{"gene":"GUCY2C","run_date":"2026-06-10T01:55:21","timeline":{"discoveries":[{"year":2011,"finding":"GUCY2C functions as an intestinal receptor for uroguanylin in a gut-brain endocrine axis regulating satiation; silencing GUCY2C in mice caused hyperphagia and obesity, and nutrient intake induced intestinal prouroguanylin secretion into circulation where it is proteolytically converted to uroguanylin in the hypothalamus to activate GUCY2C and anorexigenic pathways.","method":"Gucy2c knockout mice, intracerebroventricular hormone delivery, measurement of food intake and metabolic parameters, proteolytic processing assays","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — multiple orthogonal methods (genetic KO, hormone replacement, circuit tracing), clear phenotypic readout, replicated across multiple experiments in single rigorous study","pmids":["21865642"],"is_preprint":false},{"year":2009,"finding":"GUCY2C suppresses intestinal tumorigenesis by inactivating AKT signaling; loss of GUCY2C in mice activated AKT phosphorylation, increased epithelial proliferation and glycolysis, and increased carcinogen-induced tumorigenesis, all of which were rescued by genetic or pharmacological AKT disruption.","method":"Gucy2c−/− mice, Gucy2c−/−Akt1−/− double-knockout mice, immunoblot, microarray, functional metabolic assays, carcinogen (azoxymethane) treatment","journal":"Gastroenterology","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic epistasis with double knockout rescue, multiple orthogonal methods, clear mechanistic pathway placement","pmids":["19737566"],"is_preprint":false},{"year":2012,"finding":"GUCY2C regulates intestinal barrier integrity by repressing AKT1, thereby increasing tight junction proteins occludin and claudin-4; Gucy2c−/− mice showed barrier hyperpermeability, reduced junctional proteins, and increased systemic genotoxicity and spontaneous/carcinogen-induced tumorigenesis.","method":"Gucy2c−/− mice, permeability assays, immunoblot for tight junction proteins, Caco2 cell in vitro experiments, carcinogen treatment for tumorigenesis","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic KO with defined cellular and molecular phenotype, in vitro validation, multiple orthogonal readouts","pmids":["22384056"],"is_preprint":false},{"year":2011,"finding":"GCC (GUCY2C) signaling maintains intestinal barrier function by regulating MLCK activation and tight junction disassembly; GCC−/− and UGN−/− mice had increased intestinal permeability associated with elevated IFNγ, MLCK, STAT1 activation, increased MLC phosphorylation, and reduced claudin-2 and JAM-A expression.","method":"GCC−/− and UGN−/− mice, intestinal permeability assays, RT-PCR, immunoblot, GCC RNAi in Caco-2 and HT-29 cells","journal":"PloS one","confidence":"High","confidence_rationale":"Tier 2 / Strong — reciprocal genetic KO models, in vitro RNAi validation, multiple downstream molecular readouts","pmids":["21305056"],"is_preprint":false},{"year":2013,"finding":"GUCY2C prevents intestinal desmoplasia by suppressing Akt-dependent TGF-β secretion from epithelial cells; silencing GUCY2C increased TGF-β secretion that activated fibroblast TGF-β type I receptors and Smad3 phosphorylation, which in turn induced fibroblast secretion of HGF that drove colon cancer cell proliferation through cMET-dependent signaling.","method":"GUCY2C silencing in human colon cancer cells, co-culture assays, anti-TGF-β antibodies, genetic silencing of Akt in Gucy2c−/− mice, phosphorylation assays","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vitro mechanistic dissection with multiple pathway components validated, genetic mouse model corroboration","pmids":["24085786"],"is_preprint":false},{"year":2012,"finding":"Activating heterozygous missense mutation (c.2519G→T) in GUCY2C causes familial diarrhea syndrome; mutant GC-C receptor produced markedly increased cGMP upon ligand exposure in HEK293T cells, consistent with hyperactivation of CFTR leading to increased chloride and water secretion.","method":"Linkage analysis, exome sequencing, functional cGMP assays in HEK293T cells expressing mutant receptor","journal":"The New England journal of medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct functional assay of mutant receptor in heterologous cells, co-segregation with disease phenotype across 32 family members","pmids":["22436048"],"is_preprint":false},{"year":2012,"finding":"Loss-of-function homozygous mutations in GUCY2C that dramatically reduce or abrogate guanylyl cyclase enzymatic activity cause autosomal-recessive meconium ileus; GUCY2C activates CFTR through local cGMP generation in the intestine.","method":"Exome/Sanger sequencing, enzymatic activity assays, genetic mapping in consanguineous Bedouin kindreds","journal":"American journal of human genetics","confidence":"High","confidence_rationale":"Tier 2 / Moderate — enzymatic activity measured directly, two unrelated kindreds with different mutations confirming loss-of-function mechanism","pmids":["22521417"],"is_preprint":false},{"year":2015,"finding":"De novo activating missense mutations in different intracellular domains of GUCY2C cause congenital sodium diarrhea by enhancing intracellular cGMP accumulation in both a ligand-independent and ligand-stimulated manner.","method":"Whole-exome sequencing, Sanger sequencing, functional cGMP accumulation assays in HEK293T cells expressing mutant receptors","journal":"Gut","confidence":"High","confidence_rationale":"Tier 2 / Strong — direct functional assay in heterologous cells for multiple independent mutations in 4 unrelated patients","pmids":["25994218"],"is_preprint":false},{"year":2014,"finding":"GUCY2C internalizes from the cell surface to lysosomes via clathrin-mediated endocytosis, independently of ligand binding and receptor activation; this mechanism was exploited to deliver an immunotoxin (anti-GUCY2C antibody conjugated via reducible disulfide to ricin A chain) that was activated in lysosomes to kill colorectal cancer cells.","method":"Live cell imaging, clathrin inhibition experiments, lysosomal trafficking assays, immunotoxin cytotoxicity assays in vitro and in vivo mouse model","journal":"Oncotarget","confidence":"High","confidence_rationale":"Tier 2 / Moderate — direct localization experiments with functional consequence, mechanistic inhibitor studies, in vivo validation","pmids":["25294806"],"is_preprint":false},{"year":2019,"finding":"GUCY2C is expressed in two distinct neuronal circuits in the brain: hypothalamic GUCY2C mRNA is confined to ventral premammillary nucleus (PMV) neurons co-expressing anorexigenic leptin receptors, and midbrain GUCY2C is produced in tyrosine hydroxylase-positive VTA/SN neurons; GUCY2C protein is distributed along axonal projections from these two origins.","method":"In situ hybridization, immunofluorescence, stereotaxic ablation of PMV or VTA/SN neurons, anterograde tracer analysis","journal":"Brain structure & function","confidence":"High","confidence_rationale":"Tier 2 / Moderate — selective stereotaxic ablation confirmed circuit origins, anterograde tracing validated projections, multiple orthogonal neuroanatomical methods","pmids":["31485718"],"is_preprint":false},{"year":2016,"finding":"Diet-induced obesity silences guanylin expression in colon through calorie-dependent induction of endoplasmic reticulum stress and the unfolded protein response in intestinal epithelial cells, thereby silencing GUCY2C signaling; transgenic restoration of guanylin expression specifically in intestinal epithelial cells restored GUCY2C signaling and eliminated intestinal tumors in mice on high-calorie diet.","method":"Genetically engineered mice on different diets, transgenic guanylin expression, ER stress pathway analysis, tumor counts","journal":"Cancer research","confidence":"High","confidence_rationale":"Tier 2 / Strong — causal rescue experiment (transgenic guanylin restoration eliminates tumors), mechanistic pathway (ER stress → UPR → guanylin loss) identified","pmids":["26773096"],"is_preprint":false},{"year":2020,"finding":"APC-β-catenin-TCF signaling transcriptionally represses guanylin hormone expression (but not the GUCY2C receptor itself) at the earliest stages of colorectal tumorigenesis, silencing GUCY2C signaling; biallelic but not monoallelic APC loss was required for hormone repression.","method":"Conditional genetic mouse models (monoallelic and biallelic Apc deletion), RNA-seq, FAP patient tissue analysis","journal":"Cancer biology & therapy","confidence":"High","confidence_rationale":"Tier 2 / Strong — genetic models with allele-specific dosage, human tissue validation, clear mechanistic pathway placement","pmids":["32037952"],"is_preprint":false},{"year":2021,"finding":"β-Catenin/TCF signaling mediates transcriptional repression of GUCY2C hormone ligands (guanylin and uroguanylin) through a locus control region upstream of the guanylin promoter; CRISPR epigenome editing of this region reconstituted hormone expression, overcoming gene inactivation by mutant β-catenin/TCF.","method":"RNA-seq in 4 conditional colon cancer cell models, luciferase reporters, ChIP-seq, CRISPR/Cas9 knockout, CRISPR epigenome editing","journal":"Cellular and molecular gastroenterology and hepatology","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple orthogonal experimental approaches including CRISPR functional validation, ChIP-seq chromatin mapping, and rescue by epigenome editing","pmids":["34954189"],"is_preprint":false},{"year":2021,"finding":"Activating mutation in Gucy2c equivalent to the Norwegian family mutation produces elevated intestinal cGMP, enhanced fecal water and sodium content, dysbiosis, up-regulation of IFN-stimulated genes, and increased susceptibility to DSS-induced colitis; intestinal cGMP acts via cGMP-dependent protein kinase II.","method":"Novel knock-in mouse model with activating Gucy2c mutation, fecal microbiome analysis, colonic gene expression, DSS colitis model, intestinal transit assays","journal":"The Journal of experimental medicine","confidence":"High","confidence_rationale":"Tier 2 / Strong — novel mouse model with activating mutation, multiple orthogonal readouts including microbiome, gene expression, and functional phenotype","pmids":["34546338"],"is_preprint":false},{"year":2023,"finding":"Intestinal GUCY2C is selectively enriched in neuropod cells (a type of enteroendocrine cell); GUCY2C-sufficient neuropod cells induced hyperexcitability in co-cultured dorsal root ganglia neurons, and the GUCY2C agonist linaclotide eliminated this neuronal hyperexcitability in a manner requiring neuropod cell GUCY2C but independent of bulk epithelial cells or extracellular cGMP; selective elimination of GUCY2C in neuropod cells increased nociceptive signaling and visceral pain refractory to linaclotide.","method":"Cell-type specific GUCY2C expression analysis, neuropod cell-DRG neuron co-culture, electrophysiology (rheobase measurement, action potential counting), selective neuropod cell GUCY2C knockout, visceral pain behavioral assays","journal":"The Journal of clinical investigation","confidence":"High","confidence_rationale":"Tier 2 / Strong — cell-type specific knockout, electrophysiology with defined phenotypic readout, multiple orthogonal experiments establishing neuropod cell-specific mechanism","pmids":["36548082"],"is_preprint":false},{"year":2017,"finding":"GUCY2C signaling opposes radiation-induced GI syndrome by activating p53 through its dissociation from MDM2, preventing mitotic catastrophe (but not apoptosis) in intestinal epithelial cells; oral delivery of exogenous GUCY2C ligand (heat-stable enterotoxin ST) reduced radiation-induced mortality.","method":"Gucy2c−/− mice, lethal irradiation model, p53/MDM2 interaction assays, oral ligand delivery, cell death mechanistic assays","journal":"Cancer research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genetic KO with defined phenotype, p53-MDM2 dissociation mechanism identified, single lab","pmids":["28916678"],"is_preprint":false},{"year":1993,"finding":"GC-C (GUCY2C) expressed at the surface of COS-7 cells binds heat-stable enterotoxin (STa) via its extracellular domain; the intracellular region is not required for dimer formation, and the truncated GC-C forms dimers on the cell surface and is glycosylated in mammalian cells.","method":"Truncated GC-C expression in COS-7 cells, photoaffinity labeling with 125I-STa, SDS-PAGE analysis of dimer formation","journal":"Microbial pathogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding assay and biochemical characterization, single lab, truncated receptor construct","pmids":["7906006"],"is_preprint":false},{"year":2000,"finding":"GC-C mRNA and STa-binding sites are uniformly expressed throughout the rat intestine, but GC-C-mediated cGMP synthesis peaks at the proximal and distal extremes (duodenum and colon) but is nearly absent in the ileum, indicating post-translational regulation of GC-C activity along the intestinal axis.","method":"Northern blot, Western blot, [125I]STa binding, STa-dependent cGMP elevation measurements across intestinal segments","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple biochemical methods, functional cGMP assay, systematic characterization across intestinal segments, single lab","pmids":["10965892"],"is_preprint":false},{"year":1993,"finding":"GCC mRNA is expressed specifically in intestinal epithelial cells throughout colonic crypts and surface epithelium, while its ligand guanylin mRNA is also expressed in the same tissue, establishing their co-localization as a paracrine signaling system.","method":"In situ hybridization, Northern blot analysis of GCA, GCC, and guanylin mRNA in rat colon","journal":"The American journal of physiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct in situ localization, Northern blot confirmation, systematic co-expression analysis","pmids":["8103637"],"is_preprint":false},{"year":2007,"finding":"An alternative non-GC-C receptor for STa exists in the intestine; STa-stimulated duodenal bicarbonate secretion in GC-C knockout mice occurred through a CFTR-independent pathway (blocked by DIDS but not glibenclamide), while uroguanylin- and guanylin-stimulated secretion was CFTR-dependent.","method":"[125I]STa binding in GC-C KO and WT mice, in vitro and in vivo duodenal bicarbonate secretion measurements, pharmacological inhibitors","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GC-C KO model, binding assays, functional secretion assays; reveals negative result about GC-C exclusivity and identifies alternative pathway","pmids":["18096816"],"is_preprint":false},{"year":2001,"finding":"Two isoforms of GC-C (GC-C1 and GC-C2) were cloned from European eel intestine; GC-C2 intestinal expression increased 100% upon seawater transfer and 60% during developmental maturation of yellow to silver eels, and was restricted to anterior/mid-gut segments in freshwater but extended to posterior gut in seawater, indicating physiological regulation of GC-C expression.","method":"cDNA cloning, Northern blot, RT-PCR, acclimation experiments","journal":"Comparative biochemistry and physiology","confidence":"Low","confidence_rationale":"Tier 3 / Moderate — expression regulation in non-mammalian ortholog, single lab, no functional mechanism beyond expression correlation","pmids":["11399493"],"is_preprint":false},{"year":2020,"finding":"GUCY2C expressed in the hypothalamus (specifically proopiomelanocortin neurons of the arcuate nucleus) mediates diet-induced thermogenesis; GC-C KO mice showed diminished activation of brown adipose tissue (iBAT) after a meal, and intranasal uroguanylin increased iBAT activity in a GC-C-dependent manner correlated with reduced blood glucose.","method":"GC-C KO mice, iBAT activity measurements, hypothalamic GC-C immunohistochemistry in POMC neurons, intranasal UGN delivery, metabolic measurements","journal":"Pflugers Archiv","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — GC-C KO with defined phenotype, specific neuronal localization, hormone rescue experiment, single lab","pmids":["31940065"],"is_preprint":false},{"year":2012,"finding":"Guanylin and GC-C expressed in mesenteric macrophages (not only intestinal epithelium) contribute to resistance to high-fat diet-induced obesity; double-transgenic rats overexpressing guanylin and GC-C in macrophages resisted HFD-induced obesity with altered expression of lipid metabolism genes, and lipid accumulation in adipocytes was inhibited by co-culture with macrophages expressing guanylin/GC-C.","method":"Microarray screen, histological analysis, double-transgenic rat generation, co-culture assays, siRNA knockdown of guanylin and GC-C","journal":"Journal of lipid research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — transgenic overexpression with phenotype rescue, in vitro siRNA validation, but unexpected macrophage expression context requires replication","pmids":["23081987"],"is_preprint":false},{"year":2009,"finding":"GUCY2C (GCC) functions as a receptor for the paracrine hormones guanylin and uroguanylin, converting GTP to cGMP, and acts as a tumor suppressor coordinating proliferative homeostasis; its signaling reverses the tumorigenic phenotype of human colon cancer cells by regulating proliferation and metabolism.","method":"GCC receptor activation in human colon cancer cells, cell cycle analysis, DNA synthesis assay, colony formation, metabolic assays","journal":"Drug news & perspectives","confidence":"Low","confidence_rationale":"Tier 3 / Moderate — review summarizing multiple experimental findings, individual mechanistic experiments described but this is primarily a summary article","pmids":["19771320"],"is_preprint":false},{"year":2009,"finding":"GUCY2C shares domain organization with other receptor guanylate cyclases (extracellular ligand-binding domain, transmembrane domain, intracellular catalytic domain) and is the primary intestinal receptor for guanylin, uroguanylin, and bacterial heat-stable enterotoxins; GC-C or ligand knockouts in mice modulate responses to stable toxin peptides, dietary salt, and intestinal cell development/differentiation.","method":"Gene knockout mice, review of structural and functional domain analyses","journal":"Molecular and cellular biochemistry","confidence":"Low","confidence_rationale":"Tier 3 / Moderate — review article summarizing findings; limited novel mechanistic data in the abstract itself","pmids":["19960363"],"is_preprint":false}],"current_model":"GUCY2C (GC-C) is a transmembrane receptor guanylyl cyclase expressed on intestinal epithelial cells that converts GTP to cGMP upon activation by the paracrine hormones guanylin and uroguanylin (or bacterial heat-stable enterotoxin); cGMP production activates cGMP-dependent protein kinase II to regulate CFTR-mediated ion and fluid secretion, while downstream repression of AKT1 signaling coordinates intestinal epithelial homeostasis, barrier integrity (via tight junction protein regulation and MLCK/MLC phosphorylation), cell proliferation/metabolism, and tumor suppression; GUCY2C is also expressed in hypothalamic PMV neurons (co-expressing leptin receptors) and dopaminergic VTA/SN neurons to regulate satiation and thermogenesis through an intestine-derived uroguanylin endocrine axis, and selectively in intestinal neuropod cells where cGMP signaling modulates visceral pain transmission to submucosal neurons."},"narrative":{"mechanistic_narrative":"GUCY2C (GC-C) is a transmembrane receptor guanylyl cyclase that serves as the principal intestinal receptor for the paracrine peptide hormones guanylin and uroguanylin and for bacterial heat-stable enterotoxin (STa), binding ligand through its extracellular domain and converting GTP to cGMP via its intracellular catalytic domain to coordinate intestinal fluid secretion, epithelial homeostasis, and tumor suppression [PMID:7906006, PMID:8103637]. Receptor-generated cGMP activates cGMP-dependent protein kinase II to drive CFTR-dependent ion and water secretion, and the clinical importance of this output is established by human mutations: activating missense alleles that elevate cGMP cause familial and congenital secretory diarrhea, while loss-of-function alleles that abrogate cyclase activity cause meconium ileus [PMID:22436048, PMID:22521417, PMID:25994218]. In its tumor-suppressive role, GUCY2C signaling restrains AKT activation, and loss of GUCY2C derepresses AKT-driven epithelial proliferation, glycolysis, and carcinogen-induced tumorigenesis, effects reversed by genetic or pharmacologic AKT disruption [PMID:19737566]. Through AKT repression GUCY2C also enforces barrier integrity by maintaining tight-junction proteins and limiting MLCK/MLC-dependent junction disassembly, and suppresses stromal desmoplasia by limiting epithelial TGF-β secretion that otherwise drives a fibroblast HGF/cMET paracrine loop [PMID:22384056, PMID:21305056, PMID:24085786]. Tumorigenesis silences this axis at the hormone level: APC–β-catenin/TCF signaling and diet-induced ER stress repress guanylin/uroguanylin expression while sparing the receptor, and restoring hormone expression reinstates signaling and eliminates tumors [PMID:26773096, PMID:32037952, PMID:34954189]. Beyond the epithelium, GUCY2C functions in a gut–brain endocrine axis in which nutrient-induced circulating prouroguanylin is processed to uroguanylin to activate hypothalamic and midbrain GUCY2C neurons regulating satiation and thermogenesis, and in intestinal neuropod cells where its cGMP signaling restrains nociceptive transmission to sensory neurons [PMID:21865642, PMID:31485718, PMID:36548082].","teleology":[{"year":1993,"claim":"Establishing that GUCY2C is a cell-surface receptor binding bacterial enterotoxin through its extracellular domain defined its receptor architecture and ligand-engagement mechanism.","evidence":"Truncated GC-C expression in COS-7 cells with photoaffinity labeling by 125I-STa and SDS-PAGE dimer analysis","pmids":["7906006"],"confidence":"Medium","gaps":["No structure of the full-length receptor or ligand-bound state","Cyclase activation mechanism downstream of binding not resolved here"]},{"year":1993,"claim":"Co-localization of GCC receptor and guanylin ligand in colonic epithelium established the system as an endogenous paracrine signaling axis rather than only a toxin target.","evidence":"In situ hybridization and Northern blot of receptor and guanylin mRNA in rat colon","pmids":["8103637"],"confidence":"Medium","gaps":["mRNA co-expression does not demonstrate functional paracrine signaling in vivo","Spatial relationship of secreting and responding cells unresolved"]},{"year":2000,"claim":"Discovery that cGMP output, but not receptor expression, varies along the gut axis revealed post-translational regulation of GUCY2C catalytic activity.","evidence":"Northern/Western blot, 125I-STa binding, and STa-stimulated cGMP measurement across rat intestinal segments","pmids":["10965892"],"confidence":"Medium","gaps":["Molecular basis of segment-specific activity regulation not identified","Physiological consequence of the activity gradient unclear"]},{"year":2009,"claim":"Genetic epistasis placed GUCY2C upstream of AKT as a tumor suppressor, answering how receptor loss promotes intestinal carcinogenesis.","evidence":"Gucy2c-/- and Gucy2c-/-Akt1-/- double-knockout mice with carcinogen treatment, immunoblot, microarray, and metabolic assays","pmids":["19737566"],"confidence":"High","gaps":["Biochemical link from cGMP to AKT inactivation not defined","Whether AKT repression accounts for all tumor-suppressive functions unknown"]},{"year":2011,"claim":"Identification of a gut-brain uroguanylin axis showed GUCY2C controls satiation, extending its role beyond the epithelium to systemic energy balance.","evidence":"Gucy2c knockout mice, intracerebroventricular hormone delivery, food intake/metabolic readouts, proteolytic processing assays","pmids":["21865642"],"confidence":"High","gaps":["Identity of central GUCY2C-expressing neurons not yet mapped at this stage","Processing enzyme for hypothalamic prouroguanylin conversion not defined"]},{"year":2011,"claim":"Linking GUCY2C/guanylin loss to MLCK activation and tight-junction disassembly defined a mechanism for receptor control of barrier permeability.","evidence":"GCC-/- and UGN-/- mice, permeability assays, RT-PCR, immunoblot, and GCC RNAi in Caco-2/HT-29 cells","pmids":["21305056"],"confidence":"High","gaps":["Causal chain from cGMP to IFNγ/STAT1/MLCK not fully ordered","Relative contribution of immune versus epithelial-intrinsic effects unresolved"]},{"year":2012,"claim":"Demonstrating that AKT1 repression by GUCY2C raises occludin and claudin-4 connected the tumor-suppressor pathway to barrier integrity and genotoxic protection.","evidence":"Gucy2c-/- mice with permeability assays, tight-junction immunoblots, Caco2 in vitro validation, and carcinogen tumorigenesis","pmids":["22384056"],"confidence":"High","gaps":["Mechanism by which AKT1 controls junctional protein levels not detailed","Apparent differences in claudin regulation versus other studies unreconciled"]},{"year":2012,"claim":"Human activating and loss-of-function mutations established cGMP dosage as the causal determinant of opposite intestinal secretory phenotypes (diarrhea versus meconium ileus).","evidence":"Linkage/exome sequencing in human kindreds with cGMP and guanylyl cyclase activity assays in HEK293T cells","pmids":["22436048","22521417"],"confidence":"High","gaps":["Structural basis for how mutations alter cyclase activity not solved","Downstream CFTR activation inferred rather than directly measured in patient tissue"]},{"year":2012,"claim":"Detection of guanylin/GC-C in mesenteric macrophages raised the possibility of an extra-epithelial cell compartment contributing to metabolic protection.","evidence":"Microarray, double-transgenic rats overexpressing guanylin/GC-C in macrophages, co-culture, and siRNA knockdown","pmids":["23081987"],"confidence":"Medium","gaps":["Unexpected macrophage expression requires independent replication","Mechanism linking macrophage GC-C to adipocyte lipid accumulation unclear"]},{"year":2013,"claim":"Dissecting an epithelial-to-fibroblast TGF-β/HGF/cMET loop explained how GUCY2C loss drives stromal desmoplasia and cancer cell proliferation.","evidence":"GUCY2C silencing in human colon cancer cells, co-culture, anti-TGF-β antibodies, Smad3 phosphorylation assays, and Akt silencing in Gucy2c-/- mice","pmids":["24085786"],"confidence":"High","gaps":["In vivo contribution of the HGF/cMET loop to tumor growth not quantified","Whether the loop operates in human tumors not established"]},{"year":2014,"claim":"Showing constitutive clathrin-mediated internalization to lysosomes defined GUCY2C trafficking and enabled lysosome-activated immunotoxin targeting of colorectal cancer.","evidence":"Live-cell imaging, clathrin inhibition, lysosomal trafficking assays, and immunotoxin cytotoxicity in vitro and in mice","pmids":["25294806"],"confidence":"High","gaps":["Regulation of internalization rate and recycling not characterized","Relationship between trafficking and signaling output unexplored"]},{"year":2015,"claim":"Demonstration that de novo activating mutations in distinct intracellular domains raise cGMP both ligand-independently and ligand-stimulated broadened the genotype spectrum for congenital sodium diarrhea.","evidence":"Whole-exome/Sanger sequencing and cGMP accumulation assays in HEK293T cells for multiple mutations across four patients","pmids":["25994218"],"confidence":"High","gaps":["Domain-specific mechanisms of constitutive activation not resolved","Patient intestinal cGMP and ion transport not directly measured"]},{"year":2016,"claim":"Identifying diet-induced ER stress/UPR as a silencer of guanylin showed how high-calorie intake disables GUCY2C signaling to permit tumorigenesis, reversible by hormone restoration.","evidence":"Engineered mice on differing diets, transgenic epithelial guanylin restoration, ER stress pathway analysis, and tumor counts","pmids":["26773096"],"confidence":"High","gaps":["Molecular link from UPR to guanylin transcriptional repression not detailed","Generalizability to human obesity-associated cancer untested here"]},{"year":2017,"claim":"Linking GUCY2C to p53 activation via MDM2 dissociation defined a radioprotective mechanism preventing mitotic catastrophe in intestinal epithelium.","evidence":"Gucy2c-/- mice, lethal irradiation, p53/MDM2 interaction assays, and oral STa ligand delivery","pmids":["28916678"],"confidence":"Medium","gaps":["Single-lab finding awaiting independent confirmation","Biochemical bridge from cGMP signaling to MDM2 dissociation not established"]},{"year":2019,"claim":"Mapping central GUCY2C to PMV (leptin-receptor) and TH-positive VTA/SN neurons with their axonal projections resolved the neuronal substrates of the gut-brain axis.","evidence":"In situ hybridization, immunofluorescence, stereotaxic ablation of PMV or VTA/SN neurons, and anterograde tracing","pmids":["31485718"],"confidence":"High","gaps":["Functional output of each neuronal circuit not assigned here","Source of ligand activating these central neurons not defined"]},{"year":2020,"claim":"Demonstrating GC-C in arcuate POMC neurons mediates diet-induced brown-fat thermogenesis extended the uroguanylin axis to energy expenditure.","evidence":"GC-C KO mice, iBAT activity, POMC GC-C immunohistochemistry, intranasal uroguanylin delivery, and metabolic measurements","pmids":["31940065"],"confidence":"Medium","gaps":["Circuit connecting POMC GC-C to BAT not traced","Reconciliation of POMC versus PMV/VTA neuronal sites of action incomplete"]},{"year":2020,"claim":"Identifying APC–β-catenin/TCF repression of guanylin (sparing the receptor) placed hormone loss at the earliest stage of colorectal tumorigenesis and showed biallelic APC loss is required.","evidence":"Conditional monoallelic/biallelic Apc-deletion mouse models, RNA-seq, and FAP patient tissue","pmids":["32037952"],"confidence":"High","gaps":["Direct transcriptional mechanism at the guanylin locus not yet mapped here","Therapeutic reversibility not tested in this study"]},{"year":2021,"claim":"Locating a β-catenin/TCF-controlled locus control region and reactivating it by CRISPR epigenome editing defined the mechanism and reversibility of hormone silencing.","evidence":"RNA-seq across four colon cancer models, luciferase reporters, ChIP-seq, CRISPR knockout, and CRISPR epigenome editing","pmids":["34954189"],"confidence":"High","gaps":["In vivo efficacy of epigenome reactivation not demonstrated","Whether restored hormone suppresses established tumors not addressed here"]},{"year":2021,"claim":"A knock-in mouse of the activating diarrhea mutation showed elevated cGMP drives fecal water/sodium loss, dysbiosis, ISG induction, and colitis susceptibility via PKG II, modeling human disease consequences.","evidence":"Activating Gucy2c knock-in mouse with microbiome analysis, colonic gene expression, DSS colitis, and transit assays","pmids":["34546338"],"confidence":"High","gaps":["Causal order of dysbiosis versus ISG induction not resolved","Direct demonstration of PKG II as the effector limited to inference"]},{"year":2023,"claim":"Showing neuropod-cell GUCY2C restrains sensory neuron excitability and visceral pain assigned a cell-type-specific neural function to the receptor and explained linaclotide analgesia.","evidence":"Cell-type-specific expression analysis, neuropod cell–DRG co-culture electrophysiology, selective neuropod GUCY2C knockout, and visceral pain behavior","pmids":["36548082"],"confidence":"High","gaps":["Signal transmitted from neuropod cell to DRG neuron not identified","Mechanism of cGMP action within neuropod cells not detailed"]},{"year":null,"claim":"The biochemical chain linking receptor-generated cGMP to its diverse effectors (AKT inactivation, p53/MDM2 dissociation, neuropod-to-neuron transmission) remains the central unresolved mechanism.","evidence":"","pmids":[],"confidence":"High","gaps":["No defined molecular intermediary between cGMP/PKG II and AKT repression","No structural model of ligand-bound active receptor","Nature of the neuropod-cell-to-sensory-neuron signal unknown"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0009975","term_label":"cyclase activity","supporting_discovery_ids":[5,6,7,16]},{"term_id":"GO:0001618","term_label":"virus receptor activity","supporting_discovery_ids":[16,18]},{"term_id":"GO:0038024","term_label":"cargo receptor activity","supporting_discovery_ids":[16,18]},{"term_id":"GO:0060089","term_label":"molecular transducer activity","supporting_discovery_ids":[0,23]}],"localization":[{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[8,16,18]},{"term_id":"GO:0005764","term_label":"lysosome","supporting_discovery_ids":[8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,5]},{"term_id":"R-HSA-382551","term_label":"Transport of small molecules","supporting_discovery_ids":[5,6,19]},{"term_id":"R-HSA-1643685","term_label":"Disease","supporting_discovery_ids":[5,6,7]},{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[0,21]}],"complexes":[],"partners":["GUCA2A","GUCA2B","CFTR","AKT1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P25092","full_name":"Guanylyl cyclase C","aliases":["Heat-stable enterotoxin receptor","STA receptor","hSTAR","Intestinal guanylate cyclase"],"length_aa":1073,"mass_kda":123.4,"function":"Guanylyl cyclase that catalyzes synthesis of cyclic GMP (cGMP) from GTP (PubMed:11950846, PubMed:1718270, PubMed:22436048, PubMed:22521417, PubMed:23269669). Receptor for the E.coli heat-stable enterotoxin; E.coli enterotoxin markedly stimulates the accumulation of cGMP in mammalian cells expressing GUCY2C (PubMed:1680854, PubMed:1718270). 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colorectal cancer: Is colorectal cancer a paracrine deficiency syndrome?","date":"2009","source":"Drug news & perspectives","url":"https://pubmed.ncbi.nlm.nih.gov/19771320","citation_count":14,"is_preprint":false},{"pmid":"34027103","id":"PMC_34027103","title":"GUCY2C as a biomarker to target precision therapies for patients with colorectal cancer.","date":"2021","source":"Expert review of precision medicine and drug development","url":"https://pubmed.ncbi.nlm.nih.gov/34027103","citation_count":14,"is_preprint":false},{"pmid":"35282333","id":"PMC_35282333","title":"Comparative Evaluation of Two SD-OCT Macular Parameters (GCC, GCL) and RNFL in Chiasmal Compression.","date":"2022","source":"Eye and brain","url":"https://pubmed.ncbi.nlm.nih.gov/35282333","citation_count":14,"is_preprint":false},{"pmid":"36176737","id":"PMC_36176737","title":"Potential Functions of the tRNA-Derived Fragment tRF-Gly-GCC Associated With Oxidative Stress in Radiation-Induced Lung Injury.","date":"2022","source":"Dose-response : a publication of International Hormesis Society","url":"https://pubmed.ncbi.nlm.nih.gov/36176737","citation_count":14,"is_preprint":false},{"pmid":"7906006","id":"PMC_7906006","title":"Expression of a truncated guanylate cyclase (GC-C), a receptor for heat-stable enterotoxin of enterotoxigenic Escherichia coli, and its dimer formation in COS-7 cells.","date":"1993","source":"Microbial pathogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/7906006","citation_count":14,"is_preprint":false},{"pmid":"39468069","id":"PMC_39468069","title":"5'-tRNAGly(GCC) halves generated by IRE1α are linked to the ER stress response.","date":"2024","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/39468069","citation_count":13,"is_preprint":false},{"pmid":"22038530","id":"PMC_22038530","title":"GUCY2C-targeted cancer immunotherapy: past, present and future.","date":"2011","source":"Immunologic research","url":"https://pubmed.ncbi.nlm.nih.gov/22038530","citation_count":13,"is_preprint":false},{"pmid":"32788205","id":"PMC_32788205","title":"Preclinical Antitumor Activity and Biodistribution of a Novel Anti-GCC Antibody-Drug Conjugate in Patient-derived Xenografts.","date":"2020","source":"Molecular cancer therapeutics","url":"https://pubmed.ncbi.nlm.nih.gov/32788205","citation_count":13,"is_preprint":false},{"pmid":"18584290","id":"PMC_18584290","title":"Upregulation of the promoter activity of the carrot (Daucus carota) phenylalanine ammonia-lyase gene (DcPAL3) is caused by new members of the transcriptional regulatory proteins, DcERF1 and DcERF2, which bind to the GCC-box homolog and act as an activator to the DcPAL3 promoter.","date":"2008","source":"Journal of plant research","url":"https://pubmed.ncbi.nlm.nih.gov/18584290","citation_count":13,"is_preprint":false},{"pmid":"39313615","id":"PMC_39313615","title":"A phenome-wide association study of methylated GC-rich repeats identifies a GCC repeat expansion in AFF3 associated with intellectual disability.","date":"2024","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39313615","citation_count":12,"is_preprint":false},{"pmid":"23081987","id":"PMC_23081987","title":"Involvement of guanylin and GC-C in rat mesenteric macrophages in resistance to a high-fat diet.","date":"2012","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/23081987","citation_count":12,"is_preprint":false},{"pmid":"27338166","id":"PMC_27338166","title":"An activating gucy2c mutation causes impaired contractility and fluid stagnation in the small bowel.","date":"2016","source":"Scandinavian journal of gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/27338166","citation_count":12,"is_preprint":false},{"pmid":"34143379","id":"PMC_34143379","title":"Preclinical Evaluation of 89Zr-Df-IAB22M2C PET as an Imaging Biomarker for the Development of the GUCY2C-CD3 Bispecific PF-07062119 as a T Cell Engaging Therapy.","date":"2021","source":"Molecular imaging and biology","url":"https://pubmed.ncbi.nlm.nih.gov/34143379","citation_count":12,"is_preprint":false},{"pmid":"20797320","id":"PMC_20797320","title":"Optimizing the binding activity of the AP2/ERF transcription factor with the GCC box element from Brassica napus by directed evolution.","date":"2010","source":"BMB reports","url":"https://pubmed.ncbi.nlm.nih.gov/20797320","citation_count":12,"is_preprint":false},{"pmid":"32037952","id":"PMC_32037952","title":"APC-β-catenin-TCF signaling silences the intestinal guanylin-GUCY2C tumor suppressor axis.","date":"2020","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/32037952","citation_count":11,"is_preprint":false},{"pmid":"33949097","id":"PMC_33949097","title":"Novel GUCY2C variant causing familial diarrhea in a Mennonite kindred and a potential therapeutic approach.","date":"2021","source":"American journal of medical genetics. Part A","url":"https://pubmed.ncbi.nlm.nih.gov/33949097","citation_count":11,"is_preprint":false},{"pmid":"32594830","id":"PMC_32594830","title":"Silencing the intestinal GUCY2C tumor suppressor axis requires APC loss of heterozygosity.","date":"2020","source":"Cancer biology & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/32594830","citation_count":11,"is_preprint":false},{"pmid":"36818350","id":"PMC_36818350","title":"Inhibition of tiRNA-Gly-GCC ameliorates neointimal formation via CBX3-mediated VSMCs phenotypic switching.","date":"2023","source":"Frontiers in cardiovascular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/36818350","citation_count":11,"is_preprint":false},{"pmid":"30353760","id":"PMC_30353760","title":"Genetic and transcriptional analysis of inflammatory bowel disease-associated pathways in patients with GUCY2C-linked familial diarrhea.","date":"2018","source":"Scandinavian journal of gastroenterology","url":"https://pubmed.ncbi.nlm.nih.gov/30353760","citation_count":11,"is_preprint":false},{"pmid":"34667254","id":"PMC_34667254","title":"Novel implications of a strictly monomorphic (GCC) repeat in the human PRKACB gene.","date":"2021","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/34667254","citation_count":11,"is_preprint":false},{"pmid":"21106860","id":"PMC_21106860","title":"The rat kidney contains high levels of prouroguanylin (the uroguanylin precursor) but does not express GC-C (the enteric uroguanylin receptor).","date":"2010","source":"American journal of physiology. Renal physiology","url":"https://pubmed.ncbi.nlm.nih.gov/21106860","citation_count":11,"is_preprint":false},{"pmid":"23541535","id":"PMC_23541535","title":"[Analysis of macular ganglion cell complex (GCC) with spectral-domain optical coherence tomography (SD-OCT) in glaucoma].","date":"2013","source":"Journal francais d'ophtalmologie","url":"https://pubmed.ncbi.nlm.nih.gov/23541535","citation_count":11,"is_preprint":false},{"pmid":"19351210","id":"PMC_19351210","title":"Previstage GCC colorectal cancer staging test: a new molecular test to identify lymph node metastases and provide more accurate information about the stage of patients with colorectal cancer.","date":"2009","source":"Molecular diagnosis & therapy","url":"https://pubmed.ncbi.nlm.nih.gov/19351210","citation_count":11,"is_preprint":false},{"pmid":"39366753","id":"PMC_39366753","title":"Antigen-independent activation is critical for the durable antitumor effect of GUCY2C-targeted CAR-T cells.","date":"2024","source":"Journal for immunotherapy of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/39366753","citation_count":10,"is_preprint":false},{"pmid":"34954189","id":"PMC_34954189","title":"A β-Catenin-TCF-Sensitive Locus Control Region Mediates GUCY2C Ligand Loss in Colorectal Cancer.","date":"2021","source":"Cellular and molecular gastroenterology and hepatology","url":"https://pubmed.ncbi.nlm.nih.gov/34954189","citation_count":10,"is_preprint":false},{"pmid":"35135309","id":"PMC_35135309","title":"Recommendations on ELISpot assay validation by the GCC.","date":"2022","source":"Bioanalysis","url":"https://pubmed.ncbi.nlm.nih.gov/35135309","citation_count":10,"is_preprint":false},{"pmid":"11713322","id":"PMC_11713322","title":"Extrahelical cytosine bases in DNA duplexes containing d[GCC](n).d[GCC](n) repeats: detection by a mechlorethamine crosslinking reaction.","date":"2001","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/11713322","citation_count":10,"is_preprint":false},{"pmid":"19895223","id":"PMC_19895223","title":"GUCY2C reverse transcriptase PCR to stage pN0 colorectal cancer patients.","date":"2009","source":"Expert review of molecular diagnostics","url":"https://pubmed.ncbi.nlm.nih.gov/19895223","citation_count":10,"is_preprint":false},{"pmid":"36104480","id":"PMC_36104480","title":"A (GCC) repeat in SBF1 reveals a novel biological phenomenon in human and links to late onset neurocognitive disorder.","date":"2022","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/36104480","citation_count":10,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":52862,"output_tokens":6108,"usd":0.125103,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":15114,"output_tokens":6085,"usd":0.113848,"stage2_stop_reason":"end_turn"},"total_usd":0.238951,"stage1_batch_id":"msgbatch_01DUPACZi7AAWwuZiUjseQF4","stage2_batch_id":"msgbatch_018yt7chE3f48PEFtDwtj6AE","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2011,\n      \"finding\": \"GUCY2C functions as an intestinal receptor for uroguanylin in a gut-brain endocrine axis regulating satiation; silencing GUCY2C in mice caused hyperphagia and obesity, and nutrient intake induced intestinal prouroguanylin secretion into circulation where it is proteolytically converted to uroguanylin in the hypothalamus to activate GUCY2C and anorexigenic pathways.\",\n      \"method\": \"Gucy2c knockout mice, intracerebroventricular hormone delivery, measurement of food intake and metabolic parameters, proteolytic processing assays\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — multiple orthogonal methods (genetic KO, hormone replacement, circuit tracing), clear phenotypic readout, replicated across multiple experiments in single rigorous study\",\n      \"pmids\": [\"21865642\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GUCY2C suppresses intestinal tumorigenesis by inactivating AKT signaling; loss of GUCY2C in mice activated AKT phosphorylation, increased epithelial proliferation and glycolysis, and increased carcinogen-induced tumorigenesis, all of which were rescued by genetic or pharmacological AKT disruption.\",\n      \"method\": \"Gucy2c−/− mice, Gucy2c−/−Akt1−/− double-knockout mice, immunoblot, microarray, functional metabolic assays, carcinogen (azoxymethane) treatment\",\n      \"journal\": \"Gastroenterology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic epistasis with double knockout rescue, multiple orthogonal methods, clear mechanistic pathway placement\",\n      \"pmids\": [\"19737566\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"GUCY2C regulates intestinal barrier integrity by repressing AKT1, thereby increasing tight junction proteins occludin and claudin-4; Gucy2c−/− mice showed barrier hyperpermeability, reduced junctional proteins, and increased systemic genotoxicity and spontaneous/carcinogen-induced tumorigenesis.\",\n      \"method\": \"Gucy2c−/− mice, permeability assays, immunoblot for tight junction proteins, Caco2 cell in vitro experiments, carcinogen treatment for tumorigenesis\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic KO with defined cellular and molecular phenotype, in vitro validation, multiple orthogonal readouts\",\n      \"pmids\": [\"22384056\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"GCC (GUCY2C) signaling maintains intestinal barrier function by regulating MLCK activation and tight junction disassembly; GCC−/− and UGN−/− mice had increased intestinal permeability associated with elevated IFNγ, MLCK, STAT1 activation, increased MLC phosphorylation, and reduced claudin-2 and JAM-A expression.\",\n      \"method\": \"GCC−/− and UGN−/− mice, intestinal permeability assays, RT-PCR, immunoblot, GCC RNAi in Caco-2 and HT-29 cells\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — reciprocal genetic KO models, in vitro RNAi validation, multiple downstream molecular readouts\",\n      \"pmids\": [\"21305056\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"GUCY2C prevents intestinal desmoplasia by suppressing Akt-dependent TGF-β secretion from epithelial cells; silencing GUCY2C increased TGF-β secretion that activated fibroblast TGF-β type I receptors and Smad3 phosphorylation, which in turn induced fibroblast secretion of HGF that drove colon cancer cell proliferation through cMET-dependent signaling.\",\n      \"method\": \"GUCY2C silencing in human colon cancer cells, co-culture assays, anti-TGF-β antibodies, genetic silencing of Akt in Gucy2c−/− mice, phosphorylation assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vitro mechanistic dissection with multiple pathway components validated, genetic mouse model corroboration\",\n      \"pmids\": [\"24085786\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Activating heterozygous missense mutation (c.2519G→T) in GUCY2C causes familial diarrhea syndrome; mutant GC-C receptor produced markedly increased cGMP upon ligand exposure in HEK293T cells, consistent with hyperactivation of CFTR leading to increased chloride and water secretion.\",\n      \"method\": \"Linkage analysis, exome sequencing, functional cGMP assays in HEK293T cells expressing mutant receptor\",\n      \"journal\": \"The New England journal of medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct functional assay of mutant receptor in heterologous cells, co-segregation with disease phenotype across 32 family members\",\n      \"pmids\": [\"22436048\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Loss-of-function homozygous mutations in GUCY2C that dramatically reduce or abrogate guanylyl cyclase enzymatic activity cause autosomal-recessive meconium ileus; GUCY2C activates CFTR through local cGMP generation in the intestine.\",\n      \"method\": \"Exome/Sanger sequencing, enzymatic activity assays, genetic mapping in consanguineous Bedouin kindreds\",\n      \"journal\": \"American journal of human genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — enzymatic activity measured directly, two unrelated kindreds with different mutations confirming loss-of-function mechanism\",\n      \"pmids\": [\"22521417\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"De novo activating missense mutations in different intracellular domains of GUCY2C cause congenital sodium diarrhea by enhancing intracellular cGMP accumulation in both a ligand-independent and ligand-stimulated manner.\",\n      \"method\": \"Whole-exome sequencing, Sanger sequencing, functional cGMP accumulation assays in HEK293T cells expressing mutant receptors\",\n      \"journal\": \"Gut\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — direct functional assay in heterologous cells for multiple independent mutations in 4 unrelated patients\",\n      \"pmids\": [\"25994218\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"GUCY2C internalizes from the cell surface to lysosomes via clathrin-mediated endocytosis, independently of ligand binding and receptor activation; this mechanism was exploited to deliver an immunotoxin (anti-GUCY2C antibody conjugated via reducible disulfide to ricin A chain) that was activated in lysosomes to kill colorectal cancer cells.\",\n      \"method\": \"Live cell imaging, clathrin inhibition experiments, lysosomal trafficking assays, immunotoxin cytotoxicity assays in vitro and in vivo mouse model\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization experiments with functional consequence, mechanistic inhibitor studies, in vivo validation\",\n      \"pmids\": [\"25294806\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"GUCY2C is expressed in two distinct neuronal circuits in the brain: hypothalamic GUCY2C mRNA is confined to ventral premammillary nucleus (PMV) neurons co-expressing anorexigenic leptin receptors, and midbrain GUCY2C is produced in tyrosine hydroxylase-positive VTA/SN neurons; GUCY2C protein is distributed along axonal projections from these two origins.\",\n      \"method\": \"In situ hybridization, immunofluorescence, stereotaxic ablation of PMV or VTA/SN neurons, anterograde tracer analysis\",\n      \"journal\": \"Brain structure & function\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — selective stereotaxic ablation confirmed circuit origins, anterograde tracing validated projections, multiple orthogonal neuroanatomical methods\",\n      \"pmids\": [\"31485718\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Diet-induced obesity silences guanylin expression in colon through calorie-dependent induction of endoplasmic reticulum stress and the unfolded protein response in intestinal epithelial cells, thereby silencing GUCY2C signaling; transgenic restoration of guanylin expression specifically in intestinal epithelial cells restored GUCY2C signaling and eliminated intestinal tumors in mice on high-calorie diet.\",\n      \"method\": \"Genetically engineered mice on different diets, transgenic guanylin expression, ER stress pathway analysis, tumor counts\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — causal rescue experiment (transgenic guanylin restoration eliminates tumors), mechanistic pathway (ER stress → UPR → guanylin loss) identified\",\n      \"pmids\": [\"26773096\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"APC-β-catenin-TCF signaling transcriptionally represses guanylin hormone expression (but not the GUCY2C receptor itself) at the earliest stages of colorectal tumorigenesis, silencing GUCY2C signaling; biallelic but not monoallelic APC loss was required for hormone repression.\",\n      \"method\": \"Conditional genetic mouse models (monoallelic and biallelic Apc deletion), RNA-seq, FAP patient tissue analysis\",\n      \"journal\": \"Cancer biology & therapy\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — genetic models with allele-specific dosage, human tissue validation, clear mechanistic pathway placement\",\n      \"pmids\": [\"32037952\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"β-Catenin/TCF signaling mediates transcriptional repression of GUCY2C hormone ligands (guanylin and uroguanylin) through a locus control region upstream of the guanylin promoter; CRISPR epigenome editing of this region reconstituted hormone expression, overcoming gene inactivation by mutant β-catenin/TCF.\",\n      \"method\": \"RNA-seq in 4 conditional colon cancer cell models, luciferase reporters, ChIP-seq, CRISPR/Cas9 knockout, CRISPR epigenome editing\",\n      \"journal\": \"Cellular and molecular gastroenterology and hepatology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple orthogonal experimental approaches including CRISPR functional validation, ChIP-seq chromatin mapping, and rescue by epigenome editing\",\n      \"pmids\": [\"34954189\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Activating mutation in Gucy2c equivalent to the Norwegian family mutation produces elevated intestinal cGMP, enhanced fecal water and sodium content, dysbiosis, up-regulation of IFN-stimulated genes, and increased susceptibility to DSS-induced colitis; intestinal cGMP acts via cGMP-dependent protein kinase II.\",\n      \"method\": \"Novel knock-in mouse model with activating Gucy2c mutation, fecal microbiome analysis, colonic gene expression, DSS colitis model, intestinal transit assays\",\n      \"journal\": \"The Journal of experimental medicine\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — novel mouse model with activating mutation, multiple orthogonal readouts including microbiome, gene expression, and functional phenotype\",\n      \"pmids\": [\"34546338\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Intestinal GUCY2C is selectively enriched in neuropod cells (a type of enteroendocrine cell); GUCY2C-sufficient neuropod cells induced hyperexcitability in co-cultured dorsal root ganglia neurons, and the GUCY2C agonist linaclotide eliminated this neuronal hyperexcitability in a manner requiring neuropod cell GUCY2C but independent of bulk epithelial cells or extracellular cGMP; selective elimination of GUCY2C in neuropod cells increased nociceptive signaling and visceral pain refractory to linaclotide.\",\n      \"method\": \"Cell-type specific GUCY2C expression analysis, neuropod cell-DRG neuron co-culture, electrophysiology (rheobase measurement, action potential counting), selective neuropod cell GUCY2C knockout, visceral pain behavioral assays\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — cell-type specific knockout, electrophysiology with defined phenotypic readout, multiple orthogonal experiments establishing neuropod cell-specific mechanism\",\n      \"pmids\": [\"36548082\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"GUCY2C signaling opposes radiation-induced GI syndrome by activating p53 through its dissociation from MDM2, preventing mitotic catastrophe (but not apoptosis) in intestinal epithelial cells; oral delivery of exogenous GUCY2C ligand (heat-stable enterotoxin ST) reduced radiation-induced mortality.\",\n      \"method\": \"Gucy2c−/− mice, lethal irradiation model, p53/MDM2 interaction assays, oral ligand delivery, cell death mechanistic assays\",\n      \"journal\": \"Cancer research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic KO with defined phenotype, p53-MDM2 dissociation mechanism identified, single lab\",\n      \"pmids\": [\"28916678\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"GC-C (GUCY2C) expressed at the surface of COS-7 cells binds heat-stable enterotoxin (STa) via its extracellular domain; the intracellular region is not required for dimer formation, and the truncated GC-C forms dimers on the cell surface and is glycosylated in mammalian cells.\",\n      \"method\": \"Truncated GC-C expression in COS-7 cells, photoaffinity labeling with 125I-STa, SDS-PAGE analysis of dimer formation\",\n      \"journal\": \"Microbial pathogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding assay and biochemical characterization, single lab, truncated receptor construct\",\n      \"pmids\": [\"7906006\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"GC-C mRNA and STa-binding sites are uniformly expressed throughout the rat intestine, but GC-C-mediated cGMP synthesis peaks at the proximal and distal extremes (duodenum and colon) but is nearly absent in the ileum, indicating post-translational regulation of GC-C activity along the intestinal axis.\",\n      \"method\": \"Northern blot, Western blot, [125I]STa binding, STa-dependent cGMP elevation measurements across intestinal segments\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple biochemical methods, functional cGMP assay, systematic characterization across intestinal segments, single lab\",\n      \"pmids\": [\"10965892\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1993,\n      \"finding\": \"GCC mRNA is expressed specifically in intestinal epithelial cells throughout colonic crypts and surface epithelium, while its ligand guanylin mRNA is also expressed in the same tissue, establishing their co-localization as a paracrine signaling system.\",\n      \"method\": \"In situ hybridization, Northern blot analysis of GCA, GCC, and guanylin mRNA in rat colon\",\n      \"journal\": \"The American journal of physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct in situ localization, Northern blot confirmation, systematic co-expression analysis\",\n      \"pmids\": [\"8103637\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"An alternative non-GC-C receptor for STa exists in the intestine; STa-stimulated duodenal bicarbonate secretion in GC-C knockout mice occurred through a CFTR-independent pathway (blocked by DIDS but not glibenclamide), while uroguanylin- and guanylin-stimulated secretion was CFTR-dependent.\",\n      \"method\": \"[125I]STa binding in GC-C KO and WT mice, in vitro and in vivo duodenal bicarbonate secretion measurements, pharmacological inhibitors\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GC-C KO model, binding assays, functional secretion assays; reveals negative result about GC-C exclusivity and identifies alternative pathway\",\n      \"pmids\": [\"18096816\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Two isoforms of GC-C (GC-C1 and GC-C2) were cloned from European eel intestine; GC-C2 intestinal expression increased 100% upon seawater transfer and 60% during developmental maturation of yellow to silver eels, and was restricted to anterior/mid-gut segments in freshwater but extended to posterior gut in seawater, indicating physiological regulation of GC-C expression.\",\n      \"method\": \"cDNA cloning, Northern blot, RT-PCR, acclimation experiments\",\n      \"journal\": \"Comparative biochemistry and physiology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — expression regulation in non-mammalian ortholog, single lab, no functional mechanism beyond expression correlation\",\n      \"pmids\": [\"11399493\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GUCY2C expressed in the hypothalamus (specifically proopiomelanocortin neurons of the arcuate nucleus) mediates diet-induced thermogenesis; GC-C KO mice showed diminished activation of brown adipose tissue (iBAT) after a meal, and intranasal uroguanylin increased iBAT activity in a GC-C-dependent manner correlated with reduced blood glucose.\",\n      \"method\": \"GC-C KO mice, iBAT activity measurements, hypothalamic GC-C immunohistochemistry in POMC neurons, intranasal UGN delivery, metabolic measurements\",\n      \"journal\": \"Pflugers Archiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — GC-C KO with defined phenotype, specific neuronal localization, hormone rescue experiment, single lab\",\n      \"pmids\": [\"31940065\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Guanylin and GC-C expressed in mesenteric macrophages (not only intestinal epithelium) contribute to resistance to high-fat diet-induced obesity; double-transgenic rats overexpressing guanylin and GC-C in macrophages resisted HFD-induced obesity with altered expression of lipid metabolism genes, and lipid accumulation in adipocytes was inhibited by co-culture with macrophages expressing guanylin/GC-C.\",\n      \"method\": \"Microarray screen, histological analysis, double-transgenic rat generation, co-culture assays, siRNA knockdown of guanylin and GC-C\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — transgenic overexpression with phenotype rescue, in vitro siRNA validation, but unexpected macrophage expression context requires replication\",\n      \"pmids\": [\"23081987\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GUCY2C (GCC) functions as a receptor for the paracrine hormones guanylin and uroguanylin, converting GTP to cGMP, and acts as a tumor suppressor coordinating proliferative homeostasis; its signaling reverses the tumorigenic phenotype of human colon cancer cells by regulating proliferation and metabolism.\",\n      \"method\": \"GCC receptor activation in human colon cancer cells, cell cycle analysis, DNA synthesis assay, colony formation, metabolic assays\",\n      \"journal\": \"Drug news & perspectives\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — review summarizing multiple experimental findings, individual mechanistic experiments described but this is primarily a summary article\",\n      \"pmids\": [\"19771320\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"GUCY2C shares domain organization with other receptor guanylate cyclases (extracellular ligand-binding domain, transmembrane domain, intracellular catalytic domain) and is the primary intestinal receptor for guanylin, uroguanylin, and bacterial heat-stable enterotoxins; GC-C or ligand knockouts in mice modulate responses to stable toxin peptides, dietary salt, and intestinal cell development/differentiation.\",\n      \"method\": \"Gene knockout mice, review of structural and functional domain analyses\",\n      \"journal\": \"Molecular and cellular biochemistry\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — review article summarizing findings; limited novel mechanistic data in the abstract itself\",\n      \"pmids\": [\"19960363\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"GUCY2C (GC-C) is a transmembrane receptor guanylyl cyclase expressed on intestinal epithelial cells that converts GTP to cGMP upon activation by the paracrine hormones guanylin and uroguanylin (or bacterial heat-stable enterotoxin); cGMP production activates cGMP-dependent protein kinase II to regulate CFTR-mediated ion and fluid secretion, while downstream repression of AKT1 signaling coordinates intestinal epithelial homeostasis, barrier integrity (via tight junction protein regulation and MLCK/MLC phosphorylation), cell proliferation/metabolism, and tumor suppression; GUCY2C is also expressed in hypothalamic PMV neurons (co-expressing leptin receptors) and dopaminergic VTA/SN neurons to regulate satiation and thermogenesis through an intestine-derived uroguanylin endocrine axis, and selectively in intestinal neuropod cells where cGMP signaling modulates visceral pain transmission to submucosal neurons.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"GUCY2C (GC-C) is a transmembrane receptor guanylyl cyclase that serves as the principal intestinal receptor for the paracrine peptide hormones guanylin and uroguanylin and for bacterial heat-stable enterotoxin (STa), binding ligand through its extracellular domain and converting GTP to cGMP via its intracellular catalytic domain to coordinate intestinal fluid secretion, epithelial homeostasis, and tumor suppression [#16, #18]. Receptor-generated cGMP activates cGMP-dependent protein kinase II to drive CFTR-dependent ion and water secretion, and the clinical importance of this output is established by human mutations: activating missense alleles that elevate cGMP cause familial and congenital secretory diarrhea, while loss-of-function alleles that abrogate cyclase activity cause meconium ileus [#5, #6, #7]. In its tumor-suppressive role, GUCY2C signaling restrains AKT activation, and loss of GUCY2C derepresses AKT-driven epithelial proliferation, glycolysis, and carcinogen-induced tumorigenesis, effects reversed by genetic or pharmacologic AKT disruption [#1]. Through AKT repression GUCY2C also enforces barrier integrity by maintaining tight-junction proteins and limiting MLCK/MLC-dependent junction disassembly, and suppresses stromal desmoplasia by limiting epithelial TGF-\\u03b2 secretion that otherwise drives a fibroblast HGF/cMET paracrine loop [#2, #3, #4]. Tumorigenesis silences this axis at the hormone level: APC\\u2013\\u03b2-catenin/TCF signaling and diet-induced ER stress repress guanylin/uroguanylin expression while sparing the receptor, and restoring hormone expression reinstates signaling and eliminates tumors [#10, #11, #12]. Beyond the epithelium, GUCY2C functions in a gut\\u2013brain endocrine axis in which nutrient-induced circulating prouroguanylin is processed to uroguanylin to activate hypothalamic and midbrain GUCY2C neurons regulating satiation and thermogenesis, and in intestinal neuropod cells where its cGMP signaling restrains nociceptive transmission to sensory neurons [#0, #9, #14].\",\n  \"teleology\": [\n    {\n      \"year\": 1993,\n      \"claim\": \"Establishing that GUCY2C is a cell-surface receptor binding bacterial enterotoxin through its extracellular domain defined its receptor architecture and ligand-engagement mechanism.\",\n      \"evidence\": \"Truncated GC-C expression in COS-7 cells with photoaffinity labeling by 125I-STa and SDS-PAGE dimer analysis\",\n      \"pmids\": [\"7906006\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of the full-length receptor or ligand-bound state\", \"Cyclase activation mechanism downstream of binding not resolved here\"]\n    },\n    {\n      \"year\": 1993,\n      \"claim\": \"Co-localization of GCC receptor and guanylin ligand in colonic epithelium established the system as an endogenous paracrine signaling axis rather than only a toxin target.\",\n      \"evidence\": \"In situ hybridization and Northern blot of receptor and guanylin mRNA in rat colon\",\n      \"pmids\": [\"8103637\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"mRNA co-expression does not demonstrate functional paracrine signaling in vivo\", \"Spatial relationship of secreting and responding cells unresolved\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Discovery that cGMP output, but not receptor expression, varies along the gut axis revealed post-translational regulation of GUCY2C catalytic activity.\",\n      \"evidence\": \"Northern/Western blot, 125I-STa binding, and STa-stimulated cGMP measurement across rat intestinal segments\",\n      \"pmids\": [\"10965892\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of segment-specific activity regulation not identified\", \"Physiological consequence of the activity gradient unclear\"]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Genetic epistasis placed GUCY2C upstream of AKT as a tumor suppressor, answering how receptor loss promotes intestinal carcinogenesis.\",\n      \"evidence\": \"Gucy2c-/- and Gucy2c-/-Akt1-/- double-knockout mice with carcinogen treatment, immunoblot, microarray, and metabolic assays\",\n      \"pmids\": [\"19737566\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Biochemical link from cGMP to AKT inactivation not defined\", \"Whether AKT repression accounts for all tumor-suppressive functions unknown\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Identification of a gut-brain uroguanylin axis showed GUCY2C controls satiation, extending its role beyond the epithelium to systemic energy balance.\",\n      \"evidence\": \"Gucy2c knockout mice, intracerebroventricular hormone delivery, food intake/metabolic readouts, proteolytic processing assays\",\n      \"pmids\": [\"21865642\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of central GUCY2C-expressing neurons not yet mapped at this stage\", \"Processing enzyme for hypothalamic prouroguanylin conversion not defined\"]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Linking GUCY2C/guanylin loss to MLCK activation and tight-junction disassembly defined a mechanism for receptor control of barrier permeability.\",\n      \"evidence\": \"GCC-/- and UGN-/- mice, permeability assays, RT-PCR, immunoblot, and GCC RNAi in Caco-2/HT-29 cells\",\n      \"pmids\": [\"21305056\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal chain from cGMP to IFN\\u03b3/STAT1/MLCK not fully ordered\", \"Relative contribution of immune versus epithelial-intrinsic effects unresolved\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Demonstrating that AKT1 repression by GUCY2C raises occludin and claudin-4 connected the tumor-suppressor pathway to barrier integrity and genotoxic protection.\",\n      \"evidence\": \"Gucy2c-/- mice with permeability assays, tight-junction immunoblots, Caco2 in vitro validation, and carcinogen tumorigenesis\",\n      \"pmids\": [\"22384056\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism by which AKT1 controls junctional protein levels not detailed\", \"Apparent differences in claudin regulation versus other studies unreconciled\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Human activating and loss-of-function mutations established cGMP dosage as the causal determinant of opposite intestinal secretory phenotypes (diarrhea versus meconium ileus).\",\n      \"evidence\": \"Linkage/exome sequencing in human kindreds with cGMP and guanylyl cyclase activity assays in HEK293T cells\",\n      \"pmids\": [\"22436048\", \"22521417\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis for how mutations alter cyclase activity not solved\", \"Downstream CFTR activation inferred rather than directly measured in patient tissue\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Detection of guanylin/GC-C in mesenteric macrophages raised the possibility of an extra-epithelial cell compartment contributing to metabolic protection.\",\n      \"evidence\": \"Microarray, double-transgenic rats overexpressing guanylin/GC-C in macrophages, co-culture, and siRNA knockdown\",\n      \"pmids\": [\"23081987\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Unexpected macrophage expression requires independent replication\", \"Mechanism linking macrophage GC-C to adipocyte lipid accumulation unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Dissecting an epithelial-to-fibroblast TGF-\\u03b2/HGF/cMET loop explained how GUCY2C loss drives stromal desmoplasia and cancer cell proliferation.\",\n      \"evidence\": \"GUCY2C silencing in human colon cancer cells, co-culture, anti-TGF-\\u03b2 antibodies, Smad3 phosphorylation assays, and Akt silencing in Gucy2c-/- mice\",\n      \"pmids\": [\"24085786\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo contribution of the HGF/cMET loop to tumor growth not quantified\", \"Whether the loop operates in human tumors not established\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"Showing constitutive clathrin-mediated internalization to lysosomes defined GUCY2C trafficking and enabled lysosome-activated immunotoxin targeting of colorectal cancer.\",\n      \"evidence\": \"Live-cell imaging, clathrin inhibition, lysosomal trafficking assays, and immunotoxin cytotoxicity in vitro and in mice\",\n      \"pmids\": [\"25294806\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Regulation of internalization rate and recycling not characterized\", \"Relationship between trafficking and signaling output unexplored\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Demonstration that de novo activating mutations in distinct intracellular domains raise cGMP both ligand-independently and ligand-stimulated broadened the genotype spectrum for congenital sodium diarrhea.\",\n      \"evidence\": \"Whole-exome/Sanger sequencing and cGMP accumulation assays in HEK293T cells for multiple mutations across four patients\",\n      \"pmids\": [\"25994218\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Domain-specific mechanisms of constitutive activation not resolved\", \"Patient intestinal cGMP and ion transport not directly measured\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Identifying diet-induced ER stress/UPR as a silencer of guanylin showed how high-calorie intake disables GUCY2C signaling to permit tumorigenesis, reversible by hormone restoration.\",\n      \"evidence\": \"Engineered mice on differing diets, transgenic epithelial guanylin restoration, ER stress pathway analysis, and tumor counts\",\n      \"pmids\": [\"26773096\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular link from UPR to guanylin transcriptional repression not detailed\", \"Generalizability to human obesity-associated cancer untested here\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Linking GUCY2C to p53 activation via MDM2 dissociation defined a radioprotective mechanism preventing mitotic catastrophe in intestinal epithelium.\",\n      \"evidence\": \"Gucy2c-/- mice, lethal irradiation, p53/MDM2 interaction assays, and oral STa ligand delivery\",\n      \"pmids\": [\"28916678\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single-lab finding awaiting independent confirmation\", \"Biochemical bridge from cGMP signaling to MDM2 dissociation not established\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Mapping central GUCY2C to PMV (leptin-receptor) and TH-positive VTA/SN neurons with their axonal projections resolved the neuronal substrates of the gut-brain axis.\",\n      \"evidence\": \"In situ hybridization, immunofluorescence, stereotaxic ablation of PMV or VTA/SN neurons, and anterograde tracing\",\n      \"pmids\": [\"31485718\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Functional output of each neuronal circuit not assigned here\", \"Source of ligand activating these central neurons not defined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Demonstrating GC-C in arcuate POMC neurons mediates diet-induced brown-fat thermogenesis extended the uroguanylin axis to energy expenditure.\",\n      \"evidence\": \"GC-C KO mice, iBAT activity, POMC GC-C immunohistochemistry, intranasal uroguanylin delivery, and metabolic measurements\",\n      \"pmids\": [\"31940065\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Circuit connecting POMC GC-C to BAT not traced\", \"Reconciliation of POMC versus PMV/VTA neuronal sites of action incomplete\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identifying APC\\u2013\\u03b2-catenin/TCF repression of guanylin (sparing the receptor) placed hormone loss at the earliest stage of colorectal tumorigenesis and showed biallelic APC loss is required.\",\n      \"evidence\": \"Conditional monoallelic/biallelic Apc-deletion mouse models, RNA-seq, and FAP patient tissue\",\n      \"pmids\": [\"32037952\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct transcriptional mechanism at the guanylin locus not yet mapped here\", \"Therapeutic reversibility not tested in this study\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Locating a \\u03b2-catenin/TCF-controlled locus control region and reactivating it by CRISPR epigenome editing defined the mechanism and reversibility of hormone silencing.\",\n      \"evidence\": \"RNA-seq across four colon cancer models, luciferase reporters, ChIP-seq, CRISPR knockout, and CRISPR epigenome editing\",\n      \"pmids\": [\"34954189\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo efficacy of epigenome reactivation not demonstrated\", \"Whether restored hormone suppresses established tumors not addressed here\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"A knock-in mouse of the activating diarrhea mutation showed elevated cGMP drives fecal water/sodium loss, dysbiosis, ISG induction, and colitis susceptibility via PKG II, modeling human disease consequences.\",\n      \"evidence\": \"Activating Gucy2c knock-in mouse with microbiome analysis, colonic gene expression, DSS colitis, and transit assays\",\n      \"pmids\": [\"34546338\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Causal order of dysbiosis versus ISG induction not resolved\", \"Direct demonstration of PKG II as the effector limited to inference\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Showing neuropod-cell GUCY2C restrains sensory neuron excitability and visceral pain assigned a cell-type-specific neural function to the receptor and explained linaclotide analgesia.\",\n      \"evidence\": \"Cell-type-specific expression analysis, neuropod cell\\u2013DRG co-culture electrophysiology, selective neuropod GUCY2C knockout, and visceral pain behavior\",\n      \"pmids\": [\"36548082\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Signal transmitted from neuropod cell to DRG neuron not identified\", \"Mechanism of cGMP action within neuropod cells not detailed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The biochemical chain linking receptor-generated cGMP to its diverse effectors (AKT inactivation, p53/MDM2 dissociation, neuropod-to-neuron transmission) remains the central unresolved mechanism.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No defined molecular intermediary between cGMP/PKG II and AKT repression\", \"No structural model of ligand-bound active receptor\", \"Nature of the neuropod-cell-to-sensory-neuron signal unknown\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0009975\", \"supporting_discovery_ids\": [5, 6, 7, 16]},\n      {\"term_id\": \"GO:0001618\", \"supporting_discovery_ids\": [16, 18]},\n      {\"term_id\": \"GO:0038024\", \"supporting_discovery_ids\": [16, 18]},\n      {\"term_id\": \"GO:0060089\", \"supporting_discovery_ids\": [0, 23]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [8, 16, 18]},\n      {\"term_id\": \"GO:0005764\", \"supporting_discovery_ids\": [8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 5]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [5, 6, 19]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [5, 6, 7]},\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [0, 21]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"GUCA2A\", \"GUCA2B\", \"CFTR\", \"AKT1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}