RUI: Mechanism of Action of the ras p21

Ras蛋白是鸟嘌呤核苷酸结合蛋白，是细胞信号转导的中心。尽管细胞形式和突变形式的ras蛋白p21的作用机制尚未完全描述，但微量注射任何一种形式都可以引起非洲爪蟾卵母细胞进行减数分裂细胞分裂。由于已发现ras蛋白可增加多磷脂酰肌醇的周转，ras可能通过该途径的细胞内信使蛋白激酶C和肌醇1,4,5-三磷酸（IP3）起作用。由于IP3在卵母细胞和其他细胞类型中释放细胞内钙，这表明ras的至少一些作用可能是由于细胞内钙的增加。当其他实验室集中研究蛋白激酶C途径时，本实验室有间接证据表明ras蛋白可以释放细胞内钙。我们提出了实验来直接确定ras蛋白是否会增加细胞内钙，以及ras的细胞或突变形式是否会通过钙的增加诱导两种反应（减数分裂细胞分裂和细胞内pH的增加）。本研究将探讨ras蛋白的作用机制，ras蛋白在细胞膜信号转导中起重要作用。在蛙卵中微量注射ras蛋白可诱导细胞分裂。多种证据表明ras效应可能涉及细胞内游离钙水平的变化。这项研究将确定ras蛋白本身是释放细胞内储存的钙还是不直接影响细胞内钙水平。这些结果将有助于更好地理解细胞信号转导的机制。

Ras proteins are guanine nucleotide-binding proteins which are central to cellular signal transduction. Although the mechanism(s) of action of cellular and mutant forms of the ras protein p21 have not been fully described, microinjection of either form can cause Xenopus oocytes to undergo meiotic cell division. Since ras protein has been found to increase polyphosphatidylinositol turnover, ras may act through the intracellular messengers of this pathway, protein kinase C and inositol 1,4,5-trisphosphate (IP3). Since IP3 has been found to release intracellular calcium in oocytes and other cell types, this suggests that at least some actions of ras may be due to increased intracellular calcium. While other laboratories have concentrated on the protein kinase C pathway, this laboratory has indirect evidence that ras protein can release intracellular calcium. Experiments are proposed to establish directly whether ras protein increases intracellular calcium and whether the cellular or mutant forms of ras induce two responses (meiotic cell division and an increase in intracellular pH) through the calcium increase. The proposed research will examine the mechanism of action of a protein, the "ras" protein, that is important in signal transduction across the cell membrane. Microinjection of ras proteins into frog eggs induces cell division. A variety of evidence suggests that ras effects may involve changes in the level of intracellular free calcium. This research will determine whether the ras protein itself releases calcium from intracellular stores or affects intracellular calcium levels less directly. The results will contribute to a better understanding of the mechanisms of cellular signal transduction.