The Activation of Matriptase Requires Its Noncatalytic Domains, Serine Protease Domain, and Its Cognate Inhibitor

Michael D Oberst,Cicely A Williams,Robert B Dickson,Michael D Johnson,Chen-Yong Lin

doi:10.1074/jbc.m304282200

Abstract

The activation of matriptase requires proteolytic cleavage at a canonical activation motif that converts the enzyme from a one-chain zymogen to an active, two-chain protease. In this study, matriptase bearing a mutation in its catalytic triad was unable to undergo this activational cleavage, suggesting that the activating cleavage occurs via a transactivation mechanism where interaction between matriptase zymogen molecules leads to activation of the protease. Using additional point and deletion mutants, we showed that activation of matriptase requires proteolytic processing at Gly-149 in the SEA domain of the protease, glycosylation of the first CUB domain and the serine protease domain, and intact low density lipoprotein receptor class A domains. Its cognate inhibitor, hepatocyte growth factor activator inhibitor-1, may also participate in the activation of matriptase, based on the observation that matriptase activation did not occur when the protease was co-expressed with hepatocyte growth factor activator inhibitor-1 mutated in its low density lipoprotein receptor class A domain. These results suggest that besides matriptase catalytic activity, matriptase activation requires post-translational modification of the protease, intact noncatalytic domains, and its cognate inhibitor.

Highlights

Matriptase is a multi-domain, transmembrane serine protease of the S1 trypsin-like family [1]
We found that matriptase was expressed in the absence of its endogenous inhibitor, the hepatocyte growth factor activator inhibitor-1 (HAI-1)1 [9], more frequently in late stage ovarian tumors, suggesting that matriptase proteolytic activity may be deregulated during tumor progression [20]
We examined whether noncatalytic domains of matriptase or HAI-1 are required in its activation

Summary

Introduction

Matriptase is a multi-domain, transmembrane serine protease of the S1 trypsin-like family [1]. Matriptase is thought to play a role in cancer invasion and metastasis through its extracellular matrix-degrading activity [7, 17] and its potential role in activating urokinase plasminogen activator and hepatocyte growth factor on the surfaces of cancer cells [13, 14]. In node-negative human breast tumors, high level expression of matriptase, and HAI-1, in addition to c-Met, were associated with poor patient outcome. Both c-Met and HAI-1 proved to be independent prognostic factors when compared with traditional breast cancer markers in multivariate analysis [21]. We have found that in breast cancer cells matriptase is constitutively activated [22], in contrast to immortalized mammary epithelial cells, where the activation of matriptase is dependent on sphingosine 1-phosphate, a blood-borne phospholipid [23, 24]

Methods

Results

Conclusion