Matriptase is a type-II transmembrane serine protease abundantly expressed in polarized epithelia. The ectodomain of matriptase is released from the cell surface. In the present study, we found that the post-translational cleavage between Gly149 and Ser150 and the existence of catalytic domain are critical for the ectodomain release of matriptase in stable transfection experiments using the polarized Madin-Darby canine kidney epithelial cell line.