Affinage

SSH1

Protein phosphatase Slingshot homolog 1 · UniProt Q8WYL5

Length
1049 aa
Mass
115.5 kDa
Annotated
2026-04-28
21 papers in source corpus 12 papers cited in narrative 12 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SSH1 is a dual-specificity phosphatase that governs actin cytoskeletal dynamics, cell migration, and selective autophagy by dephosphorylating cofilin at Ser-3 and SQSTM1/p62 at Ser403. SSH1-mediated cofilin reactivation drives F-actin remodeling required for membrane ruffling and macropinocytosis (downstream of PKCδ), NOD1-dependent NF-κB innate immune signaling at F-actin-rich sites, endothelial and cancer cell migration, and mechanosensitive cardiomyocyte myofilament maturation via vinculin-dependent recruitment (PMID:25187968, PMID:30261270, PMID:31495694, PMID:25684665). Independent of its cofilin activity, SSH1 dephosphorylates SQSTM1/p62 at Ser403, impairing autophagic cargo recognition and phospho-tau clearance in neurons (PMID:33044112). SSH1 is negatively regulated by PKD1-mediated phosphorylation downstream of RhoA/PLCε, and loss of this inhibition prevents cofilin-2 translocation to mitochondria and Bax-dependent apoptosis in cardiomyocytes (PMID:24345679). Loss-of-function mutations in SSH1 are linked to disseminated superficial actinic porokeratosis (DSAP) (PMID:15459975).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2004 Medium

    The first genetic link between SSH1 and human disease was established when loss-of-function mutations in SSH1 were identified as causal for disseminated superficial actinic porokeratosis (DSAP), connecting SSH1 phosphatase activity to epidermal cytoskeletal integrity.

    Evidence Genome-wide linkage analysis and mutation screening in DSAP families identifying missense and frameshift SSH1 variants

    PMID:15459975

    Open questions at the time
    • No functional rescue of DSAP phenotype with wild-type SSH1
    • Mechanism linking cofilin phosphorylation to keratinization defects uncharacterized
  2. 2013 High

    The upstream regulation of SSH1 was resolved: PKD1 phosphorylates and inhibits SSH1 downstream of RhoA/PLCε, establishing SSH1 as a regulated node controlling whether cofilin-2 translocates to mitochondria to trigger apoptosis in cardiomyocytes.

    Evidence Genetic deletion of PKD1/PLCε, SSH1 knockdown, S1P treatment in isolated hearts, mitochondrial fractionation and western blotting

    PMID:24345679

    Open questions at the time
    • Direct phosphorylation site(s) on SSH1 by PKD1 not mapped
    • Whether PKD1-SSH1 axis operates in non-cardiac contexts not tested
  3. 2014 High

    SSH1 was shown to function beyond canonical cytoskeletal remodeling: it is required for NOD1-dependent innate immune signaling, where NOD1 directly interacts with SSH1 at F-actin sites and SSH1-mediated cofilin activation is necessary for NF-κB-driven cytokine release.

    Evidence Genome-wide siRNA screen, NF-κB reporter assay, cytokine measurement, cytochalasin D rescue, co-localization imaging

    PMID:25187968

    Open questions at the time
    • How actin remodeling mechanistically links to NF-κB activation is unclear
    • Whether SSH1 participates in NOD2 or other NLR signaling not addressed
  4. 2015 Medium

    SSH1 was confirmed as the principal cofilin-1 Ser-3 phosphatase controlling directed cell migration, with knockdown specifically blocking migration without affecting proliferation in pancreatic cancer cells.

    Evidence siRNA knockdown, p-cofilin western blotting, migration versus proliferation assays

    PMID:25684665

    Open questions at the time
    • Relative contribution of SSH1 versus SSH2/SSH3 not compared
    • In vivo relevance for metastasis not tested
  5. 2018 Medium

    PKCδ was identified as an activating upstream kinase for SSH1 in macrophages, linking SSH1-cofilin dephosphorylation to membrane ruffle formation and macropinocytosis.

    Evidence SSH1 siRNA, PKCδ pharmacological inhibition, scanning electron microscopy, FITC-dextran macropinocytosis assay

    PMID:30261270

    Open questions at the time
    • Mechanism by which PKCδ activates SSH1 (direct phosphorylation vs. scaffold) not determined
    • Single lab finding
  6. 2019 High

    The mechanism of SSH1 recruitment in mechanosensitive contexts was elucidated: vinculin recruits SSH1 and cofilin in contracting cardiomyocytes, forming a VCL-SSH1-CFL axis that drives F-actin rearrangement and myofilament maturation.

    Evidence Interactome analysis comparing contracting vs. non-contracting cardiomyocytes, genetic epistasis in zebrafish, live imaging

    PMID:31495694

    Open questions at the time
    • Structural basis of vinculin-SSH1 interaction unknown
    • Whether vinculin-SSH1 interaction is relevant in non-cardiac mechano-transduction not explored
  7. 2020 High

    A cofilin-independent substrate of SSH1 was discovered: SSH1 dephosphorylates SQSTM1/p62 at Ser403, impairing autophagic cargo recognition and phospho-tau clearance, revealing a novel role in selective autophagy regulation in neurons.

    Evidence RNAi and overexpression, phospho-mutant SQSTM1 constructs, fluorescent autophagy reporters, primary neurons, in vivo AAV experiments, proximity ligation assay

    PMID:33044112

    Open questions at the time
    • Full substrate spectrum of SSH1 beyond cofilin and SQSTM1 unknown
    • Whether SSH1 activity on p62 is regulated by the same upstream kinases (PKD1, PKCδ) not tested
  8. 2024 Medium

    SSH1 was shown to dephosphorylate not only cofilin but also LIMK1 in the medial prefrontal cortex, modulating neuronal density and neuropathic pain/emotional phenotypes, expanding the substrate repertoire to include a kinase in the cofilin regulatory cascade.

    Evidence Lentiviral overexpression and knockdown of SSH1 in mPFC, co-immunoprecipitation, behavioral assays in SNI mice

    PMID:39701356

    Open questions at the time
    • Whether SSH1 directly dephosphorylates LIMK1 or acts indirectly not resolved by Co-IP alone
    • Single lab, awaits independent replication

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key unresolved questions include the full substrate spectrum of SSH1 beyond cofilin/SQSTM1/LIMK1, structural determinants of substrate selectivity, and the integration of activating (PKCδ) and inhibitory (PKD1) signals in different cell types.
  • No crystal structure or cryo-EM model of SSH1 catalytic domain with substrate
  • Systematic phosphoproteomics to identify additional substrates not performed
  • How SSH1 is differentially regulated in immune, neuronal, and cardiac contexts remains fragmented

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 5
Localization
GO:0005856 cytoskeleton 2 GO:0005829 cytosol 1
Pathway
R-HSA-162582 Signal Transduction 2 R-HSA-168256 Immune System 1 R-HSA-5357801 Programmed Cell Death 1 R-HSA-9612973 Autophagy 1
Partners
CFL1CFL2LIMK1NOD1PRKD1SQSTM1VCL

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2013 PKD1 phosphorylates and inhibits SSH1L (SSH1) downstream of RhoA/PLCε signaling; SSH1L knockdown mimics S1P-mediated cardioprotection by preventing cofilin-2 translocation to mitochondria and Bax-mediated apoptosis. Genetic deletion of PKD1/PLCε, SSH1L knockdown in cardiomyocytes, S1P treatment in isolated hearts, western blotting for phosphorylation, mitochondrial fractionation Science signaling High 24345679
2014 SSH1 is an essential component of NOD1 innate immune signaling: NOD1 directly interacts with SSH1 at F-actin-rich sites, and SSH1-mediated cofilin activation is required for NOD1-induced NF-κB activation and cytokine release; chemical inhibition of actin polymerization rescues loss of SSH1. Genome-wide siRNA screen, NF-κB reporter assay, cytokine measurement, cytochalasin D rescue, co-localization of NOD1 and SSH1 at F-actin sites PLoS pathogens High 25187968
2015 SSH1L dephosphorylates cofilin-1 at Ser-3 to promote cell migration; SSH1L knockdown increases cofilin-1 phosphorylation and specifically inhibits migration (not proliferation) in pancreatic cancer cells. SSH1L siRNA knockdown, western blotting for p-cofilin-1, migration assays, actin polymerization inhibitor (cytochalasin-D) Cancer letters Medium 25684665
2019 Vinculin (VCL) recruits SSH1 and its effector cofilin (CFL) in cardiomyocytes; this VCL-SSH1-CFL axis regulates F-actin rearrangement and myofilament maturation in response to mechanical forces from cardiac contractility. Interactome analysis (contracting vs. non-contracting cardiomyocytes), genetic epistasis in zebrafish, live imaging, F-actin quantification Developmental cell High 31495694
2018 PKCδ activates SSH1 to dephosphorylate cofilin at Ser-3, promoting membrane ruffle formation and macropinocytosis in macrophages; SSH1 silencing blocks cofilin dephosphorylation and macropinocytosis. siRNA knockdown of SSH1, western blotting for p-cofilin, scanning electron microscopy of ruffles, FITC-dextran flow cytometry for macropinocytosis, pharmacological PKCδ inhibition Cellular signalling Medium 30261270
2020 SSH1, the canonical cofilin phosphatase, also dephosphorylates SQSTM1/p62 at Ser403, impairing SQSTM1 flux and phospho-MAPT/tau clearance; this action on SQSTM1 is separable from SSH1-mediated cofilin activation and requires Ser403 phosphorylation status on SQSTM1. RNAi knockdown and overexpression, fluorescent autophagy reporters, defined phospho-mutant constructs, primary neurons, in vivo AAV experiments, proximity ligation assay Autophagy High 33044112
2020 NRP2 promotes PNET angiogenesis by activating SSH1, which dephosphorylates cofilin to drive F-actin polymerization and endothelial cell migration; SSH1 silencing abrogates NRP2-induced cofilin activation and migration. SSH1 siRNA in HUVECs, western blotting, immunofluorescence, wound-healing and tube formation assays Cell & bioscience Medium 32983407
2004 Missense mutation p.Ser63Asn and frameshift mutations in SSH1 are linked to disseminated superficial actinic porokeratosis (DSAP), implicating SSH1 phosphatase function in cytoskeleton organization of epidermal cells. Genome-wide linkage analysis, mutation screening of candidate genes, identification of loss-of-function variants in DSAP families Human mutation Medium 15459975
2023 SSH1 promotes intrahepatic cholangiocarcinoma (iCCA) cell migration and invasion through activation of the p38 MAPK pathway and upregulation of CXCL8. SSH1 overexpression and knockdown in iCCA cell lines, western blotting for p38 MAPK pathway components, migration/invasion assays Carcinogenesis Low 36857607
2024 SSH1 in the medial prefrontal cortex dephosphorylates cofilin and LIMK1 to modulate neuropathic pain processing; SSH1 overexpression ameliorates neuronal density loss and behavioral pain/emotional phenotypes in SNI mice, while SSH1 knockdown exacerbates them. Lentiviral overexpression and knockdown of SSH1 in mPFC, behavioral assays, co-immunoprecipitation, western blotting for phospho-cofilin and phospho-LIMK1 Experimental cell research Medium 39701356
2012 SSH1L overexpression promotes cytoskeletal rearrangement (microfilament remodeling) and differentiation of human bone marrow mesenchymal stem cells into cardiomyocyte-like cells; this effect is blocked by cytochalasin D (actin polymerization inhibitor), linking SSH1L activity to actin dynamics during differentiation. SSH1L overexpression in hMSCs, cytochalasin D inhibition, immunofluorescence for microfilament morphology, cardiac-specific protein/gene expression analysis Molecules Low 23247370
2025 RBMS1 promotes SSH1 expression in glioma cells by inducing c-Myc binding to the SSH1 promoter; elevated SSH1 downstream of this axis promotes glioma cell proliferation. c-Myc ChIP at SSH1 promoter, SSH1 knockdown/overexpression, proliferation assays, xenograft mouse models Biochemical and biophysical research communications Low 40120347

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2013 PLCε, PKD1, and SSH1L transduce RhoA signaling to protect mitochondria from oxidative stress in the heart. Science signaling 65 24345679
2019 Mechanical Forces Regulate Cardiomyocyte Myofilament Maturation via the VCL-SSH1-CFL Axis. Developmental cell 43 31495694
2015 Cofilin-phosphatase slingshot-1L (SSH1L) is over-expressed in pancreatic cancer (PC) and contributes to tumor cell migration. Cancer letters 43 25684665
2014 The cofilin phosphatase slingshot homolog 1 (SSH1) links NOD1 signaling to actin remodeling. PLoS pathogens 43 25187968
2004 Fine mapping and identification of a candidate gene SSH1 in disseminated superficial actinic porokeratosis. Human mutation 30 15459975
2018 PKCδ stimulates macropinocytosis via activation of SSH1-cofilin pathway. Cellular signalling 21 30261270
2021 Cofilin-1, LIMK1 and SSH1 are differentially expressed in locally advanced colorectal cancer and according to consensus molecular subtypes. Cancer cell international 18 33482809
2020 SSH1 impedes SQSTM1/p62 flux and MAPT/Tau clearance independent of CFL (cofilin) activation. Autophagy 15 33044112
2020 Vascular NRP2 triggers PNET angiogenesis by activating the SSH1-cofilin axis. Cell & bioscience 13 32983407
2012 The role of slingshot-1L (SSH1L) in the differentiation of human bone marrow mesenchymal stem cells into cardiomyocyte-like cells. Molecules (Basel, Switzerland) 13 23247370
2019 In vitro import experiments with semi-intact cells suggest a role of the Sec61 paralog Ssh1 in mitochondrial biogenesis. Biological chemistry 12 31199753
2018 Overexpression of SSH1 in gastric adenocarcinoma and its correlation with clinicopathological features. Journal of gastrointestinal oncology 11 30151269
2023 A systematic proximity ligation approach to studying protein-substrate specificity identifies the substrate spectrum of the Ssh1 translocon. The EMBO journal 7 37073826
2023 SSH1 promotes progression of intrahepatic cholangiocarcinoma via p38 MAPK-CXCL8 axis. Carcinogenesis 5 36857607
2022 Ruscogenin Attenuates Lipopolysaccharide-Induced Septic Vascular Endothelial Dysfunction by Modulating the miR-146a-5p/NRP2/SSH1 Axis. Drug design, development and therapy 5 35440867
2025 Characterization of a novel virulent mycobacteriophage Kashi-SSH1 (KSSH1) depicting genus-specific broad-spectrum anti-mycobacterial activity. Life sciences 1 40058575
2024 Age-dependent sex differences in cofilin1 pathway (LIMK1/SSH1) and its association with AD biomarkers after chronic systemic inflammation in mice. Neurobiology of aging 1 39265451
2024 Unraveling the role of SSH1 in chronic neuropathic pain: A focus on LIMK1 and Cofilin Dephosphorylation in the prefrontal cortex. Experimental cell research 1 39701356
2023 Dysregulated expression of slingshot protein phosphatase 1 (SSH1) disrupts circadian rhythm and WNT signaling associated to hepatocellular carcinoma pathogenesis. Aging 1 37837551
2019 [Expression and clinical significance of SSH1 in gastrointestinal stromal tumors]. Zhonghua yi xue za zhi 1 30884629
2025 RBMS1 promotes the proliferation of glioma cells via regulation of the c-Myc-SSH1 axis. Biochemical and biophysical research communications 0 40120347