Nox1 redox signaling mediates oncogenic Ras-induced disruption of stress fibers and focal adhesions by down-regulating Rho
Nox1 redox signaling mediates oncogenic Ras-induced disruption of stress fibers and focal adhesions by down-regulating Rho
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DOI：
10.1074/jbc.m609450200
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发表时间：
2007-06-15
影响因子：
4.8
通讯作者：
Kamata, Tohru
中科院分区：
文献类型：
--
作者：
Shinohara, Masahiro;Shang, Wei-Hao;Kamata, Tohru
Ras 癌基因诱导的 NADPH 氧化酶 (Nox) 1 产生活性氧 (ROS) 是 Ras 转化表型（包括贴壁依赖性生长、形态转化和肿瘤发生）所必需的，但 Nox1 下游的信号传导机制仍不清楚。众所周知，Rho 是肌动蛋白应力纤维形成的关键调节因子。尽管如此，据报道，尽管 Rho 活性升高，但在 Ras 转化的 Swiss3T3 细胞中，Rho 不再与肌动蛋白应力纤维的损失偶联。然而，在这项研究中，我们证明 Rho 在 K-Ras 转化的正常大鼠肾细胞中失活，并且 Nox1 小干扰 RNA 或二亚苯基碘消除 Nox1 产生的 ROS 可恢复 Rho 激活，表明 Nox1 产生的氧化剂介导 Rho 活性的下调。这种下调涉及 Nox1 产生的 ROS 对低分子量蛋白酪氨酸磷酸酶的氧化失活，以及随后磷酸酶直接靶点 p190RhoGAP 酪氨酸磷酸化活性形式的升高。此外，Rho 活性降低会导致 Ras 转化细胞中肌动蛋白应力纤维和粘着斑的破坏。至于 Rac1，Rac1 似乎也通过 Nox1 参与 Rho 的下调。我们的发现定义了 Nox1-氧化还原信号在 Ras 癌基因诱导的肌动蛋白细胞骨架变化中的介导作用。
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.