A Matriptase-Prostasin Reciprocal Zymogen Activation Complex with Unique Features

Abstract

Background: Matriptase and prostasin form a proteolytic pathway in which the hierarchical placement of the two proteases is unclear. Results: Prostasin stimulates matriptase activation non-enzymatically. Matriptase zymogen can activate prostasin. Conclusion: Matriptase and prostasin form a reciprocal zymogen activation complex with unique features. Significance: A general model for activation of the two membrane-anchored serine proteases is proposed.

Distinct Developmental Functions of Prostasin (CAP1/PRSS8) Zymogen and Activated Prostasin

“…1A). This dinucleotide change generated a Prss8 allele (hereafter referred to as Prss8 zym ) that encodes a prostasin in which Arg-44 is substituted by Gln, thus rendering the mutant prostasin refractory to activation site cleavage, as previously demonstrated in vitro (13). Introduction of the dinucleotide change was verified by sequencing analysis of DNA from mice bred to homozygosity for the mutated allele (Fig.…”

“…Prostasin, however, is upstream of matriptase in other epithelia (6), and zymogen-locked prostasin supports matriptase auto-activation in cell-based overexpression systems (13). We, therefore, next directly examined the status of matriptase activation in the epidermis of newborn Prss8 Ϫ/Ϫ , Prss8 zym/zym , and Prss8 ϩ/ϩ pups.…”

“…However, this activation, which can be inhibited by the broad-spectrum serine protease inhibitor, aprotinin, can also be efficiently executed by mutant prostasin variants that lack the catalytic histidine-aspartate-serine triad (10 -12). Likewise, catalytically inactive prostasin mutants can stimulate the activation of protease-activated receptor-2 in a reconstituted mammalian cell-based system (13). Strong support for a non-proteolytic function of prostasin in vivo has been gained from the observation that mis-expressed catalytically inactive prostasin induces severe skin pathology in transgenic mice (13,14), and in particular, by our recent demonstration that mice expressing only catalytically inactive endogenous prostasin, unlike prostasin null mice, display normal long-term survival (15).…”

The Membrane-anchored Serine Protease Prostasin (CAP1/PRSS8) Supports Epidermal Development and Postnatal Homeostasis Independent of Its Enzymatic Activity

“…In this regard, a catalytically inactive prostasin mutant was able to both activate matriptase and to stimulate the activity of matriptase toward a physiological target substrate, proteinase-activated receptor-2 (11).…”

Sequence and Conformational Specificity in Substrate Recognition

“…It potently inhibits many serine proteases with subnanomolar affinities (66) and is believed to be a physiological inhibitor of hepatocyte growth factor (HGF) activator (67) as well as hepsin (68) and matriptase (69,70), two type II transmembrane serine proteases that, like HGF activator, can convert latent pro-hepatocyte growth factor/scatter factor (pro-HGF/SF) into the two-chain active signaling heterodimer. Additionally, HAI2 is a physiological inhibitor of prostasin, a glycosylphosphatidylinositol-anchored protease involved in regulation of matriptase activation and shedding (71,72). HAI2-KD1, shown here to be a good substrate for mesotrypsin, has been found to be the domain responsible for inhibition of HGF activator (67).…”