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作为一个信号传导节点，调节正常细胞的增殖、分化和存活。Ras的不同细胞作用是通过Ras调节多个功能不同的下游信号传导网络介导的，其中Raf-MEK-ERK促分裂原活化蛋白激酶（MARK）级联是最好理解的。Ras的突变激活导致持续的、失调的信号传导，其促进恶性癌细胞的异常生长和行为。因此，人们对靶向Ras信号传导以开发用于癌症治疗的新方法有相当大的兴趣和努力。特别是，目前的评价集中在Raf-MEK-ERK途径的小分子激酶抑制剂的临床评价。然而，这些努力已经复杂的事实，Ras也可以利用多种Raf-independent效应途径，以促进肿瘤发生。此外，Raf-MEK-ERK级联不是简单的线性信号传导途径，而是代表了复杂信号传导网络的核心，该网络由功能多样的信号传导分子的不断扩大的名册调节。特别是，几种支架蛋白决定了激活这种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蛋白信号转导（RGS）蛋白（RGS 12和RGS 14）的亚家族-D调节子是Ras的推定效应子，（B）RGS 12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RGS 12和RGS 14将被发现是Ras介导的肿瘤发生的重要效应物，并且RGS 12将是Raf-MEK-ERK信号传导和功能的关键调节剂。提出了四个具体目标来严格评估亚家族D 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RGS 12和RGS 14作为Ras介导的癌基因的效应物的作用，（2）确定RGS 12是否对突变体B-Raf介导的肿瘤发生至关重要，（3）确定RGS 12是否是Ras功能的内体特异性效应物，和（4）确定具有Ras-MAPK结合配偶体的RGS 12（和/或RGS 14）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.