Nox1 redox signaling mediates oncogenic Ras-induced disruption of stress fibers and focal adhesions by down-regulating Rho.
Generation of reactive oxygen species (ROS) by Ras oncogene-induced NADPH oxidase (Nox) 1 is required for Ras transformation phenotypes including anchorage-independent growth, morphological transformation, and tumorigenesity, but the signaling mechanism downstream of Nox1 remains elusive. Rho is known to be a critical regulator of actin stress fiber formation. Nonetheless, Rho was reported to no longer couple to loss of actin stress fibers in Ras-transformed Swiss3T3 cells despite the elevation of Rho activity. In this study, however, we demonstrate that Rho is inactivated in K-Ras-transformed normal rat kidney cells, and that abrogation of Nox1-generated ROS by Nox1 small interference RNAs or diphenyleneiodonium restores Rho activation, suggesting that Nox1-generated oxidants mediate down-regulation of the Rho activity. This down-regulation involves oxidative inactivation of the low molecular weight protein-tyrosine phosphatase by Nox1-generated ROS and a subsequent elevation in the tyrosine-phosphorylated active form of p190RhoGAP, the direct target of the phosphatase. Furthermore, the decreased Rho activity leads to disruption of both actin stress fibers and focal adhesions in Ras-transformed cells. As for Rac1, Rac1 also appears to participate in the down-regulation of Rho via Nox1. Our discovery defines a mediating role of Nox1-redox signaling for Ras oncogene-induced actin cytoskeletal changes.
Shinohara
Masahiro
M
Department of Molecular Biology and Biochemistry, Shinshu University Graduate School of Medicine, Matsumoto, Nagano 390-8621, Japan.
Shang
Wei-Hao
WH
Kubodera
Makoto
M
Harada
Saori
S
Mitsushita
Junji
J
Kato
Masayoshi
M
Miyazaki
Hitoshi
H
Sumimoto
Hideke
H
Kamata
Tohru
T
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D003599:Cytoskeleton / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D022001:Focal Adhesions / Q000378:metabolism*; D011905:Genes, ras; D051379:Mice; D009247:NADH, NADPH Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D000074624:NADPH Oxidase 1; D010084:Oxidation-Reduction; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D022502:Stress Fibers / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D000199:Actins; C513040:Arhgap35 protein, rat; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D009247:NADH, NADPH Oxidoreductases; D000074624:NADPH Oxidase 1; C000614711:NOX1 protein, mouse; C000614712:NOX1 protein, rat; D017027:Protein Tyrosine Phosphatases; D018631:ras Proteins; D020741:rho GTP-Binding Proteins