Abstract
Matriptase is an epithelial-derived, integral membrane, trypsin-like serine protease. We have shown previously that matriptase exists both in complexed and noncomplexed forms. We now show that the complexed matriptase is an activated, two-chain form, which is inhibited in an acid-sensitive, reversible manner through binding to its cognate, Kunitz-type inhibitor, HAI-1 (hepatocyte growth factor activator inhibitor-1). Conversely, the majority of the noncomplexed matriptase is a single-chain zymogen, which lacks binding affinity to HAI-1, suggesting that matriptase, similar to most other serine proteases, is activated by proteolytic cleavage at a canonical activation motif. We have now generated mAbs specific for the conformational changes associated with the proteolytic activation of matriptase. Using these mAbs, which specifically recognize the two-chain form of matriptase, we demonstrate that matriptase is transiently activated on 184A1N4 human mammary epithelial cell surfaces following their exposure to serum. The ability of serum to activate matriptase is highly conserved across reptilian, avian, and mammalian species. This serum-dependent activation of matriptase on epithelial cell surfaces is followed by ectodomain shedding of both matriptase and its Kunitz-type inhibitor.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Antibodies, Monoclonal / immunology
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Antibody Specificity
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Biological Factors / pharmacology*
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Blood*
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Breast / cytology
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Breast / drug effects
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Breast / enzymology*
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Breast / metabolism
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Cell Membrane / drug effects
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Cell Membrane / enzymology*
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Cell Membrane / metabolism
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Enzyme Activation / drug effects
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Epithelial Cells / cytology
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Epithelial Cells / drug effects*
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Epithelial Cells / enzymology*
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Epithelial Cells / metabolism
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Female
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Fluorescent Antibody Technique
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Humans
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Membrane Glycoproteins / metabolism
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Membrane Glycoproteins / pharmacology
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Milk, Human
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Molecular Sequence Data
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Molecular Weight
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Peptide Fragments / chemistry
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Peptide Fragments / metabolism
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Protein Binding
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Protein Conformation
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Proteinase Inhibitory Proteins, Secretory
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Serine Endopeptidases / chemistry
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Serine Endopeptidases / immunology
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Serine Endopeptidases / metabolism*
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Serine Proteinase Inhibitors / metabolism
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Serine Proteinase Inhibitors / pharmacology
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Trypsin / chemistry
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Trypsin / immunology
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Trypsin / metabolism*
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Tumor Cells, Cultured
Substances
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Antibodies, Monoclonal
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Biological Factors
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Membrane Glycoproteins
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Peptide Fragments
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Proteinase Inhibitory Proteins, Secretory
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SPINT1 protein, human
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Serine Proteinase Inhibitors
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Serine Endopeptidases
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matriptase
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ST14 protein, human
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Trypsin