Affinage

SSH1

Protein phosphatase Slingshot homolog 1 · UniProt Q8WYL5

Length
1049 aa
Mass
115.5 kDa
Annotated
2026-06-10
21 papers in source corpus 12 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SSH1 (Slingshot Homolog 1) is a protein phosphatase that governs actin cytoskeletal dynamics by dephosphorylating cofilin at Ser3, reactivating it to drive F-actin remodeling across diverse cell types and physiological processes including cell migration, macropinocytosis, angiogenesis, and myofilament maturation (PMID:25684665, PMID:30261270, PMID:32983407). Its cofilin-directed activity is embedded in defined signaling axes: it is activated downstream of PKCδ in macrophages to drive membrane ruffling and macropinocytosis (PMID:30261270) and downstream of NRP2 in endothelial cells to promote migration and angiogenesis (PMID:32983407), whereas PKD1 phosphorylates and inhibits SSH1 downstream of RhoA/PLCε, an event that controls cofilin-2 and Bax mitochondrial translocation and thereby cardiomyocyte survival (PMID:24345679). SSH1 also operates within mechanotransduction, where vinculin recruits SSH1 and cofilin to remodel F-actin and promote myofilament maturation in response to contractile force (PMID:31495694), and it acts as an essential component of NOD1 innate immune signaling, interacting directly with NOD1 at F-actin-rich sites to enable NF-κB activation and cytokine release (PMID:25187968). Beyond cofilin, SSH1 dephosphorylates SQSTM1/p62 at Ser403 in a manner mechanistically separable from its cofilin activity, impairing autophagic flux and reducing clearance of phospho-tau in neurons and brain (PMID:33044112). SSH1 also dephosphorylates LIMK1 and modulates neuropathic pain in the prefrontal cortex (PMID:39701356), and it is co-opted in multiple cancers — supporting proliferation and invasion via p38 MAPK/CXCL8, WNT/β-catenin, and a c-Myc transcriptional axis (PMID:36857607, PMID:37837551, PMID:40120347). Mutations in SSH1 are linked to disseminated superficial actinic porokeratosis, connecting its phosphatase function to epidermal cytoskeletal organization (PMID:15459975).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2004 Medium

    Established the first human disease link for SSH1, indicating its phosphatase function is relevant to epidermal cytoskeletal integrity in vivo.

    Evidence Linkage analysis and candidate gene sequencing identifying missense and frameshift mutations in DSAP families

    PMID:15459975

    Open questions at the time
    • No biochemical characterization of mutant phosphatase activity
    • Mechanism connecting loss of SSH1 to porokeratosis pathology not defined
  2. 2013 High

    Defined an upstream inhibitory regulator of SSH1, showing that PKD1 phosphorylation suppresses SSH1 to control cofilin-2/Bax mitochondrial translocation and cell survival.

    Evidence siRNA knockdown, pharmacology, mitochondrial fractionation and survival assays in cardiomyocytes establishing RhoA→PLCε→PKD1→SSH1→cofilin2 epistasis

    PMID:24345679

    Open questions at the time
    • Direct phosphatase activity on the mitochondrial pool not biochemically reconstituted
    • How cofilin-2 translocation triggers Bax import is unresolved
  3. 2014 High

    Revealed a non-canonical role for SSH1 in innate immunity, placing its actin-regulatory activity upstream of NOD1-dependent NF-κB signaling.

    Evidence Genome-wide siRNA screen, NOD1-SSH1 Co-IP at F-actin sites, NF-κB reporter, cytokine measurement, and cytochalasin D rescue

    PMID:25187968

    Open questions at the time
    • Whether SSH1 phosphatase activity is required versus a scaffolding role not fully separated
    • Direct binding interface with NOD1 not mapped
  4. 2015 Medium

    Confirmed SSH1 as a cofilin-1 Ser3 phosphatase driving cancer cell migration independently of proliferation.

    Evidence siRNA knockdown, phospho-cofilin western blot, wound-healing assays and cytochalasin D rescue in pancreatic cancer cells

    PMID:25684665

    Open questions at the time
    • Single cancer context
    • Upstream activators in this setting not identified
  5. 2018 Medium

    Identified PKCδ as an activating upstream kinase coupling SSH1/cofilin activity to membrane ruffling and macropinocytosis.

    Evidence siRNA knockdown, phospho-cofilin western blot, scanning EM of ruffles, and FITC-dextran flow cytometry in macrophages

    PMID:30261270

    Open questions at the time
    • Whether PKCδ acts directly on SSH1 not biochemically shown
    • Single lab
  6. 2019 High

    Positioned SSH1 within mechanotransduction, showing vinculin recruits it to convert contractile force into actin remodeling during myofilament maturation.

    Evidence VCL interactome MS in contracting vs non-contracting cardiomyocytes, reciprocal Co-IP, loss-of-function and live F-actin imaging with VCL→SSH1→CFL epistasis in zebrafish

    PMID:31495694

    Open questions at the time
    • Direct VCL-SSH1 binding interface not mapped
    • How force modulates SSH1 catalytic activity unknown
  7. 2020 High

    Established a cofilin-independent substrate, showing SSH1 dephosphorylates SQSTM1/p62 Ser403 to impair autophagy and phospho-tau clearance.

    Evidence RNAi/overexpression, phospho-site mutant constructs, proximity ligation assay, and validation in cell lines, primary neurons and mouse brain

    PMID:33044112

    Open questions at the time
    • Structural basis for substrate selection between p62 and cofilin not defined
    • Regulation of SSH1 activity toward p62 in neurodegeneration unresolved
  8. 2020 Medium

    Added NRP2 as an activator of SSH1 driving VEGF/VEGFR2-independent endothelial migration and tumor angiogenesis.

    Evidence siRNA knockdown, phospho-cofilin western blot, F-actin staining, tube formation assays and in vivo PNET model

    PMID:32983407

    Open questions at the time
    • Direct NRP2-SSH1 coupling mechanism not shown
    • Single lab
  9. 2023 Medium

    Extended SSH1's pro-tumorigenic role to additional cancers via distinct downstream pathways (p38 MAPK/CXCL8 and WNT/β-catenin plus circadian regulators).

    Evidence Gain/loss-of-function with pathway western blots, CRISPR knockout, pharmacological inhibition, and in vivo tumor models in iCCA and HCC

    PMID:36857607 PMID:37837551

    Open questions at the time
    • Whether phosphatase catalytic activity links SSH1 to these pathways not established
    • Connection to canonical cofilin axis in these contexts unclear
  10. 2024 Medium

    Showed SSH1 acts on LIMK1 in addition to cofilin in the prefrontal cortex to modulate neuropathic pain and neuronal health.

    Evidence Lentiviral overexpression/knockdown in mouse mPFC, behavioral assays, phospho-cofilin/phospho-LIMK1 western blots and SSH1-LIMK1 Co-IP

    PMID:39701356

    Open questions at the time
    • Direct dephosphorylation of LIMK1 versus indirect effect not resolved
    • Single lab
  11. 2025 Medium

    Defined transcriptional control of SSH1, showing an RBMS1/c-Myc axis drives SSH1 expression to support glioma proliferation.

    Evidence ChIP for c-Myc binding to the SSH1 promoter, knockdown/overexpression, proliferation assays and xenografts

    PMID:40120347

    Open questions at the time
    • Downstream SSH1 effector in glioma not defined
    • Single lab

Open questions

Synthesis pass · forward-looking unresolved questions
  • How SSH1 selects between its substrates (cofilin, SQSTM1/p62, LIMK1) and how distinct upstream inputs are integrated to direct context-specific outputs remains unresolved.
  • No structural model of substrate recognition
  • Mechanism integrating activating (PKCδ, NRP2) and inhibitory (PKD1) inputs unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140096 catalytic activity, acting on a protein 4 GO:0016787 hydrolase activity 3 GO:0008092 cytoskeletal protein binding 2
Localization
GO:0005856 cytoskeleton 2 GO:0005829 cytosol 1
Pathway
R-HSA-162582 Signal Transduction 3 R-HSA-168256 Immune System 1 R-HSA-9612973 Autophagy 1

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 in cardiomyocytes. SSH1L inhibition prevents cofilin 2 translocation to mitochondria and blocks Bax mitochondrial translocation, thereby promoting cell survival after oxidative stress/ischemia-reperfusion injury. Genetic knockdown (SSH1L siRNA), pharmacological manipulation, western blotting for cofilin phosphorylation, mitochondrial fractionation, cardiomyocyte survival assays; epistasis established RhoA→PLCε→PKD1→SSH1L→cofilin2 pathway Science signaling High 24345679
2014 SSH1 directly interacts with NOD1 at F-actin-rich sites and is an essential component of the NOD1 innate immune signaling pathway; SSH1-mediated cofilin activation is required for NOD1-dependent NF-κB activation and cytokine release. Cytochalasin D (actin polymerization inhibitor) rescued NOD1 signaling loss upon SSH1 depletion. Genome-wide siRNA screen, co-immunoprecipitation/interaction assay showing NOD1-SSH1 interaction at F-actin sites, NF-κB reporter assay, cytokine measurement, chemical rescue with cytochalasin D PLoS pathogens High 25187968
2015 SSH1 (SSH1L) acts as a cofilin-1 phosphatase in pancreatic cancer cells; SSH1L knockdown increased cofilin-1 Ser3 phosphorylation (inactivation) and inhibited cell migration without affecting proliferation. Cytochalasin D abrogated migration independently of SSH1L expression. siRNA-mediated knockdown of SSH1L in PC cell lines, western blotting for phospho-cofilin-1 (Ser3), wound-healing/migration assays, cytochalasin D rescue Cancer letters Medium 25684665
2004 Missense mutation p.Ser63Asn and frameshift mutations in SSH1 were identified in families with disseminated superficial actinic porokeratosis (DSAP), implicating SSH1 phosphatase function in epidermal cytoskeleton organization. Genome-wide linkage analysis, candidate gene sequencing, mutation identification in affected families Human mutation Medium 15459975
2019 In zebrafish cardiomyocytes, the mechanosensitive protein vinculin (VCL) recruits SSH1 and its effector cofilin (CFL) to regulate F-actin rearrangement and promote myofilament maturation in response to mechanical forces from heartbeat contraction. VCL interactome by mass spectrometry in contracting vs. non-contracting cardiomyocytes, co-immunoprecipitation, loss-of-function studies, live imaging of F-actin; genetic epistasis (VCL→SSH1→CFL) Developmental cell High 31495694
2018 PKCδ activates SSH1 in macrophages, which dephosphorylates cofilin at Ser3, leading to membrane ruffle formation and macropinocytosis. SSH1 silencing blocked cofilin dephosphorylation and inhibited macropinocytosis stimulated by phorbol ester or HGF. siRNA knockdown of SSH1, western blot for phospho-cofilin, scanning electron microscopy of ruffles, flow cytometry (FITC-dextran internalization), pharmacological inhibitors Cellular signalling Medium 30261270
2020 SSH1 dephosphorylates phospho-Ser403-SQSTM1/p62, thereby impairing SQSTM1 autophagic flux and reducing clearance of phospho-MAPT/tau. This action is fully dependent on SQSTM1 Ser403 phosphorylation status and is mechanistically separable from SSH1-mediated cofilin dephosphorylation. RNAi knockdown and overexpression of SSH1, genetically encoded fluorescent reporters, defined phospho-site mutant constructs, western blotting, proximity ligation assay, experiments in cell lines, primary neurons, and mouse brains Autophagy High 33044112
2020 NRP2 activates SSH1 in endothelial cells, which in turn activates cofilin to promote F-actin polymerization, HUVEC migration, and PNET angiogenesis via a VEGF/VEGFR2-independent pathway. SSH1 silencing blocked NRP2-induced cofilin activation and cell migration. siRNA knockdown of SSH1, western blot for cofilin phosphorylation, F-actin staining, wound-healing/tube formation assays, in vivo mouse PNET model Cell & bioscience Medium 32983407
2023 SSH1 promotes intrahepatic cholangiocarcinoma (iCCA) cell proliferation, migration, and invasion through activation of the p38 MAPK pathway and enhanced expression of CXCL8. SSH1 overexpression and knockdown in iCCA cell lines, western blotting for p38 MAPK pathway components, CXCL8 measurement, proliferation/migration/invasion assays Carcinogenesis Medium 36857607
2023 CRISPR-mediated SSH1 knockout or pharmacological inhibition suppressed HCC cell viability, migration, and invasion, and downregulated WNT/β-catenin pathway components (WNT3, β-catenin, LRP5/6) and circadian clock regulators (CLOCK, BMAL1), while upregulating CFL-1/2 and CRY1. CRISPR SSH1 knockout, pharmacological inhibition (Sennoside A), cell viability/migration/invasion assays, western blotting, in vivo mouse tumor model Aging Medium 37837551
2024 SSH1 modulates neuropathic pain and neuronal health in the medial prefrontal cortex by dephosphorylating cofilin and LIMK1; co-immunoprecipitation demonstrated interaction between SSH1 and LIMK1. Lentiviral overexpression and knockdown of SSH1 in mouse mPFC, behavioral assays, western blotting for p-cofilin and p-LIMK1, co-immunoprecipitation, immunofluorescence Experimental cell research Medium 39701356
2025 RBMS1 promotes glioma cell proliferation through a c-Myc-SSH1 axis: RBMS1 induces c-Myc binding to SSH1 promoters, increasing SSH1 expression, which in turn supports proliferative behavior. Patient datasets, glioma cell lines, mouse xenograft models, chromatin immunoprecipitation (c-Myc binding to SSH1 promoter), knockdown/overexpression experiments, proliferation assays Biochemical and biophysical research communications Medium 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 44 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 18 33044112
2020 Vascular NRP2 triggers PNET angiogenesis by activating the SSH1-cofilin axis. Cell & bioscience 14 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 6 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
2023 Dysregulated expression of slingshot protein phosphatase 1 (SSH1) disrupts circadian rhythm and WNT signaling associated to hepatocellular carcinoma pathogenesis. Aging 2 37837551
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
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

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