Regulated and constitutive activity by CDC25Mm (GRF), a Ras-specific exchange factor
Regulated and constitutive activity by CDC25Mm (GRF), a Ras-specific exchange factor
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由 Ras 特异性交换因子 CDC25Mm (GRF) 调节和组成的活性
DOI：
10.1128/mcb.13.12.7718-7724.1993
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发表时间：
1993
影响因子：
5.3
通讯作者：
D. Lowy
中科院分区：
文献类型：
--
作者：
H. Cen;A. Papageorge;W. Vass;K. Zhang;D. Lowy
血清刺激细胞增加其活性GTP结合状态的Ras蛋白的比例。我们最近从一个哺乳动物基因中鉴定了四种类型（I至IV）的全长cDNA，称为CDC 25 Mm或GRF，其与S.啤酒。最大的cDNA（IV型）是脑特异性的，其他三类虽然具有不同的5'末端，但基本上代表该cDNA的进行性N-末端缺失。当置于逆转录病毒表达载体中时，所有四种类型的cDNA均诱导NIH 3 T3细胞的形态转化和GTP. Ras基础水平的增加。这些转化体的血清刺激导致GTP.Ras仅在表达IV型cDNA的细胞中进一步增加。GRF蛋白存在于胞浆和胞膜组分中，且各组分中的GRF蛋白在体外均能刺激GDP.Ras释放鸟嘌呤核苷酸。当NIH 3 T3细胞和表达IV型蛋白的细胞用两种形式的突变型ras基因转染时，一种编码膜相关Ras蛋白，另一种编码胞质Ras蛋白，与两种形式的突变型Ras蛋白结合的GTP的基础水平在表达IV型蛋白的细胞中显著更高。然而，血清增加了GTP结合到NIH 3 T3细胞和表达IV型蛋白的细胞中的膜相关突变型Ras蛋白的水平，但在表达Ras蛋白的胞质版本的细胞中不增加。我们的结论是，每种类型的CDC 25 Mm诱导细胞转化的能力，其C端刺激鸟嘌呤核苷酸交换Ras，N-端序列的存在与血清依赖性的变化在GTP.Ras，和血清依赖性增加GTP.Ras通过外源性CDC 25 Mm或内源性交换因子可能需要膜协会的Ras和交换因子。
Serum stimulates cells to increase their proportion of Ras protein in the active GTP-bound state. We have recently identified four types (I to IV) of apparently full-length cDNAs from a single mammalian gene, called CDC25Mm or GRF, which is homologous to the Ras-specific exchange factor CDC25 of S. cerevisiae. The largest cDNA (type IV) is brain specific, with the other three classes, although they have distinct 5' ends, essentially representing progressive N-terminal deletions of this cDNA. When placed in a retroviral expression vector, all four types of cDNAs induced morphologic transformation of NIH 3T3 cells and an increase in the basal level of GTP.Ras. Serum stimulation of these transformants lead to a further increase in GTP.Ras only in cells expressing the type IV cDNA. Each type of GRF protein was found in cytosolic and membrane fractions, and the protein in each fraction could stimulate guanine nucleotide release from GDP.Ras in vitro. When NIH 3T3 cells and cells expressing the type IV protein were transfected with two versions of a mutant ras gene, one encoding membrane-associated Ras protein and the other encoding a cytosolic Ras protein, the basal levels of GTP bound to both forms of the mutant Ras protein were significantly higher in the cells expressing the type IV protein. However, serum increased the level of GTP bound to the membrane-associated mutant Ras protein in NIH 3T3 cells and in cells expressing the type IV protein but not in cells expressing the cytosolic version of the Ras protein. We conclude that each type of CDC25Mm induces cell transformation via the ability of its C terminus to stimulate guanine nucleotide exchange on Ras, the presence of N-terminal sequences is associated with a serum-dependent change in GTP.Ras, and the serum-dependent increase in GTP.Ras by exogenous CDC25Mm or by endogenous exchange factors probably requires membrane association of both Ras and the exchange factor.