title: Protein C is an autocrine growth factor for human skin keratinocytes.
abstract: The protein C (PC) pathway plays an important role in coagulation and inflammation. Many components of the PC pathway have been identified in epidermal keratinocytes, including endothelial protein C receptor (EPCR), which is the specific receptor for PC/activated PC (APC), but the core member of this pathway, PC, and its function in keratinocytes has not been defined. In this study, we reveal that PC is strongly expressed by human keratinocytes at both gene and protein levels. When endogenous PC was blocked by siRNA the proliferation of keratinocytes was significantly decreased. This inhibitory effect was restored by the addition of recombinant APC. PC siRNA treatment also increased cell apoptosis by 3-fold and inhibited cell migration by more than 20%. When keratinocytes were pretreated with RCR252, an EPCR-blocking antibody, or PD153035, an epidermal growth factor receptor (EGFR) inhibitor, cell proliferation was hindered by more than 30%. These inhibitors also completely abolished recombinant APC (10 mug/ml)-stimulated proliferation. Blocking PC expression or inhibiting its binding to EPCR/EGFR decreased the phosphorylation of ERK1/2 but increased p38 activation. Furthermore, inhibition of ERK decreased cell proliferation by approximately 30% and completely abolished the stimulatory effect of APC on proliferation. Taken together, these results indicate that keratinocyte-derived PC promotes cell survival, growth, and migration in an autocrine manner via EPCR, EGFR, and activation of ERK1/2. Our results highlight a novel role for the PC pathway in normal skin physiology and wound healing.
authors.affiliation: Sutton Research Laboratories, The University of Sydney at Royal North Shore Hospital, St Leonards, New South Wales 2065, Australia. mlxue@med.usyd.edu.au
authors.forename: Meilang
authors.initials: M
authors.lastname: Xue
authors.forename: David
authors.initials: D
authors.lastname: Campbell
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Jackson
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D019898:Autocrine Communication / Q000187:drug effects / Q000502:physiology*; D001777:Blood Coagulation / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D000074283:Endothelial Protein C Receptor; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D011486:Protein C / Q000378:metabolism* / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000074283:Endothelial Protein C Receptor; D004791:Enzyme Inhibitors; C478370:PROCR protein, human; D011486:Protein C; D011799:Quinazolines; D034741:RNA, Small Interfering; D011956:Receptors, Cell Surface; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C088860:4-((3-bromophenyl)amino)-6,7-dimethoxyquinazoline