{"gene":"CAPNS1","run_date":"2026-04-28T17:28:52","timeline":{"discoveries":[{"year":2000,"finding":"Homozygous disruption of murine Capn4 (the common small regulatory subunit) eliminates both µ-calpain and m-calpain proteolytic activities, demonstrating that CAPNS1 is essential for the activity of both calpain heterodimers. Loss of Capn4 does not affect ES cell or fibroblast proliferation but causes embryonic lethality at midgestation with cardiovascular defects.","method":"Knockout mouse (homozygous gene disruption), enzymatic activity assays, cell viability assays","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular and in vivo phenotype, replicated across cell types and whole animal","pmids":["10825211"],"is_preprint":false},{"year":1986,"finding":"The amino-terminal hydrophobic, glycine-rich region of the CANP small subunit (CAPNS1) is required for phosphatidylinositol-mediated reduction of the Ca²⁺ requirement for calpain autolysis; trimming this region abolishes the phosphatidylinositol effect, implicating CAPNS1 in membrane-dependent regulation of calpain Ca²⁺ sensitivity.","method":"Proteolytic trimming of small subunit followed by in vitro autolysis assay with phosphatidylinositol","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro reconstitution with deletion variant and functional Ca²⁺-sensitivity assay","pmids":["3011770"],"is_preprint":false},{"year":1986,"finding":"The Ca²⁺ sensitivity of calpain is determined by the structural state of the large subunit N-terminus after autolysis, not by the small subunit (CAPNS1). Hybrid reconstitution experiments showed that swapping autolyzed vs. intact large subunits changed Ca²⁺ requirements, while swapping small subunits did not.","method":"Subunit dissociation and hybrid reconstitution in vitro; enzymatic activity assays","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — reconstitution with hybrid heterodimers and defined Ca²⁺-sensitivity readout","pmids":["3023314"],"is_preprint":false},{"year":1987,"finding":"The COOH-terminal E-F hand structure of the calpain small subunit (CAPNS1) is essential for subunit association and resulting proteolytic activity. Carboxypeptidase Y digestion destroying the C-terminal E-F hand helical region of both subunits abolished complex formation and enzyme activity.","method":"Carboxypeptidase Y limited digestion of calpain subunits, subunit reassociation assay, enzymatic activity assay","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro mutagenic digestion with functional reconstitution test","pmids":["3034871"],"is_preprint":false},{"year":1987,"finding":"The E-F hand domain of the calpain small subunit (CAPNS1) binds Ca²⁺ ions; expressed E-F hand domains from rabbit small subunit bound 2–4 mol Ca²⁺, and the Ca²⁺-binding affinity roughly corresponds to the Ca²⁺ concentration required for calpain activity.","method":"Bacterial expression of E-F hand domain fragments, microscale filter Ca²⁺-binding assay","journal":"Journal of biochemistry","confidence":"High","confidence_rationale":"Tier 1 — in vitro domain expression and direct Ca²⁺-binding measurement","pmids":["3038855"],"is_preprint":false},{"year":2013,"finding":"CAPNS1 is required for stability of the deubiquitinating enzyme USP1. In CAPNS1-depleted cells, APC/C(Cdh1)-mediated destruction of USP1 is upregulated, leading to accumulation of ubiquitinated PCNA, increased loading of polymerase-η on chromatin, and elevated mutagenesis. Calpain stabilizes USP1 by activating Cdk5, which represses Cdh1.","method":"siRNA knockdown of CAPNS1 in U2OS cells and MEFs, co-immunoprecipitation, western blot for ubiquitinated PCNA, rescue with Cdk5/p25 forced expression","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — multiple orthogonal methods (KD, rescue, IP) in two cell systems establishing a defined pathway","pmids":["23589330"],"is_preprint":false},{"year":2008,"finding":"The calpain small subunit (CAPNS1/Capn4) directly binds to the intracellular C-terminal tail of the PTH/PTHrP receptor and is required for proper osteoblast proliferation, differentiation, and matrix mineralization. Osteoblast-specific Capn4 knockout mice show reduced trabecular bone and decreased osteoblast number.","method":"Osteoblast-specific Cre-LoxP conditional knockout, in vitro osteoblast function assays (proliferation, differentiation, mineralization)","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with multiple in vitro and in vivo functional readouts","pmids":["18515801"],"is_preprint":false},{"year":2010,"finding":"Chondrocyte-specific deletion of Capn4 impairs cell cycle G1/S progression, reduces cyclin D gene transcription, and causes accumulation of calpain substrate cell-cycle proteins (e.g., p27Kip1). Silencing p27Kip1 rescues impaired growth, and reintroduction of the small subunit normalizes cyclin D levels dose-dependently.","method":"Chondrocyte-specific Capn4 knockout (Cre-LoxP), cell cycle analysis, siRNA rescue experiments, western blot","journal":"Molecular and cellular biology","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with mechanistic rescue experiments placing Capn4 upstream of p27Kip1 and cyclin D","pmids":["20368361"],"is_preprint":false},{"year":2012,"finding":"Cardiomyocyte-specific deletion of Capn4 eliminates calpain-1 and calpain-2 activities, prevents IκB degradation and NF-κB activation after myocardial infarction, thereby suppressing proinflammatory cytokines, limiting infarct expansion, and reducing adverse cardiac remodeling.","method":"Cardiomyocyte-specific Capn4 knockout mouse, myocardial infarction model, calpain activity assay, NF-κB/IκB western blot, histology","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with defined signaling pathway readouts in vivo","pmids":["22753411"],"is_preprint":false},{"year":2015,"finding":"Mitochondrial calpain-1 (dependent on Capn4) cleaves ATP synthase-α (ATP5A1) during endotoxemia, disrupting ATP synthase and generating mitochondrial superoxide that drives proinflammatory signaling. Capn4 cardiomyocyte-specific KO or ATP5A1 overexpression prevents this cascade.","method":"Capn4 cardiomyocyte-specific KO, lipopolysaccharide endotoxemia model, mitochondrial fractionation, co-localization and cleavage assays, mitochondria-targeted calpastatin overexpression","journal":"Circulation. Heart failure","confidence":"High","confidence_rationale":"Tier 2 — conditional KO plus mechanistic rescue with substrate overexpression and mitochondria-targeted inhibitor","pmids":["26246018"],"is_preprint":false},{"year":2008,"finding":"CAPNS1 (Capns1) was identified as a binding partner of the RasGAP-SH3 domain in K-Ras(V12) oncogenic cells. The interaction, confirmed by co-immunoprecipitation, occurs specifically in oncogenic Ras-expressing cells and co-localizes to cell protrusions. Capns1 knockdown increases apoptosis and reduces migration speed.","method":"Yeast two-hybrid screening, co-immunoprecipitation, confocal co-localization, siRNA knockdown with migration and apoptosis assays","journal":"Cellular signalling","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP confirmed interaction but functional consequences from single lab","pmids":["18761085"],"is_preprint":false},{"year":2014,"finding":"Capn4 physically associates with FAK and promotes hyperphosphorylation of FAK, Src, and p130Cas, activating the FAK-Src signaling pathway. This leads to upregulation of MMP2 and increased invasion/metastasis of hepatocellular carcinoma cells.","method":"Co-immunoprecipitation, protein microarray, phosphorylation assays, siRNA knockdown, in vivo tumor/metastasis models","journal":"The Journal of pathology","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP demonstrates physical association; functional pathway placed by KD/OE with phosphorylation readouts","pmids":["24962955"],"is_preprint":false},{"year":2007,"finding":"The human CAPNS1 promoter is regulated by transcription factors NRF-1 and AP-1. The core promoter maps to -187/+174; NRF-1 mutation reduces promoter activity by 70%, AP-1 by 50%, and double mutation by 90%. NRF-1 binding to the natural promoter was confirmed by ChIP.","method":"Promoter deletion analysis, site-directed mutagenesis, EMSA, supershift assay, ChIP, siRNA against NRF-1","journal":"Gene","confidence":"High","confidence_rationale":"Tier 1–2 — multiple orthogonal methods (EMSA, ChIP, mutagenesis, siRNA) in two cell lines","pmids":["18234454"],"is_preprint":false},{"year":2016,"finding":"CAPNS1 positively regulates calpain-1 and calpain-2 (the catalytic subunits), and loss of CAPNS1 via miR-99a/miR-491-mediated silencing reduces cleaved caspase-3 and PARP1 cleavage, thereby reducing apoptosis and conferring cisplatin resistance in gastric cancer cells.","method":"miRNA mimics/inhibitors, siRNA knockdown of CAPNS1, western blot for calpain-1/2 and cleaved caspase-3/PARP1, dual-luciferase reporter assay","journal":"International journal of biological sciences","confidence":"Medium","confidence_rationale":"Tier 3 — single lab, mechanistic link between CAPNS1 and calpain catalytic subunit stability with apoptosis readout","pmids":["27994509"],"is_preprint":false},{"year":2019,"finding":"Epstein-Barr virus LMP1 upregulates Capn4 transcription through its CTAR1 and CTAR2 domains by activating AP-1 via ERK/JNK phosphorylation. Capn4 in turn promotes actin rearrangement and NPC cell migration.","method":"Luciferase promoter assay, western blot, siRNA, ERK/JNK phosphorylation assays, migration assays","journal":"Cancer science","confidence":"Medium","confidence_rationale":"Tier 3 — single lab with promoter assay and pathway assays, moderate mechanistic depth","pmids":["31691433"],"is_preprint":false},{"year":2021,"finding":"CAPN4 promotes macrophage M1 polarization and NLRP3 inflammasome activation during CVB3 infection through upregulation of CHOP, which activates STAT1 and STAT3 phosphorylation. Macrophage-specific CAPN4 conditional KO reduces M1 transformation and myocardial injury in vivo.","method":"Macrophage-specific conditional KO (LYZ2-Cre), CVB3 infection model, NLRP3 and cytokine assays, STAT1/STAT3 phosphorylation western blot, CHOP modulation","journal":"Free radical biology & medicine","confidence":"Medium","confidence_rationale":"Tier 2 — conditional KO with mechanistic pathway readouts, single lab","pmids":["37660839"],"is_preprint":false},{"year":2021,"finding":"CAPN4 directly interacts with CNOT3 and promotes its degradation. In renal cancer cells, CAPN4 loss (via miR-124) stabilizes CNOT3 and enhances cisplatin-induced necroptosis; this was confirmed by co-immunoprecipitation.","method":"Co-immunoprecipitation, qPCR, western blot, flow cytometry for necroptosis, in vivo xenograft","journal":"Translational andrology and urology","confidence":"Medium","confidence_rationale":"Tier 3 — co-IP identifies interaction, functional consequence shown in single lab study","pmids":["34733662"],"is_preprint":false}],"current_model":"CAPNS1 (calpain small subunit 1) is the obligate regulatory subunit shared by µ-calpain and m-calpain heterodimers: it stabilizes both catalytic subunits and is required for their proteolytic activity, contributes Ca²⁺-binding through its C-terminal E-F hand domain to enable heterodimer assembly, and uses its N-terminal hydrophobic region to mediate membrane/phosphatidylinositol-dependent modulation of Ca²⁺ sensitivity; loss of CAPNS1 ablates both calpain activities and disrupts downstream processes including USP1/PCNA-mediated DNA damage response, IκB–NF-κB signaling, FAK-Src pathway activation, mitochondrial ATP synthase integrity, and cell-cycle progression, while CAPNS1 transcription is driven primarily by the NRF-1 and AP-1 transcription factors."},"narrative":{"teleology":[{"year":1986,"claim":"Establishing how the small subunit modulates Ca²⁺ sensitivity: the N-terminal hydrophobic region of CAPNS1 was shown to be required for phosphatidylinositol-mediated lowering of the Ca²⁺ threshold for calpain autolysis, while hybrid reconstitution showed the large subunit N-terminus, not the small subunit, directly sets Ca²⁺ sensitivity for catalysis.","evidence":"In vitro proteolytic trimming and subunit-swap reconstitution with Ca²⁺-sensitivity autolysis assays","pmids":["3011770","3023314"],"confidence":"High","gaps":["Precise lipid-binding residues in the N-terminal region not mapped","Physiological membrane context not tested"]},{"year":1987,"claim":"The C-terminal EF-hand domain of CAPNS1 was identified as the structural determinant for Ca²⁺ binding and for heterodimer assembly with the catalytic subunit, establishing CAPNS1 as a Ca²⁺-sensing scaffold essential for calpain complex integrity.","evidence":"Carboxypeptidase Y digestion destroying the EF-hand abolished complex formation; recombinant EF-hand domain bound 2–4 mol Ca²⁺ at physiologically relevant concentrations","pmids":["3034871","3038855"],"confidence":"High","gaps":["Stoichiometry of Ca²⁺ binding per individual EF-hand not resolved","No crystal structure at this stage"]},{"year":2000,"claim":"Genetic proof that CAPNS1 is indispensable in vivo: homozygous Capn4 knockout eliminated both µ- and m-calpain activities, caused midgestational embryonic lethality with cardiovascular defects, and established CAPNS1 as the obligate regulatory subunit for both heterodimers.","evidence":"Knockout mouse with enzymatic activity assays, cell viability assays, and developmental phenotyping","pmids":["10825211"],"confidence":"High","gaps":["Specific calpain substrates driving cardiovascular lethality not identified","Relative contribution of µ- vs. m-calpain loss to the phenotype unclear"]},{"year":2007,"claim":"The transcriptional control of CAPNS1 was defined: NRF-1 and AP-1 are the principal transcription factors driving the core promoter, with NRF-1 mutation reducing activity ~70% and double mutation ~90%.","evidence":"Promoter deletion/mutagenesis, EMSA, ChIP, and siRNA against NRF-1 in two cell lines","pmids":["18234454"],"confidence":"High","gaps":["Epigenetic regulation and chromatin context not addressed","Tissue-specific transcription factor usage not explored"]},{"year":2008,"claim":"CAPNS1 was linked to specific receptor signaling and tissue homeostasis: it directly binds the PTH/PTHrP receptor tail and is required for osteoblast proliferation, differentiation, and bone mineralization; separately, it was identified as a RasGAP-SH3 interactor in oncogenic Ras cells, linking it to migration and survival.","evidence":"Osteoblast-specific conditional KO with functional assays; yeast two-hybrid, co-IP, and siRNA in K-Ras(V12) cells","pmids":["18515801","18761085"],"confidence":"High","gaps":["Structural basis of CAPNS1–PTH1R interaction unknown","RasGAP interaction confirmed in single lab; reciprocal validation limited"]},{"year":2010,"claim":"CAPNS1 was placed upstream of G1/S cell-cycle control: chondrocyte-specific Capn4 deletion caused p27Kip1 accumulation and reduced cyclin D transcription, and p27 silencing rescued growth, demonstrating calpain-dependent cell-cycle regulation.","evidence":"Chondrocyte-specific Capn4 KO, cell-cycle analysis, siRNA rescue, dose-dependent small-subunit reintroduction","pmids":["20368361"],"confidence":"High","gaps":["Whether calpain directly cleaves p27Kip1 or acts indirectly not definitively resolved","Generalizability beyond chondrocytes not tested"]},{"year":2012,"claim":"CAPNS1-dependent calpain activity was shown to drive inflammatory signaling via IκB degradation and NF-κB activation in cardiomyocytes after myocardial infarction, establishing calpain as a proximal activator of the NF-κB–cytokine axis in cardiac injury.","evidence":"Cardiomyocyte-specific Capn4 KO, MI model, NF-κB/IκB western blot, histology","pmids":["22753411"],"confidence":"High","gaps":["Whether IκB is a direct calpain substrate or an indirect target not resolved","Contribution of non-calpain pathways to residual NF-κB signaling unclear"]},{"year":2013,"claim":"A non-canonical pathway was uncovered: CAPNS1 stabilizes the deubiquitinase USP1 via Cdk5 activation, preventing APC/C(Cdh1)-mediated USP1 degradation and thereby controlling PCNA ubiquitination and translesion synthesis fidelity.","evidence":"CAPNS1 siRNA in U2OS cells and MEFs, co-IP, ubiquitinated PCNA detection, rescue with Cdk5/p25","pmids":["23589330"],"confidence":"High","gaps":["Whether calpain directly cleaves a Cdk5 inhibitor or activates Cdk5 through another intermediate unknown","In vivo mutagenesis phenotype not tested"]},{"year":2014,"claim":"CAPNS1 was shown to physically associate with FAK and promote FAK-Src-p130Cas hyperphosphorylation, linking calpain activity to MMP2-dependent invasion in hepatocellular carcinoma.","evidence":"Co-IP, protein microarray, phosphorylation assays, siRNA, in vivo metastasis models","pmids":["24962955"],"confidence":"Medium","gaps":["Direct versus calpain-mediated nature of FAK interaction not distinguished","Single lab; independent replication lacking"]},{"year":2015,"claim":"Mitochondria-localized calpain-1 (dependent on CAPNS1) was shown to cleave ATP synthase-α during endotoxemia, disrupting oxidative phosphorylation and generating mitochondrial superoxide that drives inflammatory signaling.","evidence":"Capn4 cardiomyocyte-specific KO, endotoxemia model, mitochondrial fractionation, ATP5A1 overexpression rescue, mitochondria-targeted calpastatin","pmids":["26246018"],"confidence":"High","gaps":["Mechanism of calpain-1 import into mitochondria not defined","Cleavage site on ATP5A1 not mapped"]},{"year":2016,"claim":"miRNA-mediated silencing of CAPNS1 (via miR-99a/miR-491) was shown to destabilize calpain-1/2 catalytic subunits, reduce caspase-3/PARP1 cleavage, and confer cisplatin resistance, linking CAPNS1 expression level to apoptotic threshold in cancer.","evidence":"miRNA mimics/inhibitors, siRNA, western blot, dual-luciferase reporter assay in gastric cancer cells","pmids":["27994509"],"confidence":"Medium","gaps":["Apoptosis readout in single cancer cell model; generalizability unclear","Relative contribution of calpain-1 vs. calpain-2 loss not dissected"]},{"year":2019,"claim":"EBV oncoprotein LMP1 was shown to upregulate CAPNS1 transcription via AP-1, activated through ERK/JNK phosphorylation, thereby promoting cytoskeletal rearrangement and migration in nasopharyngeal carcinoma cells.","evidence":"Luciferase promoter assay, ERK/JNK phosphorylation, siRNA, migration assays","pmids":["31691433"],"confidence":"Medium","gaps":["Whether LMP1 regulation of CAPNS1 occurs in primary NPC tissue not confirmed","Contribution of NRF-1 in LMP1-driven upregulation not examined"]},{"year":2021,"claim":"CAPNS1 was implicated in innate immune polarization and additional substrate regulation: macrophage-specific KO reduced NLRP3 inflammasome activation and M1 polarization via CHOP-STAT1/3 during viral myocarditis, while CAPNS1 was shown to interact with and promote degradation of CNOT3 in renal cancer.","evidence":"Macrophage-specific Capn4 conditional KO with CVB3 infection model; co-IP and xenograft studies for CNOT3 interaction","pmids":["37660839","34733662"],"confidence":"Medium","gaps":["CHOP as a direct calpain substrate not demonstrated","CNOT3 interaction from single lab; cleavage site and directness not established"]},{"year":null,"claim":"Key unresolved questions include: how CAPNS1-containing calpain heterodimers are targeted to distinct subcellular compartments (e.g., mitochondria, membrane protrusions), the structural basis for CAPNS1's non-catalytic interactions with partners like FAK and PTH1R, and whether CAPNS1 has calpain-independent functions.","evidence":"","pmids":[],"confidence":"High","gaps":["Mechanism of mitochondrial calpain import unknown","No high-resolution structure of full-length heterodimer with membrane lipids","Calpain-independent roles of CAPNS1 not tested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0098772","term_label":"molecular function regulator activity","supporting_discovery_ids":[0,1,3,4,7,8]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[0,7,8]},{"term_id":"GO:0005739","term_label":"mitochondrion","supporting_discovery_ids":[9]},{"term_id":"GO:0005886","term_label":"plasma membrane","supporting_discovery_ids":[1,10]}],"pathway":[{"term_id":"R-HSA-392499","term_label":"Metabolism of proteins","supporting_discovery_ids":[0,3,4,5,13]},{"term_id":"R-HSA-168256","term_label":"Immune System","supporting_discovery_ids":[8,15]},{"term_id":"R-HSA-1640170","term_label":"Cell Cycle","supporting_discovery_ids":[7]},{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[8,11,14]},{"term_id":"R-HSA-5357801","term_label":"Programmed Cell Death","supporting_discovery_ids":[13]},{"term_id":"R-HSA-73894","term_label":"DNA Repair","supporting_discovery_ids":[5]}],"complexes":["µ-calpain (CAPN1–CAPNS1 heterodimer)","m-calpain (CAPN2–CAPNS1 heterodimer)"],"partners":["CAPN1","CAPN2","FAK","PTH1R","USP1","RASA1","CNOT3"],"other_free_text":[]},"mechanistic_narrative":"CAPNS1 encodes the obligate small regulatory subunit shared by the µ-calpain and m-calpain heterodimers, and is essential for the stability and proteolytic activity of both calcium-dependent cysteine proteases. Its C-terminal EF-hand domain binds Ca²⁺ and mediates heterodimerization with the catalytic large subunits, while its N-terminal glycine-rich hydrophobic region enables phosphatidylinositol-dependent reduction of the Ca²⁺ requirement for calpain activation [PMID:3038855, PMID:3034871, PMID:3011770]. Genetic ablation of CAPNS1 eliminates both calpain activities and disrupts diverse downstream processes including IκB–NF-κB inflammatory signaling, cell-cycle G1/S progression through p27Kip1 accumulation, USP1-dependent PCNA deubiquitination in the DNA damage response, FAK-Src pathway activation, and mitochondrial ATP synthase integrity [PMID:10825211, PMID:22753411, PMID:20368361, PMID:23589330, PMID:26246018]. CAPNS1 transcription is driven primarily by NRF-1 and AP-1 transcription factors, and AP-1-mediated upregulation can be co-opted by viral oncoproteins such as EBV LMP1 [PMID:18234454, PMID:31691433]."},"prefetch_data":{"uniprot":{"accession":"P04632","full_name":"Calpain small subunit 1","aliases":["Calcium-activated neutral proteinase small subunit","CANP small subunit","Calcium-dependent protease small subunit","CDPS","Calcium-dependent protease small subunit 1","Calpain regulatory subunit"],"length_aa":268,"mass_kda":28.3,"function":"Regulatory subunit of the calcium-regulated non-lysosomal thiol-protease which catalyzes limited proteolysis of substrates involved in cytoskeletal remodeling and signal transduction. Essential for embryonic development (By similarity)","subcellular_location":"Cytoplasm; Cell membrane","url":"https://www.uniprot.org/uniprotkb/P04632/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/CAPNS1","classification":"Not Classified","n_dependent_lines":20,"n_total_lines":1208,"dependency_fraction":0.016556291390728478},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"MAP4","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/CAPNS1","total_profiled":1310},"omim":[{"mim_id":"620777","title":"PULMONARY HYPERTENSION, PRIMARY, 6; PPH6","url":"https://www.omim.org/entry/620777"},{"mim_id":"617573","title":"C-TYPE LECTIN DOMAIN FAMILY 12, MEMBER B; CLEC12B","url":"https://www.omim.org/entry/617573"},{"mim_id":"617237","title":"IMMUNODEFICIENCY 49, SEVERE COMBINED; IMD49","url":"https://www.omim.org/entry/617237"},{"mim_id":"616767","title":"CALPAIN, SMALL SUBUNIT 2; CAPNS2","url":"https://www.omim.org/entry/616767"},{"mim_id":"610033","title":"PENTA-EF-HAND DOMAIN-CONTAINING PROTEIN 1; PEF1","url":"https://www.omim.org/entry/610033"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Approved","locations":[{"location":"Nucleoplasm","reliability":"Approved"},{"location":"Cytosol","reliability":"Approved"}],"tissue_specificity":"Low tissue specificity","tissue_distribution":"Detected in all","driving_tissues":[],"url":"https://www.proteinatlas.org/search/CAPNS1"},"hgnc":{"alias_symbol":["CANP","CANPS","30K","CDPS"],"prev_symbol":["CAPN4"]},"alphafold":{"accession":"P04632","domains":[{"cath_id":"1.10.238.10","chopping":"95-268","consensus_level":"medium","plddt":93.8491,"start":95,"end":268}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P04632","model_url":"https://alphafold.ebi.ac.uk/files/AF-P04632-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P04632-F1-predicted_aligned_error_v6.png","plddt_mean":75.25},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=CAPNS1","jax_strain_url":"https://www.jax.org/strain/search?query=CAPNS1"},"sequence":{"accession":"P04632","fasta_url":"https://rest.uniprot.org/uniprotkb/P04632.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P04632/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P04632"}},"corpus_meta":[{"pmid":"10825211","id":"PMC_10825211","title":"Disruption of the murine calpain small subunit gene, Capn4: calpain is essential for embryonic development but not for cell growth and division.","date":"2000","source":"Molecular and cellular biology","url":"https://pubmed.ncbi.nlm.nih.gov/10825211","citation_count":291,"is_preprint":false},{"pmid":"10640565","id":"PMC_10640565","title":"The '30K' superfamily of viral movement proteins.","date":"2000","source":"The Journal of general virology","url":"https://pubmed.ncbi.nlm.nih.gov/10640565","citation_count":221,"is_preprint":false},{"pmid":"18644574","id":"PMC_18644574","title":"Localization by immunogold cytochemistry of the virus-coded 30K protein in plasmodesmata of leaves infected with tobacco mosaic virus.","date":"1987","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/18644574","citation_count":174,"is_preprint":false},{"pmid":"6270080","id":"PMC_6270080","title":"Limited autolysis of Ca2+-activated neutral protease (CANP) changes its sensitivity to Ca2+ ions.","date":"1981","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/6270080","citation_count":168,"is_preprint":false},{"pmid":"3011770","id":"PMC_3011770","title":"The amino-terminal hydrophobic region of the small subunit of calcium-activated neutral protease (CANP) is essential for its activation by phosphatidylinositol.","date":"1986","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/3011770","citation_count":120,"is_preprint":false},{"pmid":"7763872","id":"PMC_7763872","title":"Identification of the soybean allergenic protein, Gly m Bd 30K, with the soybean seed 34-kDa oil-body-associated protein.","date":"1993","source":"Bioscience, biotechnology, and biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/7763872","citation_count":118,"is_preprint":false},{"pmid":"3023314","id":"PMC_3023314","title":"Limited autolysis of calcium-activated neutral protease (CANP): reduction of the Ca2+-requirement is due to the NH2-terminal processing of the large subunit.","date":"1986","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/3023314","citation_count":100,"is_preprint":false},{"pmid":"1990065","id":"PMC_1990065","title":"The tobacco mosaic virus 30K movement protein in transgenic tobacco plants is localized to plasmodesmata.","date":"1991","source":"The Journal of general virology","url":"https://pubmed.ncbi.nlm.nih.gov/1990065","citation_count":99,"is_preprint":false},{"pmid":"18639805","id":"PMC_18639805","title":"Synthesis of TMV-specific RNAs and proteins at the early stage of infection in tobacco protoplasts: transient expression of the 30K protein and its mRNA.","date":"1984","source":"Virology","url":"https://pubmed.ncbi.nlm.nih.gov/18639805","citation_count":91,"is_preprint":false},{"pmid":"6088474","id":"PMC_6088474","title":"Comparison of low and high calcium requiring forms of the calcium-activated neutral protease (CANP) from rabbit skeletal muscle.","date":"1984","source":"Journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/6088474","citation_count":86,"is_preprint":false},{"pmid":"19053044","id":"PMC_19053044","title":"Capn4 overexpression underlies tumor invasion and metastasis after liver transplantation for hepatocellular carcinoma.","date":"2009","source":"Hepatology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/19053044","citation_count":77,"is_preprint":false},{"pmid":"3012012","id":"PMC_3012012","title":"Fodrin degradation by calcium-activated neutral proteinase (CANP) in retinal ganglion cell neurons and optic glia: preferential localization of CANP activities in neurons.","date":"1986","source":"The Journal of neuroscience : the official journal of the Society for Neuroscience","url":"https://pubmed.ncbi.nlm.nih.gov/3012012","citation_count":68,"is_preprint":false},{"pmid":"183014","id":"PMC_183014","title":"Conditional lethal mutants of adenovirus type 2-simian virus 40 hybrids. 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letters","url":"https://pubmed.ncbi.nlm.nih.gov/30655802","citation_count":9,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":45246,"output_tokens":4091,"usd":0.098552},"stage2":{"model":"claude-opus-4-6","input_tokens":7628,"output_tokens":3611,"usd":0.192623},"total_usd":0.291175,"stage1_batch_id":"msgbatch_011kfMfE81o6CTcyhVUqumuW","stage2_batch_id":"msgbatch_01DTputS6WNkH745x1nVSoBo","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2000,\n      \"finding\": \"Homozygous disruption of murine Capn4 (the common small regulatory subunit) eliminates both µ-calpain and m-calpain proteolytic activities, demonstrating that CAPNS1 is essential for the activity of both calpain heterodimers. Loss of Capn4 does not affect ES cell or fibroblast proliferation but causes embryonic lethality at midgestation with cardiovascular defects.\",\n      \"method\": \"Knockout mouse (homozygous gene disruption), enzymatic activity assays, cell viability assays\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular and in vivo phenotype, replicated across cell types and whole animal\",\n      \"pmids\": [\"10825211\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"The amino-terminal hydrophobic, glycine-rich region of the CANP small subunit (CAPNS1) is required for phosphatidylinositol-mediated reduction of the Ca²⁺ requirement for calpain autolysis; trimming this region abolishes the phosphatidylinositol effect, implicating CAPNS1 in membrane-dependent regulation of calpain Ca²⁺ sensitivity.\",\n      \"method\": \"Proteolytic trimming of small subunit followed by in vitro autolysis assay with phosphatidylinositol\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro reconstitution with deletion variant and functional Ca²⁺-sensitivity assay\",\n      \"pmids\": [\"3011770\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1986,\n      \"finding\": \"The Ca²⁺ sensitivity of calpain is determined by the structural state of the large subunit N-terminus after autolysis, not by the small subunit (CAPNS1). Hybrid reconstitution experiments showed that swapping autolyzed vs. intact large subunits changed Ca²⁺ requirements, while swapping small subunits did not.\",\n      \"method\": \"Subunit dissociation and hybrid reconstitution in vitro; enzymatic activity assays\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — reconstitution with hybrid heterodimers and defined Ca²⁺-sensitivity readout\",\n      \"pmids\": [\"3023314\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"The COOH-terminal E-F hand structure of the calpain small subunit (CAPNS1) is essential for subunit association and resulting proteolytic activity. Carboxypeptidase Y digestion destroying the C-terminal E-F hand helical region of both subunits abolished complex formation and enzyme activity.\",\n      \"method\": \"Carboxypeptidase Y limited digestion of calpain subunits, subunit reassociation assay, enzymatic activity assay\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro mutagenic digestion with functional reconstitution test\",\n      \"pmids\": [\"3034871\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1987,\n      \"finding\": \"The E-F hand domain of the calpain small subunit (CAPNS1) binds Ca²⁺ ions; expressed E-F hand domains from rabbit small subunit bound 2–4 mol Ca²⁺, and the Ca²⁺-binding affinity roughly corresponds to the Ca²⁺ concentration required for calpain activity.\",\n      \"method\": \"Bacterial expression of E-F hand domain fragments, microscale filter Ca²⁺-binding assay\",\n      \"journal\": \"Journal of biochemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro domain expression and direct Ca²⁺-binding measurement\",\n      \"pmids\": [\"3038855\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"CAPNS1 is required for stability of the deubiquitinating enzyme USP1. In CAPNS1-depleted cells, APC/C(Cdh1)-mediated destruction of USP1 is upregulated, leading to accumulation of ubiquitinated PCNA, increased loading of polymerase-η on chromatin, and elevated mutagenesis. Calpain stabilizes USP1 by activating Cdk5, which represses Cdh1.\",\n      \"method\": \"siRNA knockdown of CAPNS1 in U2OS cells and MEFs, co-immunoprecipitation, western blot for ubiquitinated PCNA, rescue with Cdk5/p25 forced expression\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple orthogonal methods (KD, rescue, IP) in two cell systems establishing a defined pathway\",\n      \"pmids\": [\"23589330\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"The calpain small subunit (CAPNS1/Capn4) directly binds to the intracellular C-terminal tail of the PTH/PTHrP receptor and is required for proper osteoblast proliferation, differentiation, and matrix mineralization. Osteoblast-specific Capn4 knockout mice show reduced trabecular bone and decreased osteoblast number.\",\n      \"method\": \"Osteoblast-specific Cre-LoxP conditional knockout, in vitro osteoblast function assays (proliferation, differentiation, mineralization)\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with multiple in vitro and in vivo functional readouts\",\n      \"pmids\": [\"18515801\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"Chondrocyte-specific deletion of Capn4 impairs cell cycle G1/S progression, reduces cyclin D gene transcription, and causes accumulation of calpain substrate cell-cycle proteins (e.g., p27Kip1). Silencing p27Kip1 rescues impaired growth, and reintroduction of the small subunit normalizes cyclin D levels dose-dependently.\",\n      \"method\": \"Chondrocyte-specific Capn4 knockout (Cre-LoxP), cell cycle analysis, siRNA rescue experiments, western blot\",\n      \"journal\": \"Molecular and cellular biology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with mechanistic rescue experiments placing Capn4 upstream of p27Kip1 and cyclin D\",\n      \"pmids\": [\"20368361\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Cardiomyocyte-specific deletion of Capn4 eliminates calpain-1 and calpain-2 activities, prevents IκB degradation and NF-κB activation after myocardial infarction, thereby suppressing proinflammatory cytokines, limiting infarct expansion, and reducing adverse cardiac remodeling.\",\n      \"method\": \"Cardiomyocyte-specific Capn4 knockout mouse, myocardial infarction model, calpain activity assay, NF-κB/IκB western blot, histology\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with defined signaling pathway readouts in vivo\",\n      \"pmids\": [\"22753411\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"Mitochondrial calpain-1 (dependent on Capn4) cleaves ATP synthase-α (ATP5A1) during endotoxemia, disrupting ATP synthase and generating mitochondrial superoxide that drives proinflammatory signaling. Capn4 cardiomyocyte-specific KO or ATP5A1 overexpression prevents this cascade.\",\n      \"method\": \"Capn4 cardiomyocyte-specific KO, lipopolysaccharide endotoxemia model, mitochondrial fractionation, co-localization and cleavage assays, mitochondria-targeted calpastatin overexpression\",\n      \"journal\": \"Circulation. Heart failure\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO plus mechanistic rescue with substrate overexpression and mitochondria-targeted inhibitor\",\n      \"pmids\": [\"26246018\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2008,\n      \"finding\": \"CAPNS1 (Capns1) was identified as a binding partner of the RasGAP-SH3 domain in K-Ras(V12) oncogenic cells. The interaction, confirmed by co-immunoprecipitation, occurs specifically in oncogenic Ras-expressing cells and co-localizes to cell protrusions. Capns1 knockdown increases apoptosis and reduces migration speed.\",\n      \"method\": \"Yeast two-hybrid screening, co-immunoprecipitation, confocal co-localization, siRNA knockdown with migration and apoptosis assays\",\n      \"journal\": \"Cellular signalling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP confirmed interaction but functional consequences from single lab\",\n      \"pmids\": [\"18761085\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Capn4 physically associates with FAK and promotes hyperphosphorylation of FAK, Src, and p130Cas, activating the FAK-Src signaling pathway. This leads to upregulation of MMP2 and increased invasion/metastasis of hepatocellular carcinoma cells.\",\n      \"method\": \"Co-immunoprecipitation, protein microarray, phosphorylation assays, siRNA knockdown, in vivo tumor/metastasis models\",\n      \"journal\": \"The Journal of pathology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP demonstrates physical association; functional pathway placed by KD/OE with phosphorylation readouts\",\n      \"pmids\": [\"24962955\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"The human CAPNS1 promoter is regulated by transcription factors NRF-1 and AP-1. The core promoter maps to -187/+174; NRF-1 mutation reduces promoter activity by 70%, AP-1 by 50%, and double mutation by 90%. NRF-1 binding to the natural promoter was confirmed by ChIP.\",\n      \"method\": \"Promoter deletion analysis, site-directed mutagenesis, EMSA, supershift assay, ChIP, siRNA against NRF-1\",\n      \"journal\": \"Gene\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — multiple orthogonal methods (EMSA, ChIP, mutagenesis, siRNA) in two cell lines\",\n      \"pmids\": [\"18234454\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"CAPNS1 positively regulates calpain-1 and calpain-2 (the catalytic subunits), and loss of CAPNS1 via miR-99a/miR-491-mediated silencing reduces cleaved caspase-3 and PARP1 cleavage, thereby reducing apoptosis and conferring cisplatin resistance in gastric cancer cells.\",\n      \"method\": \"miRNA mimics/inhibitors, siRNA knockdown of CAPNS1, western blot for calpain-1/2 and cleaved caspase-3/PARP1, dual-luciferase reporter assay\",\n      \"journal\": \"International journal of biological sciences\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab, mechanistic link between CAPNS1 and calpain catalytic subunit stability with apoptosis readout\",\n      \"pmids\": [\"27994509\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2019,\n      \"finding\": \"Epstein-Barr virus LMP1 upregulates Capn4 transcription through its CTAR1 and CTAR2 domains by activating AP-1 via ERK/JNK phosphorylation. Capn4 in turn promotes actin rearrangement and NPC cell migration.\",\n      \"method\": \"Luciferase promoter assay, western blot, siRNA, ERK/JNK phosphorylation assays, migration assays\",\n      \"journal\": \"Cancer science\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single lab with promoter assay and pathway assays, moderate mechanistic depth\",\n      \"pmids\": [\"31691433\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CAPN4 promotes macrophage M1 polarization and NLRP3 inflammasome activation during CVB3 infection through upregulation of CHOP, which activates STAT1 and STAT3 phosphorylation. Macrophage-specific CAPN4 conditional KO reduces M1 transformation and myocardial injury in vivo.\",\n      \"method\": \"Macrophage-specific conditional KO (LYZ2-Cre), CVB3 infection model, NLRP3 and cytokine assays, STAT1/STAT3 phosphorylation western blot, CHOP modulation\",\n      \"journal\": \"Free radical biology & medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with mechanistic pathway readouts, single lab\",\n      \"pmids\": [\"37660839\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"CAPN4 directly interacts with CNOT3 and promotes its degradation. In renal cancer cells, CAPN4 loss (via miR-124) stabilizes CNOT3 and enhances cisplatin-induced necroptosis; this was confirmed by co-immunoprecipitation.\",\n      \"method\": \"Co-immunoprecipitation, qPCR, western blot, flow cytometry for necroptosis, in vivo xenograft\",\n      \"journal\": \"Translational andrology and urology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — co-IP identifies interaction, functional consequence shown in single lab study\",\n      \"pmids\": [\"34733662\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"CAPNS1 (calpain small subunit 1) is the obligate regulatory subunit shared by µ-calpain and m-calpain heterodimers: it stabilizes both catalytic subunits and is required for their proteolytic activity, contributes Ca²⁺-binding through its C-terminal E-F hand domain to enable heterodimer assembly, and uses its N-terminal hydrophobic region to mediate membrane/phosphatidylinositol-dependent modulation of Ca²⁺ sensitivity; loss of CAPNS1 ablates both calpain activities and disrupts downstream processes including USP1/PCNA-mediated DNA damage response, IκB–NF-κB signaling, FAK-Src pathway activation, mitochondrial ATP synthase integrity, and cell-cycle progression, while CAPNS1 transcription is driven primarily by the NRF-1 and AP-1 transcription factors.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"CAPNS1 encodes the obligate small regulatory subunit shared by the µ-calpain and m-calpain heterodimers, and is essential for the stability and proteolytic activity of both calcium-dependent cysteine proteases. Its C-terminal EF-hand domain binds Ca²⁺ and mediates heterodimerization with the catalytic large subunits, while its N-terminal glycine-rich hydrophobic region enables phosphatidylinositol-dependent reduction of the Ca²⁺ requirement for calpain activation [PMID:3038855, PMID:3034871, PMID:3011770]. Genetic ablation of CAPNS1 eliminates both calpain activities and disrupts diverse downstream processes including IκB–NF-κB inflammatory signaling, cell-cycle G1/S progression through p27Kip1 accumulation, USP1-dependent PCNA deubiquitination in the DNA damage response, FAK-Src pathway activation, and mitochondrial ATP synthase integrity [PMID:10825211, PMID:22753411, PMID:20368361, PMID:23589330, PMID:26246018]. CAPNS1 transcription is driven primarily by NRF-1 and AP-1 transcription factors, and AP-1-mediated upregulation can be co-opted by viral oncoproteins such as EBV LMP1 [PMID:18234454, PMID:31691433].\",\n  \"teleology\": [\n    {\n      \"year\": 1986,\n      \"claim\": \"Establishing how the small subunit modulates Ca²⁺ sensitivity: the N-terminal hydrophobic region of CAPNS1 was shown to be required for phosphatidylinositol-mediated lowering of the Ca²⁺ threshold for calpain autolysis, while hybrid reconstitution showed the large subunit N-terminus, not the small subunit, directly sets Ca²⁺ sensitivity for catalysis.\",\n      \"evidence\": \"In vitro proteolytic trimming and subunit-swap reconstitution with Ca²⁺-sensitivity autolysis assays\",\n      \"pmids\": [\"3011770\", \"3023314\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise lipid-binding residues in the N-terminal region not mapped\", \"Physiological membrane context not tested\"]\n    },\n    {\n      \"year\": 1987,\n      \"claim\": \"The C-terminal EF-hand domain of CAPNS1 was identified as the structural determinant for Ca²⁺ binding and for heterodimer assembly with the catalytic subunit, establishing CAPNS1 as a Ca²⁺-sensing scaffold essential for calpain complex integrity.\",\n      \"evidence\": \"Carboxypeptidase Y digestion destroying the EF-hand abolished complex formation; recombinant EF-hand domain bound 2–4 mol Ca²⁺ at physiologically relevant concentrations\",\n      \"pmids\": [\"3034871\", \"3038855\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Stoichiometry of Ca²⁺ binding per individual EF-hand not resolved\", \"No crystal structure at this stage\"]\n    },\n    {\n      \"year\": 2000,\n      \"claim\": \"Genetic proof that CAPNS1 is indispensable in vivo: homozygous Capn4 knockout eliminated both µ- and m-calpain activities, caused midgestational embryonic lethality with cardiovascular defects, and established CAPNS1 as the obligate regulatory subunit for both heterodimers.\",\n      \"evidence\": \"Knockout mouse with enzymatic activity assays, cell viability assays, and developmental phenotyping\",\n      \"pmids\": [\"10825211\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Specific calpain substrates driving cardiovascular lethality not identified\", \"Relative contribution of µ- vs. m-calpain loss to the phenotype unclear\"]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The transcriptional control of CAPNS1 was defined: NRF-1 and AP-1 are the principal transcription factors driving the core promoter, with NRF-1 mutation reducing activity ~70% and double mutation ~90%.\",\n      \"evidence\": \"Promoter deletion/mutagenesis, EMSA, ChIP, and siRNA against NRF-1 in two cell lines\",\n      \"pmids\": [\"18234454\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Epigenetic regulation and chromatin context not addressed\", \"Tissue-specific transcription factor usage not explored\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"CAPNS1 was linked to specific receptor signaling and tissue homeostasis: it directly binds the PTH/PTHrP receptor tail and is required for osteoblast proliferation, differentiation, and bone mineralization; separately, it was identified as a RasGAP-SH3 interactor in oncogenic Ras cells, linking it to migration and survival.\",\n      \"evidence\": \"Osteoblast-specific conditional KO with functional assays; yeast two-hybrid, co-IP, and siRNA in K-Ras(V12) cells\",\n      \"pmids\": [\"18515801\", \"18761085\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Structural basis of CAPNS1–PTH1R interaction unknown\", \"RasGAP interaction confirmed in single lab; reciprocal validation limited\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"CAPNS1 was placed upstream of G1/S cell-cycle control: chondrocyte-specific Capn4 deletion caused p27Kip1 accumulation and reduced cyclin D transcription, and p27 silencing rescued growth, demonstrating calpain-dependent cell-cycle regulation.\",\n      \"evidence\": \"Chondrocyte-specific Capn4 KO, cell-cycle analysis, siRNA rescue, dose-dependent small-subunit reintroduction\",\n      \"pmids\": [\"20368361\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether calpain directly cleaves p27Kip1 or acts indirectly not definitively resolved\", \"Generalizability beyond chondrocytes not tested\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"CAPNS1-dependent calpain activity was shown to drive inflammatory signaling via IκB degradation and NF-κB activation in cardiomyocytes after myocardial infarction, establishing calpain as a proximal activator of the NF-κB–cytokine axis in cardiac injury.\",\n      \"evidence\": \"Cardiomyocyte-specific Capn4 KO, MI model, NF-κB/IκB western blot, histology\",\n      \"pmids\": [\"22753411\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether IκB is a direct calpain substrate or an indirect target not resolved\", \"Contribution of non-calpain pathways to residual NF-κB signaling unclear\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"A non-canonical pathway was uncovered: CAPNS1 stabilizes the deubiquitinase USP1 via Cdk5 activation, preventing APC/C(Cdh1)-mediated USP1 degradation and thereby controlling PCNA ubiquitination and translesion synthesis fidelity.\",\n      \"evidence\": \"CAPNS1 siRNA in U2OS cells and MEFs, co-IP, ubiquitinated PCNA detection, rescue with Cdk5/p25\",\n      \"pmids\": [\"23589330\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether calpain directly cleaves a Cdk5 inhibitor or activates Cdk5 through another intermediate unknown\", \"In vivo mutagenesis phenotype not tested\"]\n    },\n    {\n      \"year\": 2014,\n      \"claim\": \"CAPNS1 was shown to physically associate with FAK and promote FAK-Src-p130Cas hyperphosphorylation, linking calpain activity to MMP2-dependent invasion in hepatocellular carcinoma.\",\n      \"evidence\": \"Co-IP, protein microarray, phosphorylation assays, siRNA, in vivo metastasis models\",\n      \"pmids\": [\"24962955\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct versus calpain-mediated nature of FAK interaction not distinguished\", \"Single lab; independent replication lacking\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Mitochondria-localized calpain-1 (dependent on CAPNS1) was shown to cleave ATP synthase-α during endotoxemia, disrupting oxidative phosphorylation and generating mitochondrial superoxide that drives inflammatory signaling.\",\n      \"evidence\": \"Capn4 cardiomyocyte-specific KO, endotoxemia model, mitochondrial fractionation, ATP5A1 overexpression rescue, mitochondria-targeted calpastatin\",\n      \"pmids\": [\"26246018\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of calpain-1 import into mitochondria not defined\", \"Cleavage site on ATP5A1 not mapped\"]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"miRNA-mediated silencing of CAPNS1 (via miR-99a/miR-491) was shown to destabilize calpain-1/2 catalytic subunits, reduce caspase-3/PARP1 cleavage, and confer cisplatin resistance, linking CAPNS1 expression level to apoptotic threshold in cancer.\",\n      \"evidence\": \"miRNA mimics/inhibitors, siRNA, western blot, dual-luciferase reporter assay in gastric cancer cells\",\n      \"pmids\": [\"27994509\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Apoptosis readout in single cancer cell model; generalizability unclear\", \"Relative contribution of calpain-1 vs. calpain-2 loss not dissected\"]\n    },\n    {\n      \"year\": 2019,\n      \"claim\": \"EBV oncoprotein LMP1 was shown to upregulate CAPNS1 transcription via AP-1, activated through ERK/JNK phosphorylation, thereby promoting cytoskeletal rearrangement and migration in nasopharyngeal carcinoma cells.\",\n      \"evidence\": \"Luciferase promoter assay, ERK/JNK phosphorylation, siRNA, migration assays\",\n      \"pmids\": [\"31691433\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether LMP1 regulation of CAPNS1 occurs in primary NPC tissue not confirmed\", \"Contribution of NRF-1 in LMP1-driven upregulation not examined\"]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"CAPNS1 was implicated in innate immune polarization and additional substrate regulation: macrophage-specific KO reduced NLRP3 inflammasome activation and M1 polarization via CHOP-STAT1/3 during viral myocarditis, while CAPNS1 was shown to interact with and promote degradation of CNOT3 in renal cancer.\",\n      \"evidence\": \"Macrophage-specific Capn4 conditional KO with CVB3 infection model; co-IP and xenograft studies for CNOT3 interaction\",\n      \"pmids\": [\"37660839\", \"34733662\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"CHOP as a direct calpain substrate not demonstrated\", \"CNOT3 interaction from single lab; cleavage site and directness not established\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include: how CAPNS1-containing calpain heterodimers are targeted to distinct subcellular compartments (e.g., mitochondria, membrane protrusions), the structural basis for CAPNS1's non-catalytic interactions with partners like FAK and PTH1R, and whether CAPNS1 has calpain-independent functions.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of mitochondrial calpain import unknown\", \"No high-resolution structure of full-length heterodimer with membrane lipids\", \"Calpain-independent roles of CAPNS1 not tested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0098772\", \"supporting_discovery_ids\": [0, 1, 3, 4, 7, 8]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [0, 7, 8]},\n      {\"term_id\": \"GO:0005739\", \"supporting_discovery_ids\": [9]},\n      {\"term_id\": \"GO:0005886\", \"supporting_discovery_ids\": [1, 10]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-392499\", \"supporting_discovery_ids\": [0, 3, 4, 5, 13]},\n      {\"term_id\": \"R-HSA-168256\", \"supporting_discovery_ids\": [8, 15]},\n      {\"term_id\": \"R-HSA-1640170\", \"supporting_discovery_ids\": [7]},\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [8, 11, 14]},\n      {\"term_id\": \"R-HSA-5357801\", \"supporting_discovery_ids\": [13]},\n      {\"term_id\": \"R-HSA-73894\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"complexes\": [\n      \"µ-calpain (CAPN1–CAPNS1 heterodimer)\",\n      \"m-calpain (CAPN2–CAPNS1 heterodimer)\"\n    ],\n    \"partners\": [\n      \"CAPN1\",\n      \"CAPN2\",\n      \"FAK\",\n      \"PTH1R\",\n      \"USP1\",\n      \"RASA1\",\n      \"CNOT3\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}