Raf-1 regulates Rho signaling and cell migration.
Raf kinases relay signals inducing proliferation, differentiation, and survival. The Raf-1 isoform has been extensively studied as the upstream kinase linking Ras activation to the MEK/ERK module. Recently, however, genetic experiments have shown that Raf-1 plays an essential role in counteracting apoptosis, and that it does so independently of its ability to activate MEK. By conditional gene ablation, we now show that Raf-1 is required for normal wound healing in vivo and for the migration of keratinocytes and fibroblasts in vitro. Raf-1-deficient cells show a symmetric, contracted appearance, characterized by cortical actin bundles and by a disordered vimentin cytoskeleton. These defects are due to the hyperactivity and incorrect localization of the Rho-effector Rok-alpha to the plasma membrane. Raf-1 physically associates with Rok-alpha in wild-type (WT) cells, and reintroduction of either WT or kinase-dead Raf-1 in knockout fibroblasts rescues their defects in shape and migration. Thus, Raf-1 plays an essential, kinase-independent function as a spatial regulator of Rho downstream signaling during migration.
Ehrenreiter
Karin
K
Department of Microbiology and Genetics, Max F. Perutz Laboratories, University Departments at the Vienna Biocenter, 1030 Vienna, Austria.
Piazzolla
Daniela
D
Velamoor
Vanishree
V
Sobczak
Izabela
I
Small
J Victor
JV
Takeda
Junji
J
Leung
Thomas
T
Baccarini
Manuela
M
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis; D015153:Blotting, Western; D019556:COS Cells; D002448:Cell Adhesion; D002465:Cell Movement; D048430:Cell Shape; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D053569:Keratin-15; D053555:Keratin-5; D015603:Keratinocytes / Q000378:metabolism; D007633:Keratins / Q000378:metabolism; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D011233:Precipitin Tests; D011498:Protein Precursors / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D013997:Time Factors; D014945:Wound Healing; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
D053569:Keratin-15; D053555:Keratin-5; D019394:Ki-67 Antigen; C492053:Krt15 protein, mouse; D011498:Protein Precursors; C032253:involucrin; D007633:Keratins; D019908:Proto-Oncogene Proteins c-raf; D020741:rho GTP-Binding Proteins