33673037","title":"Authentic and Ectopically Expressed MRGPRX2 Elicit Similar Mechanisms to Stimulate Degranulation of Mast Cells.","date":"2021","source":"Cells","url":"https://pubmed.ncbi.nlm.nih.gov/33673037","citation_count":18,"is_preprint":false},{"pmid":"30875538","id":"PMC_30875538","title":"Isosalvianolic acid C-induced pseudo-allergic reactions via the mast cell specific receptor MRGPRX2.","date":"2019","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/30875538","citation_count":17,"is_preprint":false},{"pmid":"33129497","id":"PMC_33129497","title":"Roxithromycin inhibits compound 48/80-induced pseudo-allergy via the MrgprX2 pathway both in vitro and in vivo.","date":"2020","source":"Cellular immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33129497","citation_count":17,"is_preprint":false},{"pmid":"36356925","id":"PMC_36356925","title":"Patient Characteristics Associated With Reactions to Mrgprx2-Activating Drugs in an Electronic Health Record-Linked Biobank.","date":"2022","source":"The journal of allergy and clinical immunology. In practice","url":"https://pubmed.ncbi.nlm.nih.gov/36356925","citation_count":17,"is_preprint":false},{"pmid":"26106044","id":"PMC_26106044","title":"The Origin, Expression, Function and Future Research Focus of a G Protein-coupled Receptor, Mas-related Gene X2 (MrgX2).","date":"2015","source":"Progress in histochemistry and cytochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26106044","citation_count":17,"is_preprint":false},{"pmid":"32999394","id":"PMC_32999394","title":"Identification of the dog orthologue of human MAS-related G protein coupled receptor X2 (MRGPRX2) essential for drug-induced pseudo-allergic reactions.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/32999394","citation_count":17,"is_preprint":false},{"pmid":"34329659","id":"PMC_34329659","title":"Cytokine Stimulation by MRGPRX2 Occurs with Lower Potency than by FcεRI Aggregation but with Similar Dependence on the Extracellular Signal-Regulated Kinase 1/2 Module in Human Skin Mast Cells.","date":"2021","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/34329659","citation_count":17,"is_preprint":false},{"pmid":"36804596","id":"PMC_36804596","title":"DOCK2 regulates MRGPRX2/B2-mediated mast cell degranulation and drug-induced anaphylaxis.","date":"2023","source":"The Journal of allergy and clinical immunology","url":"https://pubmed.ncbi.nlm.nih.gov/36804596","citation_count":16,"is_preprint":false},{"pmid":"38184723","id":"PMC_38184723","title":"Proinflammatory chemokine CXCL14 activates MAS-related G protein-coupled receptor MRGPRX2 and its putative mouse ortholog MRGPRB2.","date":"2024","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/38184723","citation_count":16,"is_preprint":false},{"pmid":"36931000","id":"PMC_36931000","title":"Rosmarinic acid ameliorates skin inflammation and pruritus in allergic contact dermatitis by inhibiting mast cell-mediated MRGPRX2/PLCγ1 signaling pathway.","date":"2023","source":"International immunopharmacology","url":"https://pubmed.ncbi.nlm.nih.gov/36931000","citation_count":16,"is_preprint":false},{"pmid":"38817611","id":"PMC_38817611","title":"MRGPRX2 antagonist GE1111 attenuated DNFB-induced atopic dermatitis in mice by reducing inflammatory cytokines and restoring skin integrity.","date":"2024","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/38817611","citation_count":15,"is_preprint":false},{"pmid":"36712922","id":"PMC_36712922","title":"Inhibition of Mast Cell Degranulation in Atopic Dermatitis by Celastrol through Suppressing MRGPRX2.","date":"2023","source":"Disease markers","url":"https://pubmed.ncbi.nlm.nih.gov/36712922","citation_count":15,"is_preprint":false},{"pmid":"32525431","id":"PMC_32525431","title":"MRGPRX2 activation as a rapid, high-throughput mechanistic-based approach for detecting peptide-mediated human mast cell degranulation liabilities.","date":"2020","source":"Journal of immunotoxicology","url":"https://pubmed.ncbi.nlm.nih.gov/32525431","citation_count":15,"is_preprint":false},{"pmid":"33857758","id":"PMC_33857758","title":"Revisiting the role of MRGPRX2 on hypersensitivity reactions to neuromuscular blocking drugs.","date":"2021","source":"Current opinion in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/33857758","citation_count":14,"is_preprint":false},{"pmid":"19230660","id":"PMC_19230660","title":"Discovery of non-peptidergic MrgX1 and MrgX2 receptor agonists and exploration of an initial SAR using solid-phase synthesis.","date":"2009","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/19230660","citation_count":14,"is_preprint":false},{"pmid":"33941653","id":"PMC_33941653","title":"MYO1F Regulates IgE and MRGPRX2-Dependent Mast Cell Exocytosis.","date":"2021","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/33941653","citation_count":13,"is_preprint":false},{"pmid":"35958589","id":"PMC_35958589","title":"The Number of MRGPRX2-Expressing Cells Is Increased in Skin Lesions of Patients With Indolent Systemic Mastocytosis, But Is Not Linked to Symptom Severity.","date":"2022","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/35958589","citation_count":13,"is_preprint":false},{"pmid":"39398230","id":"PMC_39398230","title":"Quercetin Attenuates MRGPRX2-Mediated Mast Cell Degranulation via the MyD88/IKK/NF-κB and PI3K/AKT/ Rac1/Cdc42 Pathway.","date":"2024","source":"Journal of inflammation research","url":"https://pubmed.ncbi.nlm.nih.gov/39398230","citation_count":13,"is_preprint":false},{"pmid":"32766979","id":"PMC_32766979","title":"Measurement and Functional Analysis of the Mas-Related G Protein-Coupled Receptor MRGPRX2 on Human Mast Cells and Basophils.","date":"2020","source":"Methods in molecular biology (Clifton, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/32766979","citation_count":13,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":53404,"output_tokens":9475,"usd":0.151169},"stage2":{"model":"claude-opus-4-6","input_tokens":13555,"output_tokens":3641,"usd":0.2382},"total_usd":0.389369,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2003,\n      \"finding\": \"MRGPRX2 (MrgX2) is a Gq-coupled GPCR that responds to cortistatin with increased intracellular Ca2+ but no effect on cAMP levels, identifying it as a high-potency cortistatin receptor expressed in dorsal root ganglia.\",\n      \"method\": \"Reverse pharmacology screening, Ca2+ mobilization assay, cAMP assay in MrgX2-expressing cells\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — functional in vitro assays with multiple readouts (Ca2+, cAMP) establishing Gq coupling and ligand identity\",\n      \"pmids\": [\"12915402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"MRGPRX2 (MrgX2) is activated by proadrenomedullin N-terminal peptides (PAMP-12 > cortistatin > PAMP-20), coupling to both Gαq and Gαi, as demonstrated by Ca2+ mobilization, inhibition of forskolin-elevated cAMP, and [35S]GTPγS binding assays; the receptor is expressed in adrenal chromaffin cells and dorsal root ganglia.\",\n      \"method\": \"Ca2+ mobilization assay, cAMP inhibition assay, [35S]GTPγS binding, immunostaining\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — multiple orthogonal biochemical assays establishing dual G protein coupling (Gαq and Gαi) and ligand rank order\",\n      \"pmids\": [\"15823563\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2005,\n      \"finding\": \"Proadrenomedullin N-terminal peptides and cortistatin share a common structural motif for activating MrgX2, explaining how two apparently unrelated peptides activate the same receptor.\",\n      \"method\": \"Structure-activity relationship (SAR) studies of PAMP analogs in MrgX2-expressing cells\",\n      \"journal\": \"European journal of pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — systematic SAR with functional assays, single lab\",\n      \"pmids\": [\"16111673\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"MRGPRX2 (MrgX2) is a novel GPCR for the antimicrobial peptide LL-37 on human mast cells; it mediates sustained Ca2+ mobilization and degranulation, but unlike most GPCRs it is resistant to agonist-induced receptor phosphorylation, desensitization, and internalization; GRK2 and GRK3 knockdown had no effect on LL-37-induced degranulation.\",\n      \"method\": \"shRNA knockdown in LAD2 and primary CD34+ mast cells, stable transfection of MrgX2 in mast cell lines, Ca2+ mobilization and degranulation assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal knockdown/transfection with functional readouts, multiple cell systems; replicated with primary cells\",\n      \"pmids\": [\"22069323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Compound 48/80 induces mast cell degranulation via both MrgX1 and MrgX2, whereas the C3a receptor superagonist E7 activates mast cells via MrgX2 but not MrgX1; C3a itself does not use MrgX1 or MrgX2 for degranulation.\",\n      \"method\": \"Stable transfection of MrgX1 and MrgX2 in RBL-2H3 cells, Ca2+ mobilization and degranulation assays comparing LAD2, HMC-1, and transfected RBL cells\",\n      \"journal\": \"European journal of pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic overexpression in orthogonal cell system with clear receptor-specific functional readouts\",\n      \"pmids\": [\"21741965\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"PMX-53 functions as both a potent CD88 antagonist and a low-affinity agonist for MrgX2 (but not MrgX1); Trp and Arg residues in PMX-53 are required for both activities.\",\n      \"method\": \"Stable transfection of MrgX1 and MrgX2 in RBL-2H3 cells, Ca2+ mobilization and degranulation assays, mutagenesis of PMX-53 (Trp→Ala and Arg→dArg substitutions)\",\n      \"journal\": \"Molecular pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — ligand mutagenesis combined with receptor-specific functional assays in transfected cells\",\n      \"pmids\": [\"21441599\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MRGPRX2 is activated by many opioid compounds (including morphine, hydrocodone, sinomenine, dextromethorphan, dynorphin A/B, neoendorphins) and mediates mast cell degranulation and Ca2+ release; mutagenesis-validated homology models were used to identify selective agonist ZINC-3573.\",\n      \"method\": \"High-throughput screening of 5,695 small molecules, mutagenesis-validated homology modeling, virtual docking of ~4 million compounds, functional assays in MRGPRX2-expressing cells and LAD2 mast cells\",\n      \"journal\": \"Nature chemical biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis-validated structural model combined with experimental screening and functional validation in multiple cell systems\",\n      \"pmids\": [\"28288109\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Vancomycin and staphylococcus δ-toxin evoke mast cell degranulation via MRGPRX2; a receptor antagonist inhibits this process.\",\n      \"method\": \"Mast cell degranulation assays with MRGPRX2 antagonist blockade\",\n      \"journal\": \"Itch (Philadelphia, Pa.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — functional assay with antagonist, single lab, limited mechanistic detail in abstract\",\n      \"pmids\": [\"28367504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"MRGPRX2-mediated sinomenine hydrochloride (SH)-induced mast cell degranulation operates through activation of PLC signaling pathways leading to Ca2+ mobilization; MrgprB2 knockout mice show reduced SH-induced inflammation, and MRGPRX2 knockdown mast cells show reduced degranulation.\",\n      \"method\": \"MrgprB2 knockout mouse model, MRGPRX2 siRNA knockdown, Ca2+ mobilization assay, hindpaw swelling/extravasation assay in vivo\",\n      \"journal\": \"Biochemical pharmacology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — combined in vivo KO and in vitro knockdown with mechanistic pathway identification\",\n      \"pmids\": [\"28987593\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"FcεRI- and MRGPRX2-triggered mast cell degranulation pathways are completely independent and show no cross-correlation; SCF potently inhibits pseudo-allergic (MRGPRX2-mediated) degranulation while simultaneously promoting allergic (FcεRI-mediated) stimulation.\",\n      \"method\": \"Human skin mast cell degranulation assays comparing FcεRI and MRGPRX2 routes with SCF treatment, MRGPRX2 mRNA quantification\",\n      \"journal\": \"Allergy\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional dissection in primary human cells with pharmacological manipulation, single lab\",\n      \"pmids\": [\"28859248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"LL-37-induced human mast cell degranulation and IL-8 release through MrgX2 is associated with activation of Gi protein, PLC/PKC/Calcium/NFAT, PI3K/Akt, and MAPK signaling pathways; MrgX2 silencing significantly inhibits both degranulation and cytokine release.\",\n      \"method\": \"siRNA knockdown of MrgX2 in LAD2 cells, Ca2+ imaging, β-hexosaminidase release, IL-8 measurement, pathway inhibitor studies\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — knockdown with multiple pathway inhibitors in a defined cell system\",\n      \"pmids\": [\"28549244\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Four naturally occurring missense variants in MRGPRX2's extracellular/transmembrane domains (G165E, D184H, W243R, H259Y) cause complete loss-of-function for mast cell degranulation in response to substance P, hemokinin-1, human β-defensin-3, and icatibant, suggesting these diverse ligands use common receptor sites.\",\n      \"method\": \"Stable and transient transfection of MRGPRX2 missense variants in RBL-2H3 cells, degranulation assay with multiple ligands\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic mutagenesis of naturally occurring variants with multiple ligands establishing shared binding sites\",\n      \"pmids\": [\"29794017\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MRGPRX2 is negatively regulated by SCF and IL-4 in skin mast cells; withdrawal of both SCF and IL-4 partially reinstates MRGPRX2 expression and pseudo-allergic responsiveness; FcεRI-triggered activation shows inverse regulation compared to MRGPRX2-mediated activation.\",\n      \"method\": \"Mast cell culture with SCF/IL-4 withdrawal, MRGPRX2 mRNA/protein quantification, functional degranulation assays\",\n      \"journal\": \"Experimental dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic cytokine manipulation with expression and functional readouts in primary human mast cells\",\n      \"pmids\": [\"30091263\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"MrgX2-mediated LL-37 internalization occurs via clathrin-mediated endocytosis requiring sialic acid at the cell surface; LL-37 co-localizes with MrgX2 in the perinuclear region; G-protein inhibition (pertussis toxin) and MrgX2 siRNA knockdown both suppress LL-37 internalization and mast cell degranulation.\",\n      \"method\": \"siRNA knockdown of MrgX2, pertussis toxin treatment, neuraminidase treatment, clathrin endocytosis inhibitors (dynasore, chlorpromazine), confocal microscopy, β-hexosaminidase release assay in LAD2 cells\",\n      \"journal\": \"Molecular medicine reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple complementary approaches identifying internalization mechanism, single lab\",\n      \"pmids\": [\"30280189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Substance P (SP) induces Ca2+ mobilization and degranulation via both Gαi and Gαq family G proteins in MRGPRX2-expressing cells; conserved TM6 residue I225 and TM7 residue Y279 are essential for SP-induced responses; intracellular loop residues R138C and R141C cause loss of function; carboxyl-terminal Ser/Thr substitution (all five to Ala) and missense variants S325L and L329Q result in gain-of-function, suggesting desensitization via C-terminal phosphorylation.\",\n      \"method\": \"Pertussis toxin and YM-254890 G protein inhibition, transient transfection of MRGPRX2 variants in RBL-2H3 cells, structural modeling, Ca2+ mobilization and degranulation assays\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis combined with pharmacological G protein pathway dissection and structural modeling\",\n      \"pmids\": [\"31652731\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"AG-30/5C and icatibant are G protein-biased agonists for MRGPRX2: they induce pertussis toxin-sensitive G protein-mediated degranulation without activating β-arrestin (Tango assay); compound 48/80 signals via both G protein and β-arrestin pathways and causes MRGPRX2 internalization and subsequent desensitization; resveratrol inhibits compound 48/80-induced Tango and mast cell degranulation.\",\n      \"method\": \"shRNA silencing of MRGPRX2 in LAD2 cells, stable transfection in RBL-2H3, Tango β-arrestin assay, pertussis toxin treatment, flow cytometry for surface receptor, degranulation assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — biased agonism demonstrated by orthogonal G protein and β-arrestin assays with receptor internalization measurements\",\n      \"pmids\": [\"30651343\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"MRGPRX2 antagonists inhibit p42/44 MAPK signaling and block MRGPRX2-mediated prostaglandin D2 synthesis (de novo lipid mediator production) in human cord blood-derived mast cells; IgE- or A23187-activated mast cells are resistant to these antagonists.\",\n      \"method\": \"Novel MRGPRX2 antagonist pharmacology in human cord blood-derived mast cells, β-hexosaminidase and PGD2 assays, MAPK western blot\",\n      \"journal\": \"Journal of leukocyte biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — selective antagonist with mechanistic readouts in primary human mast cells\",\n      \"pmids\": [\"31299111\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"IL-33 chronically reduces MRGPRX2 expression in skin mast cells via a mechanism partially requiring JNK, thereby eliminating pseudo-allergic responsiveness; in contrast, acute IL-33 priming enhances MRGPRX2-triggered degranulation through p38-dependent signaling.\",\n      \"method\": \"Chronic and acute IL-33 stimulation of human skin mast cells, Accell-mediated JNK/p38 knockdown, kinase inhibition, MRGPRX2 quantification, histamine release assay\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — RNA interference + pharmacological inhibition with mechanistic pathway dissection in primary human skin mast cells\",\n      \"pmids\": [\"30979016\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Store-operated Ca2+ entry (SOCE) via STIM1 is required for MRGPRX2-induced mast cell degranulation in vitro and MrgprB2-dependent inflammation in vivo, as shown by pharmacological and genetic ablation of STIM1.\",\n      \"method\": \"Pharmacologic SOCE inhibition and STIM1 genetic ablation in LAD2 cells, mouse peritoneal mast cells, in vivo MrgprB2-dependent models\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic and pharmacological approaches in complementary in vitro and in vivo models\",\n      \"pmids\": [\"32038646\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"MRGPRX2 is the dominant codeine receptor in human skin mast cells; codeine binding triggers rapid MRGPRX2 internalization in a β-arrestin-1-dependent manner; prestimulation with MRGPRX2 agonists causes cross-desensitization to subsequent MRGPRX2 ligands but not to C3a or FcεRI aggregation.\",\n      \"method\": \"MRGPRX2 silencing, Tango β-arrestin assay, flow cytometry for MRGPRX2 surface expression, cross-desensitization experiments, degranulation assay in skin mast cells and RBL-MRGPRX2 cells\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods in primary and engineered cells establishing receptor identity and internalization mechanism\",\n      \"pmids\": [\"33058860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Morphine and substance P selectively induce histamine and tryptase (but not eicosanoid) release from human skin mast cells and synovial mast cells via MRGPRX2, but not from lung or cardiac mast cells, demonstrating heterogeneous MRGPRX2 expression and function across anatomical sites.\",\n      \"method\": \"Histamine, tryptase, PGD2, and LTC4 release assays from purified human mast cells from skin, synovium, lung, and heart\",\n      \"journal\": \"Frontiers in cellular neuroscience\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional comparison across primary human mast cell subsets with multiple mediator readouts\",\n      \"pmids\": [\"31333418\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"TSLP selectively cooperates with MRGPRX2 (but not FcεRI) to enhance skin mast cell granule discharge in a STAT5-dependent manner with JNK as a contributory factor; STAT5 silencing completely abolishes the priming effect.\",\n      \"method\": \"TSLP stimulation of human skin mast cells, STAT5/JNK RNA interference and pharmacological inhibition, degranulation and CD107a assays\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — RNA interference confirmed by pharmacological inhibition in primary human skin mast cells with MRGPRX2-selective vs FcεRI comparison\",\n      \"pmids\": [\"33429916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Substance P serves as a balanced agonist for MRGPRX2, inducing both G protein-mediated degranulation and β-arrestin recruitment/receptor internalization independently of G proteins; the conserved tyrosine residue Y279 in the NPxxY motif is required for both G protein- and β-arrestin-mediated responses.\",\n      \"method\": \"Tango β-arrestin assay, MRGPRX2 internalization imaging, Y279A mutagenesis in transfected RBL-2H3 cells, pertussis toxin treatment\",\n      \"journal\": \"International journal of molecular sciences\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis of conserved receptor residue with orthogonal G protein and β-arrestin assays\",\n      \"pmids\": [\"34070125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"DOCK2 regulates MRGPRX2/B2-mediated mast cell degranulation through Rac activation and PAK1 phosphorylation; DOCK2-deficient mast cells show impaired Rac activation and PAK1 phosphorylation downstream of MRGPRB2 despite normal calcium influx and proximal signaling.\",\n      \"method\": \"DOCK2-deficient mice, genetic inactivation in human/murine mast cells, small-molecule DOCK2 inhibitors, Rac activation assay, PAK1 phosphorylation western blot, in vivo anaphylaxis models\",\n      \"journal\": \"The Journal of allergy and clinical immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — genetic KO combined with pharmacological inhibition and mechanistic biochemical readouts in vivo and in vitro\",\n      \"pmids\": [\"36804596\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Both β-arrestin-1 and β-arrestin-2 restrain MRGPRX2-triggered degranulation and ERK1/2 activation in human skin mast cells: β-arrestin-1 controls MRGPRX2 surface abundance (internalization), while β-arrestin-2 mediates signal termination without receptor internalization.\",\n      \"method\": \"RNA interference of β-arrestin-1 and β-arrestin-2 in human skin mast cells, MRGPRX2 surface expression quantification, ERK1/2 and AKT phosphorylation, degranulation assays with three MRGPRX2 agonists\",\n      \"journal\": \"Frontiers in allergy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — isoform-specific knockdown with mechanistic separation of internalization vs signal termination functions\",\n      \"pmids\": [\"35910860\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"MRGPRX2-mediated degranulation in human skin mast cells requires Gαi (more prominent) and Gαq G proteins, Ca2+ channels, PI3K, and ERK1/2; Gαi inhibition also reduces pERK1/2 and pAKT, placing Gαi upstream of these kinase cascades.\",\n      \"method\": \"Pertussis toxin (Gαi inhibition), YM-254890 (Gαq inhibition), Ca2+ channel blockers, PI3K/ERK/JNK inhibitors, immunoblotting for phosphorylation events in purified primary human skin mast cells\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic pharmacological dissection of G protein signaling cascade in primary human skin mast cells with multiple inhibitors and phosphoprotein readouts\",\n      \"pmids\": [\"35326404\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The inverse MRGPRX2 agonist C9 inhibits both G protein-mediated degranulation and β-arrestin recruitment/MRGPRX2 internalization in response to SP, PAMP-12, and rocuronium, but has no effect on C3a, FcεRI-mediated responses, or MrgprB2 in mouse mast cells, demonstrating specificity for human MRGPRX2.\",\n      \"method\": \"Stable MRGPRX2-expressing RBL-2H3 cells, LAD2 cells, primary human skin mast cells, β-arrestin recruitment assay, CD63/CD107a flow cytometry, β-hexosaminidase assay, pertussis toxin treatment in mouse peritoneal mast cells\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — comprehensive pharmacological characterization with multiple cell systems and readouts distinguishing MRGPRX2 from related pathways\",\n      \"pmids\": [\"36275683\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MrgprB2-mediated MRGPRX2 activation drives tryptase release from mast cells, and tryptase is involved in the release of type 2 cytokines contributing to inflammatory development in atopic dermatitis; MrgprB2 conditional knockout mice show milder AD phenotypes.\",\n      \"method\": \"MrgprB2 conditional KO mouse model with MC903-induced AD, tryptase antagonist treatment, cytokine and IgE correlation analysis\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic KO model with mechanistic downstream (tryptase axis) identification\",\n      \"pmids\": [\"37482287\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MRGPRX2 cytokine induction (TNF-α, IL-8, IL-13, CCL1, CCL2) in skin mast cells is ERK1/2-dependent; rapid and durable ERK1/2 phosphorylation follows MRGPRX2 ligation; PI3K and JNK have variable contributions; cytokine profiles from MRGPRX2 and FcεRI activation are similar but MRGPRX2 is less potent.\",\n      \"method\": \"MRGPRX2 agonist (compound 48/80, substance P) stimulation of human skin mast cells, MEK/ERK inhibitors, PI3K/JNK/p38 inhibitors, mRNA/protein cytokine quantification, ERK1/2 phosphorylation immunoblot\",\n      \"journal\": \"The Journal of investigative dermatology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic pharmacological kinase dissection in primary human skin mast cells\",\n      \"pmids\": [\"34329659\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MYO1F (unconventional myosin) is required for full MRGPRX2-mediated mast cell degranulation; MYO1F knockdown reduces cortical actin ring reassembly after activation, Cdc42 GTPase activation, granule membrane localization, and mitochondria translocation to exocytic sites, with reduced AKT and DRP1 phosphorylation.\",\n      \"method\": \"shRNA knockdown of MYO1F in human mast cells, cortical actin imaging, Cdc42 activation assay, granule/mitochondria localization microscopy, AKT/DRP1 phosphorylation western blot, degranulation assay\",\n      \"journal\": \"Journal of immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockdown with multiple mechanistic readouts establishing cytoskeletal regulation of MRGPRX2-mediated exocytosis\",\n      \"pmids\": [\"33941653\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"MRGPRX2 is activated by PACAP in a dose-dependent manner on human mast cells; meningeal MrgprB2-expressing mast cells contribute to PACAP-induced migraine-like pain behavior in mice, and MRGPRX2 transgenic mice show increased PACAP-induced migraine-like pain vs receptor-absent controls.\",\n      \"method\": \"MRGPRX2 transgenic mouse model, mast cell enzyme release assay, behavioral migraine pain assay\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — transgenic animal model with functional behavioral readout and in vitro confirmation\",\n      \"pmids\": [\"37516794\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"The downstream signaling of MRGPRX2 involves PLCγ/PI3K/AKT and ERK1/2 pathways; authentic MRGPRX2 in LAD2 cells and ectopically expressed MRGPRX2 in RBL-2H3 cells share similar dose-response, kinetics, and signaling including ERK1/2 MAPK, PLC, and autophagy-related signaling; underlying mechanisms differ from those of rodent MrgprB2 orthologs.\",\n      \"method\": \"Comparative pharmacological profiling (signaling inhibitors) of LAD2 and RBL-MRGPRX2 cells with compound 48/80, substance P, and vancomycin; ERK1/2, PLC, autophagy inhibitors; degranulation assays\",\n      \"journal\": \"Cells\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — systematic parallel comparison with multiple pharmacological inhibitors in two cell systems\",\n      \"pmids\": [\"33673037\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"MRGPRX2 signals via PLCγ–IP3R-related Ca2+ fluctuations downstream of PI3K/AKT pathway; MrgprX2 knockdown in LAD2 cells reduces C48/80-induced calcium flux and downstream cytokine/chemokine release; p-AKT and PLCγ are upregulated upon MrgprX2 activation and downregulated upon knockdown.\",\n      \"method\": \"MrgprX2 siRNA knockdown in LAD2 cells, PI3K/PLCγ inhibitors, intracellular Ca2+ imaging, β-hexosaminidase assay, western blot for p-AKT and PLCγ\",\n      \"journal\": \"International immunopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockdown with pharmacological pathway inhibition and phosphoprotein readouts\",\n      \"pmids\": [\"34920312\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"The chemokine CXCL14 potently and selectively activates MRGPRX2 and MrgprB2 through both G protein-dependent and β-arrestin recruitment pathways; truncation and mutagenesis identified the C-terminal 4-11 amino acid pharmacophoric sequence of CXCL14 responsible for receptor activation.\",\n      \"method\": \"GPCR panel screening, G protein and β-arrestin functional assays, truncation and mutagenesis of CXCL14, selective MRGPRX2/B2 antagonist blockade, computational docking\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — systematic truncation/mutagenesis with orthogonal G protein and β-arrestin assays plus antagonist validation\",\n      \"pmids\": [\"38184723\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"Small molecule MRGPRX2 antagonists potently inhibit agonist-induced mast cell degranulation in vitro (LAD2, stem cell-derived, and isolated skin mast cells), in vivo (MRGPRX2 knock-in mice, Mrgprb2 KO controls), and ex vivo (human skin microdialysis), demonstrating that orally administered MRGPRX2 antagonism blocks skin mast cell degranulation.\",\n      \"method\": \"Multiple mast cell functional assays, MRGPRX2 knock-in transgenic mice, Mrgprb2 KO mice, skin vascular permeability assay, human skin ex vivo microdialysis\",\n      \"journal\": \"The Journal of allergy and clinical immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — comprehensive pharmacological characterization across in vitro, ex vivo, and transgenic/KO in vivo systems\",\n      \"pmids\": [\"38971540\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"The P17 ant venom peptide activates MRGPRX2 in a dose-dependent manner; residue Lys8 of P17 forms a cation-π interaction with Phe172 of MRGPRX2, demonstrated by mutagenesis ([Ala8]P17 loses activity); MRGPRX2-activated mast cells recruit and differentiate monocytes via chemokine release.\",\n      \"method\": \"GPCR screening of 314 receptors, β-arrestin recruitment assay, in silico docking and in vitro mutagenesis, β-hexosaminidase/cytokine assays, MRGPRX2 shRNA knockdown, monocyte migration/differentiation assays\",\n      \"journal\": \"The Journal of allergy and clinical immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — mutagenesis of both ligand and receptor combined with functional cellular assays establishing binding residues\",\n      \"pmids\": [\"34111449\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Osthole inhibits MRGPRX2-induced mast cell Ca2+ mobilization, degranulation, and chemokine/cytokine production; molecular docking suggests allosteric binding rather than competition at the orthosteric site; osthole reduces both surface and intracellular MRGPRX2 expression.\",\n      \"method\": \"Ca2+ mobilization assay, degranulation assay in LAD2 cells, in vivo MrgprB2-dependent mouse models, molecular docking, flow cytometry and confocal microscopy for MRGPRX2 expression\",\n      \"journal\": \"Frontiers in immunology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — complementary in vitro and in vivo data with docking analysis, single lab\",\n      \"pmids\": [\"32391014\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"A UC-protective MRGPRX2 variant (Asn62Ser) enhances β-arrestin recruitment, decreases IP-1 accumulation, and increases phosphorylated ERK (pERK) in response to MRGPRX2 agonists, demonstrating genotype-dependent biased signaling; adrenomedullin (processed to PAMP-12 agonist) is produced by activated fibroblasts and epithelial cells in inflamed UC regions.\",\n      \"method\": \"Variant transfection into CHO and HMC 1.1 cells, β-arrestin recruitment assay, IP-1 accumulation assay, pERK measurement; single-cell RNA sequencing for cellular source of adrenomedullin\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — functional cell-based assays for variant signaling with single-cell transcriptomics for ligand source\",\n      \"pmids\": [\"33421512\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"MRGPRX2 is a promiscuous class A GPCR expressed predominantly on human skin mast cells that couples to Gαi (primarily) and Gαq to activate PLC, PI3K/AKT, ERK1/2, Ca2+ channels, STIM1-dependent store-operated Ca2+ entry, and DOCK2-Rac-PAK1 signaling, leading to granule exocytosis; it is activated by an expanding array of cationic ligands (neuropeptides, host defense peptides, opioids, neuromuscular blocking agents, fluoroquinolones, and other drugs) and endogenous peptides (cortistatin, PAMP, LL-37, CXCL14, albumin fragments), signals additionally through β-arrestin-1/2-dependent internalization and desensitization (with biased agonists bypassing this route), is negatively regulated by SCF, IL-4, and chronic IL-33 and positively primed by acute IL-33 and TSLP via STAT5/JNK, and is the mechanistic basis for IgE-independent pseudo-allergic mast cell degranulation.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"MRGPRX2 is a promiscuous class A GPCR expressed predominantly on human skin mast cells that functions as the principal receptor for IgE-independent pseudo-allergic mast cell degranulation. It couples to both Gαi (predominant) and Gαq to activate PLC/PKC, PI3K/AKT, ERK1/2 MAPK, and STIM1-dependent store-operated Ca²⁺ entry, driving granule exocytosis, cytokine/chemokine release, and prostaglandin D₂ synthesis in response to a broad array of cationic ligands including neuropeptides (substance P, cortistatin, PAMP-12, PACAP), host defense peptides (LL-37, human β-defensin-3), opioids (morphine, codeine), neuromuscular blockers, fluoroquinolones, and the chemokine CXCL14 [PMID:35326404, PMID:28288109, PMID:38184723, PMID:12915402]. Receptor desensitization is governed by β-arrestin-1-dependent internalization controlling surface abundance and β-arrestin-2-mediated signal termination, while certain ligands (AG-30/5C, icatibant) act as G protein-biased agonists that bypass β-arrestin recruitment; naturally occurring gain-of-function C-terminal variants and biased-signaling variants (Asn62Ser) further modulate pathway selectivity [PMID:35910860, PMID:30651343, PMID:33421512]. MRGPRX2 expression and responsiveness are negatively regulated by SCF, IL-4, and chronic IL-33, and positively primed by acute IL-33 (via p38) and TSLP (via STAT5/JNK), while downstream exocytosis requires the DOCK2–Rac–PAK1 cytoskeletal remodeling axis and MYO1F-dependent cortical actin reorganization [PMID:28859248, PMID:30979016, PMID:33429916, PMID:36804596, PMID:33941653].\",\n  \"teleology\": [\n    {\n      \"year\": 2003,\n      \"claim\": \"Establishing MRGPRX2 as a functional GPCR: reverse pharmacology identified cortistatin as a high-potency ligand that activates Gq-coupled Ca²⁺ mobilization without affecting cAMP, defining the receptor's initial coupling mode and ligand identity.\",\n      \"evidence\": \"Ca²⁺ mobilization and cAMP assays in MrgX2-expressing cells\",\n      \"pmids\": [\"12915402\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Only Gq coupling demonstrated; Gi coupling not tested\", \"Expression limited to DRG; mast cell expression not yet recognized\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Revealing dual G protein coupling and ligand promiscuity: PAMP-12 was identified as a more potent agonist than cortistatin, and GTPγS binding/cAMP inhibition established that MRGPRX2 couples to both Gαq and Gαi, expanding its signaling repertoire beyond initial Gq-only reports.\",\n      \"evidence\": \"Ca²⁺ mobilization, cAMP inhibition, [³⁵S]GTPγS binding assays; SAR studies of PAMP analogs\",\n      \"pmids\": [\"15823563\", \"16111673\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for how unrelated peptides share a common pharmacophore not resolved at atomic level\", \"Downstream signaling cascades beyond G protein activation not mapped\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Defining MRGPRX2 as a mast cell degranulation receptor with unusual desensitization properties: LL-37 and compound 48/80 were shown to trigger mast cell degranulation via MRGPRX2, while LL-37 uniquely resisted GRK-mediated phosphorylation, desensitization, and internalization, revealing ligand-dependent differences in receptor regulation.\",\n      \"evidence\": \"shRNA knockdown in LAD2/primary mast cells, stable transfection in RBL-2H3, GRK2/3 knockdown, Ca²⁺ and degranulation assays\",\n      \"pmids\": [\"22069323\", \"21741965\", \"21441599\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis for resistance to GRK phosphorylation not identified\", \"Full spectrum of endogenous mast cell ligands unknown\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Massively expanding the MRGPRX2 ligand repertoire and establishing receptor independence from FcεRI: high-throughput screening identified opioids, vancomycin, and δ-toxin as MRGPRX2 agonists; mutagenesis-validated homology modeling defined the binding pocket; SCF was found to selectively suppress MRGPRX2 while enhancing FcεRI responses, establishing that the two degranulation pathways are independent and inversely regulated.\",\n      \"evidence\": \"HTS of 5,695 compounds, virtual docking of ~4M compounds, mutagenesis-validated homology model, PLC pathway dissection, MrgprB2 KO mice, SCF manipulation of human skin mast cells\",\n      \"pmids\": [\"28288109\", \"28987593\", \"28859248\", \"28549244\", \"28367504\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"High-resolution experimental structure not available\", \"Relative contribution of Gαi vs Gαq in primary mast cells not quantified\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Identifying critical receptor residues and cytokine regulation: naturally occurring loss-of-function missense variants (G165E, D184H, W243R, H259Y) established shared binding sites for diverse ligands; SCF/IL-4 withdrawal experiments showed that these cytokines tonically suppress MRGPRX2 expression; LL-37 internalization was shown to require clathrin-mediated endocytosis and sialic acid.\",\n      \"evidence\": \"Systematic missense variant mutagenesis with multiple ligands, cytokine withdrawal in primary mast cells, clathrin/neuraminidase inhibitors with confocal microscopy\",\n      \"pmids\": [\"29794017\", \"30091263\", \"30280189\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for how single mutations abolish responses to structurally diverse ligands not resolved\", \"Whether loss-of-function variants confer clinical protection from pseudo-allergy not tested\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Establishing biased agonism and delineating G protein vs β-arrestin signaling: AG-30/5C and icatibant were identified as G protein-biased agonists (no β-arrestin recruitment), while compound 48/80 and substance P activate both pathways; C-terminal Ser/Thr-to-Ala substitutions produced gain-of-function, implicating C-terminal phosphorylation in desensitization; IL-33 was shown to have dual temporal regulation (acute priming via p38, chronic suppression via JNK).\",\n      \"evidence\": \"Tango β-arrestin assay, pertussis toxin/YM-254890 G protein inhibition, C-terminal mutagenesis, IL-33 time-course with kinase knockdown in primary skin mast cells\",\n      \"pmids\": [\"30651343\", \"31652731\", \"30979016\", \"31299111\", \"34111449\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural determinants distinguishing balanced from biased agonists not resolved\", \"Whether biased agonism translates to differential clinical outcomes unknown\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Defining store-operated Ca²⁺ entry as essential and confirming β-arrestin-1-dependent codeine receptor identity: STIM1-dependent SOCE was shown to be required for MRGPRX2-mediated degranulation; codeine was identified as an MRGPRX2 agonist that triggers β-arrestin-1-dependent internalization and homologous desensitization; tissue heterogeneity was established as skin/synovial mast cells respond via MRGPRX2 while lung/cardiac mast cells do not.\",\n      \"evidence\": \"STIM1 genetic ablation and SOCE pharmacology in LAD2/mouse models, β-arrestin Tango assay, cross-desensitization, tissue-specific mast cell mediator profiling\",\n      \"pmids\": [\"32038646\", \"33058860\", \"31333418\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of tissue-selective MRGPRX2 expression not identified\", \"Whether SOCE is the exclusive Ca²⁺ entry route or supplementary unclear\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Mapping the cytoskeletal effector arm and separating β-arrestin isoform functions: DOCK2–Rac–PAK1 was identified as essential for granule exocytosis downstream of MRGPRX2 despite normal Ca²⁺ influx; MYO1F was shown to control cortical actin remodeling, Cdc42 activation, and mitochondrial translocation to exocytic sites; β-arrestin-1 was found to control receptor internalization while β-arrestin-2 mediates signal termination without internalization; TSLP was shown to selectively prime MRGPRX2 responses via STAT5.\",\n      \"evidence\": \"DOCK2 KO mice and inhibitors, MYO1F shRNA, β-arrestin-1/2 isoform-specific knockdown, TSLP/STAT5 RNAi in primary skin mast cells\",\n      \"pmids\": [\"36804596\", \"33941653\", \"35910860\", \"33429916\", \"34070125\", \"34329659\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How DOCK2–Rac and MYO1F pathways are coordinated or sequenced is unknown\", \"Contribution of β-arrestin-dependent signaling to cytokine production vs degranulation not separated\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Consolidating the signaling hierarchy and demonstrating genotype-dependent biased signaling: systematic inhibitor studies in primary skin mast cells placed Gαi upstream of ERK1/2 and AKT; a UC-protective Asn62Ser variant was shown to enhance β-arrestin recruitment while decreasing IP-1 accumulation, establishing that naturally occurring variants can bias signaling; human-selective inverse agonist C9 blocked both G protein and β-arrestin arms.\",\n      \"evidence\": \"Pertussis toxin/YM-254890 with phospho-ERK/AKT immunoblotting, variant transfection with β-arrestin/IP-1/pERK assays, C9 characterization across multiple cell systems\",\n      \"pmids\": [\"35326404\", \"33421512\", \"36275683\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Cryo-EM or crystal structure of MRGPRX2 with agonist/antagonist not available\", \"Whether Asn62Ser biased signaling explains UC protection mechanistically unresolved\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Identifying CXCL14 as an endogenous chemokine agonist and demonstrating therapeutic MRGPRX2 antagonism in vivo: the C-terminal pharmacophoric sequence of CXCL14 was mapped by truncation/mutagenesis; orally administered small-molecule MRGPRX2 antagonists blocked skin mast cell degranulation in MRGPRX2 knock-in mice and human ex vivo skin microdialysis.\",\n      \"evidence\": \"CXCL14 truncation/mutagenesis with G protein and β-arrestin assays, MRGPRX2 knock-in/MrgprB2 KO mice, ex vivo human skin microdialysis\",\n      \"pmids\": [\"38184723\", \"38971540\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Clinical efficacy of MRGPRX2 antagonists in human pseudo-allergic disease not established\", \"Full endogenous ligand landscape (additional chemokines, albumin fragments) incompletely mapped\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the high-resolution structure of MRGPRX2 in active/inactive states, the molecular basis for how structurally diverse cationic ligands converge on common binding determinants, the mechanism controlling tissue-selective expression in skin vs lung mast cells, and whether biased agonism or genotype-dependent signaling can be exploited therapeutically.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No experimental atomic-resolution structure\", \"Tissue-specific transcriptional regulation unexplored\", \"Clinical translation of MRGPRX2 antagonism pending\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 1, 6, 33]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [15, 22, 24]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [3, 11, 19, 24]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 8, 10, 14, 25, 32]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 9, 17, 21, 27]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ARRB1\",\n      \"ARRB2\",\n      \"STIM1\",\n      \"DOCK2\",\n      \"MYO1F\",\n      \"GNAI1\",\n      \"GNAQ\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}