REGULATION OF THE RAS TRANSFORMATION PATHWAY

Ras癌蛋白在细胞生长和生长中起关键作用 上游蛋白酪氨酸的分化、信号转导 与核转录机制有关的蛋白酪氨酸激酶(PTK)。近年来， 在识别更多蛋白质方面已经取得了相当大的进展 它将刺激生长的信号传递到“ras途径”。然而， 现有蛋白质之间的相互作用还知之甚少，而且它 很明显，更多的调控分子仍有待确定。这个 这项建议的目标是将机制(S)描述为三个 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物)和Grb2调节RAS 活性并确定其所需的新的分子缔合 功能。 虽然PL20 GAP显然是ras功能的负调节因子，但其 作为ras信号的下游靶点和效应者的假定角色仍然存在 有争议的。我们最近获得了这样一个角色的证据，并已经 已将此属性范围缩小到包含SH3域的区域。我们 将通过隔离、删除来进一步表征该区域的作用 和突变分析，并确定可能的下游效应因子(S) 与GAP-SH3相互作用的RAS转化途径。 最新的生化和遗传学证据表明CDC25同源物 (mCDC25、mSOS1和2)作为ras功能的激活剂。然而，除了他们的 作为GTP/GDP循环的刺激因素，人们对 它们与ras蛋白相互作用的生物学后果。因此， 我们将确定这些RAS GDSS在调解正常和 致癌ras的功能，并确定是否解除对GDS活性的调控 在没有ras突变的情况下可能会引起转化。 最后，最近的研究表明，GRB-2是 将激活的受体PTKs的有丝分裂信号传递给ras，并 刺激SOS交换因素的作用。然而，我们已经获得了 初步证据表明Grb2在细胞内信号转导中的作用可能 更加复杂，可能涉及与其他蛋白质的相互作用 受体-PTKs。我们已经提议进行研究，以澄清这些额外的 Grb2的功能。 总而言之，这些研究将提供有关 RAS激活的机制，并可能识别其他组件 参与调节ras途径。

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.