Ras signaling in leukemogenesis

描述（由申请人提供）：Ras蛋白是细胞增殖、存活和分化的关键调节因子。Ras蛋白的异常激活，无论是通过Ras突变或通过改变直接或间接调节Ras的基因，在实体瘤和血液恶性肿瘤中很常见。Ras蛋白可以与广泛的Ras效应物相互作用，这些Ras效应物在控制细胞增殖和存活中发挥积极或消极的作用。与质膜以及其他内部细胞膜的不同微结构域的缔合可以允许不同的Ras蛋白进入不同的Ras效应物库并产生不同的信号输出。在过去，Ras效应子在肿瘤发生中的作用的实验室研究主要在培养细胞中进行。即使在这些试验中，不同细胞类型的细胞转化也显示需要不同的Ras效应物。白血病发生是一个复杂的过程，不仅涉及靶细胞内致癌突变的影响，还涉及此类细胞与体内环境其余部分的相互作用。该建议的总体假设是，致癌Ras在体内白血病的发生可能涉及独特的Ras信号网络。我们先前已经研究了使用改进的小鼠骨髓转导和移植模型的致癌N-Ras的致白血病性，并发现致癌N-Ras有效地诱导小鼠骨髓增生性疾病和急性髓性白血病样疾病。我们将使用这种小鼠模型来测试上述假设，通过检查的作用，各种翻译后修饰和效应的Ras在N-Ras白血病。该提案的具体目标是：1.通过致癌N-Ras修饰位点的突变分析，以及通过分析Reel或Icmt（分别编码Ras转化酶和异戊二烯半胱氨酸羧基甲基转移酶的基因）条件性敲除等位基因小鼠中的N-Ras白血病发生，确定N-Ras翻译后修饰在白血病发生中的作用。2.通过结合生物学和生物化学方法，使用致癌N-Ras的效应子结构域突变体以及Ras的各种效应子的激活和抑制形式，确定Ras下游效应子在N-Ras白血病发生中的作用。这些研究的最终目标是确定Ras白血病发生中的关键分子事件，从而对涉及Ras的白血病进行治疗干预。

DESCRIPTION (provided by applicant): Ras proteins are crucial regulators of cell proliferation, survival and differentiation. Aberrant activation of Ras proteins, either by Ras mutations or by altering genes that directly or indirectly regulate Ras, is common in both solid tumors and hematologic malignancies. Ras proteins can interact with a wide spectrum of Ras effectors that play either positive or negative roles in the control of cell proliferation and survival. The association with different microdomains of the plasma membrane as well as other internal cell membranes may allow different Ras proteins to access to different pools of Ras effectors and to generate distinct signal outputs. In the past, laboratory studies of the roles of Ras effectors in oncogenesis have been performed mostly in cultured cells. And even in these assays, cellular transformation of different cell types was shown to require different Ras effectors. Leukemogenesis is a complex process that not only involves the effects of oncogenic mutation(s) within the target cells, but interactions of such cells with the rest of the in vivo environment. The overall hypothesis of this proposal is that the in vivo leukemogenesis by oncogenic Ras may involve unique Ras signaling networks. We have previously examined the leukemogenicity of oncogenic N-Ras using an improved mouse bone marrow transduction and transplantation model and found that oncogenic N-Ras efficiently induced myeloproliferative disorder and acute myelogenous leukemia-like disease in mice. We will use this mouse model to test the hypothesis stated above by examining the roles of various post-translational modifications and effectors of Ras in N-Ras leukemogenesis. The specific aims for this proposal are: 1. To determine the roles of post-translational modifications of N-Ras in leukemogenesis by a mutational analysis of the modification sites of oncogenic N-Ras, as well as by analyzing N-Ras leukemogenesis in mice with conditional knockout alleles of Reel or Icmt (genes encoding the Ras converting enzyme and isoprenylcysteine carboxyl methyltransferase, respectively). 2. To determine the roles of downstream effectors of Ras in N-Ras leukemogenesis by a combination of biological and biochemical approaches, using effector domain mutants of the oncogenic N-Ras, as well as activated and inhibitory forms of various effectors of Ras. The ultimate goal of these studies is to identify critical molecular events in Ras leukemogenesis, allowing therapeutic interventions of leukemias involving Ras.