title: A+-helix of protein C inhibitor (PCI) is a cell-penetrating peptide that mediates cell membrane permeation of PCI.
abstract: Protein C inhibitor (PCI) is a serpin with broad protease reactivity. It binds glycosaminoglycans and certain phospholipids that can modulate its inhibitory activity. PCI can penetrate through cellular membranes via binding to phosphatidylethanolamine. The exact mechanism of PCI internalization and the intracellular role of the serpin are not well understood. Here we showed that testisin, a glycosylphosphatidylinositol-anchored serine protease, cleaved human PCI and mouse PCI (mPCI) at their reactive sites as well as at sites close to their N terminus. This cleavage was observed not only with testisin in solution but also with cell membrane-anchored testisin on U937 cells. The cleavage close to the N terminus released peptides rich in basic amino acids. Synthetic peptides corresponding to the released peptides of human PCI (His(1)-Arg(11)) and mPCI (Arg(1)-Ala(18)) functioned as cell-penetrating peptides. Because intact mPCI but not testisin-cleaved mPCI was internalized by Jurkat T cells, a truncated mPCI mimicking testisin-cleaved mPCI was created. The truncated mPCI lacking 18 amino acids at the N terminus was not taken up by Jurkat T cells. Therefore our model suggests that testisin or other proteases could regulate the internalization of PCI by removing its N terminus. This may represent one of the mechanisms regulating the intracellular functions of PCI.
authors.affiliation: From the Center of Physiology and Pharmacology, Department of Vascular Biology and Thrombosis Research, Medical University of Vienna, A-1090 Vienna, Austria and.
authors.forename: Hanjiang
authors.initials: H
authors.lastname: Yang
authors.affiliation: From the Center of Physiology and Pharmacology, Department of Vascular Biology and Thrombosis Research, Medical University of Vienna, A-1090 Vienna, Austria and.
authors.forename: Felix Christof
authors.initials: FC
authors.lastname: Wahlmüller
authors.affiliation: Biocenter, Division of Clinical Biochemistry, Innsbruck Medical University, A-6020 Innsbruck, Austria.
authors.forename: Bettina
authors.initials: B
authors.lastname: Sarg
authors.affiliation: From the Center of Physiology and Pharmacology, Department of Vascular Biology and Thrombosis Research, Medical University of Vienna, A-1090 Vienna, Austria and.
authors.forename: Margareta
authors.initials: M
authors.lastname: Furtmüller
authors.affiliation: From the Center of Physiology and Pharmacology, Department of Vascular Biology and Thrombosis Research, Medical University of Vienna, A-1090 Vienna, Austria and margarethe.geiger@meduniwien.ac.at.
authors.forename: Margarethe
authors.initials: M
authors.lastname: Geiger
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002463:Cell Membrane Permeability / Q000502:physiology; D057846:Cell-Penetrating Peptides / Q000737:chemistry* / Q000378:metabolism*; D058851:GPI-Linked Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D018046:Protein C Inhibitor / Q000737:chemistry* / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000378:metabolism; D020298:U937 Cells
chemical_list: D057846:Cell-Penetrating Peptides; D058851:GPI-Linked Proteins; D018046:Protein C Inhibitor; C120203:PRSS21 protein, human; D012697:Serine Endopeptidases
keywords: Cell Permeabilization; Cell-penetrating Peptide (CPP); Nuclear Translocation; Peptides; Protein C Inhibitor; Serpin; Testisin