HAI-1 regulates activation and expression of matriptase, a membrane-bound serine protease

Abstract

Hepatocyte growth factor activator inhibitor-1 (HAI-1) was initially identified as cognate inhibitor of matriptase, a membrane-bound serine protease. Paradoxically, HAI-1 is also required for matriptase activation, a process that requires sphingosine 1-phosphate (S1P)-mediated translocation of the protease to cell-cell junctions in human mammary epithelial cells. In the present study, we further explored how HAI-1 regulates this protease. First, we observed that after S1P treatment HAI-1 was cotranslocated with matriptase to cell-cell junctions and that the cellular ratio of HAI-1 to matriptase was maintained during this process. However, when this ratio was changed by cell treatment with HAI-1 small interfering RNA or anti-HAI-1 MAb M19, spontaneous activation of matriptase occurred in the absence of S1P-induced translocation; S1P-induced matriptase activation was also enhanced. These results support a role for HAI-1 in protection of cell from uncontrolled matriptase activation. We next expressed matriptase, either alone or with HAI-1 in breast cancer cells that do not endogenously express either protein. A defect in matriptase trafficking to the cell surface occurred if wild-type matriptase was expressed in the absence of HAI-1; this defect appeared to result from matriptase toxicity to cells. Coexpression with matriptase of wild-type HAI-1, but not HAI-1 mutants altered in its Kunitz domain 1, corrected the trafficking defect. In contrast, catalytically defective matriptase mutants were normal in their trafficking in the absence of HAI-1. These results are also consistent with a role for HAI-1 to prevent inappropriate matriptase proteolytic activity during its protein synthesis and trafficking. Taken together, these results support multiple roles for HAI-1 to regulate matriptase, including its proper expression, intracellular trafficking, activation, and inhibition.

Requirement of the activity of hepatocyte growth factor activator inhibitor type 1 for the extracellular appearance of a transmembrane serine protease matriptase in monkey kidney COS-1 cells

“…In the present study, we found that HAI58K-R260A was detected at a low level in the co-expression with WT-matriptase (Fig. 4), this being consistent with the observation that R260L HAI-1 was produced poorly in the co-expression with matriptase (Oberst et al 2005). It is plausible that the HAI58K-R260A variant, which lacks matriptase-inhibitory activity (Kojima et al 2008), is susceptible to degradation by the protease.…”

“…It has been found that, when full-length matriptase cDNA is transfected alone into human breast carcinoma BT549 cells, the enzyme is poorly produced and retained in the endoplasmic reticulum and Golgi apparatus and that the trafficking defect is corrected by co-expression of full-length HAI-1 (Oberst et al 2005). We also found in a transient-expression system using monkey kidney COS-1 cells that fulllength rat matriptase (hereinafter, called WT-matriptase, see Fig.…”

“…In the system using BT549 cells, matriptase was poorly produced when co-transfected with a cDNA for full-length r-HAI-1 bearing mutation at the active site Arg260 (designated R260L HAI-1) (Oberst et al 2005). This suggests that the inhibition activity of HAI-1 toward matriptase is essential for production of this protease in the cell line.…”

“…2, middle lane) is thought to be due to its impaired intracellular trafficking or, for instance, to the intracellular self-degradation (Oberst et al 2005). However, there remains the possibility that WT-matriptase occurs in the medium after which it undergoes self-degradation in the absence of HAI-1.…”

Involvement of the cytoplasmic juxtamembrane region of matriptase in its exclusive localization to the basolateral membrane domain of Madin–Darby canine kidney epithelial cells

“…It has been shown in a transient-expression system using human breast cancer BT549 cells that hepatocyte growth factor activator inhibitor type I (HAI-1), the cognate inhibitor of matriptase, is required for the proper intracellular trafficking of the protease (Oberst et al 2005). Indeed, when expressed alone in this cell line, matriptase was retained in the endoplasmic reticulum and Golgi apparatus.…”