title: Natural Endogenous Human Matriptase and Prostasin Undergo Zymogen Activation via Independent Mechanisms in an Uncoupled Manner.
abstract: The membrane-associated serine proteases matriptase and prostasin are believed to function in close partnership. Their zymogen activation has been reported to be tightly coupled, either as a matriptase-initiated proteolytic cascade or through a mutually dependent mechanism involving the formation of a reciprocal zymogen activation complex. Here we show that this putative relationship may not apply in the context of human matriptase and prostasin. First, the tightly coupled proteolytic cascade between matriptase and prostasin might not occur when modest matriptase activation is induced by sphingosine 1-phospahte in human mammary epithelial cells. Second, prostasin is not required and/or involved in matriptase autoactivation because matriptase can undergo zymogen activation in cells that do not endogenously express prostasin. Third, matriptase is not required for and/or involved in prostasin activation, since activated prostasin can be detected in cells expressing no endogenous matriptase. Finally, matriptase and prostasin both undergo zymogen activation through an apparently un-coupled mechanism in cells endogenously expressing both proteases, such as in Caco-2 cells. In these human enterocytes, matriptase is detected primarily in the zymogen form and prostasin predominantly as the activated form, either in complexes with protease inhibitors or as the free active form. The negligible levels of prostasin zymogen with high levels of matriptase zymogen suggests that the reciprocal zymogen activation complex is likely not the mechanism for matriptase zymogen activation. Furthermore, high level prostasin activation still occurs in Caco-2 variants with reduced or absent matriptase expression, indicating that matriptase is not required and/or involved in prostasin zymogen activation. Collectively, these data suggest that any functional relationship between natural endogenous human matriptase and prostasin does not occur at the level of zymogen activation.
authors.affiliation: Department of Pharmacy, Chi-Mei Medical Center, Tainan, Taiwan.
authors.forename: Hui Chen
authors.initials: HC
authors.lastname: Su
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Yan A
authors.initials: YA
authors.lastname: Liang
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Ying-Jung J
authors.initials: YJ
authors.lastname: Lai
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Yi-Lin
authors.initials: YL
authors.lastname: Chiu
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Barndt
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Frank
authors.initials: F
authors.lastname: Shiao
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.|Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Hsiang-Hua D
authors.initials: HD
authors.lastname: Chang
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Dajun D
authors.initials: DD
authors.lastname: Lu
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Nanxi
authors.initials: N
authors.lastname: Huang
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Chun-Che
authors.initials: CC
authors.lastname: Tseng
authors.affiliation: Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Jehng-Kang
authors.initials: JK
authors.lastname: Wang
authors.affiliation: Graduate Institute of Biochemistry and Molecular Biology, College of Medicine National Taiwan University, Taipei, Taiwan.
authors.forename: Ming-Shyue
authors.initials: MS
authors.lastname: Lee
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Johnson
authors.affiliation: Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Shih-Ming
authors.initials: SM
authors.lastname: Huang
authors.affiliation: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University, Washington DC, United States of America.
authors.forename: Chen-Yong
authors.initials: CY
authors.lastname: Lin
mesh_terms: D045744:Cell Line, Tumor; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D006801:Humans; D012697:Serine Endopeptidases / Q000378:metabolism*; D000099271:Prostasin
chemical_list: D004792:Enzyme Precursors; D012697:Serine Endopeptidases; D000099271:Prostasin; C485595:matriptase