{"gene":"CLCA4","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2024,"finding":"CLCA4 is a self-cleaving metalloprotease whose N-terminal portion (N-CLCA4) is secreted and potentiates Ca2+-activated Cl- current (ICaCC) by directly engaging TMEM16B at the cell surface; this activity requires the von Willebrand factor type A (VWA) domain and the metal ion-dependent adhesion site (MIDAS) motif within VWA, demonstrating specificity for TMEM16B over TMEM16A (which is the partner for the related CLCA1).","method":"Functional electrophysiology in HEK293T cells, domain deletion/mutagenesis of VWA and MIDAS motif, secretion assays, cell-surface engagement experiments","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution in human cells with mutagenesis of catalytic and adhesion domains, multiple orthogonal methods","pmids":["38825009"],"is_preprint":false},{"year":2013,"finding":"CLCA4 is expressed in mammary epithelial cells and its knockdown by shRNA causes downregulation of epithelial marker E-cadherin and CLCA2, and upregulation of mesenchymal markers N-cadherin, vimentin, and fibronectin, indicating CLCA4 is required to maintain the epithelial state and suppress EMT in breast epithelial cells.","method":"shRNA knockdown in immortalized mammary epithelial cells, transcriptional profiling, colony formation assay, qRT-PCR for EMT markers","journal":"PloS one","confidence":"Medium","confidence_rationale":"Tier 2 — clean KD with defined cellular EMT phenotype and multiple marker readouts, single lab","pmids":["24386311"],"is_preprint":false},{"year":2017,"finding":"Overexpression of CLCA4 in bladder cancer cells attenuates proliferation, migration, and invasion, and suppresses PI3K/AKT pathway activation as well as EMT marker changes; CLCA4 knockdown has the opposite effect, placing CLCA4 upstream of PI3K/AKT signaling.","method":"Overexpression and shRNA knockdown in bladder cancer cell lines, proliferation and invasion assays, Western blot for PI3K/AKT phosphorylation and EMT markers","journal":"Oncotarget","confidence":"Medium","confidence_rationale":"Tier 2 — bidirectional gain/loss-of-function with defined signaling readouts, single lab","pmids":["29190973"],"is_preprint":false},{"year":2018,"finding":"Knockdown of CLCA4 in hepatocellular carcinoma cells increases migration and invasion, upregulates PI3K/AKT phosphorylation, and alters EMT marker expression; CLCA4 overexpression reverses these effects, establishing CLCA4 as a suppressor of PI3K/AKT-mediated EMT in HCC.","method":"siRNA knockdown and plasmid overexpression in HCC cell lines, Transwell migration/invasion assays, Western blot for PI3K/AKT phosphorylation and EMT markers, immunohistochemistry","journal":"Aging","confidence":"Medium","confidence_rationale":"Tier 2 — bidirectional gain/loss-of-function with signaling and phenotypic readouts, single lab","pmids":["30312171"],"is_preprint":false},{"year":2019,"finding":"Overexpression of CLCA4 in colorectal cancer cells inhibits migration and invasion by suppressing EMT via PI3K/AKT signaling, altering expression patterns of EMT markers in gain-of-function models.","method":"Gain-of-function overexpression in SW620 and LoVo CRC cells, wound healing assay, Transwell assay, Western blot for EMT markers and PI3K/AKT pathway","journal":"Medical science monitor","confidence":"Medium","confidence_rationale":"Tier 2 — gain-of-function with defined cellular and signaling phenotype, single lab","pmids":["31164625"],"is_preprint":false},{"year":2012,"finding":"Genetic variants encompassing the CLCA4 promoter region are associated with the manifestation of residual chloride secretion (Ca2+-mediated) in colonic tissue of cystic fibrosis patients, suggesting CLCA4 modulates chloride secretion as part of signal transduction in colonic epithelial cells.","method":"Genetic association study with fine-mapping in CF twin/sibling cohort (101 families, 171 patients), analysis of endophenotypes (CFTR-mediated vs. Ca2+-mediated residual Cl- conductance)","journal":"European journal of human genetics","confidence":"Low","confidence_rationale":"Tier 3 — genetic association without direct functional validation of CLCA4 mechanism","pmids":["23073314"],"is_preprint":false},{"year":2022,"finding":"miR-19a directly targets the CLCA4 3'UTR (confirmed by luciferase reporter assay) to repress CLCA4 expression, and this miR-19a/CLCA4 axis modulates phospho-activation of the PI3K/AKT pathway in colorectal cancer cells to promote proliferation, migration, and invasion.","method":"Luciferase reporter assay for miR-19a targeting CLCA4 3'UTR, miR-19a mimics/inhibitors with CLCA4 knockdown rescue, proliferation and invasion assays, Western blot for PI3K/AKT","journal":"European journal of histochemistry","confidence":"Medium","confidence_rationale":"Tier 2 — luciferase validation of miRNA-target relationship plus epistasis rescue experiment, single lab","pmids":["35266369"],"is_preprint":false},{"year":2020,"finding":"miR-501-5p directly targets CLCA4 (confirmed by luciferase assay) and suppresses its expression in head and neck squamous cell carcinoma cells, thereby promoting proliferation and metastasis; co-transfection experiments established the miR-501-5p/CLCA4 axis as a functional regulatory pair.","method":"Luciferase reporter assay for miR-501-5p targeting CLCA4, co-transfection assay, cell proliferation and Transwell invasion assays","journal":"Molecular biology reports","confidence":"Medium","confidence_rationale":"Tier 2 — luciferase validation plus functional co-transfection rescue, single lab","pmids":["32072405"],"is_preprint":false},{"year":2021,"finding":"Overexpression of CLCA4 in esophageal carcinoma cells inhibits proliferation, migration, invasion, and EMT progression in vitro, and suppresses tumor growth in vivo in animal experiments.","method":"CLCA4 overexpression in ESCA cell lines, CCK-8 proliferation assay, Transwell assay, in vivo xenograft tumor growth, Western blot for EMT markers","journal":"Journal of oncology","confidence":"Medium","confidence_rationale":"Tier 2 — gain-of-function with in vitro and in vivo phenotypic readouts, single lab","pmids":["34194494"],"is_preprint":false}],"current_model":"CLCA4 is a self-cleaving metalloprotease that is secreted (N-terminal fragment) and potentiates Ca2+-activated Cl- currents by engaging TMEM16B via its VWA/MIDAS domain at the cell surface; in epithelial contexts, CLCA4 also suppresses EMT and cell invasion by inhibiting PI3K/AKT signaling, and its expression is post-transcriptionally regulated by miR-19a and miR-501-5p targeting its 3'UTR."},"narrative":{"teleology":[{"year":2012,"claim":"Before CLCA4's molecular mechanism was known, a genetic association study linked CLCA4 promoter variants to residual Ca2+-mediated chloride secretion in cystic fibrosis colonic tissue, providing the first human evidence that CLCA4 influences chloride conductance in vivo.","evidence":"Fine-mapping genetic association in a CF twin/sibling cohort (101 families) correlating promoter SNPs with Ca2+-mediated Cl- conductance endophenotype","pmids":["23073314"],"confidence":"Low","gaps":["Association only; no direct functional validation of CLCA4 variants on chloride channel activity","Causative variant and target channel were not identified","No in vitro reconstitution to distinguish CLCA4 effect from neighboring gene effects"]},{"year":2013,"claim":"Establishing that CLCA4 is required to maintain epithelial identity, knockdown in mammary epithelial cells revealed that CLCA4 loss drives a full EMT program — the first demonstration of a non-ion-channel role for CLCA4.","evidence":"shRNA knockdown in immortalized mammary epithelial cells with qRT-PCR and protein analysis of E-cadherin, N-cadherin, vimentin, and fibronectin","pmids":["24386311"],"confidence":"Medium","gaps":["Signaling pathway downstream of CLCA4 was not identified","Whether the EMT-suppressive role depends on CLCA4's protease or secreted activity was untested","Single cell-type study without rescue by re-expression"]},{"year":2017,"claim":"Bidirectional gain- and loss-of-function experiments in bladder and later hepatocellular and colorectal cancer cells converged on PI3K/AKT as the signaling axis suppressed by CLCA4, mechanistically linking CLCA4 to inhibition of AKT phosphorylation and downstream EMT.","evidence":"Overexpression and shRNA knockdown in bladder cancer (2017), HCC (2018), CRC (2019), and esophageal carcinoma (2021) cell lines with Western blot for phospho-AKT/PI3K, Transwell invasion assays, and in vivo xenografts","pmids":["29190973","30312171","31164625","34194494"],"confidence":"Medium","gaps":["Direct physical target linking CLCA4 to PI3K/AKT inhibition is unknown","Whether the secreted N-terminal fragment or membrane-tethered C-terminal fragment mediates EMT suppression is unresolved","No genetic knockout or CRISPR-based validation in non-cancer primary epithelial cells"]},{"year":2020,"claim":"Identification of miR-501-5p and miR-19a as direct post-transcriptional repressors of CLCA4 revealed how CLCA4 is silenced in cancer, establishing upstream regulatory axes that derepress PI3K/AKT signaling.","evidence":"Luciferase reporter assays confirming direct 3′-UTR targeting plus co-transfection epistasis rescue experiments in HNSCC (miR-501-5p) and CRC (miR-19a) cells","pmids":["32072405","35266369"],"confidence":"Medium","gaps":["Whether these miRNAs regulate CLCA4 in normal physiology or only in cancer contexts is unknown","No in vivo validation of the miRNA/CLCA4/PI3K axis","Other post-transcriptional regulators or promoter-level silencing mechanisms not explored"]},{"year":2024,"claim":"Reconstitution of CLCA4's ion-channel-modulatory function demonstrated that the secreted N-terminal metalloprotease fragment potentiates TMEM16B-mediated Ca2+-activated Cl- currents through VWA/MIDAS domain-dependent engagement, resolving the molecular basis and target specificity of CLCA4's channel-regulatory activity.","evidence":"Electrophysiology in HEK293T cells co-expressing TMEM16A or TMEM16B with wild-type or VWA/MIDAS-mutant CLCA4, secretion assays, domain deletion constructs","pmids":["38825009"],"confidence":"High","gaps":["Whether VWA/MIDAS-mediated TMEM16B engagement is related to the PI3K/AKT-suppressive EMT phenotype is unknown","Structural basis of CLCA4–TMEM16B interaction not determined","Physiological tissues where CLCA4–TMEM16B signaling operates in vivo not defined"]},{"year":null,"claim":"The mechanistic link between CLCA4's two established activities — TMEM16B-dependent chloride current potentiation and PI3K/AKT-mediated EMT suppression — remains unresolved, and it is unknown whether these reflect the same or independent pathways.","evidence":"","pmids":[],"confidence":"Low","gaps":["No study has tested whether CLCA4's protease activity or secreted fragment is required for EMT suppression","The direct molecular target linking CLCA4 to PI3K inhibition has not been identified","In vivo physiological roles of CLCA4 in normal epithelial homeostasis have not been established with genetic models"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0]},{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,2,3]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[0]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[2,3,4]}],"complexes":[],"partners":["TMEM16B"],"other_free_text":[]},"mechanistic_narrative":"CLCA4 is a secreted self-cleaving metalloprotease that modulates calcium-activated chloride currents and suppresses epithelial-to-mesenchymal transition across multiple epithelial tissues. The N-terminal cleavage product (N-CLCA4) is secreted and potentiates Ca2+-activated Cl- currents by engaging TMEM16B at the cell surface through its von Willebrand factor type A (VWA) domain and metal ion-dependent adhesion site (MIDAS) motif, with specificity for TMEM16B over TMEM16A [PMID:38825009]. In epithelial cells of the breast, bladder, liver, colon, and esophagus, CLCA4 maintains the epithelial phenotype by suppressing PI3K/AKT signaling and EMT marker switching; its loss upregulates mesenchymal markers and promotes cell invasion [PMID:24386311, PMID:29190973, PMID:30312171]. CLCA4 expression is post-transcriptionally repressed by miR-19a and miR-501-5p, which directly target its 3′-UTR to relieve its inhibition of PI3K/AKT-driven proliferation and invasion [PMID:35266369, PMID:32072405]."},"prefetch_data":{"uniprot":{"accession":"Q14CN2","full_name":"Calcium-activated chloride channel regulator 4","aliases":["Calcium-activated chloride channel family member 4","hCLCA4","Calcium-activated chloride channel protein 2","CaCC-2","hCaCC-2","Chloride channel accessory 4"],"length_aa":919,"mass_kda":101.3,"function":"May be involved in mediating calcium-activated chloride conductance","subcellular_location":"Cell membrane; Apical cell membrane; Secreted","url":"https://www.uniprot.org/uniprotkb/Q14CN2/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CLCA4","classification":"Not Classified","n_dependent_lines":2,"n_total_lines":1208,"dependency_fraction":0.0016556291390728477},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CLCA4","total_profiled":1310},"omim":[{"mim_id":"616857","title":"CHLORIDE CHANNEL ACCESSORY 4; CLCA4","url":"https://www.omim.org/entry/616857"},{"mim_id":"604003","title":"CHLORIDE CHANNEL ACCESSORY 2; CLCA2","url":"https://www.omim.org/entry/604003"},{"mim_id":"603906","title":"CHLORIDE CHANNEL ACCESSORY 1; CLCA1","url":"https://www.omim.org/entry/603906"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Plasma membrane","reliability":"Approved"},{"location":"Nucleoplasm","reliability":"Additional"},{"location":"Aggresome","reliability":"Additional"}],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"esophagus","ntpm":352.4},{"tissue":"intestine","ntpm":241.9}],"url":"https://www.proteinatlas.org/search/CLCA4"},"hgnc":{"alias_symbol":["CaCC2"],"prev_symbol":[]},"alphafold":{"accession":"Q14CN2","domains":[{"cath_id":"-","chopping":"26-168_276-302","consensus_level":"medium","plddt":95.0981,"start":26,"end":302},{"cath_id":"3.40.50.410","chopping":"306-474","consensus_level":"medium","plddt":94.095,"start":306,"end":474},{"cath_id":"2.60.40.10","chopping":"763-865","consensus_level":"high","plddt":90.1643,"start":763,"end":865}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14CN2","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q14CN2-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q14CN2-F1-predicted_aligned_error_v6.png","plddt_mean":89.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CLCA4","jax_strain_url":"https://www.jax.org/strain/search?query=CLCA4"},"sequence":{"accession":"Q14CN2","fasta_url":"https://rest.uniprot.org/uniprotkb/Q14CN2.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q14CN2/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q14CN2"}},"corpus_meta":[{"pmid":"24386311","id":"PMC_24386311","title":"Loss of CLCA4 promotes epithelial-to-mesenchymal transition in breast cancer cells.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/24386311","citation_count":53,"is_preprint":false},{"pmid":"31164625","id":"PMC_31164625","title":"Calcium-Activated Chloride Channel A4 (CLCA4) Plays Inhibitory Roles in Invasion and Migration Through Suppressing Epithelial-Mesenchymal Transition via PI3K/AKT Signaling in Colorectal Cancer.","date":"2019","source":"Medical science monitor : international medical journal of experimental and clinical research","url":"https://pubmed.ncbi.nlm.nih.gov/31164625","citation_count":35,"is_preprint":false},{"pmid":"29190973","id":"PMC_29190973","title":"CLCA4 inhibits bladder cancer cell proliferation, migration, and invasion by suppressing the PI3K/AKT pathway.","date":"2017","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/29190973","citation_count":34,"is_preprint":false},{"pmid":"30312171","id":"PMC_30312171","title":"CLCA4 inhibits cell proliferation and invasion of hepatocellular carcinoma by suppressing epithelial-mesenchymal transition via PI3K/AKT signaling.","date":"2018","source":"Aging","url":"https://pubmed.ncbi.nlm.nih.gov/30312171","citation_count":30,"is_preprint":false},{"pmid":"32565987","id":"PMC_32565987","title":"Downregulation of CLCA4 expression is associated with the development and progression of colorectal cancer.","date":"2020","source":"Oncology letters","url":"https://pubmed.ncbi.nlm.nih.gov/32565987","citation_count":14,"is_preprint":false},{"pmid":"32797167","id":"PMC_32797167","title":"CLCA4 and MS4A12 as the significant gene biomarkers of primary colorectal cancer.","date":"2020","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/32797167","citation_count":12,"is_preprint":false},{"pmid":"23073314","id":"PMC_23073314","title":"CLCA4 variants determine the manifestation of the cystic fibrosis basic defect in the intestine.","date":"2012","source":"European journal of human genetics : EJHG","url":"https://pubmed.ncbi.nlm.nih.gov/23073314","citation_count":11,"is_preprint":false},{"pmid":"35266369","id":"PMC_35266369","title":"<em>miR-19a</em> targeting <em>CLCA4</em> to regulate the proliferation, migration, and invasion of colorectal cancer cells.","date":"2022","source":"European journal of histochemistry : EJH","url":"https://pubmed.ncbi.nlm.nih.gov/35266369","citation_count":9,"is_preprint":false},{"pmid":"32072405","id":"PMC_32072405","title":"MiR-501-5p acts as an energetic regulator in head and neck squamous cell carcinoma cells growth and aggressiveness via reducing CLCA4.","date":"2020","source":"Molecular biology reports","url":"https://pubmed.ncbi.nlm.nih.gov/32072405","citation_count":9,"is_preprint":false},{"pmid":"32773719","id":"PMC_32773719","title":"Frameshift Mutations and Loss of Expression of CLCA4 Gene are Frequent in Colorectal Cancers With Microsatellite Instability.","date":"2020","source":"Applied immunohistochemistry & molecular morphology : AIMM","url":"https://pubmed.ncbi.nlm.nih.gov/32773719","citation_count":6,"is_preprint":false},{"pmid":"34194494","id":"PMC_34194494","title":"Expression of the CLCA4 Gene in Esophageal Carcinoma and Its Impact on the Biologic Function of Esophageal Carcinoma Cells.","date":"2021","source":"Journal of oncology","url":"https://pubmed.ncbi.nlm.nih.gov/34194494","citation_count":5,"is_preprint":false},{"pmid":"30887952","id":"PMC_30887952","title":"Chloride Channel Accessory 4 (CLCA4) Gene Polymorphisms and Non-Obstructive Azoospermia: A Case-Control Study.","date":"2019","source":"Medical science monitor : international medical journal of experimental and clinical research","url":"https://pubmed.ncbi.nlm.nih.gov/30887952","citation_count":2,"is_preprint":false},{"pmid":"38825009","id":"PMC_38825009","title":"Modulation of TMEM16B channel activity by the calcium-activated chloride channel regulator 4 (CLCA4) in human cells.","date":"2024","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/38825009","citation_count":2,"is_preprint":false},{"pmid":"30847028","id":"PMC_30847028","title":"Correction: CLCA4 inhibits bladder cancer cell proliferation, migration, and invasion by suppressing the PI3K/AKT pathway.","date":"2019","source":"Oncotarget","url":"https://pubmed.ncbi.nlm.nih.gov/30847028","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.02.28.25323104","title":"Intragenic deletions from whole genome sequencing of 1054 suicide deaths","date":"2025-03-06","source":"bioRxiv","url":"https://doi.org/10.1101/2025.02.28.25323104","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8200,"output_tokens":2211,"usd":0.028882},"stage2":{"model":"claude-opus-4-6","input_tokens":5500,"output_tokens":4125,"usd":0.195937},"total_usd":0.224819,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2024,\n      \"finding\": \"CLCA4 is a self-cleaving metalloprotease whose N-terminal portion (N-CLCA4) is secreted and potentiates Ca2+-activated Cl- current (ICaCC) by directly engaging TMEM16B at the cell surface; this activity requires the von Willebrand factor type A (VWA) domain and the metal ion-dependent adhesion site (MIDAS) motif within VWA, demonstrating specificity for TMEM16B over TMEM16A (which is the partner for the related CLCA1).\",\n      \"method\": \"Functional electrophysiology in HEK293T cells, domain deletion/mutagenesis of VWA and MIDAS motif, secretion assays, cell-surface engagement experiments\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution in human cells with mutagenesis of catalytic and adhesion domains, multiple orthogonal methods\",\n      \"pmids\": [\"38825009\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CLCA4 is expressed in mammary epithelial cells and its knockdown by shRNA causes downregulation of epithelial marker E-cadherin and CLCA2, and upregulation of mesenchymal markers N-cadherin, vimentin, and fibronectin, indicating CLCA4 is required to maintain the epithelial state and suppress EMT in breast epithelial cells.\",\n      \"method\": \"shRNA knockdown in immortalized mammary epithelial cells, transcriptional profiling, colony formation assay, qRT-PCR for EMT markers\",\n      \"journal\": \"PloS one\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean KD with defined cellular EMT phenotype and multiple marker readouts, single lab\",\n      \"pmids\": [\"24386311\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Overexpression of CLCA4 in bladder cancer cells attenuates proliferation, migration, and invasion, and suppresses PI3K/AKT pathway activation as well as EMT marker changes; CLCA4 knockdown has the opposite effect, placing CLCA4 upstream of PI3K/AKT signaling.\",\n      \"method\": \"Overexpression and shRNA knockdown in bladder cancer cell lines, proliferation and invasion assays, Western blot for PI3K/AKT phosphorylation and EMT markers\",\n      \"journal\": \"Oncotarget\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — bidirectional gain/loss-of-function with defined signaling readouts, single lab\",\n      \"pmids\": [\"29190973\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Knockdown of CLCA4 in hepatocellular carcinoma cells increases migration and invasion, upregulates PI3K/AKT phosphorylation, and alters EMT marker expression; CLCA4 overexpression reverses these effects, establishing CLCA4 as a suppressor of PI3K/AKT-mediated EMT in HCC.\",\n      \"method\": \"siRNA knockdown and plasmid overexpression in HCC cell lines, Transwell migration/invasion assays, Western blot for PI3K/AKT phosphorylation and EMT markers, immunohistochemistry\",\n      \"journal\": \"Aging\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — bidirectional gain/loss-of-function with signaling and phenotypic readouts, single lab\",\n      \"pmids\": [\"30312171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Overexpression of CLCA4 in colorectal cancer cells inhibits migration and invasion by suppressing EMT via PI3K/AKT signaling, altering expression patterns of EMT markers in gain-of-function models.\",\n      \"method\": \"Gain-of-function overexpression in SW620 and LoVo CRC cells, wound healing assay, Transwell assay, Western blot for EMT markers and PI3K/AKT pathway\",\n      \"journal\": \"Medical science monitor\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with defined cellular and signaling phenotype, single lab\",\n      \"pmids\": [\"31164625\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Genetic variants encompassing the CLCA4 promoter region are associated with the manifestation of residual chloride secretion (Ca2+-mediated) in colonic tissue of cystic fibrosis patients, suggesting CLCA4 modulates chloride secretion as part of signal transduction in colonic epithelial cells.\",\n      \"method\": \"Genetic association study with fine-mapping in CF twin/sibling cohort (101 families, 171 patients), analysis of endophenotypes (CFTR-mediated vs. Ca2+-mediated residual Cl- conductance)\",\n      \"journal\": \"European journal of human genetics\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — genetic association without direct functional validation of CLCA4 mechanism\",\n      \"pmids\": [\"23073314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-19a directly targets the CLCA4 3'UTR (confirmed by luciferase reporter assay) to repress CLCA4 expression, and this miR-19a/CLCA4 axis modulates phospho-activation of the PI3K/AKT pathway in colorectal cancer cells to promote proliferation, migration, and invasion.\",\n      \"method\": \"Luciferase reporter assay for miR-19a targeting CLCA4 3'UTR, miR-19a mimics/inhibitors with CLCA4 knockdown rescue, proliferation and invasion assays, Western blot for PI3K/AKT\",\n      \"journal\": \"European journal of histochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — luciferase validation of miRNA-target relationship plus epistasis rescue experiment, single lab\",\n      \"pmids\": [\"35266369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"miR-501-5p directly targets CLCA4 (confirmed by luciferase assay) and suppresses its expression in head and neck squamous cell carcinoma cells, thereby promoting proliferation and metastasis; co-transfection experiments established the miR-501-5p/CLCA4 axis as a functional regulatory pair.\",\n      \"method\": \"Luciferase reporter assay for miR-501-5p targeting CLCA4, co-transfection assay, cell proliferation and Transwell invasion assays\",\n      \"journal\": \"Molecular biology reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — luciferase validation plus functional co-transfection rescue, single lab\",\n      \"pmids\": [\"32072405\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"Overexpression of CLCA4 in esophageal carcinoma cells inhibits proliferation, migration, invasion, and EMT progression in vitro, and suppresses tumor growth in vivo in animal experiments.\",\n      \"method\": \"CLCA4 overexpression in ESCA cell lines, CCK-8 proliferation assay, Transwell assay, in vivo xenograft tumor growth, Western blot for EMT markers\",\n      \"journal\": \"Journal of oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — gain-of-function with in vitro and in vivo phenotypic readouts, single lab\",\n      \"pmids\": [\"34194494\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CLCA4 is a self-cleaving metalloprotease that is secreted (N-terminal fragment) and potentiates Ca2+-activated Cl- currents by engaging TMEM16B via its VWA/MIDAS domain at the cell surface; in epithelial contexts, CLCA4 also suppresses EMT and cell invasion by inhibiting PI3K/AKT signaling, and its expression is post-transcriptionally regulated by miR-19a and miR-501-5p targeting its 3'UTR.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CLCA4 is a secreted self-cleaving metalloprotease that modulates calcium-activated chloride currents and suppresses epithelial-to-mesenchymal transition across multiple epithelial tissues. The N-terminal cleavage product (N-CLCA4) is secreted and potentiates Ca2+-activated Cl- currents by engaging TMEM16B at the cell surface through its von Willebrand factor type A (VWA) domain and metal ion-dependent adhesion site (MIDAS) motif, with specificity for TMEM16B over TMEM16A [PMID:38825009]. In epithelial cells of the breast, bladder, liver, colon, and esophagus, CLCA4 maintains the epithelial phenotype by suppressing PI3K/AKT signaling and EMT marker switching; its loss upregulates mesenchymal markers and promotes cell invasion [PMID:24386311, PMID:29190973, PMID:30312171]. CLCA4 expression is post-transcriptionally repressed by miR-19a and miR-501-5p, which directly target its 3′-UTR to relieve its inhibition of PI3K/AKT-driven proliferation and invasion [PMID:35266369, PMID:32072405].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Before CLCA4's molecular mechanism was known, a genetic association study linked CLCA4 promoter variants to residual Ca2+-mediated chloride secretion in cystic fibrosis colonic tissue, providing the first human evidence that CLCA4 influences chloride conductance in vivo.\",\n      \"evidence\": \"Fine-mapping genetic association in a CF twin/sibling cohort (101 families) correlating promoter SNPs with Ca2+-mediated Cl- conductance endophenotype\",\n      \"pmids\": [\"23073314\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Association only; no direct functional validation of CLCA4 variants on chloride channel activity\",\n        \"Causative variant and target channel were not identified\",\n        \"No in vitro reconstitution to distinguish CLCA4 effect from neighboring gene effects\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing that CLCA4 is required to maintain epithelial identity, knockdown in mammary epithelial cells revealed that CLCA4 loss drives a full EMT program — the first demonstration of a non-ion-channel role for CLCA4.\",\n      \"evidence\": \"shRNA knockdown in immortalized mammary epithelial cells with qRT-PCR and protein analysis of E-cadherin, N-cadherin, vimentin, and fibronectin\",\n      \"pmids\": [\"24386311\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Signaling pathway downstream of CLCA4 was not identified\",\n        \"Whether the EMT-suppressive role depends on CLCA4's protease or secreted activity was untested\",\n        \"Single cell-type study without rescue by re-expression\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Bidirectional gain- and loss-of-function experiments in bladder and later hepatocellular and colorectal cancer cells converged on PI3K/AKT as the signaling axis suppressed by CLCA4, mechanistically linking CLCA4 to inhibition of AKT phosphorylation and downstream EMT.\",\n      \"evidence\": \"Overexpression and shRNA knockdown in bladder cancer (2017), HCC (2018), CRC (2019), and esophageal carcinoma (2021) cell lines with Western blot for phospho-AKT/PI3K, Transwell invasion assays, and in vivo xenografts\",\n      \"pmids\": [\"29190973\", \"30312171\", \"31164625\", \"34194494\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct physical target linking CLCA4 to PI3K/AKT inhibition is unknown\",\n        \"Whether the secreted N-terminal fragment or membrane-tethered C-terminal fragment mediates EMT suppression is unresolved\",\n        \"No genetic knockout or CRISPR-based validation in non-cancer primary epithelial cells\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of miR-501-5p and miR-19a as direct post-transcriptional repressors of CLCA4 revealed how CLCA4 is silenced in cancer, establishing upstream regulatory axes that derepress PI3K/AKT signaling.\",\n      \"evidence\": \"Luciferase reporter assays confirming direct 3′-UTR targeting plus co-transfection epistasis rescue experiments in HNSCC (miR-501-5p) and CRC (miR-19a) cells\",\n      \"pmids\": [\"32072405\", \"35266369\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether these miRNAs regulate CLCA4 in normal physiology or only in cancer contexts is unknown\",\n        \"No in vivo validation of the miRNA/CLCA4/PI3K axis\",\n        \"Other post-transcriptional regulators or promoter-level silencing mechanisms not explored\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Reconstitution of CLCA4's ion-channel-modulatory function demonstrated that the secreted N-terminal metalloprotease fragment potentiates TMEM16B-mediated Ca2+-activated Cl- currents through VWA/MIDAS domain-dependent engagement, resolving the molecular basis and target specificity of CLCA4's channel-regulatory activity.\",\n      \"evidence\": \"Electrophysiology in HEK293T cells co-expressing TMEM16A or TMEM16B with wild-type or VWA/MIDAS-mutant CLCA4, secretion assays, domain deletion constructs\",\n      \"pmids\": [\"38825009\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether VWA/MIDAS-mediated TMEM16B engagement is related to the PI3K/AKT-suppressive EMT phenotype is unknown\",\n        \"Structural basis of CLCA4–TMEM16B interaction not determined\",\n        \"Physiological tissues where CLCA4–TMEM16B signaling operates in vivo not defined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The mechanistic link between CLCA4's two established activities — TMEM16B-dependent chloride current potentiation and PI3K/AKT-mediated EMT suppression — remains unresolved, and it is unknown whether these reflect the same or independent pathways.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No study has tested whether CLCA4's protease activity or secreted fragment is required for EMT suppression\",\n        \"The direct molecular target linking CLCA4 to PI3K inhibition has not been identified\",\n        \"In vivo physiological roles of CLCA4 in normal epithelial homeostasis have not been established with genetic models\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005215\", \"supporting_discovery_ids\": []},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TMEM16B\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\nWait, I need to fix the pathway section — I accidentally put a GO term in there. Let me correct:\n\n```json\n{\n  \"mechanistic_narrative\": \"CLCA4 is a secreted self-cleaving metalloprotease that modulates calcium-activated chloride currents and suppresses epithelial-to-mesenchymal transition across multiple epithelial tissues. The N-terminal cleavage product (N-CLCA4) is secreted and potentiates Ca2+-activated Cl- currents by engaging TMEM16B at the cell surface through its von Willebrand factor type A (VWA) domain and metal ion-dependent adhesion site (MIDAS) motif, with specificity for TMEM16B over TMEM16A [PMID:38825009]. In epithelial cells of the breast, bladder, liver, colon, and esophagus, CLCA4 maintains the epithelial phenotype by suppressing PI3K/AKT signaling and EMT marker switching; its loss upregulates mesenchymal markers and promotes cell invasion [PMID:24386311, PMID:29190973, PMID:30312171]. CLCA4 expression is post-transcriptionally repressed by miR-19a and miR-501-5p, which directly target its 3′-UTR to relieve its inhibition of PI3K/AKT-driven proliferation and invasion [PMID:35266369, PMID:32072405].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"Before CLCA4's molecular mechanism was known, a genetic association study linked CLCA4 promoter variants to residual Ca2+-mediated chloride secretion in cystic fibrosis colonic tissue, providing the first human evidence that CLCA4 influences chloride conductance in vivo.\",\n      \"evidence\": \"Fine-mapping genetic association in a CF twin/sibling cohort (101 families) correlating promoter SNPs with Ca2+-mediated Cl- conductance endophenotype\",\n      \"pmids\": [\"23073314\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"Association only; no direct functional validation of CLCA4 variants on chloride channel activity\",\n        \"Causative variant and target channel were not identified\",\n        \"No in vitro reconstitution to distinguish CLCA4 effect from neighboring gene effects\"\n      ]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Establishing that CLCA4 is required to maintain epithelial identity, knockdown in mammary epithelial cells revealed that CLCA4 loss drives a full EMT program — the first demonstration of a non-ion-channel role for CLCA4.\",\n      \"evidence\": \"shRNA knockdown in immortalized mammary epithelial cells with qRT-PCR and protein analysis of E-cadherin, N-cadherin, vimentin, and fibronectin\",\n      \"pmids\": [\"24386311\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Signaling pathway downstream of CLCA4 was not identified\",\n        \"Whether the EMT-suppressive role depends on CLCA4's protease or secreted activity was untested\",\n        \"Single cell-type study without rescue by re-expression\"\n      ]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Bidirectional gain- and loss-of-function experiments in bladder and later hepatocellular and colorectal cancer cells converged on PI3K/AKT as the signaling axis suppressed by CLCA4, mechanistically linking CLCA4 to inhibition of AKT phosphorylation and downstream EMT.\",\n      \"evidence\": \"Overexpression and shRNA knockdown in bladder cancer (2017), HCC (2018), CRC (2019), and esophageal carcinoma (2021) cell lines with Western blot for phospho-AKT/PI3K, Transwell invasion assays, and in vivo xenografts\",\n      \"pmids\": [\"29190973\", \"30312171\", \"31164625\", \"34194494\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct physical target linking CLCA4 to PI3K/AKT inhibition is unknown\",\n        \"Whether the secreted N-terminal fragment or membrane-tethered C-terminal fragment mediates EMT suppression is unresolved\",\n        \"No genetic knockout or CRISPR-based validation in non-cancer primary epithelial cells\"\n      ]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Identification of miR-501-5p and miR-19a as direct post-transcriptional repressors of CLCA4 revealed how CLCA4 is silenced in cancer, establishing upstream regulatory axes that derepress PI3K/AKT signaling.\",\n      \"evidence\": \"Luciferase reporter assays confirming direct 3′-UTR targeting plus co-transfection epistasis rescue experiments in HNSCC (miR-501-5p) and CRC (miR-19a) cells\",\n      \"pmids\": [\"32072405\", \"35266369\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Whether these miRNAs regulate CLCA4 in normal physiology or only in cancer contexts is unknown\",\n        \"No in vivo validation of the miRNA/CLCA4/PI3K axis\",\n        \"Other post-transcriptional regulators or promoter-level silencing mechanisms not explored\"\n      ]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Reconstitution of CLCA4's ion-channel-modulatory function demonstrated that the secreted N-terminal metalloprotease fragment potentiates TMEM16B-mediated Ca2+-activated Cl- currents through VWA/MIDAS domain-dependent engagement, resolving the molecular basis and target specificity of CLCA4's channel-regulatory activity.\",\n      \"evidence\": \"Electrophysiology in HEK293T cells co-expressing TMEM16A or TMEM16B with wild-type or VWA/MIDAS-mutant CLCA4, secretion assays, domain deletion constructs\",\n      \"pmids\": [\"38825009\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether VWA/MIDAS-mediated TMEM16B engagement is related to the PI3K/AKT-suppressive EMT phenotype is unknown\",\n        \"Structural basis of CLCA4–TMEM16B interaction not determined\",\n        \"Physiological tissues where CLCA4–TMEM16B signaling operates in vivo not defined\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The mechanistic link between CLCA4's two established activities — TMEM16B-dependent chloride current potentiation and PI3K/AKT-mediated EMT suppression — remains unresolved, and it is unknown whether these reflect the same or independent pathways.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No study has tested whether CLCA4's protease activity or secreted fragment is required for EMT suppression\",\n        \"The direct molecular target linking CLCA4 to PI3K inhibition has not been identified\",\n        \"In vivo physiological roles of CLCA4 in normal epithelial homeostasis have not been established with genetic models\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 2, 3]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [2, 3, 4]},\n      {\"term_id\": \"R-HSA-382551\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"TMEM16B\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}