Activation of H-ras61L-specific signaling pathways does not require posttranslational processing of H-ras

被引:5
作者
Hart, KC
Robertson, SC
Donoghue, DJ [1 ]
机构
[1] Univ Calif San Diego, Ctr Mol Genet, La Jolla, CA 92093 USA
[2] Univ Calif San Diego, Dept Chem & Biochem, La Jolla, CA 92093 USA
关键词
H-ras; MAPK cascade; posttranslational modifications; protein localization; signal transduction;
D O I
10.1006/excr.2000.4874
中图分类号
R73 [肿瘤学];
学科分类号
100214 ;
摘要
We have previously demonstrated that H-ras(61L) retained transforming activity when lacking C-terminal lipid modifications, provided that plasma membrane localization was restored by an N-terminal transmembrane domain. Since several ras-activated pathways contribute to the transformed phenotype, we utilized a novel set of transmembrane domain-anchored H-ras derivatives to examine if lipids are required for activation of any specific signaling pathways. We demonstrate here that H-ras(61L)-induced activation of the Rafl MEK/MAPK pathway, including recruitment of Raf to the plasma membrane and activation of Raf and MAPK, does not require C-terminal processing of H-ras(61L). Biochemical fractionation experiments confirm the localization of TM-ras derivatives to the plasma membrane, as well as the ras-mediated recruitment of c-Raf-1. Changes in the actin cytoskeleton, controlled by H-ras(61L)-mediated activation of the Rac/ Rho pathway, as well as PI 3-kinase activation, can also occur in the absence of C-terminal lipid modifications. Finally, downstream events, such as the induction of the immediate-early gene c-fos or neurite outgrowth in PC12 cells, are stimulated by the expression of plasma membrane-anchored, nonlipidated H-ras(61L) These results demonstrate that H-ras can be functionally targeted to the plasma membrane using a transmembrane domain sequence and that several signal transduction pathways downstream of H-ras can be activated without the presence of normal lipid modifications. (C) 2000 Academic Press.
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页码:89 / 100
页数:12
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