{"gene":"CRTC2","run_date":"2026-06-09T22:57:19","timeline":{"discoveries":[{"year":2005,"finding":"CRTC2 (TORC2) is sequestered in the cytoplasm under feeding conditions via phosphorylation-dependent interaction with 14-3-3 proteins, and is dephosphorylated and transported to the nucleus in response to fasting/glucagon stimuli where it enhances CREB-dependent transcription of gluconeogenic genes. AMPK activation promotes CRTC2 phosphorylation and blocks its nuclear accumulation, attenuating gluconeogenesis.","method":"Subcellular fractionation, reporter assays, adenoviral overexpression/knockdown in mice, pharmacological AMPK activation","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal co-IP, nuclear localization experiments, in vivo mouse models, replicated in multiple subsequent studies","pmids":["16148943"],"is_preprint":false},{"year":2004,"finding":"Under resting conditions, CRTC2 is sequestered in the cytoplasm via phosphorylation-dependent interaction with 14-3-3 proteins. The calcium-regulated phosphatase calcineurin and the Ser/Thr kinase SIK2 both associate with CRTC2. Calcium influx activates calcineurin to dephosphorylate CRTC2, while cAMP inhibits SIK2 kinase activity; together these signals promote CRTC2 nuclear entry and CREB coactivation.","method":"Co-immunoprecipitation, subcellular localization imaging, kinase assays, calcineurin inhibitor studies, SIK2 knockdown","journal":"Cell","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal methods (Co-IP, kinase assay, imaging, pharmacological), replicated across subsequent studies","pmids":["15454081"],"is_preprint":false},{"year":2007,"finding":"Insulin promotes phosphorylation and ubiquitin-dependent degradation of CRTC2 via induction of SIK2, which undergoes AKT2-mediated phosphorylation at Ser358. Activated SIK2 stimulates Ser171 phosphorylation and cytoplasmic translocation of CRTC2. Phosphorylated CRTC2 is degraded by the 26S proteasome through an association with COP1, an E3 ligase substrate receptor that promotes CRTC2 ubiquitination at Lys628.","method":"In vivo mouse studies, co-immunoprecipitation, site-directed mutagenesis (Ser171, Ser358, Lys628), ubiquitination assays, proteasome inhibitor experiments","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — mutagenesis of specific residues, Co-IP, in vivo validation, multiple orthogonal methods in one study","pmids":["17805301"],"is_preprint":false},{"year":2009,"finding":"CRTC2 functions as a dual sensor for ER stress and fasting signals. Acute ER stress triggers dephosphorylation and nuclear entry of CRTC2, which promotes expression of ER quality control genes through an association with ATF6α. ATF6α also disrupts the CREB-CRTC2 interaction, inhibiting CRTC2 occupancy over gluconeogenic genes and reducing hepatic glucose output.","method":"Co-immunoprecipitation, chromatin immunoprecipitation, adenoviral knockdown/overexpression in mouse liver, reporter assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, ChIP, in vivo mouse liver experiments, multiple orthogonal methods","pmids":["19543265"],"is_preprint":false},{"year":2008,"finding":"Glucose regulates CRTC2 phosphorylation at Ser275, a 14-3-3 binding site, in addition to the known Ser171 site. Calcineurin dephosphorylates Ser275 in response to glucose influx, and dephosphorylation of Ser275 is essential for both glucose- and cAMP-mediated activation of CREB in beta cells. MARK2, an AMPK family kinase, was identified as a Ser275 kinase.","method":"Cell-based kinase screen (180 human kinases), site-directed mutagenesis (Ser275), subcellular localization imaging, calcineurin inhibition, islet studies","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1-2 / Moderate — kinome screen plus mutagenesis plus functional imaging, single lab but multiple orthogonal methods","pmids":["18626018"],"is_preprint":false},{"year":2012,"finding":"The CREB-binding domain (CBD) of CRTC2 folds into a single isolated 28-residue helix that interacts with the CREB bZip domain. The CBD and CREB assemble on the CRE with 2:2:1 stoichiometry. Mutation of relevant bZip residues disrupts CRTC interaction without affecting DNA binding.","method":"NMR/structural analysis, mutagenesis, binding affinity measurements, reporter assays","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 1 / Moderate — structural determination with mutagenesis validation, single lab","pmids":["23213254"],"is_preprint":false},{"year":2018,"finding":"Crystal structures of a complex containing the CRTC2 CREB-binding domain, the CREB bZip domain and CRE-containing DNA revealed that CRTC and CREB form a 2:2 complex on CRE-containing DNA. CRTC2 interacts with both CREB and DNA through conserved residues, and the CRTC-DNA interaction confers selectivity toward intrinsic DNA shape. Structure-guided mutagenesis confirmed both interactions are required for complex assembly and CREB stabilization on DNA.","method":"X-ray crystallography, structure-guided mutagenesis, functional reporter assays","journal":"Journal of molecular biology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — crystal structure with mutagenesis and functional validation, single lab but multiple orthogonal methods","pmids":["29733854"],"is_preprint":false},{"year":2015,"finding":"CRTC2 functions as a mediator of mTOR signaling to modulate COPII-dependent SREBP1 processing for lipid synthesis. CRTC2 competes with Sec23A (COPII subunit) to interact with Sec31A (another COPII subunit), disrupting SREBP1 ER-to-Golgi transport. During feeding, mTOR phosphorylates CRTC2 and attenuates its inhibitory effect on COPII-dependent SREBP1 maturation.","method":"Co-immunoprecipitation, competition binding assays, adenoviral overexpression of mTOR-defective CRTC2 mutant in obese mice, SREBP1 processing assays","journal":"Nature","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal Co-IP, competition assay, in vivo mouse model with mutant, multiple orthogonal methods","pmids":["26147081"],"is_preprint":false},{"year":2010,"finding":"CRTC2 stimulates hepatic gene expression through an N-terminal CREB binding domain that enhances CREB occupancy over relevant gluconeogenic promoters. CRTC2 knockout mice have decreased circulating glucose during fasting due to attenuation of the gluconeogenic program.","method":"Genetic knockout mouse model, chromatin immunoprecipitation, reporter assays, glucose tolerance tests","journal":"Proceedings of the National Academy of Sciences of the United States of America","confidence":"High","confidence_rationale":"Tier 2 / Strong — KO mouse with defined metabolic phenotype, ChIP, replicated the established mechanism with loss-of-function genetics","pmids":["20133702"],"is_preprint":false},{"year":2009,"finding":"CRTC2 hyperactivation in the liver upregulates LIPIN1, a mammalian phosphatidic acid phosphatase for DAG synthesis, which then disturbs hepatic insulin signaling via DAG-PKCε activation. TORC2-mediated insulin resistance is partially rescued by concomitant knockdown of LIPIN1.","method":"Adenoviral overexpression/knockdown in mouse liver, DAG and PKCε activity measurements, genetic rescue experiments","journal":"Cell metabolism","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo mouse models with genetic rescue, single lab","pmids":["19254569"],"is_preprint":false},{"year":2010,"finding":"Pin1 associates with CRTC2 at Ser136 (located in the nuclear localization signal) and promotes cytoplasmic translocation of CRTC2, thereby suppressing CRE transcriptional activity. CRTC2 associated with Pin1 does not bind to CREB.","method":"Co-immunoprecipitation (endogenous and overexpressed), site-directed mutagenesis (Ser136), subcellular localization imaging, siRNA knockdown, adenoviral gene transfer in diabetic mice","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP of endogenous proteins, mutagenesis, localization imaging, single lab","pmids":["20675384"],"is_preprint":false},{"year":2015,"finding":"CRTC2 functions as a coactivator for the glucocorticoid receptor (GR) in addition to CREB. CRTC2 physically interacts with the ligand-binding domain of GR through a region spanning amino acids 561–693, and is required for GR-induced transcription of gluconeogenic genes (G6P, PEPCK).","method":"Co-immunoprecipitation, domain mapping with deletion mutants, chromatin immunoprecipitation, reporter assays, knockout mouse studies","journal":"Molecular endocrinology (Baltimore, Md.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, ChIP, reporter assays, single lab","pmids":["26652733"],"is_preprint":false},{"year":2015,"finding":"CRTC2 promotes Th17 cell differentiation via the CREB pathway in response to PGE2. Following dephosphorylation, CRTC2 stimulates expression of IL-17A and IL-17F by binding to CREB at both promoters. CRTC2-mutant mice have decreased Th17 cell numbers and are protected from experimental autoimmune encephalitis.","method":"Chromatin immunoprecipitation, CRTC2 knockout mouse model, Th17 differentiation assays, EAE model","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP, KO mouse phenotype, single lab with multiple methods","pmids":["26031354"],"is_preprint":false},{"year":2009,"finding":"CRTC2 nuclear localization and activity is regulated by AMPK-mediated phosphorylation in hypothalamic neurons. Glucose regulates hypothalamic CRTC2 activity via AMPK, and CRTC2 occupancy of the Irs2 promoter controls its expression. CRTC2 is required for appropriate expression of specific hypothalamic CRE genes.","method":"Subcellular fractionation, chromatin immunoprecipitation, adenoviral siRNA knockdown, metabolic assays","journal":"EMBO reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP, localization, knockdown with functional readout, single lab","pmids":["19713961"],"is_preprint":false},{"year":2009,"finding":"CRTC2 is required for CREB target gene activation in islet beta cells. CRTC2 activation is achieved by physiological increases in glucose via calcineurin-mediated dephosphorylation at Ser171 and Ser275. Constitutively active CRTC2 (S171A/S275A) rescues CREB target gene activation when calcineurin is inhibited by immunosuppressants.","method":"Site-directed mutagenesis (Ser171, Ser275), insulin secretion assays, glucose-stimulated reporter assays, calcineurin inhibitor experiments, beta cell survival assays","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phospho-site mutagenesis, functional beta cell assays, single lab","pmids":["23677932"],"is_preprint":false},{"year":2019,"finding":"CRTC2 is constitutively unphosphorylated and activated in LKB1-mutant NSCLC, where it promotes tumor growth via induction of ID1, a CREB target gene. LKB1 loss causes SIK inactivation leading to CRTC2 activation.","method":"Genetic analysis of LKB1-mutant cells, shRNA knockdown, chromatin immunoprecipitation, tumor growth assays","journal":"Science advances","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — KD with defined tumor phenotype, ChIP, epistasis analysis, single lab","pmids":["31355336"],"is_preprint":false},{"year":2009,"finding":"TORC2 (CRTC2) interacts with the EBV BZLF1 protein through both CREB-binding and BZLF1-dependent mechanisms, and is recruited to the BZLF1 promoter (Zp). Calcineurin-dependent dephosphorylation of TORC2 promotes its nuclear translocation to viral replication compartments and activation of viral lytic replication.","method":"Co-immunoprecipitation, chromatin immunoprecipitation, reporter assays, RNAi knockdown, immunofluorescence localization","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP, ChIP, reporter assays with endogenous knockdown, single lab","pmids":["19164291"],"is_preprint":false},{"year":2006,"finding":"CRTC2 (TORC2) physically interacts with HTLV-1 Tax protein and functions as a coactivator for Tax-dependent activation of HTLV-1 LTR. TORC coactivation requires CREB and depletion of TORC1/2/3 inhibited Tax activity. TORC coactivation can be further enhanced by p300.","method":"Co-immunoprecipitation, reporter assays, siRNA knockdown, luciferase assays","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — Co-IP, reporter assays, knockdown, single lab with multiple methods","pmids":["16809310"],"is_preprint":false},{"year":2010,"finding":"TORC2 (CRTC2) cooperates with phosphorylated CREB and p300 to activate CRE-dependent cyclin D1 transcription in response to HTLV-1 Tax. Tax-pCREB complex recruits p300, and TORC2 further enhances p300 recruitment to the cyclin D1 promoter.","method":"In vitro binding assays, chromatin immunoprecipitation, reporter assays, co-immunoprecipitation","journal":"Oncogene","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — ChIP, in vitro binding, reporter assays, single lab","pmids":["20101207"],"is_preprint":false},{"year":2023,"finding":"LKB1 loss triggers elevated CRTC2-CREB signaling downstream of salt-inducible kinases (SIKs), increasing inflammatory gene expression. Mechanistically, CRTC2 cooperates with histone acetyltransferases CBP/p300 to deposit H3K27ac marks at inflammatory gene loci (cytokine/chemokine genes), promoting cytokine expression. This defines an anti-inflammatory program regulated by LKB1 through CRTC2-dependent histone modification.","method":"ChIP-seq, H3K27ac profiling, CRTC2 knockdown/overexpression, LKB1 knockout cells, cytokine secretion assays, co-immunoprecipitation with CBP/p300","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — ChIP-seq, epigenome profiling, genetic KO, multiple orthogonal methods","pmids":["37172591"],"is_preprint":false},{"year":2021,"finding":"Sam68 interacts with CRTC2, reduces CRTC2 ubiquitination, and stabilizes CRTC2 protein (not mRNA) levels, thereby promoting hepatic gluconeogenesis. Sam68 truncation mutants lacking C-terminal (Sam68ΔC) or N-terminal (Sam68ΔN) domains fail to bind CRTC2 or stabilize CRTC2 protein respectively.","method":"Co-immunoprecipitation, domain-mapping with deletion mutants, ubiquitination assays, global and hepatic Sam68 KO mice, gluconeogenesis assays","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — Co-IP with domain mapping, ubiquitination assay, KO mouse, single lab","pmids":["34099657"],"is_preprint":false},{"year":2014,"finding":"Glucagon activates the CREB/CRTC2 transcriptional complex, which is recruited to the Bmal1 promoter to induce its expression. CRTC2 is required for basal transcriptional regulation of Bmal1 as demonstrated by adenovirus-mediated CRTC2 RNAi knockdown and primary Crtc2 null hepatocytes. Insulin suppresses fasting-induced Bmal1 expression by inhibiting CRTC2 activity.","method":"Chromatin immunoprecipitation, adenoviral RNAi knockdown, Crtc2 null primary hepatocytes, reporter assays","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP, KO hepatocytes, knockdown, single lab","pmids":["25480789"],"is_preprint":false},{"year":2012,"finding":"CRTC2 dephosphorylation and nuclear translocation mediated by FSH-induced calcineurin activation promotes steroidogenic gene expression (StAR, P450scc, 3β-HSD) in granulosa cells. TGFβ1 augments FSH action through calcineurin in a PKA-independent manner. ChIP confirmed CRTC2, CREB, and CBP binding to steroidogenic gene promoters.","method":"Chromatin immunoprecipitation, co-immunoprecipitation, immunofluorescence, calcineurin inhibitor studies, progesterone synthesis assays","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — ChIP, Co-IP, immunofluorescence, pharmacological inhibition, single lab","pmids":["21826657"],"is_preprint":false},{"year":2015,"finding":"Loss of CRTC2 results in deficiency in DNA mismatch repair (MMR) and increased mutation frequency. CRTC2, together with CREB1 and CBP, directly activates transcription of MMR genes including EXO1, MSH6, PMS1, and POLD2.","method":"CRTC2 knockdown/overexpression, chromatin immunoprecipitation, mutation frequency assays, MMR gene expression analysis, patient sample analysis","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ChIP showing CRTC2 at MMR gene promoters, functional mutation assay, single lab","pmids":["26004186"],"is_preprint":false},{"year":2020,"finding":"FXR overexpression in hippocampal CA1 induces cytoplasmic translocation of CRTC2, thereby disrupting CREB-BDNF signaling and producing depression-like behaviors. FXR shRNA prevented CUS-induced cytoplasmic translocation of CRTC2. CRTC2 overexpression and shRNA abrogated the regulatory effect of FXR manipulations on depression-like behaviors, placing CRTC2 downstream of FXR in this pathway.","method":"Viral-mediated gene transfer (FXR overexpression/shRNA, CRTC2 overexpression/shRNA), co-immunoprecipitation, immunofluorescence, behavioral testing","journal":"The international journal of neuropsychopharmacology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — viral genetic epistasis with defined behavioral phenotype, Co-IP, localization imaging, single lab","pmids":["32453814"],"is_preprint":false},{"year":2022,"finding":"ER stress reduces nuclear levels of CRTC2 in skeletal muscle via mTOR/S6K1 signaling. The mTOR inhibitor torin 1 restored CRTC2 and PGC-1α protein levels. siRNA against S6K1 (an mTORC1 downstream target) prevented the ER-stress-induced reduction in CRTC2 and PGC-1α expression, placing CRTC2 downstream of mTORC1-S6K1 in this pathway.","method":"siRNA knockdown of S6K1, mTOR inhibitor (torin 1), Western blot, nuclear fractionation, human myotubes and mouse skeletal muscle","journal":"Cell communication and signaling : CCS","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — genetic epistasis (siRNA) with defined phenotype, pharmacological validation, single lab","pmids":["35428325"],"is_preprint":false},{"year":2018,"finding":"CRTC2 controls GLP-1 secretion in intestinal L cells by transcriptionally regulating not only proglucagon but also PC1/3 (the endopeptidase for GLP-1 maturation) and PGC-1α (regulating mitochondrial ATP production and calcium levels required for exocytosis). Intestine-specific CRTC2 KO mice display reduced GLP-1 levels, impaired glucose tolerance, and decreased pancreatic β cells.","method":"Intestine-specific CRTC2 KO mice, chromatin immunoprecipitation, reporter assays, GLP-1 secretion assays, ATP/calcium measurements","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific KO with defined metabolic phenotype, ChIP, mechanistic follow-up, single lab","pmids":["29118086"],"is_preprint":false},{"year":2017,"finding":"Hepatic CRTC2 negatively regulates the Sirt1/Pparα/Fgf21 axis by inducing miR-34a expression, thereby controlling whole-body energy metabolism. Liver-specific CRTC2 KO reduces miR-34a, which increases Sirt1/Pparα activity and hepatic/plasma Fgf21. Ectopic expression of miR-34a reverses the metabolic changes in KO liver.","method":"Liver-specific CRTC2 KO mice, miR-34a overexpression (rescue), metabolic phenotyping, ChIP for CREB/CRTC2 at miR-34a locus","journal":"Nature communications","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific KO with genetic rescue, ChIP, single lab","pmids":["29192248"],"is_preprint":false},{"year":2009,"finding":"VIP activates HCMV MIE gene expression through the PKA-CREB-TORC2 signaling cascade. VIP induces PKA-dependent CRTC2 Ser171 dephosphorylation and nuclear entry. A CRTC2 S171A mutant (devoid of Ser171 phosphorylation) exhibits enhanced nuclear entry and desilences MIE genes in the absence of VIP stimulation.","method":"Site-directed mutagenesis (Ser171), nuclear localization imaging, reporter assays, PKA inhibitor studies","journal":"Journal of virology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — mutagenesis of key regulatory site with functional readout, localization imaging, single lab","pmids":["19369332"],"is_preprint":false},{"year":2014,"finding":"Metformin inhibits StAR expression in endometriotic stromal cells by increasing AMPK phosphorylation, which prevents nuclear translocation of CRTC2 and disrupts formation of the CREB-CRTC2 complex, thereby inhibiting transcription of StAR by reducing CREB-CRTC2 binding to the StAR promoter CRE.","method":"Co-immunoprecipitation, chromatin immunoprecipitation, subcellular localization imaging, AMPK activation assays, CRTC2 localization by Western blot","journal":"The Journal of clinical endocrinology and metabolism","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP, ChIP, localization imaging, pharmacological manipulation, single lab","pmids":["24823468"],"is_preprint":false},{"year":2020,"finding":"PFOS decreases interaction between CREB and CRTC2 and binding of CREB/CRTC2 to the StAR promoter region via activation of p38 MAPK and PKA pathways, leading to decreased testosterone biosynthesis.","method":"Co-immunoprecipitation, chromatin immunoprecipitation, Western blot, inhibitors (SB203580 for p38, H89 for PKA), in vivo and in vitro models","journal":"Toxicology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — Co-IP and ChIP without detailed mechanistic dissection of direct vs indirect effects, single lab","pmids":["33359577"],"is_preprint":false},{"year":2018,"finding":"mTORC1 suppresses COX-2 expression in adipocytes by phosphorylating CRTC2, causing dissociation of CREB from the cox-2 promoter. Adipose-specific Raptor depletion relieves this suppression, promoting COX-2-derived prostaglandin synthesis and beige adipogenesis.","method":"Adipose-specific Raptor KO mice, adenoviral CRTC2 overexpression, chromatin immunoprecipitation, COX-2 reporter assays","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — tissue-specific KO, ChIP, reporter assay, single lab","pmids":["30232001"],"is_preprint":false},{"year":2017,"finding":"TSH activates CRTC2 via TSHR/cAMP/PKA pathway: TSH stimulates CRTC2 dephosphorylation and increases CRTC2 expression. CRTC2 forms a complex with CREB, and this complex drives hepatic gluconeogenic gene expression. Deletion of TSHR reduces levels of the CRTC2:CREB complex in mouse livers.","method":"Co-immunoprecipitation, reporter assays (PEPCK-luciferase), siRNA knockdown, Western blot, TSHR KO mice","journal":"Molecular and cellular endocrinology","confidence":"Medium","confidence_rationale":"Tier 2-3 / Moderate — Co-IP, reporter assays, genetic KO, single lab","pmids":["28212844"],"is_preprint":false}],"current_model":"CRTC2 is a phosphorylation-regulated transcriptional coactivator that, under basal/fed conditions, is sequestered in the cytoplasm via 14-3-3 binding to phosphorylated Ser171 and Ser275; upon fasting, glucagon-induced cAMP inhibits SIK2 while calcium activates calcineurin to dephosphorylate both sites, allowing nuclear translocation where CRTC2's N-terminal CREB-binding domain (a 28-residue helix) directly contacts the CREB bZip in a 2:2:1 stoichiometry on CRE promoters to drive gluconeogenic gene expression; insulin reverses this by inducing AKT2-activated SIK2 to re-phosphorylate CRTC2 at Ser171, leading to COP1-mediated ubiquitination at Lys628 and 26S proteasomal degradation; beyond gluconeogenesis, CRTC2 also modulates hepatic lipid synthesis by competing with COPII subunit Sec23A for Sec31A binding to inhibit SREBP1 processing (relieved by mTOR phosphorylation during feeding), cooperates with GR, ATF6α, and CBP/p300, regulates Th17 differentiation, MMR gene transcription, and inflammatory gene expression via H3K27ac deposition, and is activated in LKB1-deficient cancers through loss of SIK-mediated inhibitory phosphorylation."},"narrative":{"mechanistic_narrative":"CRTC2 (TORC2) is a phosphorylation-gated transcriptional coactivator that couples nutrient and hormonal signals to CREB-dependent gene programs, most prominently the hepatic gluconeogenic response to fasting [PMID:16148943, PMID:20133702]. Under fed/resting conditions it is held in the cytoplasm through phosphorylation-dependent 14-3-3 binding, with SIK2 and the phosphatase calcineurin both associating with CRTC2 to set its phosphorylation state at the 14-3-3 sites Ser171 and Ser275; fasting-induced cAMP inhibits SIK2 while calcium-activated calcineurin dephosphorylates these sites, driving nuclear entry and CREB coactivation [PMID:15454081, PMID:18626018]. Insulin reverses this by AKT2-dependent activation of SIK2, which rephosphorylates Ser171 and triggers COP1-mediated ubiquitination at Lys628 and 26S proteasomal degradation of CRTC2 [PMID:17805301]. In the nucleus, CRTC2's N-terminal CREB-binding domain folds into a single 28-residue helix that contacts the CREB bZip and CRE-containing DNA, assembling a 2:2 CRTC2–CREB complex on DNA that stabilizes CREB occupancy and confers DNA-shape selectivity [PMID:23213254, PMID:29733854]. Beyond gluconeogenesis, CRTC2 governs hepatic lipogenesis by competing with the COPII subunit Sec23A for Sec31A to restrain SREBP1 ER-to-Golgi processing, an inhibition relieved by mTOR phosphorylation during feeding [PMID:26147081], and acts as a broad CREB-axis coactivator across additional programs by partnering with CBP/p300 to deposit H3K27ac at inflammatory loci downstream of LKB1–SIK signaling [PMID:37172591] and by coactivating the glucocorticoid receptor [PMID:26652733]. Its activity is constitutively elevated in LKB1-deficient cancers, where loss of SIK-mediated inhibitory phosphorylation drives CREB target genes such as ID1 [PMID:31355336].","teleology":[{"year":2004,"claim":"Established the core regulatory logic of CRTC2: how opposing kinase and phosphatase inputs gate its cytoplasmic sequestration versus nuclear CREB coactivation.","evidence":"Co-IP, kinase assays, calcineurin inhibition and SIK2 knockdown with subcellular imaging","pmids":["15454081"],"confidence":"High","gaps":["Did not map the specific phospho-sites bound by 14-3-3","Physiological signal triggering calcineurin/SIK2 not yet placed in a whole-animal context"]},{"year":2005,"claim":"Placed CRTC2 in vivo as the fasting/glucagon-responsive driver of the hepatic gluconeogenic transcriptional program and identified AMPK as an opposing input.","evidence":"Subcellular fractionation, reporter assays and adenoviral gain/loss-of-function in mice with pharmacological AMPK activation","pmids":["16148943"],"confidence":"High","gaps":["Did not resolve how multiple kinases converge on the same 14-3-3 sites","Mechanism of insulin-mediated shut-off unresolved"]},{"year":2007,"claim":"Defined the insulin-driven OFF switch — how CRTC2 is targeted for degradation rather than merely re-exported.","evidence":"In vivo mouse studies, site-directed mutagenesis (Ser171, Ser358, Lys628), ubiquitination and proteasome-inhibitor assays","pmids":["17805301"],"confidence":"High","gaps":["Did not address regulation of COP1 activity itself","Relative contribution of degradation versus cytoplasmic retention to CRTC2 silencing not quantified"]},{"year":2008,"claim":"Extended the phospho-code beyond Ser171 by identifying Ser275 as a second glucose-regulated 14-3-3 site essential for CREB activation in beta cells.","evidence":"Cell-based kinase screen of 180 kinases, Ser275 mutagenesis, calcineurin inhibition and islet studies","pmids":["18626018"],"confidence":"High","gaps":["Hierarchy/interplay between Ser171 and Ser275 phosphorylation not fully resolved","Role of MARK2 in vivo not established"]},{"year":2009,"claim":"Broadened CRTC2 from a metabolic to a stress-integrating coactivator and showed ER stress can redirect it away from gluconeogenic genes via ATF6α.","evidence":"Reciprocal Co-IP, ChIP and adenoviral knockdown/overexpression in mouse liver","pmids":["19543265"],"confidence":"High","gaps":["Structural basis of ATF6α disruption of CREB-CRTC2 not defined","Whether ER-stress and fasting inputs are integrated at the same molecule simultaneously unclear"]},{"year":2010,"claim":"Confirmed by loss-of-function genetics that the N-terminal CREB-binding domain mediates promoter occupancy and is required for the fasting glucose response.","evidence":"CRTC2 knockout mice with ChIP, reporter assays and glucose tolerance tests","pmids":["20133702"],"confidence":"High","gaps":["Atomic detail of the CBD-CREB interface not yet resolved","Did not address CREB-independent CRTC2 functions"]},{"year":2012,"claim":"Resolved the molecular architecture of coactivation, showing the CBD is an isolated helix forming a defined 2:2:1 CRTC-CREB-CRE assembly.","evidence":"NMR/structural analysis, mutagenesis and binding-affinity measurements with reporter validation","pmids":["23213254"],"confidence":"High","gaps":["Did not capture direct CRTC2-DNA contacts","How phosphorylation alters the helix or its accessibility not addressed"]},{"year":2018,"claim":"Crystallography revealed that CRTC2 contacts DNA directly and reads intrinsic DNA shape, explaining promoter selectivity and CREB stabilization on the CRE.","evidence":"X-ray crystallography of the CBD-bZip-CRE complex with structure-guided mutagenesis and reporter assays","pmids":["29733854"],"confidence":"High","gaps":["Structure of full-length phospho-regulated CRTC2 not determined","How DNA-shape selectivity is modulated in vivo by chromatin unknown"]},{"year":2015,"claim":"Identified a transcription-independent CRTC2 function — control of hepatic lipogenesis by competing for COPII subunits to gate SREBP1 trafficking.","evidence":"Reciprocal/competition Co-IP, SREBP1 processing assays and adenoviral mTOR-defective CRTC2 mutant in obese mice","pmids":["26147081"],"confidence":"High","gaps":["Stoichiometry of CRTC2 versus Sec23A at COPII coats not quantified","Whether nuclear and ER pools of CRTC2 are distinct populations unresolved"]},{"year":2023,"claim":"Connected CRTC2 to chromatin modification, showing it recruits CBP/p300 to deposit H3K27ac at inflammatory loci downstream of LKB1-SIK signaling.","evidence":"ChIP-seq/H3K27ac profiling, LKB1 knockout cells, CRTC2 manipulation and Co-IP with CBP/p300","pmids":["37172591"],"confidence":"High","gaps":["Whether CRTC2 itself directs HAT specificity or is a passive scaffold unclear","Generality of CRTC2-driven H3K27ac beyond inflammatory genes not tested"]},{"year":2015,"claim":"Expanded the transcription-factor partner repertoire beyond CREB by showing CRTC2 coactivates the glucocorticoid receptor for gluconeogenic genes.","evidence":"Co-IP with domain mapping (aa 561–693 to GR LBD), ChIP, reporter assays and knockout mice","pmids":["26652733"],"confidence":"Medium","gaps":["Single lab; reciprocal structural validation of the GR interface absent","Whether GR and CREB coactivation occur on shared or distinct promoters not resolved"]},{"year":2019,"claim":"Demonstrated a pathological gain-of-function: constitutive CRTC2 activation in LKB1-mutant cancer drives tumor growth through CREB target genes.","evidence":"LKB1-mutant NSCLC analysis, shRNA knockdown, ChIP and tumor growth assays","pmids":["31355336"],"confidence":"Medium","gaps":["Single-lab epistasis; direct dependence on SIK reactivation not fully separated from other LKB1 effectors","Breadth of CRTC2-dependent oncogenic targets beyond ID1 not defined"]},{"year":2021,"claim":"Identified Sam68 as a stabilizing partner that limits CRTC2 ubiquitination, adding a post-translational tuning node controlling gluconeogenesis.","evidence":"Co-IP with deletion mapping, ubiquitination assays and global/hepatic Sam68 KO mice","pmids":["34099657"],"confidence":"Medium","gaps":["Single lab; how Sam68 competes with COP1 mechanistically not defined","Whether Sam68 acts on cytoplasmic or nuclear CRTC2 unclear"]},{"year":null,"claim":"How the many context-specific CRTC2 functions (lipogenesis, chromatin marking, GR/ATF6α/viral coactivation, neuronal and reproductive programs) are partitioned within a single cell — and what determines partner and promoter selectivity beyond phosphorylation state — remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No unified model linking the cytoplasmic COPII-gating role to nuclear coactivation","Determinants of transcription-factor partner choice (CREB vs GR vs ATF6α) not established","Structure of phospho-regulated full-length CRTC2 unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140110","term_label":"transcription regulator activity","supporting_discovery_ids":[0,5,6,8]},{"term_id":"GO:0003677","term_label":"DNA binding","supporting_discovery_ids":[6]},{"term_id":"GO:0060090","term_label":"molecular adaptor activity","supporting_discovery_ids":[5,6,19]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[7]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,1]},{"term_id":"GO:0005634","term_label":"nucleus","supporting_discovery_ids":[0,1,8]},{"term_id":"GO:0005783","term_label":"endoplasmic reticulum","supporting_discovery_ids":[7]}],"pathway":[{"term_id":"R-HSA-74160","term_label":"Gene expression 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activation and PKB substrate phosphorylation in Dictyostelium.","date":"2009","source":"Methods in molecular biology (Clifton, N.J.)","url":"https://pubmed.ncbi.nlm.nih.gov/19763972","citation_count":30,"is_preprint":false},{"pmid":"31893525","id":"PMC_31893525","title":"RNA-seq reveal role of bovine TORC2 in the regulation of adipogenesis.","date":"2019","source":"Archives of biochemistry and biophysics","url":"https://pubmed.ncbi.nlm.nih.gov/31893525","citation_count":29,"is_preprint":false},{"pmid":"26342077","id":"PMC_26342077","title":"Hepatic Insulin Resistance Following Chronic Activation of the CREB Coactivator CRTC2.","date":"2015","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/26342077","citation_count":28,"is_preprint":false},{"pmid":"26452980","id":"PMC_26452980","title":"Co-administration of the mTORC1/TORC2 inhibitor INK128 and the Bcl-2/Bcl-xL antagonist ABT-737 kills human myeloid leukemia cells through Mcl-1 down-regulation and AKT inactivation.","date":"2015","source":"Haematologica","url":"https://pubmed.ncbi.nlm.nih.gov/26452980","citation_count":28,"is_preprint":false},{"pmid":"23393158","id":"PMC_23393158","title":"Tuberous sclerosis complex regulates Drosophila neuromuscular junction growth via the TORC2/Akt pathway.","date":"2013","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/23393158","citation_count":28,"is_preprint":false},{"pmid":"24360963","id":"PMC_24360963","title":"Chemical genetics of rapamycin-insensitive TORC2 in S. cerevisiae.","date":"2013","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/24360963","citation_count":27,"is_preprint":false},{"pmid":"19381067","id":"PMC_19381067","title":"Adiponectin and thiazolidinedione targets CRTC2 to regulate hepatic gluconeogenesis.","date":"2009","source":"Experimental & molecular 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endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/25057110","citation_count":26,"is_preprint":false},{"pmid":"24054871","id":"PMC_24054871","title":"The combination of an mTORc1/TORc2 inhibitor with lapatinib is synergistic in bladder cancer in vitro.","date":"2013","source":"Urologic oncology","url":"https://pubmed.ncbi.nlm.nih.gov/24054871","citation_count":25,"is_preprint":false},{"pmid":"35428325","id":"PMC_35428325","title":"Endoplasmic reticulum stress downregulates PGC-1α in skeletal muscle through ATF4 and an mTOR-mediated reduction of CRTC2.","date":"2022","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/35428325","citation_count":25,"is_preprint":false},{"pmid":"32174060","id":"PMC_32174060","title":"Role of CRTC2 in Metabolic Homeostasis: Key Regulator of Whole-Body Energy Metabolism?","date":"2020","source":"Diabetes & metabolism 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increases glucose uptake via phosphorylation of CRTC2 and HDAC5.","date":"2015","source":"Bioorganic & medicinal chemistry letters","url":"https://pubmed.ncbi.nlm.nih.gov/26471090","citation_count":23,"is_preprint":false},{"pmid":"26489398","id":"PMC_26489398","title":"TORC2: a novel target for treating age-associated memory impairment.","date":"2015","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/26489398","citation_count":23,"is_preprint":false},{"pmid":"25662274","id":"PMC_25662274","title":"Stimulation of StAR expression by cAMP is controlled by inhibition of highly inducible SIK1 via CRTC2, a co-activator of CREB.","date":"2015","source":"Molecular and cellular endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/25662274","citation_count":23,"is_preprint":false},{"pmid":"26004186","id":"PMC_26004186","title":"The CREB Coactivator CRTC2 Is a Lymphoma Tumor Suppressor that Preserves Genome Integrity through Transcription of DNA Mismatch Repair Genes.","date":"2015","source":"Cell reports","url":"https://pubmed.ncbi.nlm.nih.gov/26004186","citation_count":23,"is_preprint":false},{"pmid":"27899413","id":"PMC_27899413","title":"Calcium channel regulator Mid1 links TORC2-mediated changes in mitochondrial respiration to autophagy.","date":"2016","source":"The Journal of cell biology","url":"https://pubmed.ncbi.nlm.nih.gov/27899413","citation_count":22,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":50477,"output_tokens":8403,"usd":0.138738,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":18002,"output_tokens":4507,"usd":0.101343,"stage2_stop_reason":"end_turn"},"total_usd":0.240081,"stage1_batch_id":"msgbatch_01ACAxJQabDsht39JXeWG22d","stage2_batch_id":"msgbatch_01QEU22A9U5sbPTgsMzTmvSf","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2005,\n      \"finding\": \"CRTC2 (TORC2) is sequestered in the cytoplasm under feeding conditions via phosphorylation-dependent interaction with 14-3-3 proteins, and is dephosphorylated and transported to the nucleus in response to fasting/glucagon stimuli where it enhances CREB-dependent transcription of gluconeogenic genes. AMPK activation promotes CRTC2 phosphorylation and blocks its nuclear accumulation, attenuating gluconeogenesis.\",\n      \"method\": \"Subcellular fractionation, reporter assays, adenoviral overexpression/knockdown in mice, pharmacological AMPK activation\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal co-IP, nuclear localization experiments, in vivo mouse models, replicated in multiple subsequent studies\",\n      \"pmids\": [\"16148943\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2004,\n      \"finding\": \"Under resting conditions, CRTC2 is sequestered in the cytoplasm via phosphorylation-dependent interaction with 14-3-3 proteins. The calcium-regulated phosphatase calcineurin and the Ser/Thr kinase SIK2 both associate with CRTC2. Calcium influx activates calcineurin to dephosphorylate CRTC2, while cAMP inhibits SIK2 kinase activity; together these signals promote CRTC2 nuclear entry and CREB coactivation.\",\n      \"method\": \"Co-immunoprecipitation, subcellular localization imaging, kinase assays, calcineurin inhibitor studies, SIK2 knockdown\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal methods (Co-IP, kinase assay, imaging, pharmacological), replicated across subsequent studies\",\n      \"pmids\": [\"15454081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Insulin promotes phosphorylation and ubiquitin-dependent degradation of CRTC2 via induction of SIK2, which undergoes AKT2-mediated phosphorylation at Ser358. Activated SIK2 stimulates Ser171 phosphorylation and cytoplasmic translocation of CRTC2. Phosphorylated CRTC2 is degraded by the 26S proteasome through an association with COP1, an E3 ligase substrate receptor that promotes CRTC2 ubiquitination at Lys628.\",\n      \"method\": \"In vivo mouse studies, co-immunoprecipitation, site-directed mutagenesis (Ser171, Ser358, Lys628), ubiquitination assays, proteasome inhibitor experiments\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — mutagenesis of specific residues, Co-IP, in vivo validation, multiple orthogonal methods in one study\",\n      \"pmids\": [\"17805301\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CRTC2 functions as a dual sensor for ER stress and fasting signals. Acute ER stress triggers dephosphorylation and nuclear entry of CRTC2, which promotes expression of ER quality control genes through an association with ATF6α. ATF6α also disrupts the CREB-CRTC2 interaction, inhibiting CRTC2 occupancy over gluconeogenic genes and reducing hepatic glucose output.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation, adenoviral knockdown/overexpression in mouse liver, reporter assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, ChIP, in vivo mouse liver experiments, multiple orthogonal methods\",\n      \"pmids\": [\"19543265\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"Glucose regulates CRTC2 phosphorylation at Ser275, a 14-3-3 binding site, in addition to the known Ser171 site. Calcineurin dephosphorylates Ser275 in response to glucose influx, and dephosphorylation of Ser275 is essential for both glucose- and cAMP-mediated activation of CREB in beta cells. MARK2, an AMPK family kinase, was identified as a Ser275 kinase.\",\n      \"method\": \"Cell-based kinase screen (180 human kinases), site-directed mutagenesis (Ser275), subcellular localization imaging, calcineurin inhibition, islet studies\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Moderate — kinome screen plus mutagenesis plus functional imaging, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"18626018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"The CREB-binding domain (CBD) of CRTC2 folds into a single isolated 28-residue helix that interacts with the CREB bZip domain. The CBD and CREB assemble on the CRE with 2:2:1 stoichiometry. Mutation of relevant bZip residues disrupts CRTC interaction without affecting DNA binding.\",\n      \"method\": \"NMR/structural analysis, mutagenesis, binding affinity measurements, reporter assays\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — structural determination with mutagenesis validation, single lab\",\n      \"pmids\": [\"23213254\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Crystal structures of a complex containing the CRTC2 CREB-binding domain, the CREB bZip domain and CRE-containing DNA revealed that CRTC and CREB form a 2:2 complex on CRE-containing DNA. CRTC2 interacts with both CREB and DNA through conserved residues, and the CRTC-DNA interaction confers selectivity toward intrinsic DNA shape. Structure-guided mutagenesis confirmed both interactions are required for complex assembly and CREB stabilization on DNA.\",\n      \"method\": \"X-ray crystallography, structure-guided mutagenesis, functional reporter assays\",\n      \"journal\": \"Journal of molecular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — crystal structure with mutagenesis and functional validation, single lab but multiple orthogonal methods\",\n      \"pmids\": [\"29733854\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CRTC2 functions as a mediator of mTOR signaling to modulate COPII-dependent SREBP1 processing for lipid synthesis. CRTC2 competes with Sec23A (COPII subunit) to interact with Sec31A (another COPII subunit), disrupting SREBP1 ER-to-Golgi transport. During feeding, mTOR phosphorylates CRTC2 and attenuates its inhibitory effect on COPII-dependent SREBP1 maturation.\",\n      \"method\": \"Co-immunoprecipitation, competition binding assays, adenoviral overexpression of mTOR-defective CRTC2 mutant in obese mice, SREBP1 processing assays\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal Co-IP, competition assay, in vivo mouse model with mutant, multiple orthogonal methods\",\n      \"pmids\": [\"26147081\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"CRTC2 stimulates hepatic gene expression through an N-terminal CREB binding domain that enhances CREB occupancy over relevant gluconeogenic promoters. CRTC2 knockout mice have decreased circulating glucose during fasting due to attenuation of the gluconeogenic program.\",\n      \"method\": \"Genetic knockout mouse model, chromatin immunoprecipitation, reporter assays, glucose tolerance tests\",\n      \"journal\": \"Proceedings of the National Academy of Sciences of the United States of America\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — KO mouse with defined metabolic phenotype, ChIP, replicated the established mechanism with loss-of-function genetics\",\n      \"pmids\": [\"20133702\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CRTC2 hyperactivation in the liver upregulates LIPIN1, a mammalian phosphatidic acid phosphatase for DAG synthesis, which then disturbs hepatic insulin signaling via DAG-PKCε activation. TORC2-mediated insulin resistance is partially rescued by concomitant knockdown of LIPIN1.\",\n      \"method\": \"Adenoviral overexpression/knockdown in mouse liver, DAG and PKCε activity measurements, genetic rescue experiments\",\n      \"journal\": \"Cell metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo mouse models with genetic rescue, single lab\",\n      \"pmids\": [\"19254569\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Pin1 associates with CRTC2 at Ser136 (located in the nuclear localization signal) and promotes cytoplasmic translocation of CRTC2, thereby suppressing CRE transcriptional activity. CRTC2 associated with Pin1 does not bind to CREB.\",\n      \"method\": \"Co-immunoprecipitation (endogenous and overexpressed), site-directed mutagenesis (Ser136), subcellular localization imaging, siRNA knockdown, adenoviral gene transfer in diabetic mice\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP of endogenous proteins, mutagenesis, localization imaging, single lab\",\n      \"pmids\": [\"20675384\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CRTC2 functions as a coactivator for the glucocorticoid receptor (GR) in addition to CREB. CRTC2 physically interacts with the ligand-binding domain of GR through a region spanning amino acids 561–693, and is required for GR-induced transcription of gluconeogenic genes (G6P, PEPCK).\",\n      \"method\": \"Co-immunoprecipitation, domain mapping with deletion mutants, chromatin immunoprecipitation, reporter assays, knockout mouse studies\",\n      \"journal\": \"Molecular endocrinology (Baltimore, Md.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, ChIP, reporter assays, single lab\",\n      \"pmids\": [\"26652733\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"CRTC2 promotes Th17 cell differentiation via the CREB pathway in response to PGE2. Following dephosphorylation, CRTC2 stimulates expression of IL-17A and IL-17F by binding to CREB at both promoters. CRTC2-mutant mice have decreased Th17 cell numbers and are protected from experimental autoimmune encephalitis.\",\n      \"method\": \"Chromatin immunoprecipitation, CRTC2 knockout mouse model, Th17 differentiation assays, EAE model\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP, KO mouse phenotype, single lab with multiple methods\",\n      \"pmids\": [\"26031354\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CRTC2 nuclear localization and activity is regulated by AMPK-mediated phosphorylation in hypothalamic neurons. Glucose regulates hypothalamic CRTC2 activity via AMPK, and CRTC2 occupancy of the Irs2 promoter controls its expression. CRTC2 is required for appropriate expression of specific hypothalamic CRE genes.\",\n      \"method\": \"Subcellular fractionation, chromatin immunoprecipitation, adenoviral siRNA knockdown, metabolic assays\",\n      \"journal\": \"EMBO reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP, localization, knockdown with functional readout, single lab\",\n      \"pmids\": [\"19713961\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"CRTC2 is required for CREB target gene activation in islet beta cells. CRTC2 activation is achieved by physiological increases in glucose via calcineurin-mediated dephosphorylation at Ser171 and Ser275. Constitutively active CRTC2 (S171A/S275A) rescues CREB target gene activation when calcineurin is inhibited by immunosuppressants.\",\n      \"method\": \"Site-directed mutagenesis (Ser171, Ser275), insulin secretion assays, glucose-stimulated reporter assays, calcineurin inhibitor experiments, beta cell survival assays\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phospho-site mutagenesis, functional beta cell assays, single lab\",\n      \"pmids\": [\"23677932\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"CRTC2 is constitutively unphosphorylated and activated in LKB1-mutant NSCLC, where it promotes tumor growth via induction of ID1, a CREB target gene. LKB1 loss causes SIK inactivation leading to CRTC2 activation.\",\n      \"method\": \"Genetic analysis of LKB1-mutant cells, shRNA knockdown, chromatin immunoprecipitation, tumor growth assays\",\n      \"journal\": \"Science advances\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — KD with defined tumor phenotype, ChIP, epistasis analysis, single lab\",\n      \"pmids\": [\"31355336\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"TORC2 (CRTC2) interacts with the EBV BZLF1 protein through both CREB-binding and BZLF1-dependent mechanisms, and is recruited to the BZLF1 promoter (Zp). Calcineurin-dependent dephosphorylation of TORC2 promotes its nuclear translocation to viral replication compartments and activation of viral lytic replication.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation, reporter assays, RNAi knockdown, immunofluorescence localization\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP, ChIP, reporter assays with endogenous knockdown, single lab\",\n      \"pmids\": [\"19164291\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"CRTC2 (TORC2) physically interacts with HTLV-1 Tax protein and functions as a coactivator for Tax-dependent activation of HTLV-1 LTR. TORC coactivation requires CREB and depletion of TORC1/2/3 inhibited Tax activity. TORC coactivation can be further enhanced by p300.\",\n      \"method\": \"Co-immunoprecipitation, reporter assays, siRNA knockdown, luciferase assays\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — Co-IP, reporter assays, knockdown, single lab with multiple methods\",\n      \"pmids\": [\"16809310\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"TORC2 (CRTC2) cooperates with phosphorylated CREB and p300 to activate CRE-dependent cyclin D1 transcription in response to HTLV-1 Tax. Tax-pCREB complex recruits p300, and TORC2 further enhances p300 recruitment to the cyclin D1 promoter.\",\n      \"method\": \"In vitro binding assays, chromatin immunoprecipitation, reporter assays, co-immunoprecipitation\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — ChIP, in vitro binding, reporter assays, single lab\",\n      \"pmids\": [\"20101207\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"LKB1 loss triggers elevated CRTC2-CREB signaling downstream of salt-inducible kinases (SIKs), increasing inflammatory gene expression. Mechanistically, CRTC2 cooperates with histone acetyltransferases CBP/p300 to deposit H3K27ac marks at inflammatory gene loci (cytokine/chemokine genes), promoting cytokine expression. This defines an anti-inflammatory program regulated by LKB1 through CRTC2-dependent histone modification.\",\n      \"method\": \"ChIP-seq, H3K27ac profiling, CRTC2 knockdown/overexpression, LKB1 knockout cells, cytokine secretion assays, co-immunoprecipitation with CBP/p300\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — ChIP-seq, epigenome profiling, genetic KO, multiple orthogonal methods\",\n      \"pmids\": [\"37172591\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Sam68 interacts with CRTC2, reduces CRTC2 ubiquitination, and stabilizes CRTC2 protein (not mRNA) levels, thereby promoting hepatic gluconeogenesis. Sam68 truncation mutants lacking C-terminal (Sam68ΔC) or N-terminal (Sam68ΔN) domains fail to bind CRTC2 or stabilize CRTC2 protein respectively.\",\n      \"method\": \"Co-immunoprecipitation, domain-mapping with deletion mutants, ubiquitination assays, global and hepatic Sam68 KO mice, gluconeogenesis assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — Co-IP with domain mapping, ubiquitination assay, KO mouse, single lab\",\n      \"pmids\": [\"34099657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Glucagon activates the CREB/CRTC2 transcriptional complex, which is recruited to the Bmal1 promoter to induce its expression. CRTC2 is required for basal transcriptional regulation of Bmal1 as demonstrated by adenovirus-mediated CRTC2 RNAi knockdown and primary Crtc2 null hepatocytes. Insulin suppresses fasting-induced Bmal1 expression by inhibiting CRTC2 activity.\",\n      \"method\": \"Chromatin immunoprecipitation, adenoviral RNAi knockdown, Crtc2 null primary hepatocytes, reporter assays\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP, KO hepatocytes, knockdown, single lab\",\n      \"pmids\": [\"25480789\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"CRTC2 dephosphorylation and nuclear translocation mediated by FSH-induced calcineurin activation promotes steroidogenic gene expression (StAR, P450scc, 3β-HSD) in granulosa cells. TGFβ1 augments FSH action through calcineurin in a PKA-independent manner. ChIP confirmed CRTC2, CREB, and CBP binding to steroidogenic gene promoters.\",\n      \"method\": \"Chromatin immunoprecipitation, co-immunoprecipitation, immunofluorescence, calcineurin inhibitor studies, progesterone synthesis assays\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — ChIP, Co-IP, immunofluorescence, pharmacological inhibition, single lab\",\n      \"pmids\": [\"21826657\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Loss of CRTC2 results in deficiency in DNA mismatch repair (MMR) and increased mutation frequency. CRTC2, together with CREB1 and CBP, directly activates transcription of MMR genes including EXO1, MSH6, PMS1, and POLD2.\",\n      \"method\": \"CRTC2 knockdown/overexpression, chromatin immunoprecipitation, mutation frequency assays, MMR gene expression analysis, patient sample analysis\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ChIP showing CRTC2 at MMR gene promoters, functional mutation assay, single lab\",\n      \"pmids\": [\"26004186\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"FXR overexpression in hippocampal CA1 induces cytoplasmic translocation of CRTC2, thereby disrupting CREB-BDNF signaling and producing depression-like behaviors. FXR shRNA prevented CUS-induced cytoplasmic translocation of CRTC2. CRTC2 overexpression and shRNA abrogated the regulatory effect of FXR manipulations on depression-like behaviors, placing CRTC2 downstream of FXR in this pathway.\",\n      \"method\": \"Viral-mediated gene transfer (FXR overexpression/shRNA, CRTC2 overexpression/shRNA), co-immunoprecipitation, immunofluorescence, behavioral testing\",\n      \"journal\": \"The international journal of neuropsychopharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — viral genetic epistasis with defined behavioral phenotype, Co-IP, localization imaging, single lab\",\n      \"pmids\": [\"32453814\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"ER stress reduces nuclear levels of CRTC2 in skeletal muscle via mTOR/S6K1 signaling. The mTOR inhibitor torin 1 restored CRTC2 and PGC-1α protein levels. siRNA against S6K1 (an mTORC1 downstream target) prevented the ER-stress-induced reduction in CRTC2 and PGC-1α expression, placing CRTC2 downstream of mTORC1-S6K1 in this pathway.\",\n      \"method\": \"siRNA knockdown of S6K1, mTOR inhibitor (torin 1), Western blot, nuclear fractionation, human myotubes and mouse skeletal muscle\",\n      \"journal\": \"Cell communication and signaling : CCS\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — genetic epistasis (siRNA) with defined phenotype, pharmacological validation, single lab\",\n      \"pmids\": [\"35428325\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"CRTC2 controls GLP-1 secretion in intestinal L cells by transcriptionally regulating not only proglucagon but also PC1/3 (the endopeptidase for GLP-1 maturation) and PGC-1α (regulating mitochondrial ATP production and calcium levels required for exocytosis). Intestine-specific CRTC2 KO mice display reduced GLP-1 levels, impaired glucose tolerance, and decreased pancreatic β cells.\",\n      \"method\": \"Intestine-specific CRTC2 KO mice, chromatin immunoprecipitation, reporter assays, GLP-1 secretion assays, ATP/calcium measurements\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific KO with defined metabolic phenotype, ChIP, mechanistic follow-up, single lab\",\n      \"pmids\": [\"29118086\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Hepatic CRTC2 negatively regulates the Sirt1/Pparα/Fgf21 axis by inducing miR-34a expression, thereby controlling whole-body energy metabolism. Liver-specific CRTC2 KO reduces miR-34a, which increases Sirt1/Pparα activity and hepatic/plasma Fgf21. Ectopic expression of miR-34a reverses the metabolic changes in KO liver.\",\n      \"method\": \"Liver-specific CRTC2 KO mice, miR-34a overexpression (rescue), metabolic phenotyping, ChIP for CREB/CRTC2 at miR-34a locus\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific KO with genetic rescue, ChIP, single lab\",\n      \"pmids\": [\"29192248\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"VIP activates HCMV MIE gene expression through the PKA-CREB-TORC2 signaling cascade. VIP induces PKA-dependent CRTC2 Ser171 dephosphorylation and nuclear entry. A CRTC2 S171A mutant (devoid of Ser171 phosphorylation) exhibits enhanced nuclear entry and desilences MIE genes in the absence of VIP stimulation.\",\n      \"method\": \"Site-directed mutagenesis (Ser171), nuclear localization imaging, reporter assays, PKA inhibitor studies\",\n      \"journal\": \"Journal of virology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — mutagenesis of key regulatory site with functional readout, localization imaging, single lab\",\n      \"pmids\": [\"19369332\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Metformin inhibits StAR expression in endometriotic stromal cells by increasing AMPK phosphorylation, which prevents nuclear translocation of CRTC2 and disrupts formation of the CREB-CRTC2 complex, thereby inhibiting transcription of StAR by reducing CREB-CRTC2 binding to the StAR promoter CRE.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation, subcellular localization imaging, AMPK activation assays, CRTC2 localization by Western blot\",\n      \"journal\": \"The Journal of clinical endocrinology and metabolism\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP, ChIP, localization imaging, pharmacological manipulation, single lab\",\n      \"pmids\": [\"24823468\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"PFOS decreases interaction between CREB and CRTC2 and binding of CREB/CRTC2 to the StAR promoter region via activation of p38 MAPK and PKA pathways, leading to decreased testosterone biosynthesis.\",\n      \"method\": \"Co-immunoprecipitation, chromatin immunoprecipitation, Western blot, inhibitors (SB203580 for p38, H89 for PKA), in vivo and in vitro models\",\n      \"journal\": \"Toxicology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — Co-IP and ChIP without detailed mechanistic dissection of direct vs indirect effects, single lab\",\n      \"pmids\": [\"33359577\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"mTORC1 suppresses COX-2 expression in adipocytes by phosphorylating CRTC2, causing dissociation of CREB from the cox-2 promoter. Adipose-specific Raptor depletion relieves this suppression, promoting COX-2-derived prostaglandin synthesis and beige adipogenesis.\",\n      \"method\": \"Adipose-specific Raptor KO mice, adenoviral CRTC2 overexpression, chromatin immunoprecipitation, COX-2 reporter assays\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — tissue-specific KO, ChIP, reporter assay, single lab\",\n      \"pmids\": [\"30232001\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"TSH activates CRTC2 via TSHR/cAMP/PKA pathway: TSH stimulates CRTC2 dephosphorylation and increases CRTC2 expression. CRTC2 forms a complex with CREB, and this complex drives hepatic gluconeogenic gene expression. Deletion of TSHR reduces levels of the CRTC2:CREB complex in mouse livers.\",\n      \"method\": \"Co-immunoprecipitation, reporter assays (PEPCK-luciferase), siRNA knockdown, Western blot, TSHR KO mice\",\n      \"journal\": \"Molecular and cellular endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 / Moderate — Co-IP, reporter assays, genetic KO, single lab\",\n      \"pmids\": [\"28212844\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CRTC2 is a phosphorylation-regulated transcriptional coactivator that, under basal/fed conditions, is sequestered in the cytoplasm via 14-3-3 binding to phosphorylated Ser171 and Ser275; upon fasting, glucagon-induced cAMP inhibits SIK2 while calcium activates calcineurin to dephosphorylate both sites, allowing nuclear translocation where CRTC2's N-terminal CREB-binding domain (a 28-residue helix) directly contacts the CREB bZip in a 2:2:1 stoichiometry on CRE promoters to drive gluconeogenic gene expression; insulin reverses this by inducing AKT2-activated SIK2 to re-phosphorylate CRTC2 at Ser171, leading to COP1-mediated ubiquitination at Lys628 and 26S proteasomal degradation; beyond gluconeogenesis, CRTC2 also modulates hepatic lipid synthesis by competing with COPII subunit Sec23A for Sec31A binding to inhibit SREBP1 processing (relieved by mTOR phosphorylation during feeding), cooperates with GR, ATF6α, and CBP/p300, regulates Th17 differentiation, MMR gene transcription, and inflammatory gene expression via H3K27ac deposition, and is activated in LKB1-deficient cancers through loss of SIK-mediated inhibitory phosphorylation.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"CRTC2 (TORC2) is a phosphorylation-gated transcriptional coactivator that couples nutrient and hormonal signals to CREB-dependent gene programs, most prominently the hepatic gluconeogenic response to fasting [#0, #8]. Under fed/resting conditions it is held in the cytoplasm through phosphorylation-dependent 14-3-3 binding, with SIK2 and the phosphatase calcineurin both associating with CRTC2 to set its phosphorylation state at the 14-3-3 sites Ser171 and Ser275; fasting-induced cAMP inhibits SIK2 while calcium-activated calcineurin dephosphorylates these sites, driving nuclear entry and CREB coactivation [#1, #4]. Insulin reverses this by AKT2-dependent activation of SIK2, which rephosphorylates Ser171 and triggers COP1-mediated ubiquitination at Lys628 and 26S proteasomal degradation of CRTC2 [#2]. In the nucleus, CRTC2's N-terminal CREB-binding domain folds into a single 28-residue helix that contacts the CREB bZip and CRE-containing DNA, assembling a 2:2 CRTC2–CREB complex on DNA that stabilizes CREB occupancy and confers DNA-shape selectivity [#5, #6]. Beyond gluconeogenesis, CRTC2 governs hepatic lipogenesis by competing with the COPII subunit Sec23A for Sec31A to restrain SREBP1 ER-to-Golgi processing, an inhibition relieved by mTOR phosphorylation during feeding [#7], and acts as a broad CREB-axis coactivator across additional programs by partnering with CBP/p300 to deposit H3K27ac at inflammatory loci downstream of LKB1–SIK signaling [#19] and by coactivating the glucocorticoid receptor [#11]. Its activity is constitutively elevated in LKB1-deficient cancers, where loss of SIK-mediated inhibitory phosphorylation drives CREB target genes such as ID1 [#15].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established the core regulatory logic of CRTC2: how opposing kinase and phosphatase inputs gate its cytoplasmic sequestration versus nuclear CREB coactivation.\",\n      \"evidence\": \"Co-IP, kinase assays, calcineurin inhibition and SIK2 knockdown with subcellular imaging\",\n      \"pmids\": [\"15454081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not map the specific phospho-sites bound by 14-3-3\", \"Physiological signal triggering calcineurin/SIK2 not yet placed in a whole-animal context\"]\n    },\n    {\n      \"year\": 2005,\n      \"claim\": \"Placed CRTC2 in vivo as the fasting/glucagon-responsive driver of the hepatic gluconeogenic transcriptional program and identified AMPK as an opposing input.\",\n      \"evidence\": \"Subcellular fractionation, reporter assays and adenoviral gain/loss-of-function in mice with pharmacological AMPK activation\",\n      \"pmids\": [\"16148943\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve how multiple kinases converge on the same 14-3-3 sites\", \"Mechanism of insulin-mediated shut-off unresolved\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Defined the insulin-driven OFF switch — how CRTC2 is targeted for degradation rather than merely re-exported.\",\n      \"evidence\": \"In vivo mouse studies, site-directed mutagenesis (Ser171, Ser358, Lys628), ubiquitination and proteasome-inhibitor assays\",\n      \"pmids\": [\"17805301\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not address regulation of COP1 activity itself\", \"Relative contribution of degradation versus cytoplasmic retention to CRTC2 silencing not quantified\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Extended the phospho-code beyond Ser171 by identifying Ser275 as a second glucose-regulated 14-3-3 site essential for CREB activation in beta cells.\",\n      \"evidence\": \"Cell-based kinase screen of 180 kinases, Ser275 mutagenesis, calcineurin inhibition and islet studies\",\n      \"pmids\": [\"18626018\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Hierarchy/interplay between Ser171 and Ser275 phosphorylation not fully resolved\", \"Role of MARK2 in vivo not established\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Broadened CRTC2 from a metabolic to a stress-integrating coactivator and showed ER stress can redirect it away from gluconeogenic genes via ATF6\\u03b1.\",\n      \"evidence\": \"Reciprocal Co-IP, ChIP and adenoviral knockdown/overexpression in mouse liver\",\n      \"pmids\": [\"19543265\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of ATF6\\u03b1 disruption of CREB-CRTC2 not defined\", \"Whether ER-stress and fasting inputs are integrated at the same molecule simultaneously unclear\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Confirmed by loss-of-function genetics that the N-terminal CREB-binding domain mediates promoter occupancy and is required for the fasting glucose response.\",\n      \"evidence\": \"CRTC2 knockout mice with ChIP, reporter assays and glucose tolerance tests\",\n      \"pmids\": [\"20133702\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Atomic detail of the CBD-CREB interface not yet resolved\", \"Did not address CREB-independent CRTC2 functions\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Resolved the molecular architecture of coactivation, showing the CBD is an isolated helix forming a defined 2:2:1 CRTC-CREB-CRE assembly.\",\n      \"evidence\": \"NMR/structural analysis, mutagenesis and binding-affinity measurements with reporter validation\",\n      \"pmids\": [\"23213254\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not capture direct CRTC2-DNA contacts\", \"How phosphorylation alters the helix or its accessibility not addressed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Crystallography revealed that CRTC2 contacts DNA directly and reads intrinsic DNA shape, explaining promoter selectivity and CREB stabilization on the CRE.\",\n      \"evidence\": \"X-ray crystallography of the CBD-bZip-CRE complex with structure-guided mutagenesis and reporter assays\",\n      \"pmids\": [\"29733854\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structure of full-length phospho-regulated CRTC2 not determined\", \"How DNA-shape selectivity is modulated in vivo by chromatin unknown\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identified a transcription-independent CRTC2 function — control of hepatic lipogenesis by competing for COPII subunits to gate SREBP1 trafficking.\",\n      \"evidence\": \"Reciprocal/competition Co-IP, SREBP1 processing assays and adenoviral mTOR-defective CRTC2 mutant in obese mice\",\n      \"pmids\": [\"26147081\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of CRTC2 versus Sec23A at COPII coats not quantified\", \"Whether nuclear and ER pools of CRTC2 are distinct populations unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Connected CRTC2 to chromatin modification, showing it recruits CBP/p300 to deposit H3K27ac at inflammatory loci downstream of LKB1-SIK signaling.\",\n      \"evidence\": \"ChIP-seq/H3K27ac profiling, LKB1 knockout cells, CRTC2 manipulation and Co-IP with CBP/p300\",\n      \"pmids\": [\"37172591\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether CRTC2 itself directs HAT specificity or is a passive scaffold unclear\", \"Generality of CRTC2-driven H3K27ac beyond inflammatory genes not tested\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Expanded the transcription-factor partner repertoire beyond CREB by showing CRTC2 coactivates the glucocorticoid receptor for gluconeogenic genes.\",\n      \"evidence\": \"Co-IP with domain mapping (aa 561\\u2013693 to GR LBD), ChIP, reporter assays and knockout mice\",\n      \"pmids\": [\"26652733\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; reciprocal structural validation of the GR interface absent\", \"Whether GR and CREB coactivation occur on shared or distinct promoters not resolved\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Demonstrated a pathological gain-of-function: constitutive CRTC2 activation in LKB1-mutant cancer drives tumor growth through CREB target genes.\",\n      \"evidence\": \"LKB1-mutant NSCLC analysis, shRNA knockdown, ChIP and tumor growth assays\",\n      \"pmids\": [\"31355336\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab epistasis; direct dependence on SIK reactivation not fully separated from other LKB1 effectors\", \"Breadth of CRTC2-dependent oncogenic targets beyond ID1 not defined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Identified Sam68 as a stabilizing partner that limits CRTC2 ubiquitination, adding a post-translational tuning node controlling gluconeogenesis.\",\n      \"evidence\": \"Co-IP with deletion mapping, ubiquitination assays and global/hepatic Sam68 KO mice\",\n      \"pmids\": [\"34099657\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single lab; how Sam68 competes with COP1 mechanistically not defined\", \"Whether Sam68 acts on cytoplasmic or nuclear CRTC2 unclear\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How the many context-specific CRTC2 functions (lipogenesis, chromatin marking, GR/ATF6\\u03b1/viral coactivation, neuronal and reproductive programs) are partitioned within a single cell — and what determines partner and promoter selectivity beyond phosphorylation state — remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No unified model linking the cytoplasmic COPII-gating role to nuclear coactivation\", \"Determinants of transcription-factor partner choice (CREB vs GR vs ATF6\\u03b1) not established\", \"Structure of phospho-regulated full-length CRTC2 unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140110\", \"supporting_discovery_ids\": [0, 5, 6, 8]},\n      {\"term_id\": \"GO:0003677\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0060090\", \"supporting_discovery_ids\": [5, 6, 19]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 1]},\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [0, 1, 8]},\n      {\"term_id\": \"GO:0005783\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [0, 5, 6, 8]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 7, 8]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 2]},\n      {\"term_id\": \"R-HSA-4839726\", \"supporting_discovery_ids\": [19]},\n      {\"term_id\": \"R-HSA-5653656\", \"supporting_discovery_ids\": [7]}\n    ],\n    \"complexes\": [\"CRTC2-CREB-CRE complex\"],\n    \"partners\": [\"CREB1\", \"YWHA?/14-3-3\", \"SIK2\", \"COP1\", \"ATF6\", \"NR3C1\", \"CREBBP/EP300\", \"KHDRBS1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}