{"gene":"KLK14","run_date":"2026-04-28T18:30:27","timeline":{"discoveries":[{"year":2007,"finding":"LEKTI fragments specifically inhibit KLK14 in a pH-dependent manner; at acidic pH, active KLK14 (and KLK5) is released from the LEKTI inhibitory complex, enabling regulated proteolytic activity in the stratum corneum. This interaction is rapid and irreversible at neutral pH, reflecting an extremely tight binding complex.","method":"Kinetic analysis of LEKTI fragment inhibition of KLK5, KLK7, and KLK14; pH-dependent binding/release assays; biochemical characterization of LEKTI fragments from cultured keratinocytes and epidermis","journal":"Molecular biology of the cell","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal biochemical methods (kinetics, fragment characterization, pH-shift assays) in a highly cited study with functional consequence in skin homeostasis","pmids":["17596512"],"is_preprint":false},{"year":2001,"finding":"KLK14 encodes a secreted serine protease with predicted trypsin-like substrate specificity, translated in vitro with a molecular mass of approximately 31 kDa, and expressed by both benign and malignant glandular epithelial cells in prostate.","method":"In vitro translation, Northern blot, in situ hybridization, genomic characterization","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 — in vitro translation confirming protein product and domain architecture, supported by expression localization","pmids":["11352573"],"is_preprint":false},{"year":2008,"finding":"KLK14 plays a major role in seminal clot liquefaction by: (1) directly cleaving semenogelins I and II; (2) activating KLK3 (PSA) bidirectionally — promoting early KLK3 activity and inactivating it via internal cleavage at higher doses; (3) being subject to Zn²⁺ inhibition that is reversible by semenogelins, providing a novel regulatory mechanism. Specific synthetic inhibition of KLK14 (ACT(G9)) significantly delayed liquefaction ex vivo, and addition of recombinant KLK14 facilitated liquefaction.","method":"Ex vivo semen liquefaction assay with synthetic KLK14 inhibitor (ACT(G9)) and recombinant active KLK14; biochemical assays measuring chymotrypsin-like and KLK1 activity; KLK3 fragmentation analysis; Zn²⁺ inhibition reversal assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1–2 — reconstituted enzymatic activity, gain- and loss-of-function with recombinant protein and specific inhibitor, multiple orthogonal assays identifying substrates and regulatory mechanism","pmids":["18482984"],"is_preprint":false},{"year":2012,"finding":"KLK14 activates proteinase-activated receptor 2 (PAR2) by cleaving and unmasking its receptor-activating sequence, triggering calcium transients, MAPK activation, β-arrestin interactions, and receptor internalization in PAR2-expressing cells. KLK14 can signal via both human and rat PAR2, distinguishing it from KLK8 which cannot activate human PAR2.","method":"Calcium transient assays, MAPK activation assays, β-arrestin interaction assays, receptor internalization assays, and peptide cleavage assays in PAR2-expressing HEK and KNRK cells","journal":"Biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal signaling readouts in cell-based systems, direct peptide cleavage assay, comparison with KLK8 clarifying specificity","pmids":["22505524"],"is_preprint":false},{"year":2025,"finding":"KLK14 mediates a pro-tumorigenic effect downstream of KLK5 and KLK7 in HPV-dependent cervical carcinogenesis by regulating PAR-2-dependent RhoA and NF-κB signaling pathways. KLK5 and KLK7 drive KLK14 activation, and absence of KLK5/KLK7 ameliorates the HPV-dependent phenotype via modulation of KLK14.","method":"Genetically engineered mice (KLK5/KLK7 knockout), bulk RNA-seq, reporter assays for RhoA and NF-κB pathway activity, human biopsy expression analysis","journal":"Translational oncology","confidence":"Medium","confidence_rationale":"Tier 2 — genetic epistasis in mouse model with pathway reporter assays, but single study without in vitro reconstitution of KLK14 enzymatic mechanism","pmids":["40753921"],"is_preprint":false}],"current_model":"KLK14 is a secreted trypsin-like serine protease that is regulated by its endogenous inhibitor LEKTI in a pH-dependent manner in skin, directly cleaves semenogelins and activates/modulates KLK3 to drive seminal clot liquefaction, activates PAR2 to trigger downstream MAPK and calcium signaling, and in epithelial carcinogenesis functions downstream of KLK5/KLK7 to promote tumor progression via PAR2-dependent RhoA and NF-κB pathways."},"narrative":{"teleology":[{"year":2001,"claim":"Establishing the identity of KLK14 as a secreted serine protease with trypsin-like specificity expressed in prostatic epithelium filled the gap of whether the KLK14 locus encodes a functional protease and where it is produced.","evidence":"In vitro translation, Northern blot, and in situ hybridization in prostate tissue","pmids":["11352573"],"confidence":"Medium","gaps":["No endogenous substrates identified","Enzymatic activity not demonstrated on native substrates","Expression survey limited to prostate"]},{"year":2007,"claim":"Demonstrating that LEKTI fragments inhibit KLK14 in a pH-dependent manner — tight binding at neutral pH and release at acidic pH — established the first endogenous regulatory mechanism for KLK14 and explained how proteolytic activity is spatially controlled in the stratum corneum.","evidence":"Kinetic inhibition assays, pH-shift binding/release experiments, and LEKTI fragment characterization from cultured keratinocytes and epidermis","pmids":["17596512"],"confidence":"High","gaps":["Downstream skin substrates of released KLK14 not identified","In vivo consequences of dysregulated KLK14 in LEKTI-deficient skin not directly tested"]},{"year":2008,"claim":"Identifying semenogelins and KLK3 as direct substrates/targets of KLK14 and showing that specific KLK14 inhibition delays semen liquefaction established a physiological role for KLK14 in male reproduction and revealed a Zn²⁺/semenogelin regulatory circuit.","evidence":"Ex vivo semen liquefaction assay with specific synthetic inhibitor (ACT-G9) and recombinant KLK14; Zn²⁺ inhibition reversal assay; KLK3 fragmentation analysis","pmids":["18482984"],"confidence":"High","gaps":["Relative contribution of KLK14 versus other seminal KLKs in vivo not quantified","No genetic loss-of-function model for reproductive phenotype"]},{"year":2012,"claim":"Showing that KLK14 proteolytically activates PAR2 to elicit calcium transients, MAPK signaling, β-arrestin recruitment, and receptor internalization identified a cell-surface receptor through which KLK14 can transduce extracellular proteolytic activity into intracellular signaling.","evidence":"Calcium flux, MAPK, β-arrestin interaction, and receptor internalization assays in PAR2-expressing HEK and KNRK cells; peptide cleavage assays","pmids":["22505524"],"confidence":"High","gaps":["Physiological tissue context for KLK14–PAR2 signaling not established","Relative potency compared to other PAR2 agonists (thrombin-family proteases) not determined in vivo"]},{"year":2025,"claim":"Genetic epistasis in HPV-driven cervical carcinogenesis placed KLK14 downstream of KLK5/KLK7 and showed it promotes tumorigenesis via PAR2-dependent RhoA and NF-κB pathways, linking the KLK14–PAR2 axis to a disease-relevant signaling cascade.","evidence":"KLK5/KLK7 knockout mice, bulk RNA-seq, RhoA and NF-κB reporter assays, human biopsy expression analysis","pmids":["40753921"],"confidence":"Medium","gaps":["Direct enzymatic activation of KLK14 by KLK5 or KLK7 not reconstituted in vitro","Whether KLK14 cleaves PAR2 in cervical epithelium in vivo not directly shown","Contribution of KLK14 independent of other downstream KLK5/KLK7 targets not isolated"]},{"year":null,"claim":"A structural basis for KLK14 substrate selectivity and the atomic details of its interaction with LEKTI remain unresolved, and no Mendelian or engineered KLK14-null phenotype has been reported in vivo.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal or cryo-EM structure of KLK14 alone or in complex with inhibitors/substrates","No KLK14 knockout mouse phenotype reported","Full in vivo substrate repertoire undefined"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,3]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,2]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[1,2]}],"pathway":[],"complexes":[],"partners":["SPINK5","KLK3","F2RL1","SEMG1","SEMG2","KLK5","KLK7"],"other_free_text":[]},"mechanistic_narrative":"KLK14 is a secreted trypsin-like serine protease that functions in skin barrier homeostasis, seminal clot liquefaction, protease-activated receptor signaling, and epithelial tumorigenesis. In skin, KLK14 activity is controlled by the endogenous inhibitor LEKTI in a pH-dependent manner: at neutral pH LEKTI binds KLK14 tightly and irreversibly, whereas acidification in the stratum corneum releases active enzyme [PMID:17596512]. In seminal fluid, KLK14 directly cleaves semenogelins I and II and bidirectionally modulates KLK3 (PSA) activity, with Zn²⁺-mediated inhibition reversed by semenogelins providing a substrate-coupled regulatory switch; specific inhibition of KLK14 delays semen liquefaction ex vivo [PMID:18482984]. KLK14 activates PAR2 by proteolytic unmasking of its tethered ligand, triggering calcium transients, MAPK activation, and β-arrestin-dependent receptor internalization, and in HPV-driven cervical carcinogenesis it operates downstream of KLK5/KLK7 to promote tumor progression through PAR2-dependent RhoA and NF-κB signaling [PMID:22505524, PMID:40753921]."},"prefetch_data":{"uniprot":{"accession":"Q9P0G3","full_name":"Kallikrein-14","aliases":["Kallikrein-like protein 6","KLK-L6"],"length_aa":251,"mass_kda":27.5,"function":"Serine-type endopeptidase with a dual trypsin-like and chymotrypsin-like substrate specificity. May activate/inactivate the proteinase-activated receptors F2R, F2RL1 and F2RL3 and other kallikreins including KLK1, KLK3, KLK5 and KLK11. May function in seminal clot liquefaction through direct cleavage of the semenogelin SEMG1 and SEMG2 and activation of KLK3. May function through desmoglein DSG1 cleavage in epidermal desquamation a process by which the most superficial corneocytes are shed from the skin surface. May be involved in several aspects of tumor progression including growth, invasion and angiogenesis","subcellular_location":"Secreted, extracellular space","url":"https://www.uniprot.org/uniprotkb/Q9P0G3/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/KLK14","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/KLK14","total_profiled":1310},"omim":[{"mim_id":"615868","title":"SERINE PEPTIDASE INHIBITOR, KAZAL-TYPE, 6; SPINK6","url":"https://www.omim.org/entry/615868"},{"mim_id":"606135","title":"KALLIKREIN-RELATED PEPTIDASE 14; KLK14","url":"https://www.omim.org/entry/606135"},{"mim_id":"605644","title":"KALLIKREIN-RELATED PEPTIDASE 8; KLK8","url":"https://www.omim.org/entry/605644"},{"mim_id":"605643","title":"KALLIKREIN-RELATED PEPTIDASE 5; KLK5","url":"https://www.omim.org/entry/605643"},{"mim_id":"605640","title":"SIALIC ACID-BINDING IMMUNOGLOBULIN-LIKE LECTIN 9; SIGLEC9","url":"https://www.omim.org/entry/605640"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enhanced","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"skin 1","ntpm":9.9}],"url":"https://www.proteinatlas.org/search/KLK14"},"hgnc":{"alias_symbol":["KLK-L6"],"prev_symbol":[]},"alphafold":{"accession":"Q9P0G3","domains":[{"cath_id":"2.40.10.10","chopping":"53-145_257-264","consensus_level":"medium","plddt":97.6151,"start":53,"end":264},{"cath_id":"2.40.10.10","chopping":"156-255","consensus_level":"medium","plddt":90.5785,"start":156,"end":255}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P0G3","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P0G3-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q9P0G3-F1-predicted_aligned_error_v6.png","plddt_mean":87.31},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=KLK14","jax_strain_url":"https://www.jax.org/strain/search?query=KLK14"},"sequence":{"accession":"Q9P0G3","fasta_url":"https://rest.uniprot.org/uniprotkb/Q9P0G3.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q9P0G3/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q9P0G3"}},"corpus_meta":[{"pmid":"17596512","id":"PMC_17596512","title":"LEKTI fragments specifically inhibit KLK5, KLK7, and KLK14 and control desquamation through a pH-dependent interaction.","date":"2007","source":"Molecular biology of the cell","url":"https://pubmed.ncbi.nlm.nih.gov/17596512","citation_count":237,"is_preprint":false},{"pmid":"11309303","id":"PMC_11309303","title":"Cloning of a new member of the human kallikrein gene family, KLK14, which is down-regulated in different malignancies.","date":"2001","source":"Cancer research","url":"https://pubmed.ncbi.nlm.nih.gov/11309303","citation_count":72,"is_preprint":false},{"pmid":"12858357","id":"PMC_12858357","title":"Differential expression of the human kallikrein gene 14 (KLK14) in normal and cancerous prostatic tissues.","date":"2003","source":"The Prostate","url":"https://pubmed.ncbi.nlm.nih.gov/12858357","citation_count":49,"is_preprint":false},{"pmid":"11352573","id":"PMC_11352573","title":"Identification and characterization of KLK14, a novel kallikrein serine protease gene located on human chromosome 19q13.4 and expressed in prostate and skeletal muscle.","date":"2001","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/11352573","citation_count":48,"is_preprint":false},{"pmid":"18482984","id":"PMC_18482984","title":"Major role of human KLK14 in seminal clot liquefaction.","date":"2008","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/18482984","citation_count":33,"is_preprint":false},{"pmid":"16434994","id":"PMC_16434994","title":"Expression of human Kallikrein 14 (KLK14) in breast cancer is associated with higher tumour grades and positive nodal status.","date":"2006","source":"British journal of cancer","url":"https://pubmed.ncbi.nlm.nih.gov/16434994","citation_count":23,"is_preprint":false},{"pmid":"22505524","id":"PMC_22505524","title":"Proteinase-activated receptors (PARs): differential signalling by kallikrein-related peptidases KLK8 and KLK14.","date":"2012","source":"Biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22505524","citation_count":19,"is_preprint":false},{"pmid":"18497543","id":"PMC_18497543","title":"High expression of KLK14 in prostatic adenocarcinoma is associated with elevated risk of prostate-specific antigen relapse.","date":"2008","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/18497543","citation_count":16,"is_preprint":false},{"pmid":"20155713","id":"PMC_20155713","title":"Human kallikrein 14 (KLK14) expression in salivary gland tumors.","date":"2010","source":"The International journal of biological markers","url":"https://pubmed.ncbi.nlm.nih.gov/20155713","citation_count":11,"is_preprint":false},{"pmid":"21057706","id":"PMC_21057706","title":"Quantitative expression analysis and study of the novel human kallikrein-related peptidase 14 gene (KLK14) in malignant and benign breast tissues.","date":"2010","source":"Thrombosis and haemostasis","url":"https://pubmed.ncbi.nlm.nih.gov/21057706","citation_count":11,"is_preprint":false},{"pmid":"23086576","id":"PMC_23086576","title":"Significant alterations in the expression pattern of kallikrein-related peptidase genes KLK4, KLK5 and KLK14 after treatment of breast cancer cells with the chemotherapeutic agents epirubicin, docetaxel and methotrexate.","date":"2012","source":"Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine","url":"https://pubmed.ncbi.nlm.nih.gov/23086576","citation_count":9,"is_preprint":false},{"pmid":"40753921","id":"PMC_40753921","title":"KLK5 and KLK7 drive cervical carcinoma via KLK14-dependent RhoA and NF-κB pathways.","date":"2025","source":"Translational oncology","url":"https://pubmed.ncbi.nlm.nih.gov/40753921","citation_count":1,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":7395,"output_tokens":1496,"usd":0.022312},"stage2":{"model":"claude-opus-4-6","input_tokens":4746,"output_tokens":3743,"usd":0.175957},"total_usd":0.198269,"stage1_batch_id":"msgbatch_01Mgbec4vM6c9vXht7JVJzss","stage2_batch_id":"msgbatch_01JkuuH5RB2BdJNsgnhjbC6s","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2007,\n      \"finding\": \"LEKTI fragments specifically inhibit KLK14 in a pH-dependent manner; at acidic pH, active KLK14 (and KLK5) is released from the LEKTI inhibitory complex, enabling regulated proteolytic activity in the stratum corneum. This interaction is rapid and irreversible at neutral pH, reflecting an extremely tight binding complex.\",\n      \"method\": \"Kinetic analysis of LEKTI fragment inhibition of KLK5, KLK7, and KLK14; pH-dependent binding/release assays; biochemical characterization of LEKTI fragments from cultured keratinocytes and epidermis\",\n      \"journal\": \"Molecular biology of the cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal biochemical methods (kinetics, fragment characterization, pH-shift assays) in a highly cited study with functional consequence in skin homeostasis\",\n      \"pmids\": [\"17596512\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"KLK14 encodes a secreted serine protease with predicted trypsin-like substrate specificity, translated in vitro with a molecular mass of approximately 31 kDa, and expressed by both benign and malignant glandular epithelial cells in prostate.\",\n      \"method\": \"In vitro translation, Northern blot, in situ hybridization, genomic characterization\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — in vitro translation confirming protein product and domain architecture, supported by expression localization\",\n      \"pmids\": [\"11352573\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"KLK14 plays a major role in seminal clot liquefaction by: (1) directly cleaving semenogelins I and II; (2) activating KLK3 (PSA) bidirectionally — promoting early KLK3 activity and inactivating it via internal cleavage at higher doses; (3) being subject to Zn²⁺ inhibition that is reversible by semenogelins, providing a novel regulatory mechanism. Specific synthetic inhibition of KLK14 (ACT(G9)) significantly delayed liquefaction ex vivo, and addition of recombinant KLK14 facilitated liquefaction.\",\n      \"method\": \"Ex vivo semen liquefaction assay with synthetic KLK14 inhibitor (ACT(G9)) and recombinant active KLK14; biochemical assays measuring chymotrypsin-like and KLK1 activity; KLK3 fragmentation analysis; Zn²⁺ inhibition reversal assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reconstituted enzymatic activity, gain- and loss-of-function with recombinant protein and specific inhibitor, multiple orthogonal assays identifying substrates and regulatory mechanism\",\n      \"pmids\": [\"18482984\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"KLK14 activates proteinase-activated receptor 2 (PAR2) by cleaving and unmasking its receptor-activating sequence, triggering calcium transients, MAPK activation, β-arrestin interactions, and receptor internalization in PAR2-expressing cells. KLK14 can signal via both human and rat PAR2, distinguishing it from KLK8 which cannot activate human PAR2.\",\n      \"method\": \"Calcium transient assays, MAPK activation assays, β-arrestin interaction assays, receptor internalization assays, and peptide cleavage assays in PAR2-expressing HEK and KNRK cells\",\n      \"journal\": \"Biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal signaling readouts in cell-based systems, direct peptide cleavage assay, comparison with KLK8 clarifying specificity\",\n      \"pmids\": [\"22505524\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"KLK14 mediates a pro-tumorigenic effect downstream of KLK5 and KLK7 in HPV-dependent cervical carcinogenesis by regulating PAR-2-dependent RhoA and NF-κB signaling pathways. KLK5 and KLK7 drive KLK14 activation, and absence of KLK5/KLK7 ameliorates the HPV-dependent phenotype via modulation of KLK14.\",\n      \"method\": \"Genetically engineered mice (KLK5/KLK7 knockout), bulk RNA-seq, reporter assays for RhoA and NF-κB pathway activity, human biopsy expression analysis\",\n      \"journal\": \"Translational oncology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — genetic epistasis in mouse model with pathway reporter assays, but single study without in vitro reconstitution of KLK14 enzymatic mechanism\",\n      \"pmids\": [\"40753921\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"KLK14 is a secreted trypsin-like serine protease that is regulated by its endogenous inhibitor LEKTI in a pH-dependent manner in skin, directly cleaves semenogelins and activates/modulates KLK3 to drive seminal clot liquefaction, activates PAR2 to trigger downstream MAPK and calcium signaling, and in epithelial carcinogenesis functions downstream of KLK5/KLK7 to promote tumor progression via PAR2-dependent RhoA and NF-κB pathways.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"KLK14 is a secreted trypsin-like serine protease that functions in skin barrier homeostasis, seminal clot liquefaction, protease-activated receptor signaling, and epithelial tumorigenesis. In skin, KLK14 activity is controlled by the endogenous inhibitor LEKTI in a pH-dependent manner: at neutral pH LEKTI binds KLK14 tightly and irreversibly, whereas acidification in the stratum corneum releases active enzyme [PMID:17596512]. In seminal fluid, KLK14 directly cleaves semenogelins I and II and bidirectionally modulates KLK3 (PSA) activity, with Zn²⁺-mediated inhibition reversed by semenogelins providing a substrate-coupled regulatory switch; specific inhibition of KLK14 delays semen liquefaction ex vivo [PMID:18482984]. KLK14 activates PAR2 by proteolytic unmasking of its tethered ligand, triggering calcium transients, MAPK activation, and β-arrestin-dependent receptor internalization, and in HPV-driven cervical carcinogenesis it operates downstream of KLK5/KLK7 to promote tumor progression through PAR2-dependent RhoA and NF-κB signaling [PMID:22505524, PMID:40753921].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing the identity of KLK14 as a secreted serine protease with trypsin-like specificity expressed in prostatic epithelium filled the gap of whether the KLK14 locus encodes a functional protease and where it is produced.\",\n      \"evidence\": \"In vitro translation, Northern blot, and in situ hybridization in prostate tissue\",\n      \"pmids\": [\"11352573\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No endogenous substrates identified\",\n        \"Enzymatic activity not demonstrated on native substrates\",\n        \"Expression survey limited to prostate\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrating that LEKTI fragments inhibit KLK14 in a pH-dependent manner — tight binding at neutral pH and release at acidic pH — established the first endogenous regulatory mechanism for KLK14 and explained how proteolytic activity is spatially controlled in the stratum corneum.\",\n      \"evidence\": \"Kinetic inhibition assays, pH-shift binding/release experiments, and LEKTI fragment characterization from cultured keratinocytes and epidermis\",\n      \"pmids\": [\"17596512\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Downstream skin substrates of released KLK14 not identified\",\n        \"In vivo consequences of dysregulated KLK14 in LEKTI-deficient skin not directly tested\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identifying semenogelins and KLK3 as direct substrates/targets of KLK14 and showing that specific KLK14 inhibition delays semen liquefaction established a physiological role for KLK14 in male reproduction and revealed a Zn²⁺/semenogelin regulatory circuit.\",\n      \"evidence\": \"Ex vivo semen liquefaction assay with specific synthetic inhibitor (ACT-G9) and recombinant KLK14; Zn²⁺ inhibition reversal assay; KLK3 fragmentation analysis\",\n      \"pmids\": [\"18482984\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Relative contribution of KLK14 versus other seminal KLKs in vivo not quantified\",\n        \"No genetic loss-of-function model for reproductive phenotype\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showing that KLK14 proteolytically activates PAR2 to elicit calcium transients, MAPK signaling, β-arrestin recruitment, and receptor internalization identified a cell-surface receptor through which KLK14 can transduce extracellular proteolytic activity into intracellular signaling.\",\n      \"evidence\": \"Calcium flux, MAPK, β-arrestin interaction, and receptor internalization assays in PAR2-expressing HEK and KNRK cells; peptide cleavage assays\",\n      \"pmids\": [\"22505524\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological tissue context for KLK14–PAR2 signaling not established\",\n        \"Relative potency compared to other PAR2 agonists (thrombin-family proteases) not determined in vivo\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Genetic epistasis in HPV-driven cervical carcinogenesis placed KLK14 downstream of KLK5/KLK7 and showed it promotes tumorigenesis via PAR2-dependent RhoA and NF-κB pathways, linking the KLK14–PAR2 axis to a disease-relevant signaling cascade.\",\n      \"evidence\": \"KLK5/KLK7 knockout mice, bulk RNA-seq, RhoA and NF-κB reporter assays, human biopsy expression analysis\",\n      \"pmids\": [\"40753921\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct enzymatic activation of KLK14 by KLK5 or KLK7 not reconstituted in vitro\",\n        \"Whether KLK14 cleaves PAR2 in cervical epithelium in vivo not directly shown\",\n        \"Contribution of KLK14 independent of other downstream KLK5/KLK7 targets not isolated\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A structural basis for KLK14 substrate selectivity and the atomic details of its interaction with LEKTI remain unresolved, and no Mendelian or engineered KLK14-null phenotype has been reported in vivo.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No crystal or cryo-EM structure of KLK14 alone or in complex with inhibitors/substrates\",\n        \"No KLK14 knockout mouse phenotype reported\",\n        \"Full in vivo substrate repertoire undefined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": []}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"SPINK5\",\n      \"KLK3\",\n      \"F2RL1\",\n      \"SEMG1\",\n      \"SEMG2\",\n      \"KLK5\",\n      \"KLK7\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```\n\nWait, I need to fix the pathway — I incorrectly used a GO term. Let me correct:\n\n```json\n{\n  \"mechanistic_narrative\": \"KLK14 is a secreted trypsin-like serine protease that functions in skin barrier homeostasis, seminal clot liquefaction, protease-activated receptor signaling, and epithelial tumorigenesis. In skin, KLK14 activity is controlled by the endogenous inhibitor LEKTI in a pH-dependent manner: at neutral pH LEKTI binds KLK14 tightly and irreversibly, whereas acidification in the stratum corneum releases active enzyme [PMID:17596512]. In seminal fluid, KLK14 directly cleaves semenogelins I and II and bidirectionally modulates KLK3 (PSA) activity, with Zn²⁺-mediated inhibition reversed by semenogelins providing a substrate-coupled regulatory switch; specific inhibition of KLK14 delays semen liquefaction ex vivo [PMID:18482984]. KLK14 activates PAR2 by proteolytic unmasking of its tethered ligand, triggering calcium transients, MAPK activation, and β-arrestin-dependent receptor internalization, and in HPV-driven cervical carcinogenesis it operates downstream of KLK5/KLK7 to promote tumor progression through PAR2-dependent RhoA and NF-κB signaling [PMID:22505524, PMID:40753921].\",\n  \"teleology\": [\n    {\n      \"year\": 2001,\n      \"claim\": \"Establishing the identity of KLK14 as a secreted serine protease with trypsin-like specificity expressed in prostatic epithelium filled the gap of whether the KLK14 locus encodes a functional protease and where it is produced.\",\n      \"evidence\": \"In vitro translation, Northern blot, and in situ hybridization in prostate tissue\",\n      \"pmids\": [\"11352573\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"No endogenous substrates identified\",\n        \"Enzymatic activity not demonstrated on native substrates\",\n        \"Expression survey limited to prostate\"\n      ]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"Demonstrating that LEKTI fragments inhibit KLK14 in a pH-dependent manner — tight binding at neutral pH and release at acidic pH — established the first endogenous regulatory mechanism for KLK14 and explained how proteolytic activity is spatially controlled in the stratum corneum.\",\n      \"evidence\": \"Kinetic inhibition assays, pH-shift binding/release experiments, and LEKTI fragment characterization from cultured keratinocytes and epidermis\",\n      \"pmids\": [\"17596512\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Downstream skin substrates of released KLK14 not identified\",\n        \"In vivo consequences of dysregulated KLK14 in LEKTI-deficient skin not directly tested\"\n      ]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Identifying semenogelins and KLK3 as direct substrates/targets of KLK14 and showing that specific KLK14 inhibition delays semen liquefaction established a physiological role for KLK14 in male reproduction and revealed a Zn²⁺/semenogelin regulatory circuit.\",\n      \"evidence\": \"Ex vivo semen liquefaction assay with specific synthetic inhibitor (ACT-G9) and recombinant KLK14; Zn²⁺ inhibition reversal assay; KLK3 fragmentation analysis\",\n      \"pmids\": [\"18482984\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Relative contribution of KLK14 versus other seminal KLKs in vivo not quantified\",\n        \"No genetic loss-of-function model for reproductive phenotype\"\n      ]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Showing that KLK14 proteolytically activates PAR2 to elicit calcium transients, MAPK signaling, β-arrestin recruitment, and receptor internalization identified a cell-surface receptor through which KLK14 can transduce extracellular proteolytic activity into intracellular signaling.\",\n      \"evidence\": \"Calcium flux, MAPK, β-arrestin interaction, and receptor internalization assays in PAR2-expressing HEK and KNRK cells; peptide cleavage assays\",\n      \"pmids\": [\"22505524\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Physiological tissue context for KLK14–PAR2 signaling not established\",\n        \"Relative potency compared to other PAR2 agonists not determined in vivo\"\n      ]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Genetic epistasis in HPV-driven cervical carcinogenesis placed KLK14 downstream of KLK5/KLK7 and showed it promotes tumorigenesis via PAR2-dependent RhoA and NF-κB pathways, linking the KLK14–PAR2 axis to a disease-relevant signaling cascade.\",\n      \"evidence\": \"KLK5/KLK7 knockout mice, bulk RNA-seq, RhoA and NF-κB reporter assays, human biopsy expression analysis\",\n      \"pmids\": [\"40753921\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Direct enzymatic activation of KLK14 by KLK5 or KLK7 not reconstituted in vitro\",\n        \"Whether KLK14 cleaves PAR2 in cervical epithelium in vivo not directly shown\",\n        \"Contribution of KLK14 independent of other downstream KLK5/KLK7 targets not isolated\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A structural basis for KLK14 substrate selectivity and the atomic details of its interaction with LEKTI remain unresolved, and no KLK14-null in vivo phenotype has been reported.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No crystal or cryo-EM structure of KLK14 alone or in complex\",\n        \"No KLK14 knockout mouse phenotype reported\",\n        \"Full in vivo substrate repertoire undefined\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 2]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [1, 2]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [3, 4]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [2]},\n      {\"term_id\": \"R-HSA-1643685\", \"supporting_discovery_ids\": [4]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"SPINK5\",\n      \"KLK3\",\n      \"F2RL1\",\n      \"SEMG1\",\n      \"SEMG2\",\n      \"KLK5\",\n      \"KLK7\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}