Multiple sites of proteolytic cleavage to release soluble forms of hepatocyte growth factor activator inhibitor type 1 from a transmembrane form.
Hepatocyte growth factor activator inhibitor type 1 (HAI-1) is a Kunitz-type serine protease inhibitor, which was identified as a potent inhibitor of hepatocyte growth factor (HGF) activator from the conditioned medium of a human carcinoma cell line. HGF activator is a blood coagulation factor XII-like serine protease that is responsible for proteolytic activation of the inactive single chain precursor of HGF in injured tissues. The predicted sequence of the primary translation product of HAI-1, which has a hydrophobic sequence in its COOH-terminal region, suggested that HAI-1 is first produced in a membrane-associated form. In this study, we identified a transmembrane form of HAI-1 integrated in the plasma membrane of cultured cells using a monoclonal antibody against HAI-1. We also identified several soluble forms of HAI-1 in the conditioned medium of the cells, indicating that multiple sites are present in the transmembrane form of HAI-1 at which proteolytic cleavage releases the extracellular domain. At least two proteases, one of which is a metalloprotease, appear to be responsible for the release. Further, the soluble forms of HAI-1 have different inhibitory activity against HGF activator. These findings suggest that proteolytic processing plays important roles in regulation of the inhibitory activity of HAI-1.
Shimomura
T
T
Research Center, Mitsubishi Chemical Corp., Kamoshida, Aoba-ku, Yokohama, 227-8502, Japan.
Denda
K
K
Kawaguchi
T
T
Matsumoto
K
K
Miyazawa
K
K
Kitamura
N
N
D001483:Base Sequence; D001665:Binding Sites; D017077:Culture Media, Conditioned; D018076:DNA, Complementary / Q000235:genetics; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008566:Membranes / Q000378:metabolism; D008970:Molecular Weight; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D053491:Proteinase Inhibitory Proteins, Secretory; D015842:Serine Proteinase Inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D017077:Culture Media, Conditioned; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D010446:Peptide Fragments; D053491:Proteinase Inhibitory Proteins, Secretory; C109149:SPINT1 protein, human; D015842:Serine Proteinase Inhibitors; D017228:Hepatocyte Growth Factor