Okazaki M, Kishida S, Murai H, Hinoi T, Kikuchi A
Department of Biochemistry, Hiroshima University School of Medicine, Japan.
Cancer Res. 1996 May 15;56(10):2387-92.
Ral GDP dissociation stimulator (RalGDS) and RalGDS like (RGL) are putative effector proteins of Ras and contain the Ras-interacting domain (RID) at their C-terminal regions. v-Ras is known to activate c-fos promoter/enhancer and Raf-1 and to transform NIH3T3 cells. It is also known that v-Raf activates c-fos promoter/enhancer and transforms NIH3T3 cells. In this study, we examined the effect of RID on the phenotype of the cells transformed by v-Ras and v-Raf. Overexpression of RID greatly reduced cell growth in low serum, colony-forming activity in soft agar, c-fos promoter/enhancer activity, and Raf-1 activity of v-Ras-transformed cells. However, overexpression of RID did not affect the phenotype of v-Raf-transformed cells. These results clearly indicate that RID of RGL specifically binds to Ras in mammalian cells, that it blocks the signal from Ras to Raf-1, and that it reverses v-Ras-induced malignant phenotype. It has been reported that Ras-binding domains of Raf-1 and neurofibromatosis type 1 (NF1) reverse v-Ras-induced malignant phenotype. Since there is no homology in primary structures of RGL, Raf-1, and NF1, there may be a similarity of secondary or tertiary structure among RID of RGL and Ras-binding domains of Raf-1 and NF1, and the structure might be useful for developing a potential medicine for human cancers caused by Ras.
Ral GDP解离刺激因子（RalGDS）和RalGDS样蛋白（RGL）是Ras的假定效应蛋白，在其C末端区域含有Ras相互作用结构域（RID）。已知v-Ras可激活c-fos启动子/增强子和Raf-1，并使NIH3T3细胞发生转化。还已知v-Raf可激活c-fos启动子/增强子并使NIH3T3细胞发生转化。在本研究中，我们检测了RID对v-Ras和v-Raf转化细胞表型的影响。RID的过表达显著降低了v-Ras转化细胞在低血清中的细胞生长、软琼脂中的集落形成活性、c-fos启动子/增强子活性以及Raf-1活性。然而，RID的过表达并未影响v-Raf转化细胞的表型。这些结果清楚地表明，RGL的RID在哺乳动物细胞中特异性结合Ras，阻断从Ras到Raf-1的信号，并逆转v-Ras诱导的恶性表型。据报道，Raf-1和1型神经纤维瘤病（NF1）的Ras结合结构域可逆转v-Ras诱导的恶性表型。由于RGL、Raf-1和NF1的一级结构没有同源性，RGL的RID与Raf-1和NF1的Ras结合结构域之间可能存在二级或三级结构的相似性，这种结构可能有助于开发针对由Ras引起的人类癌症的潜在药物。
