title: Transport via the transcytotic pathway makes prostasin available as a substrate for matriptase.
abstract: The matriptase-prostasin proteolytic cascade is essential for epidermal tight junction formation and terminal epidermal differentiation. This proteolytic pathway may also be operative in a variety of other epithelia, as both matriptase and prostasin are involved in tight junction formation in epithelial monolayers. However, in polarized epithelial cells matriptase is mainly located on the basolateral plasma membrane whereas prostasin is mainly located on the apical plasma membrane. To determine how matriptase and prostasin interact, we mapped the subcellular itinerary of matriptase and prostasin in polarized colonic epithelial cells. We show that zymogen matriptase is activated on the basolateral plasma membrane where it is able to cleave relevant substrates. After activation, matriptase forms a complex with the cognate matriptase inhibitor, hepatocyte growth factor activator inhibitor (HAI)-1 and is efficiently endocytosed. The majority of prostasin is located on the apical plasma membrane albeit a minor fraction of prostasin is present on the basolateral plasma membrane. Basolateral prostasin is endocytosed and transcytosed to the apical plasma membrane where a long retention time causes an accumulation of prostasin. Furthermore, we show that prostasin on the basolateral membrane is activated before it is transcytosed. This study shows that matriptase and prostasin co-localize for a brief period of time at the basolateral plasma membrane after which prostasin is transported to the apical membrane as an active protease. This study suggests a possible explanation for how matriptase or other basolateral serine proteases activate prostasin on its way to its apical destination.
authors.affiliation: Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark.
authors.forename: Stine
authors.initials: S
authors.lastname: Friis
authors.forename: Sine
authors.initials: S
authors.lastname: Godiksen
authors.forename: Jette
authors.initials: J
authors.lastname: Bornholdt
authors.forename: Joanna
authors.initials: J
authors.lastname: Selzer-Plon
authors.forename: Hanne Borger
authors.initials: HB
authors.lastname: Rasmussen
authors.forename: Thomas H
authors.initials: TH
authors.lastname: Bugge
authors.forename: Chen-Yong
authors.initials: CY
authors.lastname: Lin
authors.forename: Lotte K
authors.initials: LK
authors.lastname: Vogel
mesh_terms: D018938:Caco-2 Cells; D002462:Cell Membrane / Q000201:enzymology*; D016764:Cell Polarity / Q000502:physiology*; D003106:Colon / Q000201:enzymology*; D004789:Enzyme Activation / Q000502:physiology; D004847:Epithelial Cells / Q000201:enzymology*; D006801:Humans; D021381:Protein Transport / Q000502:physiology; D012697:Serine Endopeptidases / Q000378:metabolism*; D000099271:Prostasin
chemical_list: D012697:Serine Endopeptidases; D000099271:Prostasin; C485596:ST14 protein, human