{"gene":"CASP5","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":1995,"finding":"CASP5 (ICErel-III) was cloned from human monocytic cells as a novel member of the ICE/CED-3 cysteine protease family. It contains the conserved catalytic pentapeptide Gln-Ala-Cys-Arg-Asp, is synthesized as a proenzyme processed to a heterodimeric active form, and can induce apoptosis when overexpressed in COS cells (pro-domain-less truncated form), but cannot process pro-IL-1β.","method":"Molecular cloning, transfection, in vitro protease activity assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 — original cloning with in vitro activity assays and mutagenesis of catalytic cysteine; foundational paper with 274 citations","pmids":["7797592"],"is_preprint":false},{"year":1996,"finding":"CASP5 (TY/transcript Y) was independently identified as an ICE-family cysteine protease (75% identity to TX/CASP4, 51% to ICE/CASP1). Auto-processing activity requires the catalytic cysteine at position 245. Despite active-site conservation, TY cannot process pro-IL-1β. Overexpression induces apoptosis in COS cells.","method":"Molecular cloning, transfection, in vitro protease activity assay, active-site mutagenesis (Cys245)","journal":"European journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — catalytic cysteine mutagenesis plus functional apoptosis and IL-1β processing assays","pmids":["8617266"],"is_preprint":false},{"year":2001,"finding":"CASP5 cleaves the transcription factor Max at an unusual glutamic acid residue (site IEVE10↓S) during Fas-induced apoptosis, making Max the first identified caspase-5 substrate. Cleavage requires full-length, DNA-binding competent Max but not corresponding peptides, indicating structural determinants are important. Phosphorylation of Max at Ser-11 by protein kinase CK2 inhibits caspase-5-mediated cleavage. Fas-mediated dephosphorylation of Max is a prerequisite for caspase-5 cleavage.","method":"In vitro cleavage assay with purified caspase-5, mutational analysis of cleavage sites, in vivo Fas-apoptosis assay, CK2 kinase phosphorylation assay","journal":"The Biochemical journal","confidence":"High","confidence_rationale":"Tier 1 — reconstituted in vitro cleavage, mutagenesis of cleavage sites, and phosphorylation regulation confirmed in vivo","pmids":["11535131"],"is_preprint":false},{"year":2002,"finding":"CASP5 is a component of the inflammasome, a multiprotein complex comprising caspase-1, caspase-5, Pycard/ASC, and NALP1, which activates proinflammatory caspases and processes pro-IL-1β. Immunodepletion of Pycard in a cell-free system abolished proinflammatory caspase activation and proIL-1β processing.","method":"Cell-free caspase activation system, immunodepletion, dominant-negative expression in THP-1 cells","journal":"Molecular cell","confidence":"High","confidence_rationale":"Tier 1-2 — reconstituted cell-free system plus dominant-negative cell-based assay; highly cited foundational paper","pmids":["12191486"],"is_preprint":false},{"year":2000,"finding":"CASP5 mRNA and protein are specifically induced by lipopolysaccharide (LPS) in THP-1 monocytic cells (unlike CASP1, which is constitutive), and CASP5 mRNA (but not protein) is induced by IFN-γ in HT-29 colon carcinoma cells. In vitro, caspase-1 subfamily members including caspase-5 display different activities toward pro-caspases 1 and 3 and pro-IL-1β.","method":"Quantitative RT-PCR, western blotting, in vitro substrate cleavage assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 — specific PCR system with protein-level confirmation and in vitro activity assays, single study","pmids":["10986288"],"is_preprint":false},{"year":2003,"finding":"The C-terminal helical domain of periphilin (a keratinocyte nuclear protein and cornified envelope constituent) is specifically cleaved by caspase-5 in vitro, identifying periphilin as a caspase-5 substrate in the context of keratinocyte differentiation.","method":"In vitro caspase cleavage assay","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 1 (in vitro assay) + Weak (single lab, single method, no in vivo validation of caspase-5-specific cleavage)","pmids":["12853457"],"is_preprint":false},{"year":2015,"finding":"Both caspase-4 and caspase-5 detect cytoplasmic LPS. Genetic deletion of caspase-4 suppressed cell death and IL-1β production after cytoplasmic LPS transfection or Salmonella infection; caspase-5 deletion reduced cell death and IL-1β after Salmonella infection but not transfected LPS. Double deletion had a synergistic protective effect. IL-1β maturation downstream of caspase-4/5 activation is mediated specifically by NLRP3 inflammasome (blocked by NLRP3 inhibitor MCC950).","method":"CRISPR/genetic deletion of caspase-4 and caspase-5 in human monocytic cell lines, NLRP3 inhibitor (MCC950), Salmonella infection, LPS transfection, IL-1β ELISA, cell death assays","journal":"European journal of immunology","confidence":"High","confidence_rationale":"Tier 2 — clean genetic KO with defined cellular phenotypes, pharmacological inhibitor validation, replicated across conditions","pmids":["26173988"],"is_preprint":false},{"year":2015,"finding":"In human monocytes, caspase-5 undergoes rapid processing (cleavage) upon LPS stimulation and mediates IL-1α and IL-1β release via a one-step non-canonical inflammasome pathway that requires Syk activity and Ca²⁺ flux downstream of CD14/TLR4-mediated LPS internalization. An additional caspase-5 cleavage product correlates with IL-1 secretion.","method":"siRNA knockdown, western blotting of caspase-5 processing, cytokine ELISA, pharmacological inhibition of Syk and Ca²⁺ signaling","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — siRNA KD with mechanistic pathway dissection (Syk, Ca²⁺, CD14/TLR4), orthogonal approaches in primary human monocytes","pmids":["26508369"],"is_preprint":false},{"year":2019,"finding":"SERPINB1 inhibits caspase-5 (along with caspase-1, -4, and -11) by suppressing CARD oligomerization and enzymatic activation. The C-terminal CARD-binding motif of SERPINB1, distinct from its reactive center loop, restrains pro-caspase-5 activation. SERPINB1 knockdown/deletion leads to spontaneous caspase-5 activation and IL-1β release.","method":"In vitro caspase activity assays, CARD oligomerization assays, SERPINB1 knockdown/KO with caspase activation and cytokine readouts","journal":"Nature immunology","confidence":"High","confidence_rationale":"Tier 1-2 — in vitro biochemical assays plus genetic KO with defined mechanistic pathway (CARD oligomerization suppression), functionally separable domains identified","pmids":["30692621"],"is_preprint":false},{"year":2021,"finding":"CASP5 mediates intestinal barrier dysfunction downstream of cytoplasmic LPS sensing. OMV internalization recruits caspase-5 and PIKfyve to early endosomal membranes via SNX10, enabling LPS release into the cytosol. Cytosolic LPS-activated caspase-5 phosphorylates Lyn kinase, which promotes nuclear translocation of Snail/Slug, downregulation of E-cadherin, and intestinal barrier disruption. SNX10 deletion or inhibition blocked caspase-5 activation and rescued barrier function.","method":"Co-immunoprecipitation, proximity ligation, genetic deletion (SNX10), pharmacological inhibition (DC-SX029), murine colitis model, Lyn phosphorylation assay, E-cadherin immunoblotting","journal":"The EMBO journal","confidence":"High","confidence_rationale":"Tier 2 — epistatic pathway defined by genetic deletion and pharmacological blockade with specific molecular readouts (Lyn phosphorylation, E-cadherin, Snail/Slug), in vivo validation","pmids":["34747049"],"is_preprint":false},{"year":2023,"finding":"Activated human caspase-5 (like caspase-4) directly and efficiently processes pro-IL-18 in vitro and during bacterial infection. Caspase-5 uses a binary (two-site) substrate recognition mechanism: the catalytic pocket engages the tetrapeptide cleavage site, and a unique exosite (similar to that used for GSDMD recognition) binds a structural element formed jointly by the IL-18 propeptide and post-cleavage-site sequences. Cleavage by caspase-5 induces conformational changes in IL-18 that generate two critical IL-18Rα receptor-binding sites.","method":"In vitro cleavage assay, crystal structure of caspase-4–pro-IL-18 complex (with exosite structure informing caspase-5 mechanism), bacterial infection model, site-directed mutagenesis","journal":"Nature","confidence":"High","confidence_rationale":"Tier 1 — crystal structure plus in vitro reconstitution and mutagenesis, with in vivo bacterial infection validation; highly cited paradigm-shifting study","pmids":["37993714"],"is_preprint":false}],"current_model":"CASP5 is an inflammatory cysteine protease that functions as a cytoplasmic LPS sensor within the non-canonical inflammasome: upon LPS binding, it undergoes CARD-mediated oligomerization and auto-activation (restrained by SERPINB1), cleaves gasdermin D to trigger pyroptosis, directly processes pro-IL-18 via a binary exosite/catalytic-pocket recognition mechanism to generate the mature cytokine, and activates NLRP3-dependent IL-1β maturation; in addition, activated caspase-5 phosphorylates Lyn kinase downstream of endosomal LPS sensing to disrupt epithelial barrier integrity, and during Fas-induced apoptosis it cleaves the transcription factor Max at an unusual glutamate residue in a phosphorylation-regulated manner."},"narrative":{"teleology":[{"year":1995,"claim":"Cloning of CASP5 established it as a new ICE/CED-3 family cysteine protease with auto-processing capability and apoptosis-inducing potential, but its natural substrates remained unknown.","evidence":"Molecular cloning from human monocytes, catalytic cysteine mutagenesis, overexpression apoptosis assay in COS cells","pmids":["7797592","8617266"],"confidence":"High","gaps":["No endogenous substrate identified","Physiological activation stimulus unknown","Inability to process pro-IL-1β left functional distinction from caspase-1 unresolved"]},{"year":2000,"claim":"Demonstration that CASP5 expression is specifically induced by LPS (at both mRNA and protein level) in monocytes, unlike constitutively expressed CASP1, linked caspase-5 to innate immune activation.","evidence":"Quantitative RT-PCR and western blotting in LPS-stimulated THP-1 cells","pmids":["10986288"],"confidence":"Medium","gaps":["Mechanism of transcriptional induction not defined","Single study without genetic loss-of-function","Whether LPS-induced caspase-5 has a distinct function from caspase-1 remained unclear"]},{"year":2001,"claim":"Identification of the transcription factor Max as the first caspase-5 substrate—cleaved at an atypical glutamate residue during Fas-induced apoptosis—revealed that caspase-5 recognizes structural determinants in substrates and is regulated by CK2-mediated phosphorylation.","evidence":"In vitro cleavage with purified caspase-5, site-directed mutagenesis of Max cleavage site, CK2 phosphorylation assay, Fas-apoptosis model","pmids":["11535131"],"confidence":"High","gaps":["Biological consequence of Max cleavage for transcription not determined","In vivo relevance beyond Fas-induced apoptosis not tested","No structural basis for atypical glutamate recognition"]},{"year":2002,"claim":"Placement of caspase-5 in the inflammasome complex alongside caspase-1, ASC/Pycard, and NALP1 established its role in a multiprotein platform for proinflammatory caspase activation and IL-1β processing.","evidence":"Cell-free caspase activation system, immunodepletion of Pycard, dominant-negative expression in THP-1 cells","pmids":["12191486"],"confidence":"High","gaps":["Whether caspase-5 directly processes pro-IL-1β or acts indirectly through caspase-1 was unresolved","Stoichiometry and architecture of the caspase-5-containing inflammasome not defined","Activation trigger within the complex not identified"]},{"year":2015,"claim":"Genetic deletion studies resolved the non-redundant roles of caspase-4 and caspase-5 as cytoplasmic LPS sensors: caspase-5 is required for pyroptosis and NLRP3-dependent IL-1β maturation upon bacterial infection, establishing the non-canonical inflammasome pathway in human cells.","evidence":"CRISPR KO of CASP4/CASP5 in monocytic lines, NLRP3 inhibitor MCC950, Salmonella infection, LPS transfection, siRNA in primary human monocytes with Syk/Ca²⁺ pathway dissection","pmids":["26173988","26508369"],"confidence":"High","gaps":["Structural basis for LPS binding by caspase-5 CARD not determined","Relative contributions of caspase-4 vs caspase-5 across different infection contexts not systematically compared","Downstream mechanism by which caspase-5 engages NLRP3 not defined"]},{"year":2019,"claim":"Identification of SERPINB1 as an endogenous inhibitor that suppresses caspase-5 CARD oligomerization—via a domain distinct from its serine protease-inhibiting reactive center loop—provided the first mechanism restraining non-canonical inflammasome assembly.","evidence":"In vitro CARD oligomerization assays, SERPINB1 KO with spontaneous caspase-5 activation and IL-1β release readouts","pmids":["30692621"],"confidence":"High","gaps":["Structural details of SERPINB1–CARD interaction not resolved","Whether SERPINB1 regulation is modulated during infection in vivo not tested","Whether other endogenous regulators cooperate with SERPINB1 unknown"]},{"year":2021,"claim":"Discovery that activated caspase-5 phosphorylates Lyn kinase to drive Snail/Slug nuclear translocation and E-cadherin downregulation revealed a non-pyroptotic effector arm of the non-canonical inflammasome that disrupts intestinal epithelial barrier integrity.","evidence":"Co-IP, proximity ligation, SNX10 KO and pharmacological inhibition, murine colitis model, Lyn phosphorylation and E-cadherin immunoblotting","pmids":["34747049"],"confidence":"High","gaps":["Whether caspase-5 directly phosphorylates Lyn or acts through an intermediate kinase not fully established","Kinase activity for a caspase is unprecedented and the catalytic mechanism is unknown","Relevance to human IBD or other barrier diseases not clinically validated"]},{"year":2023,"claim":"Structural and biochemical demonstration that caspase-5 directly processes pro-IL-18 using a binary recognition mechanism (catalytic pocket plus exosite) resolved a long-standing question about whether non-canonical inflammasome caspases can generate mature cytokines independently of caspase-1.","evidence":"In vitro cleavage assay, crystal structure of homologous caspase-4–pro-IL-18 complex informing caspase-5 mechanism, site-directed mutagenesis, bacterial infection model","pmids":["37993714"],"confidence":"High","gaps":["Caspase-5–specific crystal structure with pro-IL-18 not yet available (inferred from caspase-4 complex)","Relative physiological contribution of caspase-5 vs caspase-1 to IL-18 maturation in vivo not quantified","Whether the exosite is shared with GSDMD recognition or represents distinct binding modes unknown"]},{"year":null,"claim":"Key unresolved questions include the structural basis of direct LPS–CARD binding, the mechanism by which a cysteine protease reportedly phosphorylates Lyn, the full spectrum of endogenous caspase-5 substrates, and whether caspase-5 has non-redundant roles in specific human infections or inflammatory diseases.","evidence":"","pmids":[],"confidence":"High","gaps":["No atomic-resolution structure of caspase-5 CARD bound to LPS","Reported Lyn kinase phosphorylation by caspase-5 lacks a defined catalytic mechanism","Systematic substrate profiling (e.g. degradomics) not reported"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[0,1,2,3,5,10]},{"term_id":"GO:0016787","term_label":"hydrolase activity","supporting_discovery_ids":[0,1,2,10]},{"term_id":"GO:0140299","term_label":"molecular sensor activity","supporting_discovery_ids":[6,7,9]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[6,7,9]},{"term_id":"GO:0005768","term_label":"endosome","supporting_discovery_ids":[9]}],"pathway":[{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[3,6,7,8,9,10]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[0,1,2,6]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[7,9]}],"complexes":["NALP1 inflammasome","Non-canonical inflammasome"],"partners":["PYCARD","NLRP1","CASP1","SERPINB1","GSDMD","IL18","LYN","SNX10"],"other_free_text":[]},"mechanistic_narrative":"Caspase-5 is an inflammatory cysteine protease that functions as a cytoplasmic sensor of lipopolysaccharide (LPS) and a key effector of the non-canonical inflammasome pathway in human myeloid and epithelial cells. Upon cytoplasmic LPS encounter, caspase-5 undergoes CARD-mediated oligomerization—normally restrained by SERPINB1—and activates to cleave gasdermin D, trigger pyroptosis, and directly process pro-IL-18 via a binary exosite/catalytic-pocket recognition mechanism, while also engaging the NLRP3 inflammasome for IL-1β maturation [PMID:26173988, PMID:30692621, PMID:37993714]. Beyond canonical inflammasome signaling, activated caspase-5 phosphorylates Lyn kinase downstream of endosomal LPS sensing to drive Snail/Slug-dependent E-cadherin loss and epithelial barrier disruption [PMID:34747049]. During Fas-induced apoptosis, caspase-5 cleaves the transcription factor Max at an atypical glutamate residue in a phosphorylation-regulated manner, linking it to apoptotic transcriptional reprogramming [PMID:11535131]."},"prefetch_data":{"uniprot":{"accession":"P51878","full_name":"Caspase-5","aliases":["ICE(rel)-III","Protease ICH-3","Protease TY"],"length_aa":434,"mass_kda":49.7,"function":"Thiol protease that acts as a mediator of programmed cell death (PubMed:28314590, PubMed:29898893). Initiates pyroptosis, a programmed lytic cell death pathway through cleavage of Gasdermin-D (GSDMD): cleavage releases the N-terminal gasdermin moiety (Gasdermin-D, N-terminal) that binds to membranes and forms pores, triggering pyroptosis (PubMed:29898893). Also mediates cleavage and maturation of IL18 (PubMed:37993714). Cleavage of GSDMD and IL18 is not strictly dependent on the consensus cleavage site but depends on an exosite interface on CASP4 (PubMed:37993714). During non-canonical inflammasome activation, cuts CGAS and may play a role in the regulation of antiviral innate immune activation (PubMed:28314590)","subcellular_location":"","url":"https://www.uniprot.org/uniprotkb/P51878/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CASP5","classification":"Not Classified","n_dependent_lines":1,"n_total_lines":1208,"dependency_fraction":0.0008278145695364238},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/CASP5","total_profiled":1310},"omim":[{"mim_id":"617042","title":"GASDERMIN D; GSDMD","url":"https://www.omim.org/entry/617042"},{"mim_id":"615680","title":"CASPASE RECRUITMENT DOMAIN-CONTAINING PROTEIN 16; CARD16","url":"https://www.omim.org/entry/615680"},{"mim_id":"609364","title":"NLR FAMILY, PYRIN DOMAIN-CONTAINING 2; NLRP2","url":"https://www.omim.org/entry/609364"},{"mim_id":"609051","title":"CASPASE RECRUITMENT DOMAIN-CONTAINING PROTEIN 8; CARD8","url":"https://www.omim.org/entry/609051"},{"mim_id":"606838","title":"PYD AND CARD DOMAIN-CONTAINING PROTEIN; PYCARD","url":"https://www.omim.org/entry/606838"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Group enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"intestine","ntpm":15.8},{"tissue":"lymphoid tissue","ntpm":13.8}],"url":"https://www.proteinatlas.org/search/CASP5"},"hgnc":{"alias_symbol":["ICE(rel)III"],"prev_symbol":[]},"alphafold":{"accession":"P51878","domains":[{"cath_id":"3.40.50.1460","chopping":"169-320_353-421","consensus_level":"high","plddt":91.0966,"start":169,"end":421}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P51878","model_url":"https://alphafold.ebi.ac.uk/files/AF-P51878-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P51878-F1-predicted_aligned_error_v6.png","plddt_mean":69.0},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CASP5","jax_strain_url":"https://www.jax.org/strain/search?query=CASP5"},"sequence":{"accession":"P51878","fasta_url":"https://rest.uniprot.org/uniprotkb/P51878.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P51878/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P51878"}},"corpus_meta":[{"pmid":"9233763","id":"PMC_9233763","title":"Involvement of 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keratinocyte cornified envelope.","date":"2003","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/12853457","citation_count":38,"is_preprint":false,"source_track":"gene2pubmed"}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":1997,"output_tokens":410,"usd":0.006071},"stage2":{"model":"claude-opus-4-6","input_tokens":3553,"output_tokens":725,"usd":0.053835},"total_usd":0.263003,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard","round2_stage1":{"model":"claude-sonnet-4-6","input_tokens":16178,"output_tokens":3164,"usd":0.047997},"round2_rules_fired":"R3","round2_stage2":{"model":"claude-opus-4-6","input_tokens":6815,"output_tokens":2773,"usd":0.1551}},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1997,\n      \"finding\": \"Caspase-4 (which shares close homology with CASP5/ICE(rel)III) is processed and activated downstream of Fas receptor stimulation, acts in a caspase cascade between caspase-8 and caspase-3, and purified caspase-4 directly cleaves pro-caspase-3 to generate its active subunit; dominant-negative active-site mutants of caspase-4 blocked Fas-mediated activation of caspase-3-like proteases and delayed apoptosis.\",\n      \"method\": \"Active-site mutagenesis (dominant-negative overexpression), microinjection of inhibitory antibodies, in vitro cleavage assay with purified caspase-4, and cell-based Fas-stimulation assays\",\n      \"journal\": \"Oncogene\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1–2 methods (in vitro cleavage assay, mutagenesis, antibody inhibition) in a single study; paper primarily characterises caspase-4 with relevance to the closely related CASP5, single lab\",\n      \"pmids\": [\"9233763\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CASP5 (and its close paralog caspase-4) functions as an intermediary caspase in the Fas-mediated apoptotic cascade, being processed downstream of caspase-8 and directly cleaving pro-caspase-3 to propagate the death signal toward executioner caspases.\"\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 1995,\n      \"finding\": \"CASP5 (ICErel-III) was cloned from human monocytic cells as a novel member of the ICE/CED-3 cysteine protease family. It contains the conserved catalytic pentapeptide Gln-Ala-Cys-Arg-Asp, is synthesized as a proenzyme processed to a heterodimeric active form, and can induce apoptosis when overexpressed in COS cells (pro-domain-less truncated form), but cannot process pro-IL-1β.\",\n      \"method\": \"Molecular cloning, transfection, in vitro protease activity assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — original cloning with in vitro activity assays and mutagenesis of catalytic cysteine; foundational paper with 274 citations\",\n      \"pmids\": [\"7797592\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1996,\n      \"finding\": \"CASP5 (TY/transcript Y) was independently identified as an ICE-family cysteine protease (75% identity to TX/CASP4, 51% to ICE/CASP1). Auto-processing activity requires the catalytic cysteine at position 245. Despite active-site conservation, TY cannot process pro-IL-1β. Overexpression induces apoptosis in COS cells.\",\n      \"method\": \"Molecular cloning, transfection, in vitro protease activity assay, active-site mutagenesis (Cys245)\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — catalytic cysteine mutagenesis plus functional apoptosis and IL-1β processing assays\",\n      \"pmids\": [\"8617266\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"CASP5 cleaves the transcription factor Max at an unusual glutamic acid residue (site IEVE10↓S) during Fas-induced apoptosis, making Max the first identified caspase-5 substrate. Cleavage requires full-length, DNA-binding competent Max but not corresponding peptides, indicating structural determinants are important. Phosphorylation of Max at Ser-11 by protein kinase CK2 inhibits caspase-5-mediated cleavage. Fas-mediated dephosphorylation of Max is a prerequisite for caspase-5 cleavage.\",\n      \"method\": \"In vitro cleavage assay with purified caspase-5, mutational analysis of cleavage sites, in vivo Fas-apoptosis assay, CK2 kinase phosphorylation assay\",\n      \"journal\": \"The Biochemical journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstituted in vitro cleavage, mutagenesis of cleavage sites, and phosphorylation regulation confirmed in vivo\",\n      \"pmids\": [\"11535131\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2002,\n      \"finding\": \"CASP5 is a component of the inflammasome, a multiprotein complex comprising caspase-1, caspase-5, Pycard/ASC, and NALP1, which activates proinflammatory caspases and processes pro-IL-1β. Immunodepletion of Pycard in a cell-free system abolished proinflammatory caspase activation and proIL-1β processing.\",\n      \"method\": \"Cell-free caspase activation system, immunodepletion, dominant-negative expression in THP-1 cells\",\n      \"journal\": \"Molecular cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — reconstituted cell-free system plus dominant-negative cell-based assay; highly cited foundational paper\",\n      \"pmids\": [\"12191486\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2000,\n      \"finding\": \"CASP5 mRNA and protein are specifically induced by lipopolysaccharide (LPS) in THP-1 monocytic cells (unlike CASP1, which is constitutive), and CASP5 mRNA (but not protein) is induced by IFN-γ in HT-29 colon carcinoma cells. In vitro, caspase-1 subfamily members including caspase-5 display different activities toward pro-caspases 1 and 3 and pro-IL-1β.\",\n      \"method\": \"Quantitative RT-PCR, western blotting, in vitro substrate cleavage assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — specific PCR system with protein-level confirmation and in vitro activity assays, single study\",\n      \"pmids\": [\"10986288\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2003,\n      \"finding\": \"The C-terminal helical domain of periphilin (a keratinocyte nuclear protein and cornified envelope constituent) is specifically cleaved by caspase-5 in vitro, identifying periphilin as a caspase-5 substrate in the context of keratinocyte differentiation.\",\n      \"method\": \"In vitro caspase cleavage assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 (in vitro assay) + Weak (single lab, single method, no in vivo validation of caspase-5-specific cleavage)\",\n      \"pmids\": [\"12853457\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Both caspase-4 and caspase-5 detect cytoplasmic LPS. Genetic deletion of caspase-4 suppressed cell death and IL-1β production after cytoplasmic LPS transfection or Salmonella infection; caspase-5 deletion reduced cell death and IL-1β after Salmonella infection but not transfected LPS. Double deletion had a synergistic protective effect. IL-1β maturation downstream of caspase-4/5 activation is mediated specifically by NLRP3 inflammasome (blocked by NLRP3 inhibitor MCC950).\",\n      \"method\": \"CRISPR/genetic deletion of caspase-4 and caspase-5 in human monocytic cell lines, NLRP3 inhibitor (MCC950), Salmonella infection, LPS transfection, IL-1β ELISA, cell death assays\",\n      \"journal\": \"European journal of immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean genetic KO with defined cellular phenotypes, pharmacological inhibitor validation, replicated across conditions\",\n      \"pmids\": [\"26173988\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"In human monocytes, caspase-5 undergoes rapid processing (cleavage) upon LPS stimulation and mediates IL-1α and IL-1β release via a one-step non-canonical inflammasome pathway that requires Syk activity and Ca²⁺ flux downstream of CD14/TLR4-mediated LPS internalization. An additional caspase-5 cleavage product correlates with IL-1 secretion.\",\n      \"method\": \"siRNA knockdown, western blotting of caspase-5 processing, cytokine ELISA, pharmacological inhibition of Syk and Ca²⁺ signaling\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — siRNA KD with mechanistic pathway dissection (Syk, Ca²⁺, CD14/TLR4), orthogonal approaches in primary human monocytes\",\n      \"pmids\": [\"26508369\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"SERPINB1 inhibits caspase-5 (along with caspase-1, -4, and -11) by suppressing CARD oligomerization and enzymatic activation. The C-terminal CARD-binding motif of SERPINB1, distinct from its reactive center loop, restrains pro-caspase-5 activation. SERPINB1 knockdown/deletion leads to spontaneous caspase-5 activation and IL-1β release.\",\n      \"method\": \"In vitro caspase activity assays, CARD oligomerization assays, SERPINB1 knockdown/KO with caspase activation and cytokine readouts\",\n      \"journal\": \"Nature immunology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro biochemical assays plus genetic KO with defined mechanistic pathway (CARD oligomerization suppression), functionally separable domains identified\",\n      \"pmids\": [\"30692621\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CASP5 mediates intestinal barrier dysfunction downstream of cytoplasmic LPS sensing. OMV internalization recruits caspase-5 and PIKfyve to early endosomal membranes via SNX10, enabling LPS release into the cytosol. Cytosolic LPS-activated caspase-5 phosphorylates Lyn kinase, which promotes nuclear translocation of Snail/Slug, downregulation of E-cadherin, and intestinal barrier disruption. SNX10 deletion or inhibition blocked caspase-5 activation and rescued barrier function.\",\n      \"method\": \"Co-immunoprecipitation, proximity ligation, genetic deletion (SNX10), pharmacological inhibition (DC-SX029), murine colitis model, Lyn phosphorylation assay, E-cadherin immunoblotting\",\n      \"journal\": \"The EMBO journal\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — epistatic pathway defined by genetic deletion and pharmacological blockade with specific molecular readouts (Lyn phosphorylation, E-cadherin, Snail/Slug), in vivo validation\",\n      \"pmids\": [\"34747049\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Activated human caspase-5 (like caspase-4) directly and efficiently processes pro-IL-18 in vitro and during bacterial infection. Caspase-5 uses a binary (two-site) substrate recognition mechanism: the catalytic pocket engages the tetrapeptide cleavage site, and a unique exosite (similar to that used for GSDMD recognition) binds a structural element formed jointly by the IL-18 propeptide and post-cleavage-site sequences. Cleavage by caspase-5 induces conformational changes in IL-18 that generate two critical IL-18Rα receptor-binding sites.\",\n      \"method\": \"In vitro cleavage assay, crystal structure of caspase-4–pro-IL-18 complex (with exosite structure informing caspase-5 mechanism), bacterial infection model, site-directed mutagenesis\",\n      \"journal\": \"Nature\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — crystal structure plus in vitro reconstitution and mutagenesis, with in vivo bacterial infection validation; highly cited paradigm-shifting study\",\n      \"pmids\": [\"37993714\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CASP5 is an inflammatory cysteine protease that functions as a cytoplasmic LPS sensor within the non-canonical inflammasome: upon LPS binding, it undergoes CARD-mediated oligomerization and auto-activation (restrained by SERPINB1), cleaves gasdermin D to trigger pyroptosis, directly processes pro-IL-18 via a binary exosite/catalytic-pocket recognition mechanism to generate the mature cytokine, and activates NLRP3-dependent IL-1β maturation; in addition, activated caspase-5 phosphorylates Lyn kinase downstream of endosomal LPS sensing to disrupt epithelial barrier integrity, and during Fas-induced apoptosis it cleaves the transcription factor Max at an unusual glutamate residue in a phosphorylation-regulated manner.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CASP5 is an inflammatory caspase closely related to caspase-4; its paralog caspase-4 has been shown to be processed downstream of Fas receptor stimulation and to directly cleave pro-caspase-3, positioning it as an intermediary in the Fas-mediated apoptotic caspase cascade [PMID:9233763]. The direct mechanistic characterization of CASP5 itself remains limited, with most functional evidence derived from studies of the highly homologous caspase-4.\",\n  \"teleology\": [\n    {\n      \"year\": 1997,\n      \"claim\": \"Establishing where the caspase-4/CASP5-related caspases sit in the Fas apoptotic cascade: caspase-4 was shown to be activated downstream of caspase-8 and to directly cleave pro-caspase-3, defining it as an intermediary between initiator and executioner caspases.\",\n      \"evidence\": \"In vitro cleavage assays with purified caspase-4, dominant-negative active-site mutant overexpression, microinjection of inhibitory antibodies, and Fas-stimulation assays in cultured cells\",\n      \"pmids\": [\"9233763\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Study characterizes caspase-4 rather than CASP5 directly; functional equivalence is inferred from homology but not experimentally verified for CASP5\",\n        \"No endogenous CASP5-specific loss-of-function experiment has been performed\",\n        \"Physiological substrates specific to CASP5 (beyond those shared with caspase-4) are unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Direct experimental characterization of CASP5's catalytic activity, endogenous substrates, and non-redundant roles relative to caspase-4 in apoptosis and inflammation remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\n        \"No CASP5-specific knockout or knockdown study reported in the timeline\",\n        \"Role in inflammasome activation and pyroptosis (known for related caspases) has not been addressed for CASP5\",\n        \"Structural basis for any substrate specificity differences between CASP5 and caspase-4 is unknown\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\n        \"term_id\": \"GO:0140096\",\n        \"supporting_discovery_ids\": [0]\n      }\n    ],\n    \"localization\": [],\n    \"pathway\": [\n      {\n        \"term_id\": \"R-HSA-5357801\",\n        \"supporting_discovery_ids\": [0]\n      }\n    ],\n    \"complexes\": [],\n    \"partners\": [],\n    \"other_free_text\": []\n  }\n}\n```\n\n--- ROUND 2 (R2/R3, augmented corpus) ---\n\n```json\n{\n  \"mechanistic_narrative\": \"Caspase-5 is an inflammatory cysteine protease that functions as a cytoplasmic sensor of lipopolysaccharide (LPS) and a key effector of the non-canonical inflammasome pathway in human myeloid and epithelial cells. Upon cytoplasmic LPS encounter, caspase-5 undergoes CARD-mediated oligomerization—normally restrained by SERPINB1—and activates to cleave gasdermin D, trigger pyroptosis, and directly process pro-IL-18 via a binary exosite/catalytic-pocket recognition mechanism, while also engaging the NLRP3 inflammasome for IL-1β maturation [PMID:26173988, PMID:30692621, PMID:37993714]. Beyond canonical inflammasome signaling, activated caspase-5 phosphorylates Lyn kinase downstream of endosomal LPS sensing to drive Snail/Slug-dependent E-cadherin loss and epithelial barrier disruption [PMID:34747049]. During Fas-induced apoptosis, caspase-5 cleaves the transcription factor Max at an atypical glutamate residue in a phosphorylation-regulated manner, linking it to apoptotic transcriptional reprogramming [PMID:11535131].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Cloning of CASP5 established it as a new ICE/CED-3 family cysteine protease with auto-processing capability and apoptosis-inducing potential, but its natural substrates remained unknown.\",\n      \"evidence\": \"Molecular cloning from human monocytes, catalytic cysteine mutagenesis, overexpression apoptosis assay in COS cells\",\n      \"pmids\": [\"7797592\", \"8617266\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No endogenous substrate identified\",\n        \"Physiological activation stimulus unknown\",\n        \"Inability to process pro-IL-1β left functional distinction from caspase-1 unresolved\"\n      ]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Demonstration that CASP5 expression is specifically induced by LPS (at both mRNA and protein level) in monocytes, unlike constitutively expressed CASP1, linked caspase-5 to innate immune activation.\",\n      \"evidence\": \"Quantitative RT-PCR and western blotting in LPS-stimulated THP-1 cells\",\n      \"pmids\": [\"10986288\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\n        \"Mechanism of transcriptional induction not defined\",\n        \"Single study without genetic loss-of-function\",\n        \"Whether LPS-induced caspase-5 has a distinct function from caspase-1 remained unclear\"\n      ]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Identification of the transcription factor Max as the first caspase-5 substrate—cleaved at an atypical glutamate residue during Fas-induced apoptosis—revealed that caspase-5 recognizes structural determinants in substrates and is regulated by CK2-mediated phosphorylation.\",\n      \"evidence\": \"In vitro cleavage with purified caspase-5, site-directed mutagenesis of Max cleavage site, CK2 phosphorylation assay, Fas-apoptosis model\",\n      \"pmids\": [\"11535131\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Biological consequence of Max cleavage for transcription not determined\",\n        \"In vivo relevance beyond Fas-induced apoptosis not tested\",\n        \"No structural basis for atypical glutamate recognition\"\n      ]\n    },\n    {\n      \"year\": 2002,\n      \"claim\": \"Placement of caspase-5 in the inflammasome complex alongside caspase-1, ASC/Pycard, and NALP1 established its role in a multiprotein platform for proinflammatory caspase activation and IL-1β processing.\",\n      \"evidence\": \"Cell-free caspase activation system, immunodepletion of Pycard, dominant-negative expression in THP-1 cells\",\n      \"pmids\": [\"12191486\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether caspase-5 directly processes pro-IL-1β or acts indirectly through caspase-1 was unresolved\",\n        \"Stoichiometry and architecture of the caspase-5-containing inflammasome not defined\",\n        \"Activation trigger within the complex not identified\"\n      ]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Genetic deletion studies resolved the non-redundant roles of caspase-4 and caspase-5 as cytoplasmic LPS sensors: caspase-5 is required for pyroptosis and NLRP3-dependent IL-1β maturation upon bacterial infection, establishing the non-canonical inflammasome pathway in human cells.\",\n      \"evidence\": \"CRISPR KO of CASP4/CASP5 in monocytic lines, NLRP3 inhibitor MCC950, Salmonella infection, LPS transfection, siRNA in primary human monocytes with Syk/Ca²⁺ pathway dissection\",\n      \"pmids\": [\"26173988\", \"26508369\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural basis for LPS binding by caspase-5 CARD not determined\",\n        \"Relative contributions of caspase-4 vs caspase-5 across different infection contexts not systematically compared\",\n        \"Downstream mechanism by which caspase-5 engages NLRP3 not defined\"\n      ]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"Identification of SERPINB1 as an endogenous inhibitor that suppresses caspase-5 CARD oligomerization—via a domain distinct from its serine protease-inhibiting reactive center loop—provided the first mechanism restraining non-canonical inflammasome assembly.\",\n      \"evidence\": \"In vitro CARD oligomerization assays, SERPINB1 KO with spontaneous caspase-5 activation and IL-1β release readouts\",\n      \"pmids\": [\"30692621\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Structural details of SERPINB1–CARD interaction not resolved\",\n        \"Whether SERPINB1 regulation is modulated during infection in vivo not tested\",\n        \"Whether other endogenous regulators cooperate with SERPINB1 unknown\"\n      ]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Discovery that activated caspase-5 phosphorylates Lyn kinase to drive Snail/Slug nuclear translocation and E-cadherin downregulation revealed a non-pyroptotic effector arm of the non-canonical inflammasome that disrupts intestinal epithelial barrier integrity.\",\n      \"evidence\": \"Co-IP, proximity ligation, SNX10 KO and pharmacological inhibition, murine colitis model, Lyn phosphorylation and E-cadherin immunoblotting\",\n      \"pmids\": [\"34747049\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Whether caspase-5 directly phosphorylates Lyn or acts through an intermediate kinase not fully established\",\n        \"Kinase activity for a caspase is unprecedented and the catalytic mechanism is unknown\",\n        \"Relevance to human IBD or other barrier diseases not clinically validated\"\n      ]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Structural and biochemical demonstration that caspase-5 directly processes pro-IL-18 using a binary recognition mechanism (catalytic pocket plus exosite) resolved a long-standing question about whether non-canonical inflammasome caspases can generate mature cytokines independently of caspase-1.\",\n      \"evidence\": \"In vitro cleavage assay, crystal structure of homologous caspase-4–pro-IL-18 complex informing caspase-5 mechanism, site-directed mutagenesis, bacterial infection model\",\n      \"pmids\": [\"37993714\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"Caspase-5–specific crystal structure with pro-IL-18 not yet available (inferred from caspase-4 complex)\",\n        \"Relative physiological contribution of caspase-5 vs caspase-1 to IL-18 maturation in vivo not quantified\",\n        \"Whether the exosite is shared with GSDMD recognition or represents distinct binding modes unknown\"\n      ]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis of direct LPS–CARD binding, the mechanism by which a cysteine protease reportedly phosphorylates Lyn, the full spectrum of endogenous caspase-5 substrates, and whether caspase-5 has non-redundant roles in specific human infections or inflammatory diseases.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\n        \"No atomic-resolution structure of caspase-5 CARD bound to LPS\",\n        \"Reported Lyn kinase phosphorylation by caspase-5 lacks a defined catalytic mechanism\",\n        \"Systematic substrate profiling (e.g. degradomics) not reported\"\n      ]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [0, 1, 2, 3, 5, 10]},\n      {\"term_id\": \"GO:0016787\", \"supporting_discovery_ids\": [0, 1, 2, 10]},\n      {\"term_id\": \"GO:0140299\", \"supporting_discovery_ids\": [6, 7, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [6, 7, 9]},\n      {\"term_id\": \"GO:0005768\", \"supporting_discovery_ids\": [9]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [3, 6, 7, 8, 9, 10]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [0, 1, 2, 6]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [7, 9]}\n    ],\n    \"complexes\": [\n      \"NALP1 inflammasome\",\n      \"Non-canonical inflammasome\"\n    ],\n    \"partners\": [\n      \"PYCARD\",\n      \"NLRP1\",\n      \"CASP1\",\n      \"SERPINB1\",\n      \"GSDMD\",\n      \"IL18\",\n      \"LYN\",\n      \"SNX10\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}