Epithelial Integrity Is Maintained by a Matriptase-Dependent Proteolytic Pathway

Abstract

A pericellular proteolytic pathway initiated by the transmembrane serine protease matriptase plays a critical role in the terminal differentiation of epidermal tissues. Matriptase is constitutively expressed in multiple other epithelia, suggesting a putative role of this membrane serine protease in general epithelial homeostasis. Here we generated mice with conditional deletion of the St14 gene, encoding matriptase, and show that matriptase indeed is essential for the maintenance of multiple types of epithelia in the mouse. Thus, embryonic or postnatal ablation of St14 in epithelial tissues of diverse origin and function caused severe organ dysfunction, which was often associated with increased permeability, loss of tight junction function, mislocation of tight junction-associated proteins, and generalized epithelial demise. The study reveals that the homeostasis of multiple simple and stratified epithelia is matriptase-dependent, and provides an important animal model for the exploration of this membrane serine protease in a range of physiological and pathological processes.

Membrane-Bound Serine Protease Inhibitor HAI-1 Is Required for Maintenance of Intestinal Epithelial Integrity

“…Immunofluorescence analysis of the tight junction-associated proteins, ZO-1 and occludin, revealed irregular expression patterns in HAI-1/ SPINT1-deficient epithelium compared with control epithelium from upper large intestine and showed foci absences and/or decreased staining intensity ( Figure 5B). Because these observations were similar to those reported for intestinal matriptase-deficient mice, 17 we then examined the expression pattern of matriptase in the mucosa showing enhanced permeability. Interestingly, the basolateral surface localization of matriptase in colonic epithelial cells became oblique in the HAI-1/SPINT1-deficient cells, showing a rather diffuse cytoplasmic staining pattern ( Figure 5C).…”

“…16 Recently, a trypsin-like transmembrane serine protease, matriptase, has emerged as an important molecule that is required for the homeostasis of multiple simple and stratified epithelia, including intestinal epithelium. 17,21 This study provides evidence that the membrane-bound serine protease inhibitor HAI-1/SPINT1 is also required to maintain epithelial integrity in intestinal tissue. Indeed, matriptase is a well-known cognate protease of HAI-1/SPINT1, and the activity of matriptase is tightly regulated by this membrane-bound inhibitor.…”

“…17 Briefly, 250 g/g body weight of fluorescein isothiocyanate (FITC)-dextran (4 kDa; Sigma-Aldrich) was administrated by gavage to 12-week-old Spint1 LoxP/LoxP /Villin-Cre ϩ/0 and control Spint1 LoxP/LoxP /Villin-Cre 0 mice. One, 3, or 6 hours after administration of FITC-dextran, the blood samples were obtained from the right ventricle, and EDTA-containing plasma samples were collected by centrifugation at 960 ϫ g for 20 minutes at 4°C.…”

“…After oral administration of FITC-dextran, tissue fluorescence was easily detected in the upper large intestine of HAI-1/SPINT1-deficient mice but not in control mice, indicating enhanced permeability in the absence of HAI-1/SPINT1 ( Figure 5A). Although this tracer permeates the intestinal barrier by paracellular diffusion, 17 fluorescence was also observed within apical cells. However, the enhanced tissue fluorescence was not observed in the small intestine and was weak in the distal aspect of the colon (data not shown).…”

“…16 Although HAI-1/SPINT1 is strongly expressed by intestinal epithelial cells, its function in the intestinal epithelium is not known. On the other hand, a recent study showed that matriptase, one of the most important target proteases of HAI-1/SPINT1, is critical for maintaining epithelial integrity 17 ; thus, HAI-1/ SPINT1 may also have an important role in sustaining intestinal epithelium integrity. Because ablation of the Spint1 gene in mice results in embryonic lethality due to impaired placental development, we rescued placental development in HAI-1/SPINT1 knockout mice to study the functions of HAI-1/SPINT1 in viable mice.…”