Affinage

SPINT1

Kunitz-type protease inhibitor 1 · UniProt O43278

Length
529 aa
Mass
58.4 kDa
Annotated
2026-06-10
77 papers in source corpus 33 papers cited in narrative 33 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SPINT1 (HAI-1) is a membrane-anchored, multidomain Kunitz-type serine protease inhibitor that governs pericellular proteolysis at epithelial surfaces by controlling the activity of the type II transmembrane serine protease matriptase and its partner proteases (PMID:19389929, PMID:24962579). Inhibitory activity resides exclusively in Kunitz domain 1 (KD1), which inhibits HGFA, matriptase, and trypsin while leaving plasminogen activators and coagulation enzymes untouched (PMID:12815039); crystallography shows KD1 occupies the protease active site in a substrate-like manner across the S1, S2, and S4 subsites (PMID:20402765), and full-length HAI-1 exists in a compact auto-inhibited conformation in which the KD1 active site is sterically blocked until target-protease engagement triggers an extended, active conformation (PMID:28348076). HAI-1 acts as a chaperone required for matriptase synthesis, cell-surface trafficking, and retention, preventing inappropriate proteolytic activity during biosynthesis, and it captures activated matriptase to form shed matriptase–HAI-1 complexes (PMID:15800053, PMID:19535514, PMID:23248048); KD1 is the minimal matriptase-binding module while KD2 negatively regulates this interaction (PMID:29386351). Genetic epistasis establishes that suppression of a matriptase- and prostasin-dependent proteolytic cascade is the essential physiological function of HAI-1 (PMID:19389929, PMID:22952456). HAI-1 is essential in vivo for placental labyrinth basement-membrane integrity (PMID:15964823, PMID:17174946), postnatal epidermal keratinization and profilaggrin processing (PMID:18832587), intestinal epithelial homeostasis (PMID:21840293), and pancreatic β-cell glucose homeostasis, where it suppresses HEPSIN to sustain MAFA and insulin expression (PMID:39627229). Loss of HAI-1 drives NF-κB–mediated upregulation of urokinase and MMP-9, linking proteolytic dysregulation to intestinal carcinogenesis and basement-membrane disruption (PMID:27612426, PMID:39730982). Its cell-surface localization, dictated by intracellular Arg/Lys-rich and EHLVY targeting motifs, distinguishes it from the predominantly intracellular HAI-2 and makes HAI-1 the default inhibitor of extracellular matriptase activity (PMID:29438412, PMID:34643933).

Mechanistic history

Synthesis pass · year-by-year structured walk · 15 steps
  1. 2003 High

    Established which proteases HAI-1 inhibits and localized inhibitory activity to a single domain, defining its target specificity.

    Evidence Recombinant soluble HAI-1B with IC50 determinations against 16 serine proteases and P1 active-site mutagenesis of both Kunitz domains

    PMID:12815039

    Open questions at the time
    • Did not address regulation of HAI-1 inhibitory activity in the membrane-anchored full-length context
    • Cellular trafficking and chaperone roles not yet examined
  2. 2005 High

    Showed HAI-1 is not merely an inhibitor but a chaperone required for matriptase trafficking and surface localization, explaining why its loss causes spontaneous protease activation.

    Evidence siRNA knockdown, anti-HAI-1 antibody blockade, and KD1-mutant co-expression rescue with immunofluorescence in S1P-stimulated cells

    PMID:15800053

    Open questions at the time
    • Molecular determinants of co-trafficking not mapped
    • Did not establish in vivo physiological consequence
  3. 2005 High

    Demonstrated an essential developmental requirement for HAI-1 in placental trophoblast branching, providing the first whole-organism phenotype.

    Evidence Homozygous Spint1 knockout mice with histology at E9.5–E10.5

    PMID:15964823

    Open questions at the time
    • Did not identify the dysregulated protease responsible
    • Embryonic lethality precluded study of postnatal roles
  4. 2006 High

    Linked HAI-1 loss mechanistically to basement-membrane destruction, implicating uncontrolled matriptase/prostasin proteolysis in the placental phenotype.

    Evidence Knockout placentas analyzed by collagen IV/laminin immunofluorescence, EM, and protease co-localization

    PMID:17174946

    Open questions at the time
    • Causal protease not formally identified by epistasis at this stage
    • Direct demonstration of excess proteolytic activity inferred from localization
  5. 2008 High

    Defined HAI-1's postnatal role in epidermal barrier formation and tied it to a specific biochemical substrate-processing event.

    Evidence Blastocyst-complementation rescue of lethality, histology, and immunoblot of profilaggrin/filaggrin processing

    PMID:18832587

    Open questions at the time
    • Did not establish whether profilaggrin defect is direct or downstream of matriptase dysregulation
    • Akt activation mechanism not resolved
  6. 2009 High

    Genetic epistasis proved matriptase suppression is the essential function of HAI-1 in tissue homeostasis, anchoring the entire mechanistic model.

    Evidence Spint1-/- × St14 hypomorph double-mutant mice with histology and survival monitoring

    PMID:19389929

    Open questions at the time
    • Did not address the contribution of prostasin or HGFA
    • Tissue-specific differences in protease dependence not resolved
  7. 2012 High

    Placed prostasin upstream as the matriptase zymogen activator and showed reducing prostasin rescues HAI-1 deficiency, refining the proteolytic cascade hierarchy.

    Evidence Compound mutant mice (HAI-1 or HAI-2 deficient × Prss8 hypomorph) with biochemical analysis of placental protease activation

    PMID:22952456

    Open questions at the time
    • Did not resolve how prostasin zymogen is itself activated
    • Relative roles of HAI-1 vs HAI-2 in this cascade left for later work
  8. 2012 High

    Extended HAI-1's essential role to adult intestinal epithelium and disease susceptibility via conditional deletion.

    Evidence Villin-Cre × Spint1-LoxP conditional KO with permeability assays, TUNEL, EM, and DSS colitis model

    PMID:21840293

    Open questions at the time
    • Did not delineate the signaling pathway driving epithelial turnover and ER stress
    • Causal protease in intestine not pinpointed here
  9. 2014 High

    Distinguished the non-redundant roles of HAI-1 versus HAI-2, showing HAI-1 controls activated matriptase while HAI-2 governs prostasin-driven zymogen activation.

    Evidence Conditional HAI-1 and HAI-2 knockout mice plus Caco-2 gene silencing with IHC and Western blot

    PMID:24962579

    Open questions at the time
    • Mechanistic basis of the division of labor (localization vs intrinsic activity) not yet defined
    • Did not address compensatory regulation
  10. 2010 High

    Provided atomic-level mechanism of inhibition, showing KD1 mimics a substrate to occupy the HGFA active site.

    Evidence X-ray crystallography of the KD1–HGFA complex compared to a substrate analog

    PMID:20402765

    Open questions at the time
    • Structure of full-length auto-inhibited HAI-1 not yet determined
    • Did not explain reduced potency of full-length inhibitor
  11. 2017 High

    Resolved why full-length HAI-1 is a weaker inhibitor than KD1 fragments by revealing a compact auto-inhibited conformation regulated by target-protease binding.

    Evidence Crystallography and SAXS of soluble full-length HAI-1 ectodomain with comparative inhibition assays

    PMID:28348076

    Open questions at the time
    • In situ conformational switching at the membrane not directly visualized
    • Kinetics of the conformational transition not measured
  12. 2020 High

    Showed HAI-1 inhibits the matriptase zymogen as effectively as the active enzyme, expanding its regulatory window to pre-activation states.

    Evidence In vitro reconstitution with purified zymogen and natural substrates pro-HGF and pro-prostasin plus cell-based assays

    PMID:32338287

    Open questions at the time
    • Structural basis of zymogen recognition not solved
    • Physiological significance of zymogen inhibition in vivo not tested
  13. 2021 High

    Identified the intracellular sequence motifs (Arg/Lys-rich and EHLVY) that direct HAI-1 to the cell surface, explaining its functional divergence from intracellular HAI-2.

    Evidence Domain-swap and point-mutation constructs with immunocytochemistry, surface biotinylation, and confocal microscopy

    PMID:34643933

    Open questions at the time
    • Trafficking machinery recognizing these motifs not identified
    • Quantitative surface vs intracellular partitioning under physiological conditions not measured
  14. 2024 High

    Revealed a distinct HAI-1 function in pancreatic β cells, suppressing HEPSIN to maintain GLP1R signaling, MAFA, and insulin expression for glucose homeostasis.

    Evidence Spint1-lacZ knock-in and pancreas-specific KO mice, siRNA silencing, SPINT1–HEPSIN co-IP, cAMP assays, Exendin-4 challenge, and glucose tolerance tests

    PMID:39627229

    Open questions at the time
    • Whether HEPSIN inhibition uses the same KD1 active-site mechanism not shown
    • Direct enzymatic inhibition of HEPSIN by HAI-1 not biochemically reconstituted
  15. 2024 Medium

    Connected HAI-1 loss to NF-κB-driven MMP-9 upregulation as the route to basement-membrane disruption in epidermis.

    Evidence SPINT1 KO HaCaT cells with gelatin zymography, Western blot, skin EM, and DHMEQ NF-κB inhibition

    PMID:39730982

    Open questions at the time
    • How protease dysregulation activates NF-κB upstream not defined
    • single-cell-line mechanism not validated across epithelial tissues

Open questions

Synthesis pass · forward-looking unresolved questions
  • How the auto-inhibited-to-active conformational switch, chaperone trafficking, and tissue-specific protease targeting (matriptase, prostasin, HGFA, HEPSIN) are coordinately controlled at the membrane in vivo remains unresolved.
  • No integrated model linking conformational regulation to target selection
  • Determinants of context-specific protease choice (e.g., HEPSIN in β cells vs matriptase in epithelium) not established

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 5 GO:0140096 catalytic activity, acting on a protein 3 GO:0140313 molecular sequestering activity 2
Localization
GO:0005886 plasma membrane 4 GO:0005576 extracellular region 3
Pathway
R-HSA-1266738 Developmental Biology 4 R-HSA-392499 Metabolism of proteins 3 R-HSA-1474244 Extracellular matrix organization 2 R-HSA-162582 Signal Transduction 2
Partners
HGFAHPNPRSS8ST14

Evidence

Reading pass · 33 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2005 HAI-1 (SPINT1) is required for matriptase activation: HAI-1 is co-translocated with matriptase to cell-cell junctions upon sphingosine 1-phosphate (S1P) stimulation, and HAI-1 knockdown or anti-HAI-1 antibody treatment causes spontaneous matriptase activation. Coexpression of wild-type HAI-1 (but not Kunitz domain 1 mutants) rescues matriptase trafficking to the cell surface in cells lacking endogenous HAI-1; catalytically defective matriptase mutants traffic normally without HAI-1, indicating HAI-1 prevents inappropriate matriptase proteolytic activity during synthesis and trafficking. siRNA knockdown, anti-HAI-1 monoclonal antibody treatment, co-expression of wild-type vs. Kunitz domain mutant HAI-1, immunofluorescence, Western blot, S1P stimulation assay American journal of physiology. Cell physiology High 15800053
2003 HAI-1B, a splice variant of HAI-1 containing an extra 16 amino acids adjacent to the C-terminus of KD1, potently inhibits HGFA (IC50=30.5 nM), matriptase (IC50=16.5 nM), and trypsin (IC50=2.4 nM), with weak inhibition of plasmin and plasma kallikrein, and no significant inhibition of plasminogen activators, coagulation enzymes, or activated protein C. P1 residue-directed mutagenesis demonstrated that inhibition is mediated exclusively by KD1 and not KD2. Soluble recombinant protein production, enzyme inhibition assays (IC50 determination against 16 serine proteases), P1 residue-directed mutagenesis of Kunitz domains The Journal of biological chemistry High 12815039
2005 HAI-1 (SPINT1) is essential for branching morphogenesis of the chorioallantoic placenta in mice. Homozygous HAI-1-/- mice die at ~E10.5 with severely impaired labyrinth layer formation but intact spongiotrophoblast and giant cell layers, indicating a specific role in trophoblast branching rather than general placental cell identity. Homozygous gene knockout by homologous recombination in mice, histological analysis at E9.5 and E10.5 Molecular and cellular biology High 15964823
2006 HAI-1 is essential for the integrity of basement membranes in the developing placental labyrinth. HAI-1-/- placentas show disrupted collagen IV and laminin-containing basement membranes at the trophoblast–allantoic mesoderm interface, resulting in failed vascularization. Matriptase and prostasin co-localize with HAI-1 in labyrinthine trophoblasts in wild-type placentas, and their localization and expression are unchanged in HAI-1-/- placentas, implying uncontrolled proteolytic activity of these enzymes underlies the basement membrane defects. Gene knockout mice, immunofluorescent staining of collagen IV and laminin, electron microscopy, immunohistochemistry Developmental biology High 17174946
2008 HAI-1/SPINT1 is required for normal epidermal keratinization and hair development. Spint1-/- mice rescued from embryonic lethality (by blastocyst complementation) develop ichthyosis-like scaly skin with hyperkeratosis, acanthosis with enhanced Akt phosphorylation, and abnormal hair shafts. HAI-1 deficiency causes altered proteolytic processing of profilaggrin with impaired generation of filaggrin monomers. Blastocyst complementation rescue of Spint1-/- embryonic lethality, histology, immunoblot for profilaggrin/filaggrin processing, immunohistochemistry for Akt phosphorylation The American journal of pathology High 18832587
2009 Loss of HAI-1 (Spint1) in mice causes ichthyosis, acanthosis, and hypotrichosis through loss of suppression of a matriptase-dependent proteolytic pathway. Genetic epistasis: Spint1-deficient mice carrying a hypomorphic St14 (matriptase) allele survive normally with no histological abnormalities, demonstrating that matriptase suppression is the essential function of HAI-1 in postnatal tissue homeostasis. Genetic epistasis analysis using Spint1-/- × St14 hypomorphic double mutant mice, histological analysis, long-term survival monitoring The American journal of pathology High 19389929
2009 HAI-1 mediates matriptase inhibition and complex formation selectively at the basolateral surface of polarized epithelial cells. Latent matriptase is targeted to the basolateral membrane; only matriptase–HAI-1 complexes (not latent matriptase) are detectable in seminal fluid and urine. In polarized Caco-2 cells, matriptase–HAI-1 complexes (but not latent matriptase) undergo transcytosis to the apical surface for secretion. Analysis of seminal fluid and urine for matriptase forms, polarized Caco-2 monolayer experiments, Western blot, immunohistochemistry of prostate and kidney American journal of physiology. Cell physiology High 19535514
2012 HAI-1 (Spint1) is required for maintenance of intestinal epithelial integrity. Intestine-specific Spint1 deletion causes crypt abnormalities, increased apoptosis, elevated epithelial turnover, increased intestinal permeability, and endoplasmic reticulum stress in colonic crypts, and greatly worsens experimental colitis (DSS model) with significantly lower survival. Conditional KO using Villin-Cre × Spint1-LoxP mice, histology, TUNEL assay, intestinal permeability assay, electron microscopy, DSS colitis model The American journal of pathology High 21840293
2012 In HAI-1/SPINT1 deficiency, prostasin activation and pericellular serine protease activity are suppressed because cell-surface localization of matriptase is impaired. HAI-1/SPINT1 knockdown in BeWo trophoblast cells decreases cell-associated matriptase protein (without altering mRNA) and reduces laminin degradation activity, demonstrating that HAI-1 is required for cell-surface retention of matriptase to enable physiological activation of prostasin. siRNA knockdown of HAI-1 in BeWo cells, immunoblot for matriptase and prostasin, laminin degradation assay, immunohistochemistry of HAI-1-deficient mouse placentas Human cell Medium 23248048
2012 Reduced prostasin (CAP1/PRSS8) activity rescues both HAI-1 and HAI-2 deficiency-associated developmental defects by preventing matriptase activation. Hypomorphic Prss8 mutations restore placentation and normal development of HAI-1-deficient embryos. Biochemical analysis revealed that prostasin is required for conversion of the matriptase zymogen to active matriptase, while prostasin zymogen activation is matriptase-independent in placental tissues. Genetic epistasis analysis with compound mutant mice (HAI-1 or HAI-2 deficient × Prss8 hypomorph), biochemical analysis of matriptase and prostasin activation in placental tissue PLoS genetics High 22952456
2014 HAI-1 (SPINT1) regulates the activity of already-activated matriptase, whereas HAI-2 (not HAI-1) has an essential role in regulating prostasin-dependent matriptase zymogen activation. In genetically engineered mice, HAI-1 ablation does not affect matriptase in intestinal epithelial cells, but HAI-2 ablation causes loss of matriptase from both small and large intestine; gene silencing in Caco-2 cells shows this is due to accelerated matriptase activation and shedding caused by loss of prostasin regulation by HAI-2. Conditional KO mice (HAI-1 and HAI-2 ablation), gene silencing in Caco-2 monolayers, immunohistochemistry, Western blot The Journal of biological chemistry High 24962579
2006 Androgen receptor-mediated transcription and new protein synthesis are required for dihydrotestosterone (DHT)-induced matriptase activation and shedding in LNCaP prostate cancer cells. Activated matriptase is shed in complex with HAI-1; both latent matriptase and free HAI-1 are also shed. DHT-induced matriptase activation is blocked by the androgen antagonist bicalutamide, transcription inhibitor actinomycin D, and translation inhibitor cycloheximide. Hormone stimulation assays, pharmacological inhibitors (bicalutamide, actinomycin D, cycloheximide), Western blot, immunoprecipitation American journal of physiology. Cell physiology Medium 16467405
2010 HAI-1 acts as a specific cell-surface binding protein and reservoir for active HGFA on the epithelial cell surface; active HGFA–HAI-1 complexes are rapidly released from the cell surface by IL-1β treatment with significant recovery of HGFA activity in culture supernatant, suggesting HAI-1 localizes HGFA to facilitate pericellular HGF activation in injured mucosa. Cell surface binding assays, immunoprecipitation, IL-1β stimulation experiments, enzyme activity assays in culture supernatant Journal of gastroenterology Medium 12572861
2010 Crystal structure of the KD1–HGFA complex reveals that HAI-1 KD1 inhibits HGFA by occupying the active site in a substrate-like manner, making contacts with all substrate specificity-determining loops and occupying subsites S1, S2, and S4. KD1 side chains occupying these sites are virtually superimposable on P1, P2, and P4 residues of a pro-HGF-derived substrate mimic. X-ray crystallography of KD1–HGFA complex, structural comparison with substrate analog-bound HGFA The FEBS journal High 20402765
2011 When HAI-1 levels are insufficient, active matriptase forms a 140-kDa homodimer (in addition to a 100-kDa complex with unidentified inhibitors) as a mechanism to control its activity. The 140-kDa dimer contains two-chain activated matriptase, lacks gelatinolytic activity, and its levels are inversely correlated with the HAI-1:matriptase ratio, suggesting it may represent a matriptase autoactivation intermediate. Western blot, gel filtration/biochemical characterization of matriptase complexes, gelatin zymography, immunoprecipitation American journal of physiology. Cell physiology Medium 22031598
2015 γ-Catenin (Plakoglobin) reduces NSCLC cell migration in a p53-dependent manner by inducing HAI-1 (SPINT1) expression, which serves as an upstream inhibitor of c-MET signaling. Re-expression of γ-catenin sensitizes NSCLC cells to c-MET inhibitor-mediated growth inhibition. γ-Catenin expression in NSCLC cells, scratch and trans-well migration assays, Western blot for HAI-1 and c-MET pathway components, c-MET inhibitor treatment The Journal of biological chemistry Medium 25925948
2016 Matriptase and prostasin both form complexes with HAI-1 in human milk (and in milk-derived mammary epithelial cells), providing in vivo evidence that HAI-1 inhibits both proteases during lactation. HAI-1 is the primary inhibitor for both matriptase and prostasin in this context. Immunoaffinity purification, ion exchange chromatography, Western blot analysis of human milk fractions and milk-derived mammary epithelial cells PloS one Medium 27043831
2017 Crystal structure and SAXS solution structure of soluble full-length HAI-1 extracellular domain (sHAI-1) reveal that it exists in a compact, auto-inhibited conformation in which the active site of Kunitz domain 1 is sterically blocked by neighboring structural elements. In the presence of target proteases, sHAI-1 adopts an extended conformation that disables auto-inhibition, explaining the lower inhibitory activity of full-length versus truncated HAI-1 fragments. X-ray crystallography, small-angle X-ray scattering (SAXS), enzyme inhibition assays comparing full-length vs. truncated HAI-1 The Journal of biological chemistry High 28348076
2017 MMP-7 cleaves HAI-1 on the cancer cell surface, primarily between Gly451 and Leu452, releasing soluble HAI-1 (sHAI-1). This sHAI-1 induces homotypic cancer cell aggregation through the HAI-1 region corresponding to amino acids 141–249, which does not include the serine protease inhibitor domain. Cell-surface cholesterol sulfate is needed for sHAI-1 generation by MMP-7, but a cholesterol sulfate-independent MMP-7 action is critical for sHAI-1-mediated aggregation induction. Cell surface biotinylation, LC-MS/MS substrate identification, site-directed cleavage site mapping, cancer cell aggregation assays with recombinant sHAI-1 fragments The Journal of biological chemistry High 29046355
2018 HAI-1 (at cell surface) is a more effective inhibitor of extracellular matriptase proteolytic activity than HAI-2 (predominantly intracellular) because of differential subcellular localization. Both HAI-1 and HAI-2 promote matriptase expression and cell-surface translocation, but HAI-1 cell-surface expression allows it to efficiently capture active matriptase before shedding, whereas HAI-2's primarily intracellular localization prevents effective suppression of extracellular active matriptase. Immunohistochemistry, Western blot, cell surface biotinylation/avidin depletion, analysis of prostasin-matriptase complexes in human skin foreskin lysates PloS one Medium 29438412
2018 TMPRSS11A-related enzymes human airway tryptase and DESC1, but not TMPRSS11A itself, are blocked by HAI-1 in their ability to activate influenza A virus hemagglutinin, demonstrating differential sensitivity of HA-activating TTSPs to HAI-1 inhibition. Cell-based HA cleavage assays, protease inhibition assays with recombinant HAI-1 The Journal of biological chemistry Medium 29976755
2018 HAI-1 (SPINT1) expression in tumor-associated macrophages is regulated by HIF-2α under hypoxia. HIF-2α-deficient bone marrow-derived macrophages show reduced Spint1 mRNA and protein secretion under hypoxia. Supernatants from HIF-2α KO macrophages (lacking Spint1) could activate pro-HGF to stimulate breast tumor cell proliferation, while wild-type macrophage supernatants containing Spint1 failed to do so. RNA-seq of sorted TAMs from HIF-2α LysM-/- vs. WT mice, RT-PCR, ELISA for secreted Spint1, pro-HGF activation assay in breast tumor cell proliferation Molecular carcinogenesis Medium 31436357
2018 CDX2 transcription factor directly regulates both ST14 (matriptase) and SPINT1 (HAI-1) gene expression in intestinal cells through binding to CDX2-enriched enhancer elements identified by ChIP-seq. CDX2 is not required for basal ST14 and SPINT1 expression, but changes in CDX2 expression alter the ST14/SPINT1 mRNA ratio in a cell-type-dependent manner. siRNA KD of CDX2, promoter-reporter assays, CDX2 ChIP-seq analysis, RT-PCR Scientific reports Medium 30087389
2018 Grhl2 transcription factor directly binds to the Spint1 gene in developing mouse submandibular salivary gland (confirmed by ChIP-PCR), and Grhl2 knockdown suppresses SPINT1 expression concomitant with retardation of epithelial development and disorganized laminin deposition. Addition of recombinant SPINT1 protein rescues the suppressive effects of Grhl2 siRNA on epithelial development and laminin deposition. siRNA knockdown of Grhl2 in ex vivo SMG culture, RT-PCR for SPINT1 mRNA, ChIP-PCR for Grhl2 binding to Spint1 gene, recombinant SPINT1 rescue experiment Biochemical and biophysical research communications High 30193734
2020 HAI-1 (and HAI-2) inhibits the zymogen form of matriptase in addition to the activated form. Using purified proteins and cell-based assays, HAI-1 inhibits matriptase zymogen activity toward peptide-based substrates and the natural protein substrates pro-HGF and pro-prostasin at concentrations comparable to inhibition of activated matriptase, suggesting interaction at the active site of the zymogen. In vitro enzyme inhibition assays with purified HAI-1 and matriptase zymogen, peptide substrate cleavage assay, pro-HGF and pro-prostasin cleavage assays, cell-based assay The Biochemical journal High 32338287
2020 HAI-1 deficiency increases prostasin proteolysis (through increased protein expression and zymogen activation) but paradoxically decreases matriptase proteolysis in HaCaT human keratinocytes. In HAI-1-deficient cells, all activated prostasin is found in complex with HAI-2, and matriptase zymogen activation and shedding are suppressed. This demonstrates that HAI-1 has opposite effects on matriptase versus prostasin proteolysis in keratinocytes. CRISPR/targeted HAI-1 deletion in HaCaT keratinocytes, Western blot for protease activation states, immunoprecipitation for complex formation Human cell High 33486722
2021 HAI-1 and HAI-2 differ in their subcellular targeting due to differences in their intracellular Arg/Lys-rich and EHLVY motifs. HAI-1 localizes both intracellularly and at the cell surface, while HAI-2 localizes predominantly in intracellular granules. Domain swap and point mutation studies combined with immunocytochemistry and cell surface biotinylation revealed these intrinsic sequence differences control the differential subcellular distribution. Domain swap constructs, site-directed point mutations, immunocytochemistry, cell surface biotinylation/avidin depletion, confocal microscopy Human cell High 34643933
2016 HAI-1 loss in intestine-specific Spint1-deleted ApcMin/+ mice promotes intestinal carcinogenesis through NF-κB signaling activation, as evidenced by upregulation of inflammatory cytokines (TNF-α, IL-6), increased nuclear NF-κB translocation in normal mucosa and tumor tissues, and upregulation of NF-κB target urokinase-type plasminogen activator. Treatment with DHMEQ (NF-κB inhibitor) reduced intestinal tumor formation in these mice. Conditional intestinal Spint1 KO in ApcMin/+ background, RT-PCR and immunohistochemistry for NF-κB targets, DHMEQ pharmacological treatment experiment Oncotarget Medium 27612426
2024 SPINT1 in pancreatic β cells controls glucose homeostasis by suppressing the serine protease HEPSIN. SPINT1 and HEPSIN interact in β cells; Hepsin silencing counteracts the downregulation of Mafa and Ins1 caused by Spint1 depletion. SPINT1 loss or HEPSIN overexpression reduces GLP1R-related cyclic AMP levels and Mafa expression. Spint1-disrupted mice show reduced Exendin-4-induced insulin secretion, and pancreas-specific Spint1 disruption diminishes islet size and mass, causing glucose intolerance. Spint1-lacZ knock-in mice, pancreas-specific Spint1 KO mice, siRNA gene silencing, co-immunoprecipitation (SPINT1–HEPSIN interaction), cAMP assays, Exendin-4 challenge, glucose tolerance tests, Western blot Nature communications High 39627229
2024 HAI-1 (SPINT1) loss in keratinocytes upregulates MMP-9 expression via NF-κB activation, leading to increased MMP gelatinolytic activity and disrupted epidermal basement membrane structure. Treatment of SPINT1 KO HaCaT cells with DHMEQ (NF-κB inhibitor) abrogates MMP-9 upregulation and associated gelatinolytic activity. SPINT1 KO HaCaT cells, gelatin zymography, Western blot, electron microscopy of Spint1-deleted skin, DHMEQ pharmacological inhibition Human cell Medium 39730982
2004 Decreased HAI-1 immunoreactivity in colorectal carcinoma cells results largely from enhanced ectodomain shedding of HAI-1. In contrast, at the invasion front, membrane-form HAI-1 is paradoxically enhanced, correlating with decreased E-cadherin expression and low proliferative activity (MIB-1 negative), revealing distinct regulation of membrane-bound versus shed HAI-1 in cancer progression. Immunohistochemistry with three anti-HAI-1 antibodies recognizing distinct epitopes, in situ hybridization for HAI-1 mRNA Cancer science Medium 15471558
2001 HAI-1 functions as a cell-surface inhibitor and reservoir of HGFA in colorectal carcinoma, where HGF activation is significantly enhanced compared to normal mucosa. HAI-1 cell-surface binding of active HGFA may paradoxically ensure concentrated pericellular HGFA activity when shedding of the HAI-1/HGFA complex is upregulated. In vitro cell-surface HGFA binding assays, immunohistochemistry, enzyme activity assays in colorectal tissue extracts Human cell Medium 11436357
2018 An engineered bivalent HAI-1 KD1-based inhibitor (KD1 duplicated via domain replacement of inactive KD2, fused to antibody Fc) inhibits matriptase with a Ki of 70 ± 5 pM (120-fold improvement over natural HAI-1), inhibits pro-HGF activation by matriptase, and inhibits matriptase on cancer cells with greater than an order-of-magnitude higher efficacy than monomeric KD1. This establishes that HAI-1 KD1 is the minimal matriptase-binding domain and that KD2 is involved in negative regulation. Rational domain engineering, combinatorial library screening, in vitro enzyme inhibition assays (Ki determination), pro-HGF cleavage assay, cancer cell surface matriptase inhibition assay The Journal of biological chemistry High 29386351

Source papers

Stage 0 corpus · 77 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2001 Matriptase and HAI-1 are expressed by normal and malignant epithelial cells in vitro and in vivo. The American journal of pathology 169 11290548
2002 Expression of the serine protease matriptase and its inhibitor HAI-1 in epithelial ovarian cancer: correlation with clinical outcome and tumor clinicopathological parameters. Clinical cancer research : an official journal of the American Association for Cancer Research 158 11948120
2005 HAI-1 regulates activation and expression of matriptase, a membrane-bound serine protease. American journal of physiology. Cell physiology 133 15800053
1999 Distribution of hepatocyte growth factor activator inhibitor type 1 (HAI-1) in human tissues. Cellular surface localization of HAI-1 in simple columnar epithelium and its modulated expression in injured and regenerative tissues. The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society 109 10219059
2003 Tissue expression, protease specificity, and Kunitz domain functions of hepatocyte growth factor activator inhibitor-1B (HAI-1B), a new splice variant of HAI-1. The Journal of biological chemistry 90 12815039
2005 Hepatocyte growth factor activator inhibitor type 1 (HAI-1) is required for branching morphogenesis in the chorioallantoic placenta. Molecular and cellular biology 83 15964823
2006 Hepatocyte growth factor activation inhibitors (HAI-1 and HAI-2) regulate HGF-induced invasion of human breast cancer cells. International journal of cancer 80 16557597
2012 Reduced prostasin (CAP1/PRSS8) activity eliminates HAI-1 and HAI-2 deficiency-associated developmental defects by preventing matriptase activation. PLoS genetics 62 22952456
2009 Polarized epithelial cells secrete matriptase as a consequence of zymogen activation and HAI-1-mediated inhibition. American journal of physiology. Cell physiology 62 19535514
2006 The ratio of Matriptase/HAI-1 mRNA is higher in colorectal cancer adenomas and carcinomas than corresponding tissue from control individuals. BMC cancer 61 16820046
2018 Hepatocyte growth factor activator inhibitors (HAI-1 and HAI-2): Emerging key players in epithelial integrity and cancer. Pathology international 59 29431273
2008 Defect of hepatocyte growth factor activator inhibitor type 1/serine protease inhibitor, Kunitz type 1 (Hai-1/Spint1) leads to ichthyosis-like condition and abnormal hair development in mice. The American journal of pathology 58 18832587
2006 Hepatocyte growth factor activator inhibitor-1 (HAI-1) is essential for the integrity of basement membranes in the developing placental labyrinth. Developmental biology 58 17174946
2021 Exosome-delivered miR-221/222 exacerbates tumor liver metastasis by targeting SPINT1 in colorectal cancer. Cancer science 54 34125460
2009 Loss of matriptase suppression underlies spint1 mutation-associated ichthyosis and postnatal lethality. The American journal of pathology 53 19389929
2006 Matriptase activation and shedding with HAI-1 is induced by steroid sex hormones in human prostate cancer cells, but not in breast cancer cells. American journal of physiology. Cell physiology 52 16467405
2014 The protease inhibitor HAI-2, but not HAI-1, regulates matriptase activation and shedding through prostasin. The Journal of biological chemistry 50 24962579
2018 TMPRSS11A activates the influenza A virus hemagglutinin and the MERS coronavirus spike protein and is insensitive against blockade by HAI-1. The Journal of biological chemistry 47 29976755
2011 Membrane-bound serine protease inhibitor HAI-1 is required for maintenance of intestinal epithelial integrity. The American journal of pathology 44 21840293
2010 The role of hepatocyte growth factor activator inhibitor (HAI)-1 and HAI-2 in endometrial cancer. International journal of cancer 40 20715109
2020 LncRNA SPINT1-AS1 promotes breast cancer proliferation and metastasis by sponging let-7 a/b/i-5p. Pathology, research and practice 37 33246290
2019 Zebrafish modeling reveals that SPINT1 regulates the aggressiveness of skin cutaneous melanoma and its crosstalk with tumor immune microenvironment. Journal of experimental & clinical cancer research : CR 33 31519199
2009 Expression of hepatocyte growth factor activator inhibitors (HAI-1 and HAI-2) in ovarian cancer. International journal of oncology 33 19148468
2012 Loss of membrane-bound serine protease inhibitor HAI-1 induces oral squamous cell carcinoma cells' invasiveness. The Journal of pathology 32 22262311
2016 Matriptase Complexes and Prostasin Complexes with HAI-1 and HAI-2 in Human Milk: Significant Proteolysis in Lactation. PloS one 28 27043831
2004 Paradoxically enhanced immunoreactivity of hepatocyte growth factor activator inhibitor type 1 (HAI-1) in cancer cells at the invasion front. Cancer science 27 15471558
2016 Usefulness of DNA Methylation Levels in COASY and SPINT1 Gene Promoter Regions as Biomarkers in Diagnosis of Alzheimer's Disease and Amnestic Mild Cognitive Impairment. PloS one 25 27992572
2015 Novel Role for γ-Catenin in the Regulation of Cancer Cell Migration via the Induction of Hepatocyte Growth Factor Activator Inhibitor Type 1 (HAI-1). The Journal of biological chemistry 25 25925948
2019 Macrophage HIF-2α regulates tumor-suppressive Spint1 in the tumor microenvironment. Molecular carcinogenesis 24 31436357
2011 Mechanisms for the control of matriptase activity in the absence of sufficient HAI-1. American journal of physiology. Cell physiology 23 22031598
2019 LncRNAs GIHCG and SPINT1-AS1 Are Crucial Factors for Pan-Cancer Cells Sensitivity to Lapatinib. Frontiers in genetics 22 30842786
2018 Tissue distribution and subcellular localizations determine in vivo functional relationship among prostasin, matriptase, HAI-1, and HAI-2 in human skin. PloS one 21 29438412
2010 Hepatocyte growth factor activator (HGFA): molecular structure and interactions with HGFA inhibitor-1 (HAI-1). The FEBS journal 21 20402765
2017 Matrix metalloproteinase-7 induces homotypic tumor cell aggregation via proteolytic cleavage of the membrane-bound Kunitz-type inhibitor HAI-1. The Journal of biological chemistry 19 29046355
2001 Pericellular activation of hepatocyte growth factor/scatter factor (HGF/SF) in colorectal carcinomas: roles of HGF activator (HGFA) and HGFA inhibitor type 1 (HAI-1). Human cell 17 11436357
2021 SPINT1-AS1 Drives Cervical Cancer Progression via Repressing miR-214 Biogenesis. Frontiers in cell and developmental biology 16 34350182
2016 Decreasing the ratio of matriptase/HAI‑1 by downregulation of matriptase as a potential adjuvant therapy in ovarian cancer. Molecular medicine reports 14 27356668
2010 Hepatocyte growth factor activator inhibitors (HAI-1 and HAI-2) are potential targets in uterine leiomyosarcoma. International journal of oncology 14 20664929
2020 Inhibition of an active zymogen protease: the zymogen form of matriptase is regulated by HAI-1 and HAI-2. The Biochemical journal 13 32338287
2020 HAI-1 regulates placental folds development by influencing trophoblast cell proliferation and invasion in pigs. Gene 13 32360842
2001 Mouse hepatocyte growth factor activator inhibitor type 1 (HAI-1) and type 2 (HAI-2)/placental bikunin genes and their promoters. Biochimica et biophysica acta 13 11406276
2012 Regulation of pericellular proteolysis by hepatocyte growth factor activator inhibitor type 1 (HAI-1) in trophoblast cells. Human cell 12 23248048
2002 Roles of hepatocyte growth factor activator (HGFA) and its inhibitor HAI-1 in the regeneration of injured gastrointestinal mucosa. Journal of gastroenterology 12 12572861
2017 The crystal structure of a multidomain protease inhibitor (HAI-1) reveals the mechanism of its auto-inhibition. The Journal of biological chemistry 11 28348076
2014 Expression of hepatocyte growth factor activator inhibitor-1 (HAI-1) gene in prostate cancer: clinical and biological significance. Journal of B.U.ON. : official journal of the Balkan Union of Oncology 11 24659667
2005 Diverse roles of hepatocyte growth factor activator inhibitor type 1 (HAI-1) in the growth of glioblastoma cells in vivo. Cancer letters 11 16051034
2020 Differential subcellular distribution renders HAI-2 a less effective protease inhibitor than HAI-1 in the control of extracellular matriptase proteolytic activity. Genes & diseases 10 35685459
2019 Promoter Hypomethylation Is Responsible for Upregulated Expression of HAI-1 in Hepatocellular Carcinoma. Disease markers 10 31558918
2018 Regulation of matriptase and HAI-1 system, a novel therapeutic target in human endometrial cancer cells. Oncotarget 10 29560101
2018 Intestinal regulation of suppression of tumorigenicity 14 (ST14) and serine peptidase inhibitor, Kunitz type -1 (SPINT1) by transcription factor CDX2. Scientific reports 10 30087389
2016 Inhibition of nuclear factor-κB signaling suppresses Spint1-deletion-induced tumor susceptibility in the ApcMin/+ model. Oncotarget 10 27612426
2022 LncRNA SPINT1-AS1/miR-433-3p/E2F3 positive feedback loop promotes the KRAS-mutant colorectal cancer cell proliferation, migration and invasion. Pathology, research and practice 9 36274378
2018 Grhl2 regulation of SPINT1 expression controls salivary gland development. Biochemical and biophysical research communications 9 30193734
2006 Augmented expression of hepatocytes growth factor activator inhibitor type 1 (HAI-1) in intrahepatic small bile ducts in primary biliary cirrhosis. Virchows Archiv : an international journal of pathology 9 16941151
2021 HAI-1 is an independent predictor of lung cancer mortality and is required for M1 macrophage polarization. PloS one 8 34185790
2018 Engineering a potent inhibitor of matriptase from the natural hepatocyte growth factor activator inhibitor type-1 (HAI-1) protein. The Journal of biological chemistry 8 29386351
2006 Identification of antibodies against HAI-1 and integrin alpha6beta4 as immunohistochemical markers of human villous cytotrophoblast. The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society 8 16495474
2013 Expression of Hepatocyte growth factor activator inhibitor type-1 (HAI-1) in prostate cancer. Anticancer research 7 23393351
2013 Down-regulation of HAI-1 is associated with poor-differentiation status of colorectal cancer. Human cell 6 23979832
2021 Targeted deletion of HAI-1 increases prostasin proteolysis but decreases matriptase proteolysis in human keratinocytes. Human cell 5 33486722
2024 Spint1 disruption in mouse pancreas leads to glucose intolerance and impaired insulin production involving HEPSIN/MAFA. Nature communications 4 39627229
2021 Targeted HAI-2 deletion causes excessive proteolysis with prolonged active prostasin and depletion of HAI-1 monomer in intestinal but not epidermal epithelial cells. Human molecular genetics 4 34089062
2021 The difference in the intracellular Arg/Lys-rich and EHLVY motifs contributes to distinct subcellular distribution of HAI-1 versus HAI-2. Human cell 4 34643933
2025 SPINT1 Expressed in Epithelial Cells of Choroid Plexus in Human and Mouse Brains. International journal of molecular sciences 3 40507942
2018 3-Cl-AHPC inhibits pro-HGF maturation by inducing matriptase/HAI-1 complex formation. Journal of cellular and molecular medicine 3 30370662
2023 HAI-1 is required for the novel role of FGFBP1 in maintenance of cell morphology and F-actin rearrangement in human keratinocytes. Human cell 2 37076641
2006 [HAI-1 expression in villous tissue of early gestational period in women]. Sichuan da xue xue bao. Yi xue ban = Journal of Sichuan University. Medical science edition 2 16909612
2025 Engineered Expression of Hepatocyte Growth Factor Activator Inhibitor-1 (HAI-1) Reduces the Growth of Bladder Cancer Cells. Biomedicines 1 40299447
2025 Overexpression of Matriptase-1 Inhibitor HAI-1 as an Effective Strategy to Reduce Proteolytic Clipping in Chinese Hamster Ovary Cells. Biotechnology journal 1 41140002
2024 Loss of hepatocyte growth factor activator inhibitor type 1 (HAI-1) upregulates MMP-9 expression and induces degradation of the epidermal basement membrane. Human cell 1 39730982
2018 [Expression and Clinical Significances of HGFA, Matriptase, HAI-1 and HAI-2 in Acute Myeloid Leukemia]. Zhongguo shi yan xue ye xue za zhi 1 30111395
2005 [Effect of HAI-1 over-expression on in vitro growth and migration/motility of SW620 cells]. Shi yan sheng wu xue bao 1 16044910
2026 The role of HAI-1 in urothelial bladder cancer: Tissue expression, ectodomain shedding and clinical outcomes. Biochemistry and biophysics reports 0 42064581
2025 LncRNA SPINT1-AS1 enhances the Warburg effect and promotes the progression of osteosarcoma via the miR-135b-5p/PGAM1 axis. Cancer cell international 0 40170094
2025 SPINT1-AS1 promotes oxidative damage and apoptosis of gastric cancer cells via the miR-656-3p/PLCXD3 axis. Discover oncology 0 40783674
2006 [Construction of prokaryotic expression vectors of HAI-1 with different domains and expression of the fusion proteins]. Xi bao yu fen zi mian yi xue za zhi = Chinese journal of cellular and molecular immunology 0 16507252
2004 [Expression of GST-HAI-1 fusion protein and development of monoclonal antibody against human hepatocyte growth factor activator inhibitor 1]. Sheng wu gong cheng xue bao = Chinese journal of biotechnology 0 15968977

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