RAPLB AS AN EFFECTOR OF CAMP MEDIATED MITOGENIC ACTION

大量证据表明cAMP是细胞的调节器 并提示cAMP可能是一种 可能成为新的治疗途径的目标。然而，具体的 调节cAMP效应的效应器/S仍然难以捉摸。这个 识别这些效应器将允许将目标对准 专门用于开发改良药物的分会。 Rap1最初是RAS超家族G蛋白的成员 被分离为RAS回复克隆。坚固的结构性和 与RAS癌基因的生化相似性结合 新的观察表明，Rap1蛋白也可能在 对控制细胞生长有积极作用，并在 恶变的过程。第一，提升营地 试剂将Rap1b转化为其活性GTP结合构象， 提供了RAP1是下游效应器的生化证据 去露营。第二，在模型系统中Rap1b的表达升高 在cAMP是有丝分裂原的地方会导致增殖增强，有迹象表明 恶变。最后，结节性硬化症(人类 遗传性综合征，其特征是肿瘤的发展 组织的多样性)最近与 Tuberin，一种显示Rap1-GAP活性的蛋白质，可能 导致这些肿瘤中RAP1的结构性激活。 总之，这些观察结果促使我们的研究确定了 Rap1b作为cAMP作用于细胞生长的效应因子，并 确定其功能失调是否与恶性肿瘤有关 转型。这项建议的具体目的是：(一) 确定Rap1b的促有丝分裂作用是否在cAMP下游，2) 评价Rap1b磷酸化在其有丝分裂中的作用 活性，3)将RGL2表征为潜在的效应因子 Raplb/cAMP促有丝分裂作用，以及4)确定Rap1b是否能够 去调节cAMP反应细胞系中的细胞生长。《长河》 这项研究的学期目标将是描述新的 研究发现Rap1b是细胞的正效应因子 扩散，强调其作为阵营执行者的作用-- 介导的有丝分裂反应。

Extensive evidence implicates cAMP as a modulator of cell proliferation in mammalian cells and suggests that cAMP could be a potential target for new therapeutic avenues. However, the specific effector/s that mediate the effects of cAMP remain elusive. The identification of these effectors would allow targeting this specific branch for the development of improved drugs. Rap1 is a member of the Ras superfamily of G-proteins originally isolated as a Ras-revertant clone. The strong structural and biochemical similarities with the Ras oncogene in combination with new observations indicate that Rap1 proteins might also exert positive effects on the control of cell growth, and collaborate in the process of malignant transformation. First, cAMP-elevating agents convert Rap1b into its active GTPbound conformation, providing biochemical evidence that Rap1 is a downstream effector for cAMP. Second, elevated expression of Rap1b in model systems where cAMP is mitogenic causes enhanced proliferation with signs of malignant transformation. Finally, tuberous sclerosis (a human genetic syndrome characterized by the development of tumors in a variety of tissues) was recently associated with the loss of tuberin, a protein that showed Rap1-GAP activity, potentially leading to constitutive activation of Rap1 in those tumors. Altogether, these observations have prompted our studies to define Rap1b as an effector of cAMP actions on cell growth, and to determine if its deregulated function is associated with malignant transformation. The specific aims of this proposal are (I) To determine if Rap1b's mitogenic effects are downstream of cAMP, 2) To assess the involvement of Rap1b phosphorylation on its mitogenic activity, 3) To characterize RGL2 as a potential effector for Raplb/cAMP mitogenic action, and 4) To determine if Rap1b is able to deregulate cell growth in cAMP responsive cell lines. The long term goal of this research will be to characterize the newly identified Rap1b function as a positive effector of cell proliferation, emphasizing its role as an effector of the cAMP- mediated mitogenic response.