{"gene":"KRT18","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2023,"finding":"KRT18 directly binds to and stabilizes cell surface E-cadherin in trophoblast cells, thereby regulating trophoblast migration, invasion, and embryo adhesion/implantation. The direct binding was demonstrated by microscale thermophoresis (MST) analysis.","method":"Microscale thermophoresis (MST), siRNA knockdown, in vitro migration/invasion assays, mouse embryo implantation model","journal":"Reproductive biology and endocrinology : RB&E","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct binding confirmed by MST plus functional knockdown with specific phenotypic readout (migration, invasion, embryo implantation), single lab with two orthogonal methods","pmids":["37620903"],"is_preprint":false},{"year":2022,"finding":"LINC02253 increases m6A modification of KRT18 mRNA by recruiting the m6A writer METTL3, thereby stabilizing KRT18 mRNA and increasing KRT18 protein levels. KRT18 in turn mediates gastric cancer cell growth, migration, and invasion through activation of the MAPK/ERK signaling pathway.","method":"RNA immunoprecipitation, m6A methylation assays, siRNA/overexpression rescue experiments, in vitro and in vivo functional assays","journal":"Carcinogenesis","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — mechanistic pathway (METTL3 → m6A on KRT18 mRNA → mRNA stability → MAPK/ERK) supported by RIP and rescue experiments in a single lab with multiple orthogonal methods","pmids":["35136989"],"is_preprint":false},{"year":2014,"finding":"The transcription factor EGR1 directly regulates KRT18 expression by binding to an EGR1 binding site in the KRT18 promoter, establishing KRT18 as a downstream transcriptional target of EGR1 in NSCLC.","method":"Promoter analysis, bioinformatics, microarray, immunohistochemistry","journal":"Scientific reports","confidence":"Low","confidence_rationale":"Tier 3 / Weak — promoter binding site identified by bioinformatics/promoter analysis without direct ChIP or reporter assay validation described in the abstract; single lab, single approach","pmids":["24990820"],"is_preprint":false},{"year":2021,"finding":"KRT18 knockdown in gastric cancer AGS cells selectively alters expression and alternative splicing of genes enriched in apoptosis and cell cycle pathways, promoting apoptosis and inhibiting proliferation, indicating KRT18 modulates post-transcriptional splicing regulation.","method":"siRNA knockdown, whole-transcriptome RNA-seq, RT-qPCR validation, flow cytometry (apoptosis)","journal":"Frontiers in genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — genome-wide RNA-seq combined with functional validation (apoptosis, proliferation assays) and RT-qPCR; single lab with multiple orthogonal methods","pmids":["34290732"],"is_preprint":false},{"year":2022,"finding":"miR-186-3p directly targets KRT18 (confirmed by dual luciferase reporter assay) and negatively regulates the MAPK signaling pathway through KRT18, suppressing colon cancer cell proliferation and promoting apoptosis.","method":"Biotin-microRNA pull-down, dual luciferase reporter assay, siRNA knockdown, BrdU/MTT/flow cytometry assays, in vivo xenograft","journal":"Cell cycle (Georgetown, Tex.)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct miRNA-target interaction confirmed by luciferase reporter plus rescue experiments and in vivo validation; single lab with multiple orthogonal methods","pmids":["35258413"],"is_preprint":false},{"year":2025,"finding":"Host cell KRT18 interacts with Cryptosporidium parvum PDI (CpPDI) in a non-redox-dependent manner (not related to disulfide bond formation catalytic activity), identified by LC-MS/MS and Co-IP. Downregulation of KRT18 impairs C. parvum infection of host cells.","method":"LC-MS/MS, co-immunoprecipitation, siRNA knockdown, parasite infection assays","journal":"Communications biology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — binding partner identified by MS and confirmed by Co-IP; functional consequence of KRT18 knockdown on infection established; single lab with two orthogonal methods","pmids":["41275047"],"is_preprint":false},{"year":2026,"finding":"The histone acetyltransferase P300 upregulates KRT18 transcription through H3K18 acetylation (H3K18ac) at the KRT18 locus. Elevated KRT18 subsequently activates the RIPK1/MLKL necroptosis pathway in tubular epithelial cells, promoting diabetic nephropathy progression. P300 knockdown or the inhibitor C646 reduces H3K18ac and KRT18, while KRT18 knockdown rescues P300-overexpression-induced cell death.","method":"shRNA knockdown, overexpression, small molecule inhibitor (C646), Western blot, qPCR, immunohistochemistry, AO/PI staining, in vivo STZ-induced DN mouse model","journal":"Acta biochimica et biophysica Sinica","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — epigenetic writer (P300) → H3K18ac → KRT18 transcription axis validated by genetic (shRNA/OE) and pharmacological (C646) perturbations plus rescue experiments; single lab with multiple orthogonal approaches","pmids":["42165125"],"is_preprint":false},{"year":2025,"finding":"In cholangiocarcinoma, miR-194-5p directly targets KRT18 (confirmed by RNA pulldown, RIP, and luciferase reporter assays). LncRNA HCG18 acts as a sponge for miR-194-5p, releasing KRT18 expression and activating MAPK signaling, thereby promoting CCA cell proliferation and stemness.","method":"RNA immunoprecipitation, RNA pulldown, luciferase reporter assay, siRNA/overexpression, CCK-8, colony formation, EdU, sphere formation, xenograft tumor model","journal":"Biochemical genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct miRNA-KRT18 interaction confirmed by multiple binding assays (RIP, pulldown, luciferase); functional rescue experiments and in vivo validation performed; single lab","pmids":["39776371"],"is_preprint":false}],"current_model":"KRT18 is a type I keratin that functions as a downstream transcriptional target of EGR1 and P300-mediated H3K18 acetylation; it directly binds E-cadherin to stabilize it at the trophoblast cell surface (facilitating embryo implantation), interacts with Cryptosporidium parvum PDI in a non-redox-dependent manner to enable parasite infection, modulates alternative splicing of apoptosis/cell-cycle genes, and activates the MAPK/ERK and RIPK1/MLKL signaling pathways; its mRNA stability is post-transcriptionally controlled via METTL3-mediated m6A modification, and its expression is negatively regulated post-transcriptionally by miR-186-3p and miR-194-5p."},"narrative":{"mechanistic_narrative":"KRT18 is a type I keratin whose expression and post-transcriptional regulation position it as an effector in epithelial cell adhesion, proliferation, and cell-death signaling [PMID:37620903, PMID:35136989]. At the cell surface it directly binds and stabilizes E-cadherin in trophoblast cells, thereby promoting trophoblast migration, invasion, and embryo adhesion/implantation [PMID:37620903]. In epithelial cancers KRT18 acts as a growth-promoting node: it activates MAPK/ERK signaling to drive gastric and cholangiocarcinoma cell proliferation, migration, and stemness [PMID:35136989, PMID:39776371], and its knockdown reprograms expression and alternative splicing of apoptosis and cell-cycle genes, promoting apoptosis and inhibiting proliferation [PMID:34290732]. In tubular epithelial cells, elevated KRT18 activates the RIPK1/MLKL necroptosis pathway, contributing to diabetic nephropathy progression [PMID:42165125]. KRT18 abundance is tightly controlled at multiple levels: transcriptionally via the transcription factor EGR1 [PMID:24990820] and via P300-mediated H3K18 acetylation at its locus [PMID:42165125]; through METTL3-dependent m6A modification that stabilizes its mRNA [PMID:35136989]; and through negative post-transcriptional repression by miR-186-3p and miR-194-5p [PMID:35258413, PMID:39776371]. Host KRT18 additionally serves as an interaction partner for Cryptosporidium parvum protein disulfide isomerase in a non-redox-dependent manner, a binding required for efficient parasite infection [PMID:41275047].","teleology":[{"year":2014,"claim":"Established an upstream transcriptional regulator of KRT18, framing it as a controlled gene rather than a constitutive structural protein.","evidence":"Promoter analysis and bioinformatics identifying an EGR1 binding site in the KRT18 promoter in NSCLC","pmids":["24990820"],"confidence":"Low","gaps":["Binding identified by bioinformatics/promoter analysis without direct ChIP or reporter validation","Functional consequence of EGR1-driven KRT18 not demonstrated","Restricted to a single cancer context"]},{"year":2021,"claim":"Showed KRT18 has a regulatory role in gene expression beyond structure, linking it to apoptosis and cell-cycle control.","evidence":"siRNA knockdown plus whole-transcriptome RNA-seq with apoptosis/proliferation validation in gastric cancer AGS cells","pmids":["34290732"],"confidence":"Medium","gaps":["Mechanism by which KRT18 influences splicing is unknown","No direct RNA or spliceosome interaction shown","Single cell line"]},{"year":2022,"claim":"Resolved how KRT18 mRNA stability is set and connected it to a growth-driving signaling output.","evidence":"RIP, m6A methylation assays, and rescue experiments linking LINC02253/METTL3-mediated m6A to KRT18 mRNA stabilization and MAPK/ERK activation in gastric cancer","pmids":["35136989"],"confidence":"Medium","gaps":["m6A reader mediating stabilization not identified","Mechanism by which KRT18 activates MAPK/ERK not defined","Single lab"]},{"year":2022,"claim":"Identified a direct microRNA brake on KRT18 controlling proliferation and survival.","evidence":"Biotin-miRNA pull-down, dual luciferase reporter, knockdown, and xenograft assays showing miR-186-3p directly targets KRT18 and represses MAPK signaling in colon cancer","pmids":["35258413"],"confidence":"Medium","gaps":["Step linking KRT18 to MAPK activation not mechanistically resolved","Single tumor type"]},{"year":2023,"claim":"Defined a direct protein-protein function for KRT18 at the cell surface, connecting it to adhesion and embryo implantation.","evidence":"Microscale thermophoresis demonstrating direct KRT18-E-cadherin binding, with knockdown and mouse embryo implantation assays","pmids":["37620903"],"confidence":"Medium","gaps":["Structural basis of KRT18/E-cadherin interaction unresolved","Whether stabilization is direct or via cytoskeletal anchoring unclear","Single lab"]},{"year":2025,"claim":"Extended a second direct microRNA-KRT18 axis and a lncRNA sponge, reinforcing KRT18 as a MAPK-linked driver of proliferation and stemness.","evidence":"RNA pulldown, RIP, luciferase, rescue, and xenograft assays showing miR-194-5p targets KRT18 and HCG18 sponges miR-194-5p in cholangiocarcinoma","pmids":["39776371"],"confidence":"Medium","gaps":["Direct mechanism of KRT18-driven MAPK activation still undefined","Stemness readout correlative","Single lab"]},{"year":2025,"claim":"Revealed a non-canonical role for host KRT18 as a pathogen interaction partner enabling infection.","evidence":"LC-MS/MS and Co-IP identifying KRT18 binding to Cryptosporidium parvum PDI in a non-redox manner, with knockdown impairing infection","pmids":["41275047"],"confidence":"Medium","gaps":["Binding interface and stoichiometry not mapped","How the interaction promotes invasion mechanistically unknown","Reciprocal validation limited"]},{"year":2026,"claim":"Linked an epigenetic writer to KRT18 transcription and to a defined cell-death pathway in disease.","evidence":"shRNA/overexpression, C646 inhibitor, and rescue experiments showing P300/H3K18ac drives KRT18, which activates RIPK1/MLKL necroptosis in an STZ diabetic nephropathy mouse model","pmids":["42165125"],"confidence":"Medium","gaps":["Mechanism by which KRT18 engages RIPK1/MLKL not defined","Whether H3K18ac at KRT18 is direct or indirect unresolved","Single lab"]},{"year":null,"claim":"The molecular mechanism by which cytoplasmic KRT18 transduces signals to MAPK/ERK and RIPK1/MLKL, and how it modulates alternative splicing, remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structural model of KRT18 signaling complexes","Direct effectors bridging KRT18 to kinase cascades not identified","Splicing regulatory mechanism uncharacterized"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0005198","term_label":"structural molecule activity","supporting_discovery_ids":[0,5]}],"localization":[{"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":[1,4,7]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[3,6]}],"complexes":[],"partners":["CDH1","PDI"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P05783","full_name":"Keratin, type I cytoskeletal 18","aliases":["Cell proliferation-inducing gene 46 protein","Cytokeratin-18","CK-18","Keratin-18","K18"],"length_aa":430,"mass_kda":48.1,"function":"Required for the formation of KRT8/KRT18 filaments that are involved in ARHGEF40-mediated actin stress fiber formation and tensional force-induced stress fiber formation and reinforcement (PubMed:26823019). Also acts downstream of ROCK kinase activation as part of a positive feedback mechanism in response to cellular mechanical stress loading (PubMed:26823019). Organization and orientation of KRT18 filaments are responsible for the properly elongated morphology of epithelial tubules (By similarity). Involved in the uptake of thrombin-antithrombin complexes by hepatic cells (By similarity). When phosphorylated, plays a role in filament reorganization. Involved in the delivery of mutated CFTR to the plasma membrane. Together with KRT8, is involved in interleukin-6 (IL-6)-mediated barrier protection","subcellular_location":"Nucleus matrix; Cytoplasm, perinuclear region; Nucleus, nucleolus; Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P05783/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KRT18","classification":"Not Classified","n_dependent_lines":84,"n_total_lines":1208,"dependency_fraction":0.0695364238410596},"opencell":{"profiled":true,"resolved_as":"","ensg_id":"ENSG00000111057","cell_line_id":"CID000727","localizations":[{"compartment":"cytoskeleton","grade":3},{"compartment":"cytoplasmic","grade":1}],"interactors":[{"gene":"YWHAG","stoichiometry":4.0},{"gene":"CDC42BPA","stoichiometry":0.2},{"gene":"MAP1B","stoichiometry":0.2},{"gene":"DSP","stoichiometry":0.2},{"gene":"EPPK1","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/target/CID000727","total_profiled":1310},"omim":[{"mim_id":"618277","title":"NHL REPEAT-CONTAINING PROTEIN 2; NHLRC2","url":"https://www.omim.org/entry/618277"},{"mim_id":"612654","title":"TRICHOPLEIN; TCHP","url":"https://www.omim.org/entry/612654"},{"mim_id":"610018","title":"RHO GUANINE NUCLEOTIDE EXCHANGE FACTOR 40; ARHGEF40","url":"https://www.omim.org/entry/610018"},{"mim_id":"606841","title":"DEATH EFFECTOR DOMAIN-CONTAINING PROTEIN; DEDD","url":"https://www.omim.org/entry/606841"},{"mim_id":"601313","title":"POLYCYSTIN 1; PKD1","url":"https://www.omim.org/entry/601313"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in many","driving_tissues":[],"url":"https://www.proteinatlas.org/search/KRT18"},"hgnc":{"alias_symbol":[],"prev_symbol":[]},"alphafold":{"accession":"P05783","domains":[],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P05783","model_url":"https://alphafold.ebi.ac.uk/files/AF-P05783-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P05783-F1-predicted_aligned_error_v6.png","plddt_mean":78.62},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KRT18","jax_strain_url":"https://www.jax.org/strain/search?query=KRT18"},"sequence":{"accession":"P05783","fasta_url":"https://rest.uniprot.org/uniprotkb/P05783.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P05783/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P05783"}},"corpus_meta":[{"pmid":"24990820","id":"PMC_24990820","title":"EGR1 decreases the malignancy of human non-small cell lung carcinoma by regulating KRT18 expression.","date":"2014","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/24990820","citation_count":71,"is_preprint":false},{"pmid":"31345960","id":"PMC_31345960","title":"KRT18 is correlated with the malignant status and acts as an oncogene in colorectal cancer.","date":"2019","source":"Bioscience reports","url":"https://pubmed.ncbi.nlm.nih.gov/31345960","citation_count":65,"is_preprint":false},{"pmid":"34290732","id":"PMC_34290732","title":"KRT18 Modulates Alternative Splicing of Genes Involved in Proliferation and Apoptosis Processes in Both Gastric Cancer Cells and Clinical Samples.","date":"2021","source":"Frontiers in genetics","url":"https://pubmed.ncbi.nlm.nih.gov/34290732","citation_count":30,"is_preprint":false},{"pmid":"35136989","id":"PMC_35136989","title":"LncRNA LINC02253 activates KRT18/MAPK/ERK pathway by mediating N6-methyladenosine modification of KRT18 mRNA in gastric cancer.","date":"2022","source":"Carcinogenesis","url":"https://pubmed.ncbi.nlm.nih.gov/35136989","citation_count":27,"is_preprint":false},{"pmid":"21548936","id":"PMC_21548936","title":"An association study on contrasting cystic fibrosis endophenotypes recognizes KRT8 but not KRT18 as a modifier of cystic fibrosis disease severity and CFTR mediated residual chloride secretion.","date":"2011","source":"BMC medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/21548936","citation_count":15,"is_preprint":false},{"pmid":"37620903","id":"PMC_37620903","title":"KRT18 regulates trophoblast cell migration and invasion which are essential for embryo implantation.","date":"2023","source":"Reproductive biology and endocrinology : RB&E","url":"https://pubmed.ncbi.nlm.nih.gov/37620903","citation_count":9,"is_preprint":false},{"pmid":"34174316","id":"PMC_34174316","title":"Proteomic and molecular evidences of Il1rl2, Ric8a, Krt18 and Hsp90b1 modulation during experimental hepatic fibrosis and pomegranate supplementation.","date":"2021","source":"International journal of biological macromolecules","url":"https://pubmed.ncbi.nlm.nih.gov/34174316","citation_count":8,"is_preprint":false},{"pmid":"35258413","id":"PMC_35258413","title":"Hsa-miR-186-3p suppresses colon cancer progression by inhibiting KRT18/MAPK signaling pathway.","date":"2022","source":"Cell cycle (Georgetown, Tex.)","url":"https://pubmed.ncbi.nlm.nih.gov/35258413","citation_count":7,"is_preprint":false},{"pmid":"39729139","id":"PMC_39729139","title":"The role of KRT18 in lung adenocarcinoma development: integrative bioinformatics and experimental validation.","date":"2024","source":"Discover oncology","url":"https://pubmed.ncbi.nlm.nih.gov/39729139","citation_count":5,"is_preprint":false},{"pmid":"39776371","id":"PMC_39776371","title":"HCG18 Promotes Cell Proliferation and Stemness in Cholangiocarcinoma via the miR-194-5p/KRT18/MAPK Signaling.","date":"2025","source":"Biochemical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/39776371","citation_count":2,"is_preprint":false},{"pmid":"39191209","id":"PMC_39191209","title":"KRT18 as a Novel Biomarker of Urothelial Papilloma while Evaluating Low-Grade Papillary Urothelial Neoplasms: Bi-Center Analysis.","date":"2024","source":"Pathobiology : journal of immunopathology, molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/39191209","citation_count":2,"is_preprint":false},{"pmid":"41705239","id":"PMC_41705239","title":"Neuroinflammatory and transcriptional dynamics during SARS-CoV-2 infection in KRT18-hACE2 mouse brain.","date":"2026","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/41705239","citation_count":0,"is_preprint":false},{"pmid":"42165125","id":"PMC_42165125","title":"P300-mediated H3K18 acetylation triggers necroptosis via modulation of KRT18 transcription in diabetic nephropathy.","date":"2026","source":"Acta biochimica et biophysica Sinica","url":"https://pubmed.ncbi.nlm.nih.gov/42165125","citation_count":0,"is_preprint":false},{"pmid":"41275047","id":"PMC_41275047","title":"Host cell KRT-18 as a non-redox dependent interactor of Cryptosporidium parvum PDI enables parasite infection.","date":"2025","source":"Communications biology","url":"https://pubmed.ncbi.nlm.nih.gov/41275047","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.05.01.651662","title":"Modeling epithelial and endothelial cell tropism for SARS-CoV-2 through restricted transgenic hACE2 expression in mice","date":"2025-05-02","source":"bioRxiv","url":"https://doi.org/10.1101/2025.05.01.651662","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2024.08.10.607363","title":"Single cell RNA sequencing reveals shifts in cell maturity and function of endogenous and infiltrating cell types in response to acute intervertebral disc injury","date":"2024-08-10","source":"bioRxiv","url":"https://doi.org/10.1101/2024.08.10.607363","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":11072,"output_tokens":2138,"usd":0.032643,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":9189,"output_tokens":2771,"usd":0.05761,"stage2_stop_reason":"end_turn"},"total_usd":0.090253,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2023,\n      \"finding\": \"KRT18 directly binds to and stabilizes cell surface E-cadherin in trophoblast cells, thereby regulating trophoblast migration, invasion, and embryo adhesion/implantation. The direct binding was demonstrated by microscale thermophoresis (MST) analysis.\",\n      \"method\": \"Microscale thermophoresis (MST), siRNA knockdown, in vitro migration/invasion assays, mouse embryo implantation model\",\n      \"journal\": \"Reproductive biology and endocrinology : RB&E\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct binding confirmed by MST plus functional knockdown with specific phenotypic readout (migration, invasion, embryo implantation), single lab with two orthogonal methods\",\n      \"pmids\": [\"37620903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"LINC02253 increases m6A modification of KRT18 mRNA by recruiting the m6A writer METTL3, thereby stabilizing KRT18 mRNA and increasing KRT18 protein levels. KRT18 in turn mediates gastric cancer cell growth, migration, and invasion through activation of the MAPK/ERK signaling pathway.\",\n      \"method\": \"RNA immunoprecipitation, m6A methylation assays, siRNA/overexpression rescue experiments, in vitro and in vivo functional assays\",\n      \"journal\": \"Carcinogenesis\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — mechanistic pathway (METTL3 → m6A on KRT18 mRNA → mRNA stability → MAPK/ERK) supported by RIP and rescue experiments in a single lab with multiple orthogonal methods\",\n      \"pmids\": [\"35136989\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"The transcription factor EGR1 directly regulates KRT18 expression by binding to an EGR1 binding site in the KRT18 promoter, establishing KRT18 as a downstream transcriptional target of EGR1 in NSCLC.\",\n      \"method\": \"Promoter analysis, bioinformatics, microarray, immunohistochemistry\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — promoter binding site identified by bioinformatics/promoter analysis without direct ChIP or reporter assay validation described in the abstract; single lab, single approach\",\n      \"pmids\": [\"24990820\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"KRT18 knockdown in gastric cancer AGS cells selectively alters expression and alternative splicing of genes enriched in apoptosis and cell cycle pathways, promoting apoptosis and inhibiting proliferation, indicating KRT18 modulates post-transcriptional splicing regulation.\",\n      \"method\": \"siRNA knockdown, whole-transcriptome RNA-seq, RT-qPCR validation, flow cytometry (apoptosis)\",\n      \"journal\": \"Frontiers in genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genome-wide RNA-seq combined with functional validation (apoptosis, proliferation assays) and RT-qPCR; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"34290732\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"miR-186-3p directly targets KRT18 (confirmed by dual luciferase reporter assay) and negatively regulates the MAPK signaling pathway through KRT18, suppressing colon cancer cell proliferation and promoting apoptosis.\",\n      \"method\": \"Biotin-microRNA pull-down, dual luciferase reporter assay, siRNA knockdown, BrdU/MTT/flow cytometry assays, in vivo xenograft\",\n      \"journal\": \"Cell cycle (Georgetown, Tex.)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct miRNA-target interaction confirmed by luciferase reporter plus rescue experiments and in vivo validation; single lab with multiple orthogonal methods\",\n      \"pmids\": [\"35258413\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Host cell KRT18 interacts with Cryptosporidium parvum PDI (CpPDI) in a non-redox-dependent manner (not related to disulfide bond formation catalytic activity), identified by LC-MS/MS and Co-IP. Downregulation of KRT18 impairs C. parvum infection of host cells.\",\n      \"method\": \"LC-MS/MS, co-immunoprecipitation, siRNA knockdown, parasite infection assays\",\n      \"journal\": \"Communications biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — binding partner identified by MS and confirmed by Co-IP; functional consequence of KRT18 knockdown on infection established; single lab with two orthogonal methods\",\n      \"pmids\": [\"41275047\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"The histone acetyltransferase P300 upregulates KRT18 transcription through H3K18 acetylation (H3K18ac) at the KRT18 locus. Elevated KRT18 subsequently activates the RIPK1/MLKL necroptosis pathway in tubular epithelial cells, promoting diabetic nephropathy progression. P300 knockdown or the inhibitor C646 reduces H3K18ac and KRT18, while KRT18 knockdown rescues P300-overexpression-induced cell death.\",\n      \"method\": \"shRNA knockdown, overexpression, small molecule inhibitor (C646), Western blot, qPCR, immunohistochemistry, AO/PI staining, in vivo STZ-induced DN mouse model\",\n      \"journal\": \"Acta biochimica et biophysica Sinica\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — epigenetic writer (P300) → H3K18ac → KRT18 transcription axis validated by genetic (shRNA/OE) and pharmacological (C646) perturbations plus rescue experiments; single lab with multiple orthogonal approaches\",\n      \"pmids\": [\"42165125\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In cholangiocarcinoma, miR-194-5p directly targets KRT18 (confirmed by RNA pulldown, RIP, and luciferase reporter assays). LncRNA HCG18 acts as a sponge for miR-194-5p, releasing KRT18 expression and activating MAPK signaling, thereby promoting CCA cell proliferation and stemness.\",\n      \"method\": \"RNA immunoprecipitation, RNA pulldown, luciferase reporter assay, siRNA/overexpression, CCK-8, colony formation, EdU, sphere formation, xenograft tumor model\",\n      \"journal\": \"Biochemical genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct miRNA-KRT18 interaction confirmed by multiple binding assays (RIP, pulldown, luciferase); functional rescue experiments and in vivo validation performed; single lab\",\n      \"pmids\": [\"39776371\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KRT18 is a type I keratin that functions as a downstream transcriptional target of EGR1 and P300-mediated H3K18 acetylation; it directly binds E-cadherin to stabilize it at the trophoblast cell surface (facilitating embryo implantation), interacts with Cryptosporidium parvum PDI in a non-redox-dependent manner to enable parasite infection, modulates alternative splicing of apoptosis/cell-cycle genes, and activates the MAPK/ERK and RIPK1/MLKL signaling pathways; its mRNA stability is post-transcriptionally controlled via METTL3-mediated m6A modification, and its expression is negatively regulated post-transcriptionally by miR-186-3p and miR-194-5p.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"KRT18 is a type I keratin whose expression and post-transcriptional regulation position it as an effector in epithelial cell adhesion, proliferation, and cell-death signaling [#0, #1]. At the cell surface it directly binds and stabilizes E-cadherin in trophoblast cells, thereby promoting trophoblast migration, invasion, and embryo adhesion/implantation [#0]. In epithelial cancers KRT18 acts as a growth-promoting node: it activates MAPK/ERK signaling to drive gastric and cholangiocarcinoma cell proliferation, migration, and stemness [#1, #7], and its knockdown reprograms expression and alternative splicing of apoptosis and cell-cycle genes, promoting apoptosis and inhibiting proliferation [#3]. In tubular epithelial cells, elevated KRT18 activates the RIPK1/MLKL necroptosis pathway, contributing to diabetic nephropathy progression [#6]. KRT18 abundance is tightly controlled at multiple levels: transcriptionally via the transcription factor EGR1 [#2] and via P300-mediated H3K18 acetylation at its locus [#6]; through METTL3-dependent m6A modification that stabilizes its mRNA [#1]; and through negative post-transcriptional repression by miR-186-3p and miR-194-5p [#4, #7]. Host KRT18 additionally serves as an interaction partner for Cryptosporidium parvum protein disulfide isomerase in a non-redox-dependent manner, a binding required for efficient parasite infection [#5].\",\n  \"teleology\": [\n    {\n      \"year\": 2014,\n      \"claim\": \"Established an upstream transcriptional regulator of KRT18, framing it as a controlled gene rather than a constitutive structural protein.\",\n      \"evidence\": \"Promoter analysis and bioinformatics identifying an EGR1 binding site in the KRT18 promoter in NSCLC\",\n      \"pmids\": [\"24990820\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Binding identified by bioinformatics/promoter analysis without direct ChIP or reporter validation\", \"Functional consequence of EGR1-driven KRT18 not demonstrated\", \"Restricted to a single cancer context\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Showed KRT18 has a regulatory role in gene expression beyond structure, linking it to apoptosis and cell-cycle control.\",\n      \"evidence\": \"siRNA knockdown plus whole-transcriptome RNA-seq with apoptosis/proliferation validation in gastric cancer AGS cells\",\n      \"pmids\": [\"34290732\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which KRT18 influences splicing is unknown\", \"No direct RNA or spliceosome interaction shown\", \"Single cell line\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Resolved how KRT18 mRNA stability is set and connected it to a growth-driving signaling output.\",\n      \"evidence\": \"RIP, m6A methylation assays, and rescue experiments linking LINC02253/METTL3-mediated m6A to KRT18 mRNA stabilization and MAPK/ERK activation in gastric cancer\",\n      \"pmids\": [\"35136989\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"m6A reader mediating stabilization not identified\", \"Mechanism by which KRT18 activates MAPK/ERK not defined\", \"Single lab\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Identified a direct microRNA brake on KRT18 controlling proliferation and survival.\",\n      \"evidence\": \"Biotin-miRNA pull-down, dual luciferase reporter, knockdown, and xenograft assays showing miR-186-3p directly targets KRT18 and represses MAPK signaling in colon cancer\",\n      \"pmids\": [\"35258413\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Step linking KRT18 to MAPK activation not mechanistically resolved\", \"Single tumor type\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Defined a direct protein-protein function for KRT18 at the cell surface, connecting it to adhesion and embryo implantation.\",\n      \"evidence\": \"Microscale thermophoresis demonstrating direct KRT18-E-cadherin binding, with knockdown and mouse embryo implantation assays\",\n      \"pmids\": [\"37620903\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Structural basis of KRT18/E-cadherin interaction unresolved\", \"Whether stabilization is direct or via cytoskeletal anchoring unclear\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Extended a second direct microRNA-KRT18 axis and a lncRNA sponge, reinforcing KRT18 as a MAPK-linked driver of proliferation and stemness.\",\n      \"evidence\": \"RNA pulldown, RIP, luciferase, rescue, and xenograft assays showing miR-194-5p targets KRT18 and HCG18 sponges miR-194-5p in cholangiocarcinoma\",\n      \"pmids\": [\"39776371\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct mechanism of KRT18-driven MAPK activation still undefined\", \"Stemness readout correlative\", \"Single lab\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Revealed a non-canonical role for host KRT18 as a pathogen interaction partner enabling infection.\",\n      \"evidence\": \"LC-MS/MS and Co-IP identifying KRT18 binding to Cryptosporidium parvum PDI in a non-redox manner, with knockdown impairing infection\",\n      \"pmids\": [\"41275047\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Binding interface and stoichiometry not mapped\", \"How the interaction promotes invasion mechanistically unknown\", \"Reciprocal validation limited\"]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Linked an epigenetic writer to KRT18 transcription and to a defined cell-death pathway in disease.\",\n      \"evidence\": \"shRNA/overexpression, C646 inhibitor, and rescue experiments showing P300/H3K18ac drives KRT18, which activates RIPK1/MLKL necroptosis in an STZ diabetic nephropathy mouse model\",\n      \"pmids\": [\"42165125\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism by which KRT18 engages RIPK1/MLKL not defined\", \"Whether H3K18ac at KRT18 is direct or indirect unresolved\", \"Single lab\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The molecular mechanism by which cytoplasmic KRT18 transduces signals to MAPK/ERK and RIPK1/MLKL, and how it modulates alternative splicing, remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structural model of KRT18 signaling complexes\", \"Direct effectors bridging KRT18 to kinase cascades not identified\", \"Splicing regulatory mechanism uncharacterized\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0005198\", \"supporting_discovery_ids\": [0, 5]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [1, 4, 7]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [3, 6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\"CDH1\", \"PDI\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"pairwise":"win","faith_supported":6,"faith_total":6,"faith_pct":100.0}}