{"gene":"CRTC3","run_date":"2026-04-28T17:28:53","timeline":{"discoveries":[{"year":2012,"finding":"Salt-inducible kinases (SIKs) phosphorylate CRTC3, causing it to associate with 14-3-3 proteins and be sequestered in the cytoplasm; SIK inhibition leads to CRTC3 dephosphorylation, dissociation from 14-3-3 proteins, nuclear translocation, and coactivation of CREB-driven IL-10 transcription in macrophages, promoting a regulatory macrophage phenotype.","method":"Pharmacological SIK inhibition, drug-resistant SIK2 mutant rescue experiment, subcellular fractionation/localization, gene transcription assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal genetic rescue with drug-resistant SIK2 mutant, localization studies, replicated across two papers (PMID:23033494 and PMID:23241891)","pmids":["23033494"],"is_preprint":false},{"year":2012,"finding":"PGE2 activates PKA, which phosphorylates SIK2 at Ser343, inhibiting SIK2's ability to phosphorylate CRTC3; this allows CRTC3 to translocate to the nucleus and coactivate CREB-driven IL-10 transcription independently of CREB Ser133 phosphorylation.","method":"Endogenous CREB Ser133Ala knock-in mutation, pharmacological and genetic SIK inhibition, subcellular localization assays, IL-10 promoter transcription assays","journal":"Journal of immunology (Baltimore, Md. : 1950)","confidence":"High","confidence_rationale":"Tier 1-2 — endogenous gene mutation plus pharmacological and genetic epistasis, multiple orthogonal methods","pmids":["23241891"],"is_preprint":false},{"year":2010,"finding":"CRTC3 is activated by catecholamine/cAMP signals in adipocytes and promotes obesity by upregulating Rgs2 expression, which inhibits adenylyl cyclase activity and attenuates β-adrenergic receptor signaling; a common human CRTC3 variant with increased transcriptional activity is associated with adiposity.","method":"Crtc3 knockout mice, adenoviral overexpression, Rgs2 expression assays, adenylyl cyclase activity measurement, human cohort SNP analysis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 — in vivo KO and OE mouse models with defined molecular pathway (CRTC3→Rgs2→adenylyl cyclase), replicated in human cohorts","pmids":["21164481"],"is_preprint":false},{"year":2018,"finding":"CRTC3 selectively interacts with B55 PP2A holoenzymes (not calcineurin, unlike CRTC1/2) via a conserved PP2A-binding region (amino acids 380–401); phosphorylation of CRTC3 at S391 by ERKs and CDKs promotes CRTC3-PP2A complex formation, facilitating dephosphorylation of 14-3-3 binding sites and nuclear translocation of CRTC3 in response to mitogenic signals.","method":"Co-immunoprecipitation, mass spectrometry, site-directed mutagenesis of PP2A-binding region and S391, kinase inhibitor studies","journal":"iScience","confidence":"High","confidence_rationale":"Tier 1-2 — biochemical reconstitution of CRTC3-PP2A interaction, mutagenesis of binding region and phosphorylation site, multiple orthogonal methods in single study","pmids":["30611118"],"is_preprint":false},{"year":2016,"finding":"Lkb1 controls intracellular localization of CRTC3 in brown adipocytes; deletion of Lkb1 causes cytoplasm-to-nucleus translocation of CRTC3, where it recruits C/EBPβ to enhance Ucp1 transcription, increasing thermogenesis and energy expenditure.","method":"Adipocyte-specific Lkb1 knockout mice, subcellular fractionation, co-immunoprecipitation of CRTC3 with C/EBPβ, Ucp1 promoter assays, metabolic phenotyping","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — clean tissue-specific KO with defined molecular mechanism (CRTC3 nuclear translocation → C/EBPβ recruitment → Ucp1), multiple orthogonal methods","pmids":["27461402"],"is_preprint":false},{"year":2018,"finding":"CRTC3 in brown adipose tissue acts as part of an inhibitory feedback pathway that antagonizes PRDM16-dependent BAT differentiation by upregulating miR-206, a microRNA that promotes myogenic differentiation and reduces VEGFA and neurotrophin expression, thereby decreasing sympathetic innervation and catecholamine signaling in BAT.","method":"BAT-specific CRTC3 knockout mice, adipose-specific constitutively active CRTC3 overexpression mice, miR-206 reexpression rescue experiment, sympathetic nerve activity measurement","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — reciprocal KO and OE mouse models, pathway rescue with miR-206 reexpression, defined molecular mechanism","pmids":["29784793"],"is_preprint":false},{"year":2011,"finding":"CRTC3, but not CRTC2, is selectively required for mitochondrial stress-induced (rotenone/complex I inhibition) PGC-1α induction and downstream mitochondrial biogenesis in liver cells.","method":"siRNA knockdown of CRTC2 and CRTC3 in HepG2 cells and primary mouse hepatocytes, PGC-1α expression assays, mitochondrial biogenesis readouts","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — clean isoform-specific KD with defined phenotype, but single lab study","pmids":["21536665"],"is_preprint":false},{"year":2018,"finding":"In osteoblasts, PTH(1-34) regulates Rankl expression through a pathway involving PKA-mediated inhibition of SIK2 and SIK3, which controls CRTC3 nuclear localization; PP1/PP2A phosphatases also play a major role in PTH-induced Rankl expression and CRTC3 localization.","method":"SIK2/SIK3 and CRTC3 knockdown in primary calvarial osteoblasts, nuclear localization assays, PP1/PP2A inhibition, Rankl expression assays in vitro and in vivo","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — genetic knockdown of pathway components with localization and gene expression readouts, in vitro and in vivo","pmids":["30377251"],"is_preprint":false},{"year":2017,"finding":"Disruption of both CRTC2 and CRTC3 causes embryonic lethality in mice; in bone marrow stromal cells, CRTC2/3 depletion decreases SOCS3 expression, leading to increased STAT3 phosphorylation and CEBPβ induction, which drives G-CSF production and neutrophilia/splenomegaly.","method":"CRTC2/CRTC3 double knockout mice, mesenchymal cell-specific Prx1-Cre conditional knockout, adoptive BM transfer, JAK inhibitor treatment, anti-G-CSF neutralizing antiserum","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 — multiple genetic models (germline and conditional KO), adoptive transfer epistasis, pharmacological rescue, defined CREB/CRTC→SOCS3→JAK/STAT pathway","pmids":["29078378"],"is_preprint":false},{"year":2021,"finding":"CRTC3 quantitatively regulates melanogenesis by directly targeting MITF transcription; CRTC3-null mice show paler coat color and reduced melanin, and CRTC3-deficient melanocytes have reduced melanogenesis-related gene expression without loss of melanocyte number.","method":"CRTC3 knockout mice, KRT14-SCF transgenic crosses, shRNA knockdown in primary melanocytes, promoter assays, melanin/tyrosinase assays, subcellular localization studies","journal":"Theranostics","confidence":"Medium","confidence_rationale":"Tier 2 — in vivo KO model with mechanistic follow-up including promoter assays and subcellular localization, single lab","pmids":["34815795"],"is_preprint":false},{"year":2021,"finding":"Dasatinib inhibits SIK2, leading to reduced CRTC3 phosphorylation and nuclear accumulation of CRTC3, which activates CREB-driven MITF transcription; MITF then transcriptionally activates Bcl-2, conferring resistance to dasatinib in c-Kit-altered melanoma cells.","method":"CRTC3 phosphorylation assays, MITF/Bcl-2 expression analysis, MITF overexpression, Bcl-2 selective inhibitor (ABT-199), Bcl-2 knockout, cell viability assays","journal":"Molecular cancer research : MCR","confidence":"Medium","confidence_rationale":"Tier 2 — genetic Bcl-2 KO and pharmacological rescue validate CRTC3/MITF/Bcl-2 pathway, multiple orthogonal approaches in single lab","pmids":["33741716"],"is_preprint":false},{"year":2023,"finding":"CRTC3 in astrocytes directly regulates transcription of amphiregulin (in complex with CREB); astrocyte-specific CRTC3 deficiency reduces prefrontal-parietal cortex functional connectivity and lowers social rank, effects reversed by astrocyte-specific amphiregulin induction dependent on its EGF domain.","method":"Systemic and astrocyte-specific CRTC3 knockout mice, functional connectivity imaging, astrocyte-specific amphiregulin rescue, promoter/CRTC3-CREB binding assays, tube test for social hierarchy","journal":"Molecular psychiatry","confidence":"Medium","confidence_rationale":"Tier 2 — cell-type-specific KO with rescue experiment and mechanistic promoter assay, single lab","pmids":["37730843"],"is_preprint":false},{"year":2024,"finding":"CRTC3 interacts with NSP12 (the catalytic subunit of SARS-CoV-2 RdRp), attenuates RdRp activity, and restricts SARS-CoV-2 genome replication and progeny virus production; CREB antagonizes this restrictive function of CRTC3.","method":"Co-immunoprecipitation of CRTC3 with NSP12, RdRp activity assays, SARS-CoV-2 replication assays, CRTC3 overexpression/knockout, CREB co-expression","journal":"Virologica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 — direct protein interaction confirmed by Co-IP, functional RdRp and viral replication assays, single lab","pmids":["39736320"],"is_preprint":false},{"year":2025,"finding":"PRMT1 methylates CRTC3 at arginine R534 within its transactivation domain; this activated CRTC3 cooperates with FOXO3a to transactivate the BAX gene, promoting apoptosis and muscle atrophy in the context of dietary advanced glycation end-products.","method":"Immunoprecipitation, mass spectrometry, co-immunoprecipitation, site-specific mutagenesis at R534, PRMT1 inhibition, BAX inhibitor in vivo, proteomic analysis of muscle tissue","journal":"Cellular and molecular life sciences : CMLS","confidence":"Medium","confidence_rationale":"Tier 1-2 — MS-identified arginine methylation site, Co-IP validation of CRTC3-FOXO3a complex, in vivo inhibitor rescue, single lab","pmids":["40192801"],"is_preprint":false},{"year":2023,"finding":"CRTC3 knockout alters tumor cell lipid patterns, increasing polyunsaturated fatty acid (PUFA) abundance and lipid peroxidation susceptibility, enhancing ferroptosis in hepatocellular carcinoma cells; IFN-γ synergizes with CRTC3 knockout by inhibiting system xc- (SLC7A11), disrupting a compensatory mechanism upregulated upon CRTC3 loss.","method":"CRISPR/Cas9 genome-wide knockout screen, CRTC3 KO in HCC cell lines, lipidomic analysis, ferroptosis inducers (RSL3, erastin, sorafenib), in vitro and in vivo tumor models","journal":"Cell death discovery","confidence":"Medium","confidence_rationale":"Tier 2 — genome-wide CRISPR screen with validation, lipidomics, in vivo confirmation, single lab","pmids":["37666810"],"is_preprint":false},{"year":2021,"finding":"SIK inhibitor HG-9-91-01 increases nuclear CRTC3 levels in colonic macrophages and promotes IL-10 production; overexpression of SIKs reduces nuclear CRTC3 and abrogates the anti-inflammatory effect both in vitro and in vivo.","method":"Lentiviral SIK overexpression in ANA-1 macrophages and in TNBS colitis mice, nuclear CRTC3 localization assays, IL-10 measurement, colitis mouse models","journal":"Inflammatory bowel diseases","confidence":"Medium","confidence_rationale":"Tier 2 — genetic pathway validation (SIK overexpression reverses CRTC3 nuclear localization and IL-10 induction) in vitro and in vivo, single lab","pmids":["33988718"],"is_preprint":false},{"year":2018,"finding":"Cold exposure induces nuclear translocation of CRTC3 in brown adipose tissue; this is associated with decreased Lkb1 expression; PKA activator forskolin also induces CRTC3 nuclear translocation in brown adipocytes, linked to UCP1 upregulation.","method":"Cold exposure mouse model, subcellular fractionation/immunofluorescence of CRTC3 localization in BAT, forskolin treatment of brown adipocytes, Lkb1 expression assays","journal":"Journal of cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 — localization assay with correlation to Lkb1/UCP1, no direct functional manipulation of CRTC3","pmids":["30506739"],"is_preprint":false}],"current_model":"CRTC3 is a CREB transcriptional coactivator that is held in the cytoplasm by SIK-mediated phosphorylation and 14-3-3 binding; inhibition of SIKs (by cAMP/PKA, catecholamines, PGE2, or pharmacological inhibitors) or activation of PP2A (recruited via a conserved CRTC3 region phosphorylated at S391 by ERKs/CDKs) leads to CRTC3 dephosphorylation and nuclear translocation, where it coactivates CREB target gene programs controlling IL-10 production in macrophages, thermogenesis (UCP1) and sympathetic innervation in brown adipose tissue (via miR-206/VEGFA/neurotrophin axis), obesity resistance (via Rgs2-dependent attenuation of β-adrenergic/adenylyl cyclase signaling), melanogenesis (via MITF), hematopoiesis (via SOCS3/JAK/STAT), and muscle integrity (via PRMT1-mediated R534 methylation activating CRTC3-FOXO3a-BAX apoptotic signaling)."},"narrative":{"teleology":[{"year":2010,"claim":"The first in vivo function of CRTC3 was established: it promotes obesity by activating Rgs2 transcription in adipocytes, which dampens β-adrenergic/adenylyl cyclase signaling and reduces energy expenditure, with a common human variant conferring increased transcriptional activity and adiposity.","evidence":"Crtc3 knockout mice, adenoviral overexpression, Rgs2 and adenylyl cyclase assays, human SNP association","pmids":["21164481"],"confidence":"High","gaps":["Mechanism by which the human CRTC3 variant increases transcriptional activity is not defined","Whether Rgs2 is the sole effector of CRTC3 in adipocytes is unclear"]},{"year":2011,"claim":"CRTC3 was shown to have isoform-specific functions distinct from CRTC2, selectively mediating mitochondrial stress-induced PGC-1α expression and mitochondrial biogenesis in hepatocytes.","evidence":"siRNA knockdown of CRTC2 vs CRTC3 in HepG2 cells and primary hepatocytes under rotenone treatment","pmids":["21536665"],"confidence":"Medium","gaps":["No in vivo validation of hepatic CRTC3-specific mitochondrial function","Mechanism distinguishing CRTC3 from CRTC2 specificity at the PGC-1α promoter is unknown"]},{"year":2012,"claim":"The core regulatory mechanism of CRTC3 was defined: SIK phosphorylation drives 14-3-3-dependent cytoplasmic retention, while SIK inhibition (by PKA downstream of PGE2 or pharmacological agents) releases CRTC3 for nuclear translocation and CREB coactivation, establishing CRTC3 as a key mediator of IL-10 transcription in macrophages independently of CREB Ser133 phosphorylation.","evidence":"Drug-resistant SIK2 mutant rescue, endogenous CREB S133A knock-in, subcellular fractionation, IL-10 promoter assays in macrophages","pmids":["23033494","23241891"],"confidence":"High","gaps":["Relative contributions of individual SIK family members to CRTC3 regulation in different tissues not delineated","Whether CRTC3 regulation of IL-10 is relevant beyond in vitro macrophage systems was not established at this time"]},{"year":2016,"claim":"The LKB1–SIK–CRTC3 axis was extended to thermogenesis: LKB1 deletion in brown adipocytes caused CRTC3 nuclear translocation, where it recruited C/EBPβ to activate UCP1 transcription, establishing CRTC3 as a direct coactivator at the UCP1 promoter.","evidence":"Adipocyte-specific Lkb1 knockout mice, co-IP of CRTC3 with C/EBPβ, UCP1 promoter assays, metabolic phenotyping","pmids":["27461402"],"confidence":"High","gaps":["Whether CRTC3 acts through CREB or exclusively through C/EBPβ at the UCP1 promoter was not resolved","Contribution of CRTC3 vs CRTC2 to thermogenic programming not distinguished"]},{"year":2017,"claim":"Combined CRTC2/CRTC3 loss revealed an essential and partially redundant role in hematopoietic regulation: the CREB/CRTC complex maintains SOCS3 expression, restraining JAK/STAT3 signaling and preventing pathological neutrophilia.","evidence":"CRTC2/3 double KO mice (embryonic lethal), mesenchymal-specific conditional KO, adoptive BM transfer, JAK inhibitor and anti-G-CSF rescue","pmids":["29078378"],"confidence":"High","gaps":["Individual contribution of CRTC3 versus CRTC2 to SOCS3 regulation not separated","Whether CRTC3 regulates other SOCS family members is unknown"]},{"year":2018,"claim":"Multiple tissue-specific and biochemical advances converged: CRTC3 was shown to antagonize BAT differentiation via miR-206/VEGFA/neurotrophin-dependent sympathetic innervation, its phosphatase specificity for B55 PP2A (not calcineurin) was biochemically defined with ERK/CDK phosphorylation of S391 as the trigger, and its role downstream of PTH signaling in osteoblasts for Rankl expression was demonstrated.","evidence":"BAT-specific CRTC3 KO and constitutively active OE mice with miR-206 rescue; Co-IP/MS of CRTC3-PP2A with S391 mutagenesis; SIK/CRTC3 knockdown in osteoblasts with Rankl assays","pmids":["29784793","30611118","30377251"],"confidence":"High","gaps":["Structural basis of CRTC3 selectivity for PP2A B55 over calcineurin is unresolved","Whether S391 phosphorylation integrates signals beyond ERK/CDK is unknown","Relative importance of CRTC3 vs other CRTCs in PTH-driven bone remodeling not defined"]},{"year":2021,"claim":"CRTC3 was established as a quantitative regulator of melanogenesis by directly coactivating MITF transcription, and this pathway was co-opted in melanoma where SIK2 inhibition by dasatinib activates CRTC3→MITF→Bcl-2 as a drug resistance mechanism; separately, SIK inhibition-induced nuclear CRTC3 and IL-10 production was validated in vivo in a colitis model.","evidence":"CRTC3 KO mice with coat color/melanin phenotype, shRNA in melanocytes, MITF promoter assays; dasatinib-treated c-Kit melanoma with Bcl-2 KO rescue; SIK OE in macrophages and TNBS colitis mice","pmids":["34815795","33741716","33988718"],"confidence":"Medium","gaps":["Whether CRTC3 regulation of MITF is relevant in human melanogenesis disorders is untested","In vivo confirmation of CRTC3-dependent drug resistance in melanoma is lacking"]},{"year":2023,"claim":"CRTC3 function was extended to brain circuitry and cancer metabolism: astrocyte-specific CRTC3 drives amphiregulin expression to maintain prefrontal-parietal connectivity and social dominance, while in hepatocellular carcinoma CRTC3 loss rewires lipid metabolism toward PUFA accumulation and ferroptosis sensitivity.","evidence":"Astrocyte-specific CRTC3 KO with amphiregulin rescue and functional connectivity imaging; CRISPR screen in HCC lines with lipidomics and in vivo tumor models","pmids":["37730843","37666810"],"confidence":"Medium","gaps":["Direct CRTC3 transcriptional targets controlling lipid remodeling in HCC are not identified","Human relevance of astrocytic CRTC3 in social behavior is unknown","Mechanism linking CRTC3 loss to PUFA accumulation not defined"]},{"year":2024,"claim":"A non-transcriptional function of CRTC3 was uncovered: direct interaction with SARS-CoV-2 NSP12 attenuates RNA-dependent RNA polymerase activity and restricts viral replication, with CREB antagonizing this restriction.","evidence":"Co-IP of CRTC3 with NSP12, RdRp activity assays, CRTC3 OE/KO viral replication assays","pmids":["39736320"],"confidence":"Medium","gaps":["Whether CRTC3 inhibits RdRp via direct catalytic interference or allosteric mechanism is unknown","Physiological relevance in human SARS-CoV-2 infection not established","How CREB antagonizes the antiviral function of CRTC3 is mechanistically undefined"]},{"year":2025,"claim":"A post-translational activation mode was defined: PRMT1-mediated methylation at R534 in the CRTC3 transactivation domain redirects CRTC3 to cooperate with FOXO3a (rather than CREB) to transactivate BAX and promote apoptosis, linking CRTC3 to muscle atrophy.","evidence":"IP-MS identification of R534 methylation, Co-IP of CRTC3-FOXO3a, R534 mutagenesis, PRMT1 inhibition, BAX inhibitor rescue in vivo","pmids":["40192801"],"confidence":"Medium","gaps":["Whether R534 methylation occurs in tissues beyond muscle is unknown","Structural basis for how methylation switches CRTC3 partner preference from CREB to FOXO3a is unresolved","Independent replication is needed"]},{"year":null,"claim":"Key unresolved questions include the structural basis of CRTC3's selective use of PP2A B55 over calcineurin, whether R534 methylation represents a general partner-switching mechanism across tissues, and how CRTC3 achieves target gene specificity when coactivating different transcription factors (CREB, C/EBPβ, MITF, FOXO3a) in distinct cell types.","evidence":"","pmids":[],"confidence":"Low","gaps":["No high-resolution structural data for CRTC3 or its complexes exist","Genome-wide identification of direct CRTC3 target genes across tissues has not been performed","Relative contributions of CRTC3 versus CRTC1/CRTC2 in most tissues are poorly defined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,1,2,4,5,9,11,13]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,1,3]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1,3,4,7,15]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,2,3,7]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[0,1,15]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[13,14]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[2,6,14]}],"complexes":[],"partners":["CREB1","SIK2","PPP2CA","CEBPB","FOXO3","PRMT1","MITF","YWHAZ"],"other_free_text":[]},"mechanistic_narrative":"CRTC3 is a transcriptional coactivator of CREB that integrates hormonal, metabolic, and stress signals to control diverse gene programs in energy homeostasis, immunity, pigmentation, and hematopoiesis. In its basal state, SIK-mediated phosphorylation promotes 14-3-3 binding and cytoplasmic sequestration of CRTC3; upstream signals—including cAMP/PKA, PGE2, and catecholamines—inhibit SIKs or activate B55-containing PP2A phosphatases (recruited via ERK/CDK-phosphorylated S391), causing CRTC3 dephosphorylation and nuclear translocation [PMID:23033494, PMID:30611118]. Once nuclear, CRTC3 coactivates CREB to drive context-specific targets: IL-10 in macrophages, Rgs2 in adipocytes (attenuating β-adrenergic/adenylyl cyclase signaling and promoting obesity), UCP1 in brown adipose tissue (via C/EBPβ recruitment), MITF in melanocytes, SOCS3 in bone marrow stromal cells (restraining JAK/STAT-driven granulopoiesis), and amphiregulin in astrocytes [PMID:23241891, PMID:21164481, PMID:27461402, PMID:34815795, PMID:29078378, PMID:37730843]. CRTC3 activity is further modulated by PRMT1-mediated arginine methylation at R534, which redirects it to cooperate with FOXO3a in BAX-dependent apoptosis in skeletal muscle [PMID:40192801]."},"prefetch_data":{"uniprot":{"accession":"Q6UUV7","full_name":"CREB-regulated transcription coactivator 3","aliases":["Transducer of regulated cAMP response element-binding protein 3","TORC-3","Transducer of CREB protein 3"],"length_aa":619,"mass_kda":67.0,"function":"Transcriptional coactivator for CREB1 which activates transcription through both consensus and variant cAMP response element (CRE) sites. Acts as a coactivator, in the SIK/TORC signaling pathway, being active when dephosphorylated and acts independently of CREB1 'Ser-133' phosphorylation. Enhances the interaction of CREB1 with TAF4. Regulates the expression of specific CREB-activated genes such as the steroidogenic gene, StAR. Potent coactivator of PPARGC1A and inducer of mitochondrial biogenesis in muscle cells. Also coactivator for TAX activation of the human T-cell leukemia virus type 1 (HTLV-1) long terminal repeats (LTR)","subcellular_location":"Nucleus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q6UUV7/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CRTC3","classification":"Not Classified","n_dependent_lines":62,"n_total_lines":1208,"dependency_fraction":0.05132450331125828},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"VAMP3","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CRTC3","total_profiled":1310},"omim":[{"mim_id":"608986","title":"CREB-REGULATED TRANSCRIPTION COACTIVATOR 3; CRTC3","url":"https://www.omim.org/entry/608986"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Enhanced","locations":[{"location":"Nucleoplasm","reliability":"Enhanced"},{"location":"Cytosol","reliability":"Additional"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CRTC3"},"hgnc":{"alias_symbol":["FLJ21868"],"prev_symbol":[]},"alphafold":{"accession":"Q6UUV7","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6UUV7","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q6UUV7-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q6UUV7-F1-predicted_aligned_error_v6.png","plddt_mean":49.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CRTC3","jax_strain_url":"https://www.jax.org/strain/search?query=CRTC3"},"sequence":{"accession":"Q6UUV7","fasta_url":"https://rest.uniprot.org/uniprotkb/Q6UUV7.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q6UUV7/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q6UUV7"}},"corpus_meta":[{"pmid":"23033494","id":"PMC_23033494","title":"Phosphorylation of CRTC3 by the salt-inducible kinases controls the interconversion of classically activated and regulatory macrophages.","date":"2012","source":"Proceedings of the National Academy of Sciences of the United States of America","url":"https://pubmed.ncbi.nlm.nih.gov/23033494","citation_count":213,"is_preprint":false},{"pmid":"23241891","id":"PMC_23241891","title":"PGE(2) induces macrophage IL-10 production and a regulatory-like phenotype via a protein kinase A-SIK-CRTC3 pathway.","date":"2012","source":"Journal of immunology (Baltimore, Md. : 1950)","url":"https://pubmed.ncbi.nlm.nih.gov/23241891","citation_count":195,"is_preprint":false},{"pmid":"19749740","id":"PMC_19749740","title":"Clinicopathological significance of the CRTC3-MAML2 fusion transcript in mucoepidermoid carcinoma.","date":"2009","source":"Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc","url":"https://pubmed.ncbi.nlm.nih.gov/19749740","citation_count":133,"is_preprint":false},{"pmid":"21164481","id":"PMC_21164481","title":"CRTC3 links catecholamine signalling to energy balance.","date":"2010","source":"Nature","url":"https://pubmed.ncbi.nlm.nih.gov/21164481","citation_count":128,"is_preprint":false},{"pmid":"27461402","id":"PMC_27461402","title":"Lkb1 controls brown adipose tissue growth and thermogenesis by regulating the intracellular localization of CRTC3.","date":"2016","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/27461402","citation_count":76,"is_preprint":false},{"pmid":"30377251","id":"PMC_30377251","title":"Parathyroid hormone(1-34) and its analogs differentially modulate osteoblastic Rankl expression via PKA/SIK2/SIK3 and PP1/PP2A-CRTC3 signaling.","date":"2018","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/30377251","citation_count":57,"is_preprint":false},{"pmid":"21536665","id":"PMC_21536665","title":"Role of cAMP-responsive element-binding protein (CREB)-regulated transcription coactivator 3 (CRTC3) in the initiation of mitochondrial biogenesis and stress response in liver cells.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/21536665","citation_count":56,"is_preprint":false},{"pmid":"24121173","id":"PMC_24121173","title":"CRTC1-MAML2 and CRTC3-MAML2 fusions were not detected in metaplastic Warthin tumor and metaplastic pleomorphic adenoma of salivary glands.","date":"2013","source":"The American journal of surgical pathology","url":"https://pubmed.ncbi.nlm.nih.gov/24121173","citation_count":37,"is_preprint":false},{"pmid":"29079171","id":"PMC_29079171","title":"A novel fusion gene CRTC3-MAML2 in hidradenoma: histopathological significance.","date":"2017","source":"Human pathology","url":"https://pubmed.ncbi.nlm.nih.gov/29079171","citation_count":33,"is_preprint":false},{"pmid":"27402217","id":"PMC_27402217","title":"Cutaneous hidradenoma: a study of 21 neoplasms revealing neither correlation between the cellular composition and CRTC1-MAML2 fusions nor presence of CRTC3-MAML2 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Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/39736320","citation_count":4,"is_preprint":false},{"pmid":"39398906","id":"PMC_39398906","title":"Breast mucoepidermoid carcinoma with a rare CRTC3-MAML2 fusion.","date":"2024","source":"International cancer conference journal","url":"https://pubmed.ncbi.nlm.nih.gov/39398906","citation_count":3,"is_preprint":false},{"pmid":"29796654","id":"PMC_29796654","title":"Rapid Communication: Porcine CRTC3 gene clone, expression pattern, and its regulatory role in intestinal epithelial cells.","date":"2018","source":"Journal of animal science","url":"https://pubmed.ncbi.nlm.nih.gov/29796654","citation_count":3,"is_preprint":false},{"pmid":"40192801","id":"PMC_40192801","title":"Dietary advanced glycation end-products exacerbate sarcopenia onset by activating apoptosis through PRMT1-mediated CRTC3 arginine methylation.","date":"2025","source":"Cellular and molecular life sciences : CMLS","url":"https://pubmed.ncbi.nlm.nih.gov/40192801","citation_count":2,"is_preprint":false},{"pmid":"39127591","id":"PMC_39127591","title":"Semaxanib, a VEGF inhibitor, suppresses melanogenesis by modulating CRTC3 independently of VEGF signaling.","date":"2024","source":"Journal of dermatological science","url":"https://pubmed.ncbi.nlm.nih.gov/39127591","citation_count":2,"is_preprint":false},{"pmid":"33947275","id":"PMC_33947275","title":"Morphological and biological properties of silica nanoparticles for CRTC3-siRNA delivery and downregulation of the RGS2 expression in preadipocytes.","date":"2021","source":"Journal of biomaterials applications","url":"https://pubmed.ncbi.nlm.nih.gov/33947275","citation_count":2,"is_preprint":false},{"pmid":"41589253","id":"PMC_41589253","title":"Penile mucoepidermoid carcinoma lacking CRTC1/CRTC3-MAML2 fusion: a case report and review of the literature.","date":"2025","source":"International cancer conference journal","url":"https://pubmed.ncbi.nlm.nih.gov/41589253","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":19526,"output_tokens":4610,"usd":0.063864},"stage2":{"model":"claude-opus-4-6","input_tokens":8105,"output_tokens":3539,"usd":0.1935},"total_usd":0.257364,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2012,\n      \"finding\": \"Salt-inducible kinases (SIKs) phosphorylate CRTC3, causing it to associate with 14-3-3 proteins and be sequestered in the cytoplasm; SIK inhibition leads to CRTC3 dephosphorylation, dissociation from 14-3-3 proteins, nuclear translocation, and coactivation of CREB-driven IL-10 transcription in macrophages, promoting a regulatory macrophage phenotype.\",\n      \"method\": \"Pharmacological SIK inhibition, drug-resistant SIK2 mutant rescue experiment, subcellular fractionation/localization, gene transcription assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal genetic rescue with drug-resistant SIK2 mutant, localization studies, replicated across two papers (PMID:23033494 and PMID:23241891)\",\n      \"pmids\": [\"23033494\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"PGE2 activates PKA, which phosphorylates SIK2 at Ser343, inhibiting SIK2's ability to phosphorylate CRTC3; this allows CRTC3 to translocate to the nucleus and coactivate CREB-driven IL-10 transcription independently of CREB Ser133 phosphorylation.\",\n      \"method\": \"Endogenous CREB Ser133Ala knock-in mutation, pharmacological and genetic SIK inhibition, subcellular localization assays, IL-10 promoter transcription assays\",\n      \"journal\": \"Journal of immunology (Baltimore, Md. : 1950)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — endogenous gene mutation plus pharmacological and genetic epistasis, multiple orthogonal methods\",\n      \"pmids\": [\"23241891\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CRTC3 is activated by catecholamine/cAMP signals in adipocytes and promotes obesity by upregulating Rgs2 expression, which inhibits adenylyl cyclase activity and attenuates β-adrenergic receptor signaling; a common human CRTC3 variant with increased transcriptional activity is associated with adiposity.\",\n      \"method\": \"Crtc3 knockout mice, adenoviral overexpression, Rgs2 expression assays, adenylyl cyclase activity measurement, human cohort SNP analysis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vivo KO and OE mouse models with defined molecular pathway (CRTC3→Rgs2→adenylyl cyclase), replicated in human cohorts\",\n      \"pmids\": [\"21164481\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CRTC3 selectively interacts with B55 PP2A holoenzymes (not calcineurin, unlike CRTC1/2) via a conserved PP2A-binding region (amino acids 380–401); phosphorylation of CRTC3 at S391 by ERKs and CDKs promotes CRTC3-PP2A complex formation, facilitating dephosphorylation of 14-3-3 binding sites and nuclear translocation of CRTC3 in response to mitogenic signals.\",\n      \"method\": \"Co-immunoprecipitation, mass spectrometry, site-directed mutagenesis of PP2A-binding region and S391, kinase inhibitor studies\",\n      \"journal\": \"iScience\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — biochemical reconstitution of CRTC3-PP2A interaction, mutagenesis of binding region and phosphorylation site, multiple orthogonal methods in single study\",\n      \"pmids\": [\"30611118\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Lkb1 controls intracellular localization of CRTC3 in brown adipocytes; deletion of Lkb1 causes cytoplasm-to-nucleus translocation of CRTC3, where it recruits C/EBPβ to enhance Ucp1 transcription, increasing thermogenesis and energy expenditure.\",\n      \"method\": \"Adipocyte-specific Lkb1 knockout mice, subcellular fractionation, co-immunoprecipitation of CRTC3 with C/EBPβ, Ucp1 promoter assays, metabolic phenotyping\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean tissue-specific KO with defined molecular mechanism (CRTC3 nuclear translocation → C/EBPβ recruitment → Ucp1), multiple orthogonal methods\",\n      \"pmids\": [\"27461402\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CRTC3 in brown adipose tissue acts as part of an inhibitory feedback pathway that antagonizes PRDM16-dependent BAT differentiation by upregulating miR-206, a microRNA that promotes myogenic differentiation and reduces VEGFA and neurotrophin expression, thereby decreasing sympathetic innervation and catecholamine signaling in BAT.\",\n      \"method\": \"BAT-specific CRTC3 knockout mice, adipose-specific constitutively active CRTC3 overexpression mice, miR-206 reexpression rescue experiment, sympathetic nerve activity measurement\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal KO and OE mouse models, pathway rescue with miR-206 reexpression, defined molecular mechanism\",\n      \"pmids\": [\"29784793\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"CRTC3, but not CRTC2, is selectively required for mitochondrial stress-induced (rotenone/complex I inhibition) PGC-1α induction and downstream mitochondrial biogenesis in liver cells.\",\n      \"method\": \"siRNA knockdown of CRTC2 and CRTC3 in HepG2 cells and primary mouse hepatocytes, PGC-1α expression assays, mitochondrial biogenesis readouts\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean isoform-specific KD with defined phenotype, but single lab study\",\n      \"pmids\": [\"21536665\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In osteoblasts, PTH(1-34) regulates Rankl expression through a pathway involving PKA-mediated inhibition of SIK2 and SIK3, which controls CRTC3 nuclear localization; PP1/PP2A phosphatases also play a major role in PTH-induced Rankl expression and CRTC3 localization.\",\n      \"method\": \"SIK2/SIK3 and CRTC3 knockdown in primary calvarial osteoblasts, nuclear localization assays, PP1/PP2A inhibition, Rankl expression assays in vitro and in vivo\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic knockdown of pathway components with localization and gene expression readouts, in vitro and in vivo\",\n      \"pmids\": [\"30377251\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Disruption of both CRTC2 and CRTC3 causes embryonic lethality in mice; in bone marrow stromal cells, CRTC2/3 depletion decreases SOCS3 expression, leading to increased STAT3 phosphorylation and CEBPβ induction, which drives G-CSF production and neutrophilia/splenomegaly.\",\n      \"method\": \"CRTC2/CRTC3 double knockout mice, mesenchymal cell-specific Prx1-Cre conditional knockout, adoptive BM transfer, JAK inhibitor treatment, anti-G-CSF neutralizing antiserum\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple genetic models (germline and conditional KO), adoptive transfer epistasis, pharmacological rescue, defined CREB/CRTC→SOCS3→JAK/STAT pathway\",\n      \"pmids\": [\"29078378\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CRTC3 quantitatively regulates melanogenesis by directly targeting MITF transcription; CRTC3-null mice show paler coat color and reduced melanin, and CRTC3-deficient melanocytes have reduced melanogenesis-related gene expression without loss of melanocyte number.\",\n      \"method\": \"CRTC3 knockout mice, KRT14-SCF transgenic crosses, shRNA knockdown in primary melanocytes, promoter assays, melanin/tyrosinase assays, subcellular localization studies\",\n      \"journal\": \"Theranostics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vivo KO model with mechanistic follow-up including promoter assays and subcellular localization, single lab\",\n      \"pmids\": [\"34815795\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Dasatinib inhibits SIK2, leading to reduced CRTC3 phosphorylation and nuclear accumulation of CRTC3, which activates CREB-driven MITF transcription; MITF then transcriptionally activates Bcl-2, conferring resistance to dasatinib in c-Kit-altered melanoma cells.\",\n      \"method\": \"CRTC3 phosphorylation assays, MITF/Bcl-2 expression analysis, MITF overexpression, Bcl-2 selective inhibitor (ABT-199), Bcl-2 knockout, cell viability assays\",\n      \"journal\": \"Molecular cancer research : MCR\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic Bcl-2 KO and pharmacological rescue validate CRTC3/MITF/Bcl-2 pathway, multiple orthogonal approaches in single lab\",\n      \"pmids\": [\"33741716\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CRTC3 in astrocytes directly regulates transcription of amphiregulin (in complex with CREB); astrocyte-specific CRTC3 deficiency reduces prefrontal-parietal cortex functional connectivity and lowers social rank, effects reversed by astrocyte-specific amphiregulin induction dependent on its EGF domain.\",\n      \"method\": \"Systemic and astrocyte-specific CRTC3 knockout mice, functional connectivity imaging, astrocyte-specific amphiregulin rescue, promoter/CRTC3-CREB binding assays, tube test for social hierarchy\",\n      \"journal\": \"Molecular psychiatry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — cell-type-specific KO with rescue experiment and mechanistic promoter assay, single lab\",\n      \"pmids\": [\"37730843\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"CRTC3 interacts with NSP12 (the catalytic subunit of SARS-CoV-2 RdRp), attenuates RdRp activity, and restricts SARS-CoV-2 genome replication and progeny virus production; CREB antagonizes this restrictive function of CRTC3.\",\n      \"method\": \"Co-immunoprecipitation of CRTC3 with NSP12, RdRp activity assays, SARS-CoV-2 replication assays, CRTC3 overexpression/knockout, CREB co-expression\",\n      \"journal\": \"Virologica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — direct protein interaction confirmed by Co-IP, functional RdRp and viral replication assays, single lab\",\n      \"pmids\": [\"39736320\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"PRMT1 methylates CRTC3 at arginine R534 within its transactivation domain; this activated CRTC3 cooperates with FOXO3a to transactivate the BAX gene, promoting apoptosis and muscle atrophy in the context of dietary advanced glycation end-products.\",\n      \"method\": \"Immunoprecipitation, mass spectrometry, co-immunoprecipitation, site-specific mutagenesis at R534, PRMT1 inhibition, BAX inhibitor in vivo, proteomic analysis of muscle tissue\",\n      \"journal\": \"Cellular and molecular life sciences : CMLS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — MS-identified arginine methylation site, Co-IP validation of CRTC3-FOXO3a complex, in vivo inhibitor rescue, single lab\",\n      \"pmids\": [\"40192801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"CRTC3 knockout alters tumor cell lipid patterns, increasing polyunsaturated fatty acid (PUFA) abundance and lipid peroxidation susceptibility, enhancing ferroptosis in hepatocellular carcinoma cells; IFN-γ synergizes with CRTC3 knockout by inhibiting system xc- (SLC7A11), disrupting a compensatory mechanism upregulated upon CRTC3 loss.\",\n      \"method\": \"CRISPR/Cas9 genome-wide knockout screen, CRTC3 KO in HCC cell lines, lipidomic analysis, ferroptosis inducers (RSL3, erastin, sorafenib), in vitro and in vivo tumor models\",\n      \"journal\": \"Cell death discovery\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genome-wide CRISPR screen with validation, lipidomics, in vivo confirmation, single lab\",\n      \"pmids\": [\"37666810\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"SIK inhibitor HG-9-91-01 increases nuclear CRTC3 levels in colonic macrophages and promotes IL-10 production; overexpression of SIKs reduces nuclear CRTC3 and abrogates the anti-inflammatory effect both in vitro and in vivo.\",\n      \"method\": \"Lentiviral SIK overexpression in ANA-1 macrophages and in TNBS colitis mice, nuclear CRTC3 localization assays, IL-10 measurement, colitis mouse models\",\n      \"journal\": \"Inflammatory bowel diseases\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic pathway validation (SIK overexpression reverses CRTC3 nuclear localization and IL-10 induction) in vitro and in vivo, single lab\",\n      \"pmids\": [\"33988718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Cold exposure induces nuclear translocation of CRTC3 in brown adipose tissue; this is associated with decreased Lkb1 expression; PKA activator forskolin also induces CRTC3 nuclear translocation in brown adipocytes, linked to UCP1 upregulation.\",\n      \"method\": \"Cold exposure mouse model, subcellular fractionation/immunofluorescence of CRTC3 localization in BAT, forskolin treatment of brown adipocytes, Lkb1 expression assays\",\n      \"journal\": \"Journal of cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — localization assay with correlation to Lkb1/UCP1, no direct functional manipulation of CRTC3\",\n      \"pmids\": [\"30506739\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CRTC3 is a CREB transcriptional coactivator that is held in the cytoplasm by SIK-mediated phosphorylation and 14-3-3 binding; inhibition of SIKs (by cAMP/PKA, catecholamines, PGE2, or pharmacological inhibitors) or activation of PP2A (recruited via a conserved CRTC3 region phosphorylated at S391 by ERKs/CDKs) leads to CRTC3 dephosphorylation and nuclear translocation, where it coactivates CREB target gene programs controlling IL-10 production in macrophages, thermogenesis (UCP1) and sympathetic innervation in brown adipose tissue (via miR-206/VEGFA/neurotrophin axis), obesity resistance (via Rgs2-dependent attenuation of β-adrenergic/adenylyl cyclase signaling), melanogenesis (via MITF), hematopoiesis (via SOCS3/JAK/STAT), and muscle integrity (via PRMT1-mediated R534 methylation activating CRTC3-FOXO3a-BAX apoptotic signaling).\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CRTC3 is a transcriptional coactivator of CREB that integrates hormonal, metabolic, and stress signals to control diverse gene programs in energy homeostasis, immunity, pigmentation, and hematopoiesis. In its basal state, SIK-mediated phosphorylation promotes 14-3-3 binding and cytoplasmic sequestration of CRTC3; upstream signals—including cAMP/PKA, PGE2, and catecholamines—inhibit SIKs or activate B55-containing PP2A phosphatases (recruited via ERK/CDK-phosphorylated S391), causing CRTC3 dephosphorylation and nuclear translocation [PMID:23033494, PMID:30611118]. Once nuclear, CRTC3 coactivates CREB to drive context-specific targets: IL-10 in macrophages, Rgs2 in adipocytes (attenuating β-adrenergic/adenylyl cyclase signaling and promoting obesity), UCP1 in brown adipose tissue (via C/EBPβ recruitment), MITF in melanocytes, SOCS3 in bone marrow stromal cells (restraining JAK/STAT-driven granulopoiesis), and amphiregulin in astrocytes [PMID:23241891, PMID:21164481, PMID:27461402, PMID:34815795, PMID:29078378, PMID:37730843]. CRTC3 activity is further modulated by PRMT1-mediated arginine methylation at R534, which redirects it to cooperate with FOXO3a in BAX-dependent apoptosis in skeletal muscle [PMID:40192801].\",\n  \"teleology\": [\n    {\n      \"year\": 2010,\n      \"claim\": \"The first in vivo function of CRTC3 was established: it promotes obesity by activating Rgs2 transcription in adipocytes, which dampens β-adrenergic/adenylyl cyclase signaling and reduces energy expenditure, with a common human variant conferring increased transcriptional activity and adiposity.\",\n      \"evidence\": \"Crtc3 knockout mice, adenoviral overexpression, Rgs2 and adenylyl cyclase assays, human SNP association\",\n      \"pmids\": [\"21164481\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which the human CRTC3 variant increases transcriptional activity is not defined\", \"Whether Rgs2 is the sole effector of CRTC3 in adipocytes is unclear\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"CRTC3 was shown to have isoform-specific functions distinct from CRTC2, selectively mediating mitochondrial stress-induced PGC-1α expression and mitochondrial biogenesis in hepatocytes.\",\n      \"evidence\": \"siRNA knockdown of CRTC2 vs CRTC3 in HepG2 cells and primary hepatocytes under rotenone treatment\",\n      \"pmids\": [\"21536665\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No in vivo validation of hepatic CRTC3-specific mitochondrial function\", \"Mechanism distinguishing CRTC3 from CRTC2 specificity at the PGC-1α promoter is unknown\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"The core regulatory mechanism of CRTC3 was defined: SIK phosphorylation drives 14-3-3-dependent cytoplasmic retention, while SIK inhibition (by PKA downstream of PGE2 or pharmacological agents) releases CRTC3 for nuclear translocation and CREB coactivation, establishing CRTC3 as a key mediator of IL-10 transcription in macrophages independently of CREB Ser133 phosphorylation.\",\n      \"evidence\": \"Drug-resistant SIK2 mutant rescue, endogenous CREB S133A knock-in, subcellular fractionation, IL-10 promoter assays in macrophages\",\n      \"pmids\": [\"23033494\", \"23241891\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative contributions of individual SIK family members to CRTC3 regulation in different tissues not delineated\", \"Whether CRTC3 regulation of IL-10 is relevant beyond in vitro macrophage systems was not established at this time\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"The LKB1–SIK–CRTC3 axis was extended to thermogenesis: LKB1 deletion in brown adipocytes caused CRTC3 nuclear translocation, where it recruited C/EBPβ to activate UCP1 transcription, establishing CRTC3 as a direct coactivator at the UCP1 promoter.\",\n      \"evidence\": \"Adipocyte-specific Lkb1 knockout mice, co-IP of CRTC3 with C/EBPβ, UCP1 promoter assays, metabolic phenotyping\",\n      \"pmids\": [\"27461402\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CRTC3 acts through CREB or exclusively through C/EBPβ at the UCP1 promoter was not resolved\", \"Contribution of CRTC3 vs CRTC2 to thermogenic programming not distinguished\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Combined CRTC2/CRTC3 loss revealed an essential and partially redundant role in hematopoietic regulation: the CREB/CRTC complex maintains SOCS3 expression, restraining JAK/STAT3 signaling and preventing pathological neutrophilia.\",\n      \"evidence\": \"CRTC2/3 double KO mice (embryonic lethal), mesenchymal-specific conditional KO, adoptive BM transfer, JAK inhibitor and anti-G-CSF rescue\",\n      \"pmids\": [\"29078378\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Individual contribution of CRTC3 versus CRTC2 to SOCS3 regulation not separated\", \"Whether CRTC3 regulates other SOCS family members is unknown\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Multiple tissue-specific and biochemical advances converged: CRTC3 was shown to antagonize BAT differentiation via miR-206/VEGFA/neurotrophin-dependent sympathetic innervation, its phosphatase specificity for B55 PP2A (not calcineurin) was biochemically defined with ERK/CDK phosphorylation of S391 as the trigger, and its role downstream of PTH signaling in osteoblasts for Rankl expression was demonstrated.\",\n      \"evidence\": \"BAT-specific CRTC3 KO and constitutively active OE mice with miR-206 rescue; Co-IP/MS of CRTC3-PP2A with S391 mutagenesis; SIK/CRTC3 knockdown in osteoblasts with Rankl assays\",\n      \"pmids\": [\"29784793\", \"30611118\", \"30377251\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of CRTC3 selectivity for PP2A B55 over calcineurin is unresolved\", \"Whether S391 phosphorylation integrates signals beyond ERK/CDK is unknown\", \"Relative importance of CRTC3 vs other CRTCs in PTH-driven bone remodeling not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"CRTC3 was established as a quantitative regulator of melanogenesis by directly coactivating MITF transcription, and this pathway was co-opted in melanoma where SIK2 inhibition by dasatinib activates CRTC3→MITF→Bcl-2 as a drug resistance mechanism; separately, SIK inhibition-induced nuclear CRTC3 and IL-10 production was validated in vivo in a colitis model.\",\n      \"evidence\": \"CRTC3 KO mice with coat color/melanin phenotype, shRNA in melanocytes, MITF promoter assays; dasatinib-treated c-Kit melanoma with Bcl-2 KO rescue; SIK OE in macrophages and TNBS colitis mice\",\n      \"pmids\": [\"34815795\", \"33741716\", \"33988718\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CRTC3 regulation of MITF is relevant in human melanogenesis disorders is untested\", \"In vivo confirmation of CRTC3-dependent drug resistance in melanoma is lacking\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"CRTC3 function was extended to brain circuitry and cancer metabolism: astrocyte-specific CRTC3 drives amphiregulin expression to maintain prefrontal-parietal connectivity and social dominance, while in hepatocellular carcinoma CRTC3 loss rewires lipid metabolism toward PUFA accumulation and ferroptosis sensitivity.\",\n      \"evidence\": \"Astrocyte-specific CRTC3 KO with amphiregulin rescue and functional connectivity imaging; CRISPR screen in HCC lines with lipidomics and in vivo tumor models\",\n      \"pmids\": [\"37730843\", \"37666810\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct CRTC3 transcriptional targets controlling lipid remodeling in HCC are not identified\", \"Human relevance of astrocytic CRTC3 in social behavior is unknown\", \"Mechanism linking CRTC3 loss to PUFA accumulation not defined\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"A non-transcriptional function of CRTC3 was uncovered: direct interaction with SARS-CoV-2 NSP12 attenuates RNA-dependent RNA polymerase activity and restricts viral replication, with CREB antagonizing this restriction.\",\n      \"evidence\": \"Co-IP of CRTC3 with NSP12, RdRp activity assays, CRTC3 OE/KO viral replication assays\",\n      \"pmids\": [\"39736320\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether CRTC3 inhibits RdRp via direct catalytic interference or allosteric mechanism is unknown\", \"Physiological relevance in human SARS-CoV-2 infection not established\", \"How CREB antagonizes the antiviral function of CRTC3 is mechanistically undefined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"A post-translational activation mode was defined: PRMT1-mediated methylation at R534 in the CRTC3 transactivation domain redirects CRTC3 to cooperate with FOXO3a (rather than CREB) to transactivate BAX and promote apoptosis, linking CRTC3 to muscle atrophy.\",\n      \"evidence\": \"IP-MS identification of R534 methylation, Co-IP of CRTC3-FOXO3a, R534 mutagenesis, PRMT1 inhibition, BAX inhibitor rescue in vivo\",\n      \"pmids\": [\"40192801\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether R534 methylation occurs in tissues beyond muscle is unknown\", \"Structural basis for how methylation switches CRTC3 partner preference from CREB to FOXO3a is unresolved\", \"Independent replication is needed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of CRTC3's selective use of PP2A B55 over calcineurin, whether R534 methylation represents a general partner-switching mechanism across tissues, and how CRTC3 achieves target gene specificity when coactivating different transcription factors (CREB, C/EBPβ, MITF, FOXO3a) in distinct cell types.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No high-resolution structural data for CRTC3 or its complexes exist\", \"Genome-wide identification of direct CRTC3 target genes across tissues has not been performed\", \"Relative contributions of CRTC3 versus CRTC1/CRTC2 in most tissues are poorly defined\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 1, 2, 4, 5, 9, 11, 13]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1, 3]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1, 3, 4, 7, 15]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0074160\", \"supporting_discovery_ids\": [0, 1, 2, 4, 9, 11, 13]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 2, 3, 7]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [0, 1, 15]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [13, 14]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [2, 6, 14]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CREB1\", \"SIK2\", \"PPP2CA\", \"CEBPB\", \"FOXO3\", \"PRMT1\", \"MITF\", \"YWHAZ\"],\n    \"other_free_text\": []\n  }\n}\n```"}