title: Selective Inhibition of Prostasin in Human Enterocytes by the Integral Membrane Kunitz-Type Serine Protease Inhibitor HAI-2.
abstract: Mutations of hepatocyte growth factor activator inhibitor (HAI)-2 in humans cause sodium loss in the gastrointestinal (GI) tract in patients with syndromic congenital sodium diarrhea (SCSD). Aberrant regulation of HAI-2 target protease(s) was proposed as the cause of the disease. Here functional linkage of HAI-2 with two membrane-associated serine proteases, matriptase and prostasin was analyzed in Caco-2 cells and the human GI tract. Immunodepletion-immunoblot analysis showed that significant proportion of HAI-2 is in complex with activated prostasin but not matriptase. Unexpectedly, prostasin is expressed predominantly in activated forms and was also detected in complex with HAI-1, a Kunitz inhibitor highly related to HAI-2. Immunohistochemistry showed a similar tissue distribution of prostasin and HAI-2 immunoreactivity with the most intense labeling near the brush borders of villus epithelial cells. In contrast, matriptase was detected primarily at the lateral plasma membrane, where HAI-1 was also detected. The tissue distribution profiles of immunoreactivity against these proteins, when paired with the species detected suggests that prostasin is under tight control by both HAI-1 and HAI-2 and matriptase by HAI-1 in human enterocytes. Furthermore, HAI-1 is a general inhibitor of prostasin in a variety of epithelial cells. In contrast, HAI-2 was not found to be a significant inhibitor for prostasin in mammary epithelial cells or keratinocytes. The high levels of constitutive prostasin zymogen activation and the selective prostasin inhibition by HAI-2 in enterocytes suggest that dysregulated prostasin proteolysis may be particularly important in the GI tract when HAI-2 function is lost and/or dysregulated.
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: College of Medicine, National Defense Medical Center, Taipei, Taiwan.
authors.forename: Li-Ching O
authors.initials: LO
authors.lastname: Liu
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: 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: Robert J
authors.initials: RJ
authors.lastname: Barndt
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: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington DC, United States of America.|Department of Gastroenterology, Henan Provincial People's Hospital, Zhengzhou, China.
authors.forename: Bailing
authors.initials: B
authors.lastname: Jia
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: Lombardi Comprehensive Cancer Center, Department of Oncology Georgetown University Washington DC, United States of America.
authors.forename: Chen-Yong
authors.identifier: http://orcid.org/0000-0002-6391-2571
authors.initials: CY
authors.lastname: Lin
mesh_terms: D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism*; D020895:Enterocytes / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism*; D000099271:Prostasin
chemical_list: D008562:Membrane Glycoproteins; D012697:Serine Endopeptidases; D000099271:Prostasin; C109148:SPINT2 protein, human; C485595:matriptase