Ras-induced spreading and wound closure in human epidermal keratinocytes.
Although it is known that growth factor signaling cascades are active during epithelial wound healing, signals that regulate reepithelialization after wounding are not very well characterized. The small GTP binding protein Ras is a molecular switch involved in the regulation of signals originating from different growth factor receptors. We have investigated consequences of its activation in primary human keratinocytes. We provide evidence that activation of Ras can lead to shape changes of keratinocytes caused by rearrangements of the actin cytoskeleton that result in membrane protrusion and ruffling. Similar shape changes were found in the migrating tip of newly formed epithelium in mouse wounds. These cytoskeletal changes occur independently of keratinocyte terminal differentiation, and they can determine the speed of wound epithelialization in vitro. Using various mutant constructs and specific pharmacological inhibitors, we found that the effects of activated Ras on the cytoskeleton of keratinocytes are mediated by a phosphatidylinositol 3 kinase-independent activation of Rac. Our results suggest that growth factor-induced, Ras-mediated changes of keratinocyte shape may be an important mechanism that determines the speed of wound epithelialization.
Tscharntke
Michael
M
Department Dermatology, University of Cologne and Centre for Molecular Medicine, University of Cologne (CMMC), Cologne, Germany.
Pofahl
Ruth
R
Krieg
Thomas
T
Haase
Ingo
I
D000199:Actins / Q000737:chemistry; D000818:Animals; D015153:Blotting, Western; D002448:Cell Adhesion; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism; D004789:Enzyme Activation; D000078404:Epidermal Cells; D004848:Epithelium / Q000473:pathology; D005434:Flow Cytometry; D006133:Growth Substances / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000737:chemistry; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D018715:Microscopy, Video; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D012190:Retroviridae / Q000235:genetics; D015398:Signal Transduction; D014162:Transfection; D014945:Wound Healing; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
D000199:Actins; D006133:Growth Substances; D019384:Nucleic Acid Synthesis Inhibitors; D015638:Cytochalasin D; D006160:Guanosine Triphosphate; D019869:Phosphatidylinositol 3-Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020830:rac1 GTP-Binding Protein; D018631:ras Proteins