MAMMALIAN RASGAP RELATED GENES

哺乳动物 RASGAP 相关基因

基本信息

批准号：
2700668
负责人：
ANDRE BERNARDS
金额：
$ 24.53万
依托单位：
MASSACHUSETTS GENERAL HOSPITAL
依托单位国家：
美国
项目类别：
财政年份：
1996
资助国家：
美国
起止时间：
1996-05-24 至 2001-04-30
项目状态：
已结题

项目摘要

This project proposes to explore the biological functions of two newly discovered Ras GTPase activating protein (RasGAP)-related human proteins, called IQGAP1&2, which may play roles in human disease and which may present novel targets for therapy. Both novel proteins share extensive similarity in their C-terminal halves with the sar1/gap1 putative RasGAP from Schizosaccharomyces pombe and may be homologs of this fission yeast Ras regulator. Further implicating IQGAPs as Ras regulators, one of these proteins resembled neurofibromin in its ability to suppress the growth of a human H=Ras dependent yeast strain. In addition, it was surprising to find that both proteins harbor IQ motifs and form stable complexes with calmodulin. Since IQGAP2 is uniquely expressed in liver and hepatocyte cell line, whereas IQGAP1 mRNA levels are especially high in placenta, lung, kidney, and peripheral blood leukocytes, these proteins may thus perform novel roles as perhaps epthelial cell specific integrators of the signaling pathways mediated by Ras and Ca2+/calmodulin. However, while in vitro experiments have suggested Ras binding, in preliminary studies to stimulation of the GTPase of Ras or its immediate relatives has yet been detected, indicating either that the activities of IQGAP1&2 are tightly regulated by Ca2+/calmodulin, or that these proteins are Ras interactors without prominent GAP activity. Since the central role of Ras and its regulators in mitogenic signal transduction is reflected by a high frequency of oncogenic Ras pathway mutations, a combination biochemical, expression, cell biological and genetic studies is proposed to further explore the biological properties and potential tumor suppressor roles of these intriguing new proteins. Specifically, this project includes biochemical studies to define the potentially calimodulin-regulated GTPase modulating activities of IQGAP1&2, expression studies to determine the exact tissues and cell types in which these proteins perform their function, cell biological analyses to test whether IQGAP1&2 form transient protein complexes in stimulated cells, as is suggested by the unexpected observation of a calcium ionophore-dependent nuclear translocation, and genetic studies to explore potential tumor suppressor roles. Beyond the fact that NF1 and p120GAP are both mutated in specific cancers, the latter studies are also proposed because IQGAP1 and IQGAP2 are heterogenously expressed in lung and liver cancer cell lines, because loss-of- heterozygosity has been detected with IQGAP1 probes in lung tumors, and because the IQGAP1 gene maps to a region involved in a recurring lung adenocarcinoma chromosome translocation. In addition to providing clues to the biological functions of these intriguing new protein, these studies may also contribute to a better understanding of other RasGAPs and provide a structural basis for often suspected links between Ras and calmodulin- mediated signal transduction.

该项目旨在探索两种新的生物功能发现了 Ras GTP 酶激活蛋白 (RasGAP) 相关的人类蛋白，称为 IQGAP1&2，可能在人类疾病中发挥作用，并且可能提出新的治疗靶点。两种新型蛋白质具有广泛的共同点它们的 C 末端半部与 sar1/gap1 假定的 RasGAP 相似来自裂殖酵母，可能是这种裂殖酵母的同源物拉斯调节器。进一步暗示 IQGAP 作为 Ras 调节器，其中之一蛋白质与神经纤维蛋白相似，具有抑制神经纤维生长的能力人类 H=Ras 依赖性酵母菌株。此外，令人惊讶的是发现这两种蛋白质都带有 IQ 基序并与钙调蛋白。由于 IQGAP2 在肝脏和肝细胞中独特表达细胞系，而 IQGAP1 mRNA 水平在胎盘中特别高，肺、肾和外周血白细胞，因此这些蛋白质可能发挥新的作用，可能是上皮细胞特异性整合剂 Ras 和 Ca2+/钙调蛋白介导的信号通路。然而，当在体外实验表明 Ras 结合，初步研究 Ras 或其近亲的 GTP 酶的刺激尚未被证实。检测到，表明 IQGAP1&2 的活性紧密结合受 Ca2+/钙调蛋白调节，或者这些蛋白质是 Ras 相互作用蛋白没有显着的 GAP 活性。由于 Ras 的核心作用及其有丝分裂信号转导中的调节因子反映在高致癌 Ras 途径突变的频率，组合生化，建议进行表达、细胞生物学和遗传学研究以进一步探索其生物学特性和潜在的抑癌作用这些有趣的新蛋白质。具体来说，该项目包括确定潜在的加调蛋白调节 GTP 酶的生化研究调节 IQGAP1&2 的活性，表达研究以确定这些蛋白质在其中发挥作用的确切组织和细胞类型功能、细胞生物学分析以测试IQGAP1&2是否形成瞬态正如意想不到的结果所表明的，受刺激的细胞中存在蛋白质复合物钙离子载体依赖性核易位的观察，以及遗传学研究探索潜在的肿瘤抑制作用。超越事实上，NF1 和 p120GAP 在特定癌症中均发生突变，后者还提出了研究，因为 IQGAP1 和 IQGAP2 是异质的在肺癌和肝癌细胞系中表达，因为丢失- 已使用 IQGAP1 探针在肺部肿瘤中检测到杂合性，并且因为 IQGAP1 基因映射到涉及复发性肺部疾病的区域腺癌染色体易位。除了提供线索外这些有趣的新蛋白质的生物学功能，这些研究可能也有助于更好地理解其他 RasGAP 并提供 Ras 和钙调蛋白之间经常被怀疑的联系的结构基础 - 介导的信号转导。