Affinage

CAPN2

Calpain-2 catalytic subunit · UniProt P17655

Length
700 aa
Mass
80.0 kDa
Annotated
2026-06-09
21 papers in source corpus 11 papers cited in narrative 11 extracted findings
Cross-family judge vs UniProt: tie faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

CAPN2 (m-calpain large subunit) is a calcium-activated cysteine protease whose subcellular partitioning is cell-type-dependent: it is predominantly membrane-associated in transformed Schwann cells but almost entirely cytosolic in mouse and human brain (PMID:1656060, PMID:1548485). During myogenesis its expression is driven transcriptionally by the myogenic regulatory factor MyoD acting through E-box elements in the capn2 promoter, with myogenin contributing synergistically (PMID:12559913). CAPN2 acts as a pro-tumorigenic effector across multiple cancers, functioning upstream of AKT/mTOR signaling to drive proliferation, migration, invasion, MMP activation, and epithelial-mesenchymal transition (PMID:28280729, PMID:29228653). It also controls programmed cell death and stress survival decisions through several routes: it mediates cisplatin-induced pyroptosis via a CAPN2–BAK/BAX–caspase-9–caspase-3–GSDME axis (PMID:35525317), promotes drug-resistance autophagy by stabilizing FOXO1 to transcriptionally upregulate ATG5 (PMID:38844946), and supports ZBP1-dependent PANoptosis in intestinal epithelium (PMID:40520022). CAPN2 protein stability is set by TRIM8-mediated ubiquitination and degradation, which is antagonized by ITLN1 (PMID:40520022). In vivo, CAPN2 is required for vertebrate cardiac ventricle morphogenesis, and hypomorphic human variants are found in hypoplastic left heart syndrome patients (PMID:37663545).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 1992 Medium

    Resolved where m-calpain resides in tissue, establishing that CAPN2 subcellular localization is context-dependent rather than fixed — membrane-associated in transformed Schwann cells but cytosolic in brain.

    Evidence Subcellular fractionation with activity assays and immunofluorescence in Schwann cells, and differential centrifugation with two antibodies plus enzyme assay in brain

    PMID:1548485 PMID:1656060

    Open questions at the time
    • Determinants of membrane vs cytosolic partitioning not defined
    • No structural basis for the localization difference
    • Functional consequence of each pool not established
  2. 2003 Medium

    Identified how CAPN2 is transcriptionally controlled during muscle differentiation, placing it within the MyoD-driven myogenic program.

    Evidence Promoter reporter assays with myogenic factor overexpression and antisense knockdown

    PMID:12559913

    Open questions at the time
    • Direct MyoD occupancy at endogenous capn2 promoter not shown
    • Physiological role of CAPN2 in myogenesis not functionally dissected
  3. 2012 Low

    Sought CAPN2 substrates relevant to metastasis, nominating a proteolytic subnetwork (SPTBN1, ATP5B, VIM) in hepatocellular carcinoma.

    Evidence PROTOMAP gel-based proteolytic-fragment proteomics with network analysis

    PMID:22623320

    Open questions at the time
    • No direct biochemical validation of individual cleavage events
    • Substrate cleavage sites not mapped
    • Causal link between cleavage and metastasis not tested
  4. 2017 Medium

    Established CAPN2 as a driver of cancer cell proliferation and invasion acting upstream of AKT/mTOR, connecting protease activity to a defined oncogenic signaling output.

    Evidence Reciprocal siRNA/shRNA knockdown and overexpression with cell cycle, Transwell, MMP and phospho-AKT/mTOR readouts in prostate and renal carcinoma cells

    PMID:28280729 PMID:29228653

    Open questions at the time
    • Direct proteolytic substrate linking CAPN2 to AKT/mTOR not identified
    • Whether the effect requires catalytic activity not tested
    • In vivo tumor relevance limited
  5. 2022 Medium

    Defined a cell-death role for CAPN2 in chemotherapy response, placing it at the head of a pyroptotic cascade.

    Evidence Calpain activity assays, LDH release, and knockout/inhibition in cisplatin-treated esophageal cancer cells

    PMID:35525317

    Open questions at the time
    • Direct CAPN2 substrate in the BAK/BAX step not identified
    • CAPN1 vs CAPN2 specific contributions not separated
  6. 2024 Medium

    Revealed CAPN2-driven protective autophagy as a mechanism of androgen-pathway drug resistance via FOXO1 stabilization and ATG5 induction.

    Evidence RNA-seq, nucleoplasmic fractionation, TEM, and dual-fluorescence autophagy assays in apalutamide-resistant prostate cancer cells

    PMID:38844946

    Open questions at the time
    • Whether FOXO1 stabilization is via direct CAPN2 proteolysis unclear
    • ATF3→CAPN2 regulation mechanism not detailed
  7. 2024 Low

    Linked CAPN2 to Wnt/β-catenin-mediated suppression of mitophagy and identified miR-124-3p as an upstream repressor.

    Evidence Dual-luciferase reporter, LC3 immunofluorescence and western blot in hepatocellular carcinoma cells

    PMID:39050595

    Open questions at the time
    • Single study, mechanism rests on reporter and western blot only
    • Direct CAPN2–β-catenin interaction not shown
    • Catalytic requirement not tested
  8. 2025 Medium

    Identified how CAPN2 protein abundance is post-translationally controlled, defining a TRIM8–ITLN1 axis governing its stability and downstream PANoptosis.

    Evidence Co-IP/MS, rescue experiments and an IL-10 KO mouse model in intestinal epithelial cells

    PMID:40520022

    Open questions at the time
    • TRIM8 ubiquitination sites on CAPN2 not mapped
    • How CAPN2 mechanistically promotes ZBP1-dependent PANoptosis not resolved
  9. 2023 Medium

    Demonstrated an in vivo developmental requirement for CAPN2 in heart formation and tied human hypomorphic alleles to congenital heart disease.

    Evidence Xenopus laevis loss-of-function model with functional validation of two human CAPN2 variants

    PMID:37663545

    Open questions at the time
    • Molecular substrates relevant to ventricle morphogenesis unknown
    • Variant functional assays limited to model system

Open questions

Synthesis pass · forward-looking unresolved questions
  • The direct proteolytic substrates that mechanistically connect CAPN2 to AKT/mTOR signaling, cell-death cascades, and cardiac morphogenesis remain largely undefined.
  • No validated catalytic substrate links CAPN2 activity to its phenotypic outputs
  • Structural basis of activation and localization unknown
  • Whether oncogenic roles require catalytic activity untested

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016787 hydrolase activity 2 GO:0140096 catalytic activity, acting on a protein 2
Localization
GO:0005829 cytosol 2 GO:0005886 plasma membrane 1
Pathway
R-HSA-162582 Signal Transduction 2 R-HSA-5357801 Programmed Cell Death 2 R-HSA-9612973 Autophagy 2 R-HSA-1266738 Developmental Biology 1
Partners
FOXO1ITLN1TRIM8

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1991 In transformed Schwann cells, mCANP (CAPN2) is predominantly membrane-associated (>75% activity in membrane fraction), while muCANP is predominantly cytosolic (~80%). Immunofluorescence of permeabilized cells confirmed intracellular distribution of mCANP throughout the cytoplasm with sparing of the perinuclear region. Subcellular fractionation (DEAE and phenyl Sepharose chromatography), enzyme activity assay, immunofluorescence on fixed/permeabilized vs. live cells Journal of neuroscience research Medium 1656060
1992 In mouse and human brain, mCANP (CAPN2) is localized predominantly within the cytosol (>95% immunoreactive content in soluble fraction after 15,000g centrifugation), with caseinolytic activity detected only in supernatant fractions; Triton X-100 extraction did not alter this distribution. Western blot immunoassay with two independent antibodies, [14C]azocasein enzymatic activity assay, differential centrifugation fractionation Journal of neurochemistry Medium 1548485
2003 The capn2 promoter contains five E-box consensus binding sites for myogenic regulatory factors and one MEF-2 binding site. MyoD transactivates capn2 via these elements and is the pivotal regulator; myogenin can upregulate capn2 with lower efficiency; Myf5 has no effect. MyoD and myogenin act synergistically on capn2 expression during myogenesis. Promoter analysis, transient transfection with reporter gene constructs, myogenic factor overexpression, antisense oligonucleotide knockdown Journal of molecular biology Medium 12559913
2022 Cisplatin activates CAPN1/CAPN2 calpain activity, which mediates pyroptosis via a CAPN1/CAPN2–BAK/BAX–caspase-9–caspase-3–GSDME signaling axis in esophageal cancer cells; calpain inhibition or knockout suppresses this cisplatin-induced pyroptosis. Western blotting, LDH release assay, calpain activity assay, cell viability assay, calpain knockout/inhibition experiments Chemico-biological interactions Medium 35525317
2017 Silencing CAPN2 in castration-resistant prostate cancer cells inhibits proliferation (G1 cell cycle arrest), reduces migration and invasion by decreasing MMP-2 and MMP-9 activation, and suppresses phosphorylation of AKT and mTOR, placing CAPN2 upstream of AKT/mTOR signaling. siRNA knockdown, cell cycle analysis, Transwell migration/invasion assay, MMP-2/MMP-9 activity assay, western blot for phospho-AKT and phospho-mTOR BioMed research international Medium 28280729
2017 CAPN2 overexpression promotes renal cell carcinoma cell migration, invasion, and proliferation by activating AKT/mTOR signaling, enhancing epithelial-mesenchymal transition (EMT), and upregulating MMP9; sh-CAPN2 knockdown reverses these effects. sh-RNA knockdown and cDNA overexpression, Transwell assays, CCK-8 proliferation assay, western blot for AKT/mTOR signaling and EMT markers Oncotarget Medium 29228653
2024 CAPN2 promotes apalutamide resistance in prostate cancer by activating protective autophagy: CAPN2 inhibits FOXO1 degradation and promotes its nuclear translocation, which transcriptionally upregulates ATG5 and thereby drives autophagy. ATF3 transcriptionally upregulates CAPN2 to reinforce this pathway. RNA sequencing, western blotting, immunofluorescence, transmission electron microscopy, nucleoplasmic protein isolation, dual-fluorescence autophagy assay Journal of translational medicine Medium 38844946
2025 TRIM8 (an E3 ubiquitin ligase) directly interacts with CAPN2 and mediates its ubiquitination and degradation. ITLN1 binds both CAPN2 and TRIM8, enhancing CAPN2 stability by antagonizing TRIM8-mediated ubiquitination, thereby promoting ZBP1-dependent PANoptosis in intestinal epithelial cells. Co-immunoprecipitation combined with mass spectrometry, RNA-seq, rescue experiments, in vivo IL-10 KO mouse model International journal of biological sciences Medium 40520022
2024 CAPN2 promotes β-catenin nuclear translocation, activating the Wnt/β-catenin pathway to inhibit mitochondrial autophagy in hepatocellular carcinoma cells; miR-124-3p directly targets the CAPN2 3'UTR to suppress CAPN2 expression and this axis is regulated by amentoflavone treatment. Dual-luciferase reporter assay, western blot, immunofluorescence (LC3), CCK-8 assay, overexpression/inhibitor experiments Toxicology research Low 39050595
2023 CAPN2 is essential for cardiac ventricle morphogenesis in Xenopus laevis; loss-of-function of calpain causes hypoplastic ventricle phenotypes in vivo, and two human CAPN2 variants (707C>T and 1112C>T) found in hypoplastic left heart syndrome patients are hypomorphic alleles. Xenopus laevis in vivo loss-of-function model, functional validation of human variants HGG advances Medium 37663545
2012 Global proteolytic profiling of hepatocellular carcinoma cell lines with different metastasis potentials identified a CAPN2-centered proteolytic subnetwork including SPTBN1, ATP5B, and VIM that is more active in the highly metastatic cell line, suggesting CAPN2 cleaves these substrates to promote metastasis. PROTOMAP platform (gel-based proteomics of proteolytic fragments), bioinformatic network analysis Proteomics Low 22623320

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2005 Identification and molecular characterization of the rainbow trout calpains (Capn1 and Capn2): their expression in muscle wasting during starvation. Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology 47 15621511
2022 Cisplatin-induced pyroptosis is mediated via the CAPN1/CAPN2-BAK/BAX-caspase-9-caspase-3-GSDME axis in esophageal cancer. Chemico-biological interactions 45 35525317
2021 hnRNPK-regulated LINC00263 promotes malignant phenotypes through miR-147a/CAPN2. Cell death & disease 32 33731671
1991 Calcium-activated neutral proteinase (CANP; calpain) activity in Schwann cells: immunofluorescence localization and compartmentation of mu- and mCANP. Journal of neuroscience research 24 1656060
2017 Silencing CAPN2 Expression Inhibited Castration-Resistant Prostate Cancer Cells Proliferation and Invasion via AKT/mTOR Signal Pathway. BioMed research international 23 28280729
1992 Immunoassay and activity of calcium-activated neutral proteinase (mCANP): distribution in soluble and membrane-associated fractions in human and mouse brain. Journal of neurochemistry 22 1548485
2017 Overexpression of CAPN2 promotes cell metastasis and proliferation via AKT/mTOR signaling in renal cell carcinoma. Oncotarget 21 29228653
2012 Global profiling of proteolytically modified proteins in human metastatic hepatocellular carcinoma cell lines reveals CAPN2 centered network. Proteomics 21 22623320
2010 Characterisation of capn1, capn2-like, capn3 and capn11 genes in Atlantic halibut (Hippoglossus hippoglossus L.): Transcriptional regulation across tissues and in skeletal muscle at distinct nutritional states. Gene 18 20093171
2020 Promotive effect of Talin-1 protein on gastric cancer progression through PTK2-PXN-VCL-E-Cadherin-CAPN2-MAPK1 signaling axis. Journal of clinical laboratory analysis 17 32951272
2003 Transactivation of capn2 by myogenic regulatory factors during myogenesis. Journal of molecular biology 17 12559913
2020 miR-124 Intensified Oxaliplatin-Based Chemotherapy by Targeting CAPN2 in Colorectal Cancer. Molecular therapy oncolytics 15 32382656
2025 ITLN1 exacerbates Crohn's colitis by driving ZBP1-dependent PANoptosis in intestinal epithelial cells through antagonizing TRIM8-mediated CAPN2 ubiquitination. International journal of biological sciences 13 40520022
2016 The CAPN2/CAPN8 Locus on Chromosome 1q Is Associated with Variation in Serum Alpha-Carotene Concentrations. Journal of nutrigenetics and nutrigenomics 10 28002826
2024 METTL16 inhibits pancreatic cancer proliferation and metastasis by promoting MROH8 RNA stability and inhibiting CAPN2 expression - experimental studies. International journal of surgery (London, England) 8 39434688
2019 CAPN2 acts as an indicator of hepatitis B virus to induce hepatic fibrosis. Journal of cellular biochemistry 8 31680308
2024 CAPN2 promotes apalutamide resistance in metastatic hormone-sensitive prostate cancer by activating protective autophagy. Journal of translational medicine 7 38844946
2024 CAPN2 correlates with insulin resistance states in PCOS as evidenced by multi-dataset analysis. Journal of ovarian research 4 38610028
2024 Amentoflavone regulates the miR-124-3p/CAPN2 axis to promote mitochondrial autophagy in HCC cells. Toxicology research 3 39050595
2023 Rare variants in CAPN2 increase risk for isolated hypoplastic left heart syndrome. HGG advances 3 37663545
2011 [Beta-carotene regulates the expression of proapoptotic BAX and CAPN2 in HL-60, U-937 and TF-1 - human acute myeloid leukemia cell lines; microarray, RQ-PCR and Western Blot analysis]. Przeglad lekarski 2 21961413

Missed literature

Know a paper Affinage missed for CAPN2? Flag it for the maintainers and the community.

No submissions yet.