Abstract
Matriptase and prostasin are part of a cell surface proteolytic pathway critical for epithelial development and homeostasis. Here we have used a reconstituted cell-based system and transgenic mice to investigate the mechanistic interrelationship between the two proteases. We show that matriptase and prostasin form a reciprocal zymogen activation complex with unique features. Prostasin serves as a critical co-factor for matriptase activation. Unexpectedly, however, prostasin-induced matriptase activation requires neither prostasin zymogen conversion nor prostasin catalytic activity. Prostasin zymogen conversion to active prostasin is dependent on matriptase but does not require matriptase zymogen conversion. Consistent with these findings, wild type prostasin, activation cleavage site-mutated prostasin, and catalytically inactive prostasin all were biologically active in vivo when overexpressed in the epidermis of transgenic mice, giving rise to a severe skin phenotype. Our finding of non-enzymatic stimulation of matriptase activation by prostasin and activation of prostasin by the matriptase zymogen provides a tentative mechanistic explanation for several hitherto unaccounted for genetic and biochemical observations regarding these two membrane-anchored serine proteases and their downstream targets.
Highlights
Matriptase and prostasin form a proteolytic pathway in which the hierarchical placement of the two proteases is unclear
We show that matriptase and prostasin form a reciprocal zymogen activation complex in which matriptase activation is induced by prostasin
hepatocyte growth factor activator inhibitor (HAI)-1 was co-expressed with matriptase and prostasin in all experiments to ensure efficient expression of the two proteases [12, 36]
Summary
Matriptase and prostasin form a proteolytic pathway in which the hierarchical placement of the two proteases is unclear. Our finding of non-enzymatic stimulation of matriptase activation by prostasin and activation of prostasin by the matriptase zymogen provides a tentative mechanistic explanation for several hitherto unaccounted for genetic and biochemical observations regarding these two membrane-anchored serine proteases and their downstream targets. The prostasin zymogen has been reported to be devoid of enzymatic activity and does not autoactivate in cell-based or in purified biochemical systems, consistent with the inability of prostasin to cleave model peptides resembling its own activation cleavage site (16 –18). Prostasin activation is matriptase-dependent, but prostasin activation by matriptase can be mediated by the matriptase zymogen Consistent with these findings, transgenic mice with epidermal overexpression of prostasin mutants that are either activation site cleavage-resistant or catalytically inactive displayed phenotypes that were indistinguishable from transgenic mice overexpressing wild type prostasin. Our proposed model for prostasin-induced allosteric activation of matriptase and matriptase zymogen activation of prostasin provides a tentative explanation for several previously reported unresolved observations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
