title: Activated protein C enhances human keratinocyte barrier integrity via sequential activation of epidermal growth factor receptor and Tie2.
abstract: Keratinocytes play a critical role in maintaining epidermal barrier function. Activated protein C (APC), a natural anticoagulant with anti-inflammatory and endothelial barrier protective properties, significantly increased the barrier impedance of keratinocyte monolayers, measured by electric cell substrate impedance sensing and FITC-dextran flux. In response to APC, Tie2, a tyrosine kinase receptor, was rapidly activated within 30 min, and relocated to cell-cell contacts. APC also increased junction proteins zona occludens, claudin-1 and VE-cadherin. Inhibition of Tie2 by its peptide inhibitor or small interfering RNA abolished the barrier protective effect of APC. Interestingly, APC did not activate Tie2 through its major ligand, angiopoietin-1, but instead acted by binding to endothelial protein C receptor, cleaving protease-activated receptor-1 and transactivating EGF receptor. Furthermore, when activation of Akt, but not ERK, was inhibited, the barrier protective effect of APC on keratinocytes was abolished. Thus, APC activates Tie2, via a mechanism requiring, in sequential order, the receptors, endothelial protein C receptor, protease-activated receptor-1, and EGF receptor, which selectively enhances the PI3K/Akt signaling to enhance junctional complexes and reduce keratinocyte permeability.
authors.affiliation: Sutton Arthritis Research Laboratories, Kolling Institute of Medical Research, University of Sydney at Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia. meilang.xue@sydney.edu.au
authors.forename: Meilang
authors.initials: M
authors.lastname: Xue
authors.forename: Shu-Oi
authors.initials: SO
authors.lastname: Chow
authors.forename: Suat
authors.initials: S
authors.lastname: Dervish
authors.forename: Yee-Ka Agnes
authors.initials: YK
authors.lastname: Chan
authors.forename: Sohel M
authors.initials: SM
authors.lastname: Julovi
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Jackson
mesh_terms: D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D007365:Intercellular Junctions / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D008297:Male; D010455:Peptides / Q000494:pharmacology; D010539:Permeability; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D011486:Protein C / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1 / Q000235:genetics / Q000378:metabolism; D042787:Receptor, TIE-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D010455:Peptides; D011486:Protein C; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1; D019869:Phosphatidylinositol 3-Kinases; C512478:EGFR protein, human; D066246:ErbB Receptors; D042787:Receptor, TIE-2; D051057:Proto-Oncogene Proteins c-akt