Ras signaling in leukemogenesis

描述（申请人提供）：Ras蛋白是细胞增殖、存活和分化的重要调节因子。Ras蛋白的异常激活，无论是通过Ras突变还是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都很常见。Ras蛋白可以与广泛的Ras效应物相互作用，这些效应物在细胞增殖和存活的控制中发挥积极或消极的作用。与质膜和其他细胞膜的不同微结构域的结合可能允许不同的Ras蛋白进入不同的Ras效应器池并产生不同的信号输出。过去，关于Ras效应物在肿瘤发生中的作用的实验室研究主要是在培养细胞中进行的。即使在这些实验中，不同细胞类型的细胞转化也显示需要不同的Ras效应器。白血病的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，还涉及这些细胞与体内其他环境的相互作用。这一建议的总体假设是，体内由致癌Ras引起的白血病发生可能涉及独特的Ras信号网络。我们之前使用改进的小鼠骨髓转导和移植模型检测了致癌N-Ras的致白血病性，发现致癌N-Ras有效地诱导小鼠骨髓增生性疾病和急性骨髓性白血病样疾病。我们将使用该小鼠模型，通过检查各种翻译后修饰和Ras效应物在N-Ras白血病发生中的作用来验证上述假设。本提案的具体目标是：1。通过对致癌N-Ras修饰位点的突变分析，以及分析具有条件敲除Reel或Icmt等位基因（分别编码Ras转化酶和异戊酰半胱氨酸羧甲基转移酶的基因）的小鼠的N-Ras白血病发生情况，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化方法，利用致癌N-Ras的效应域突变体，以及Ras的各种效应体的激活和抑制形式，确定Ras的下游效应体在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，从而允许对涉及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.