MITOGEN-ACTIVATED PROTEIN KINASES--REGULATION BY CAMP

自从发现cAMP(CAMP)作为重要的第二信使以来 Sutherland和他的同事们发现，其受体蛋白 CAMP依赖的蛋白激酶(PKA)已被广泛研究。一个 重要的早期发现是环状AMP抑制了许多 细胞类型，包括由ras等癌基因转化的细胞类型。尽管 这一众所周知的观察结果，对这种现象仍然知之甚少 这一天。更复杂的分析是，cAMP在某些情况下可能是有丝分裂的 细胞，这种增殖作用的机制尚不清楚。最近，它 研究发现，cAMP可以阻止一种主要的RAS依赖的激活， 生长因子刺激的蛋白激酶级联信号通路称为MAP激酶 路径。这一发现详细描述了第一个生理学的例子 抑制RAS信号，并提出了至少一种解释 CAMP对细胞增殖的影响。然而，实现这一目标的手段 已经实现，并且这种调节对细胞生长的影响仍然存在 有待澄清。这项建议的目标是确定 PKA抑制MAPK通路的机制及对其的认识 与细胞增殖调控的相关性。 我们将重点关注地图中特定组件的监管 激酶级联，尤其是PKA对Raf激酶的影响 监管。RAF是PKA的直接目标，还是其他方面 目前所涉及的监管活动，问题是 有争议。我们将研究可能调节Raf-2的PKA底物。 依赖的、生长因子刺激的信号以及是否具有特异性 PKA的本地化影响Raf的调节。最后，我们会 试图在MAPK信号的拮抗性和 CAMP抑制细胞生长。这项提议的具体目的是 目的：(1)确定PKA调节Raf活性的机制，(2) 确定参与生长因子信号转导的PKA靶点，(3)调查 PKA同工酶和定位的PKA活性在对照中的重要性 以及(4)确定抑制MAPK的后果 PKA对细胞增殖的信号转导。 这项研究的目的是为了更好地了解 细胞增殖是由癌基因或有丝分裂原刺激的，具有 特别强调抑制这一过程的信号。最近的 发现cAMP抑制了MAP级联的激活 许多新的可能性，这项研究无疑将有助于 我们对不同类型的信号(如荷尔蒙， 异三聚体G蛋白、生长因子等)可以修改法线和 病理性生长状态。

Since the discovery of cyclic AMP (cAMP) as an essential second messenger by Sutherland and colleagues, the actions of its receptor protein, the cAMP-dependent protein kinase (PKA) have been extensively studied. An important early finding was that cyclic AMP inhibited the growth of many cell types, including those transformed by oncogenes such as Ras. Despite this well known observation, this phenomena remains poorly understood to this day. To further complicate analysis, cAMP can be mitogenic in some cells, the mechanism of this proliferative action is unknown. Recently, it was found that cAMP could prevent the activation of a major Ras-dependent, growth factor-stimulated protein kinase cascade known as the MAP kinase pathway. This finding detailed the first physiological example of inhibition of Ras signaling and suggested at least one explanation for the effects of cAMP on cell proliferation. However, the means by which this is achieved and the implications for this regulation on cell growth remains to be elucidated. The objective of this proposal is to determine the mechanism by which PKA inhibits the MAPK pathway and to understand its relevance to the regulation of cell proliferation. We will focus on the regulation of specific components within the MAP kinase cascade and in particular, the effects of PKA on Raf kinase regulation. Whether Raf is the direct target of PKA, or if other aspects of the regulation of activity are involved is at present, a matter of controversy. We will investigate PKA substrates that may regulate Raf- dependent, growth factor-stimulated signals and whether the specificity and localization of PKA influences Raf regulation. Finally, we will attempt to establish a link between the antagonism of MAPK signaling and inhibition of cell growth by cAMP. The specific aims of this proposal are to: (1) determine the mechanism by which PKA regulates Raf activity, (2) identify PKA targets involved in growth factor signaling, (3) investigate the importance of PKA isozymes and localized PKA activity in the control of MAPK signaling, and (4) determine the consequence of inhibiting MAPK signaling by PKA on cell proliferation. The objective of this research is to gain a better understanding of how cell proliferation is stimulated by oncogenes or by mitogens, with a particular emphasis on the signals that inhibit this process. The recent finding that cAMP inhibits the activation of the MAP cascade has opened up many new possibilities and this research will undoubtedly contribute to our knowledge of how diverse types of signals (e.g. hormone, heterotrimeric G protein, growth factor etc.) can modify normal and pathologic growth states.