Role of RGS proteins in Ras- and B-Raf--mediated transformation

描述（由申请人提供）：Ras 小 GTP 酶在正常细胞生理学和癌细胞异常行为中的重要性已得到充分证实。 Ras 充当调节正常细胞增殖、分化和存活的信号传导节点。 Ras 的多种细胞作用是通过 Ras 对多个功能不同的下游信号网络的调节来介导的，其中对 Raf-MEK-ERK 丝裂原激活蛋白激酶 (MARK) 级联反应最为了解。 Ras 的突变激活会导致持续的、失调的信号传导，从而促进恶性癌细胞的异常生长和行为。因此，人们对靶向 Ras 信号传导以开发新的癌症治疗方法产生了极大的兴趣和努力。目前的评估尤其集中于 Raf-MEK-ERK 通路小分子激酶抑制剂的临床评估。然而，Ras 还可以利用多个不依赖于 Raf 的效应途径来促进肿瘤发生，这一事实使这些努力变得复杂。此外，Raf-MEK-ERK级联并不是简单的线性信号通路，而是代表复杂信号网络的核心，该网络由不断扩大的功能多样的信号分子名单调节。特别是，几种支架蛋白决定激活该激酶级联的输入信号，并用于使信号输出的空间和时间性质多样化。我们最近的初步观察确定 (a) G 蛋白信号传导 (RGS) 蛋白的 D 亚家族调节因子（RGS12 和 RGS14）是 Ras 的推定效应子，并且 (b) RGS12 可能作为调节 Raf-MEK-ERK 级联的支架蛋白发挥作用。鉴于 ERK MARK 通路在肿瘤细胞生物学中的重要作用，我们假设 RGS12 和 RGS14 将被发现是 Ras 介导的肿瘤发生的重要效应器，并且 RGS12 将是 Raf-MEK-ERK 信号传导和功能的关键调节因子。提出了四个具体目标来严格评估 D 亚家族 RGS 蛋白在异常 Ras 和 Raf 信号传导和肿瘤发生中的作用，以：(1) 确定 RGS12 和 RGS14 作为 Ras 介导的癌基因效应子的作用，(2) 确定 RGS12 是否对突变 B-Raf 介导的肿瘤发生至关重要，(3) 确定 RGS12 是否是 Ras 功能的内体特异性效应子，以及 (4) 确定 RGS12 的结构RGS12（和/或 RGS14）与 Ras-MAPK 结合伴侣。

DESCRIPTION (provided by applicant): The importance of the Ras small GTPases in normal cell physiology and the aberrant behavior of cancer cells is well-established. Ras functions' as a signaling node that regulates normal cell proliferation, differentiation and survival. The diverse cellular roles of Ras are mediated through Ras regulation of multiple, functionally distinct, downstream signaling networks, with the Raf-MEK-ERK mitogen-activated protein kinase (MARK) cascade the best understood. The mutational activation of Ras results in persistent, deregulated signaling that promotes the aberrant growth and behavior of malignant cancer cells. Consequently, there is considerable interest and effort in targeting Ras signaling for the development of novel approaches for cancer treatment. In particular, current evaluation is focused on clinical evaluation of small molecule kinase inhibitors of the Raf-MEK-ERK pathway. However, these efforts have been complicated by the fact that Ras can also utilize multiple Raf-independent effector pathways to promote oncogenesis. Furthermore, the Raf-MEK-ERK cascade is not a simple linear signaling pathway, but instead, represents the core of a complex signaling network that is regulated by an ever-expanding roster of functionally diverse signaling molecules. In particular, several scaffold proteins dictate the input signals that activate this kinase cascade and serve to diversify the spatial and temporal nature of the signaling output. Our recent preliminary observations determined that (a) the subfamily-D regulators of G protein signaling (RGS) proteins (RGS12 and RGS14) are putative effectors of Ras and that (b) RGS12 may function as a scaffold protein that regulates the Raf-MEK-ERK cascade. In light of the important role of the ERK MARK pathway in neoplastic cell biology, we hypothesize that RGS12 and RGS14 will be found to be important effectors of Ras-mediated oncogenesis and that RGS12 will be a critical regulator of Raf-MEK-ERK signaling and function. Four specific aims are proposed to critically evaluate the role of subfamily D RGS proteins in aberrant Ras and Raf signaling and oncogenesis to: (1) determine the roles of RGS12 and RGS14 as effectors of Ras-mediated oncogenes, (2) determine if RGS12 is critical for mutant B-Raf-mediated oncogenesis, (3) determine if RGS12 is an endosome-specific effector of Ras function, and (4) determine the structures of RGS12 (and/or RGS14) with Ras-MAPK binding partners.