REGULATION OF THE RAS TRANSFORMATION PATHWAY

Ras癌蛋白在细胞生长中起关键作用， 分化，从上游蛋白酪氨酸转导信号 蛋白激酶（PTKs）与核转录机制的相互作用。近年来， 在鉴定其他蛋白质方面已经取得了相当大的进展 其将生长刺激信号传递到“RAS途径”。 然而，在这方面， 现有蛋白质之间的相互作用知之甚少， 很明显，进一步的调节分子仍有待鉴定。的 本提案的目的是描述三个国家 Ras途径的关键成员，GAP（GTP酶激活蛋白），GDS （鸟嘌呤核苷酸解离刺激剂），和GRB 2调节Ras 活性，并确定其所需的新的分子缔合， 功能 虽然pl 20 GAP明显是ras功能的负调节因子，但其 作为ras信号传导的下游靶点和效应物的推定作用仍然存在 争议我们最近获得了这种作用的证据， 将该属性缩小到包括SH 3结构域的区域。我们 将通过分离、缺失和/或缺失来进一步表征该区域的作用， 和突变分析，并鉴定推定的下游效应子， 与GAP-SH 3相互作用Ras转化途径。 最近的生物化学和遗传学证据表明， （mCDC 25、mSOS 1和2）作为ras功能的激活剂。然而，除了他们的 作为GTP/GDP周期的刺激因素，人们对GTP/GDP周期的作用知之甚少。 它们与Ras蛋白相互作用的生物学后果。因此，我们认为， 我们将确定这些ras GDS在介导正常和 癌基因ras功能，并确定是否失调的GDS活性 可能在没有ras突变的情况下引起转化。 最后，最近的研究表明，GRB-2是 将促有丝分裂信号从活化的受体PTKs传递至ras，和 激发SOS交换因子。然而，我们已经获得了 初步证据表明，GRB 2在细胞内信号传导中的作用可能 更复杂，可能涉及与蛋白质的相互作用， 受体-PTKs。 我们已建议进行研究，以澄清这些额外的 GRB 2的功能。 总之，这些研究将提供关于 Ras激活的机制，并可能识别其他组件 参与调节ras通路。

The Ras oncoproteins play a critical role in cell growth and differentiation, transducing signals from upstream protein tyrosine kinases (PTKs) to the nuclear transcriptional machinery. In recent years, considerable progress has been made in identifying additional proteins that relay growth stimulatory signals down the "ras pathway". However, interactions between existing proteins are only poorly understood, and it is clear that further regulatory molecules remain to be identified. The goal of this proposal is to characterize the mechanism(s) by which three critical members of the Ras pathway, GAP (GTPase-activating protein), GDS (guanine nucleotide dissociation stimulator), and GRB2 regulate Ras activity and to identify novel molecular associations required for their function. While pl20 GAP is clearly a negative regulator of ras function, its putative role as a downstream target and effector of ras signaling remains controversial. We have recently obtained evidence for such a role and have narrowed this property down to a region that includes the SH3 domain. We will further characterize the role of this region by isolation, deletion and mutational analysis, and identify putative downstream effector(s) of the Ras transformation pathway that interact with GAP-SH3. Recent biochemical and genetic evidence has implicated CDC25 homologs (mCDC25, mSOS1 and 2) as activators of ras function. However, beyond their function as stimulators of the GTP/GDP cycle, little is known about the biological consequences of their interaction with ras proteins. Therefore, we will establish the role of these ras GDSs in mediating normal and oncogenic ras functions, and determine whether deregulated GDS activity may cause transformation in the absence of ras mutations. Finally, recent studies have implicated GRB-2 as the critical link that transmits the mitogenic signal from activated receptor PTKs to ras, and acts to stimulate the SOS exchange factor. However, we have obtained preliminary evidence that the role of GRB2 in intracellular signaling may be more complex, and may involve interactions with proteins other than receptor-PTKs. We have proposed studies to clarify these additional functions of GRB2. Taken together, these studies will provide fundamental information on the mechanisms of Ras activation and may identify additional components involved in regulating the ras pathway.