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

描述（由申请人提供）：Ras小gtpase在正常细胞生理和癌细胞异常行为中的重要性是公认的。Ras是调节正常细胞增殖、分化和存活的信号节点。Ras的多种细胞作用是通过Ras调节多种功能不同的下游信号网络介导的，其中Raf-MEK-ERK丝裂原活化蛋白激酶（MARK）级联最为清楚。Ras的突变激活导致持续的、不受控制的信号传导，促进恶性癌细胞的异常生长和行为。因此，有相当大的兴趣和努力，以Ras信号为目标，开发新的癌症治疗方法。特别是，目前的评估主要集中在Raf-MEK-ERK途径的小分子激酶抑制剂的临床评估上。然而，Ras也可以利用多种与raf无关的效应通路来促进肿瘤发生，这一事实使这些努力变得复杂。此外，Raf-MEK-ERK级联不是一个简单的线性信号通路，而是一个复杂信号网络的核心，该网络由不断扩大的功能多样化的信号分子调节。特别是，一些支架蛋白决定了激活这种激酶级联的输入信号，并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（RGS）蛋白的亚家族d调节因子（RGS12和RGS14）是Ras的推测效应因子，(b) RGS12可能作为支架蛋白调节Raf-MEK-ERK级联。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因子，RGS12将是Raf-MEK-ERK信号传导和功能的关键调节因子。为了严格评估RGS亚家族D蛋白在异常Ras和Raf信号传导和肿瘤发生中的作用，提出了四个特定的目标：(1)确定RGS12和RGS14作为Ras介导的癌基因效应器的作用，(2)确定RGS12是否对突变的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器，以及(4)确定RGS12（和/或RGS14）与Ras- mapk结合伙伴的结构。

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.