Potent inhibition and global co-localization implicate the transmembrane Kunitz-type serine protease inhibitor hepatocyte growth factor activator inhibitor-2 in the regulation of epithelial matriptase activity.
Hepatocyte growth factor activator inhibitors (HAI)-1 and -2 are recently identified and closely related Kunitz-type transmembrane serine protease inhibitors. Whereas HAI-1 is well established as an inhibitor of the serine proteases matriptase and hepatocyte growth factor activator, the physiological targets of HAI-2 are unknown. Here we show that HAI-2 displays potent inhibitory activity toward matriptase, forms SDS-stable complexes with the serine protease, and blocks matriptase-dependent activation of its candidate physiological substrates proprostasin and cell surface-bound pro-urokinase plasminogen activator. To further explore the potential functional relationship between HAI-2 and matriptase, we generated a transgenic mouse strain with a promoterless beta-galactosidase marker gene inserted into the endogenous locus encoding HAI-2 protein and performed a global high resolution mapping of the expression of HAI-2, matriptase, and HAI-1 proteins in all adult tissues. This analysis showed striking co-localization of HAI-2 with matriptase and HAI-1 in epithelial cells of all major organ systems, thus strongly supporting a role of HAI-2 as a physiological regulator of matriptase activity, possibly acting in a redundant or partially redundant manner with HAI-1. Unlike HAI-1 and matriptase, however, HAI-2 expression was also detected in non-epithelial cells of brain and lymph nodes, suggesting that HAI-2 may also be involved in inhibition of serine proteases other than matriptase.
Szabo
Roman
R
Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, Maryland 20892, USA.
Hobson
John P
JP
List
Karin
K
Molinolo
Alfredo
A
Lin
Chen-Yong
CY
Bugge
Thomas H
TH
D000595:Amino Acid Sequence; D000818:Animals; D004848:Epithelium / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D008969:Molecular Sequence Data; D053491:Proteinase Inhibitory Proteins, Secretory / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000096:biosynthesis*; D014018:Tissue Distribution
D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D053491:Proteinase Inhibitory Proteins, Secretory; C109149:SPINT1 protein, human; C109148:SPINT2 protein, human; C504591:Spint1 protein, mouse; C533525:Spint2 protein, mouse; D012697:Serine Endopeptidases; C485595:matriptase