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.

该项目建议探索两个新的生物学功能发现RAS GTPase激活蛋白（RasGAP）相关的人蛋白，称为IQGAP1和2，它可能在人类疾病中扮演角色，并且可能目前的治疗目标。两种新型蛋白质都有广泛的 C末端与SAR1/GAP1推定的RasGap的相似性来自schizosaccharomyces pombe，可能是这种裂变酵母的同源物 RAS调节器。进一步将IQGAP作为RAS调节器，其中之一蛋白质类似于神经纤维蛋白抑制其生长的能力人H =依赖性酵母菌菌株。此外，令人惊讶的是发现两种蛋白质都含有智商基序，并与钙调蛋白。由于IQGAP2在肝脏和肝细胞中唯一表达细胞系，而IQGAP1 mRNA水平在胎盘中特别高，肺，肾脏和外周血白细胞，这些蛋白可能因此作为遗传细胞特有的集成剂，发挥新颖的作用由RAS和Ca2+/钙调蛋白介导的信号通路。但是，在体外实验提示了RAS结合，在初步研究中刺激RAS或其直接亲戚的GTPase尚未检测到，表明IQGAP1和2的活动紧密由Ca2+/钙调蛋白调节，或者这些蛋白质是RAS相互作用者没有突出的差距活动。由于Ras及其的核心作用有丝分裂信号转导的调节剂反映致癌性RAS途径突变的频率，一种结合生化的频率提出了表达，细胞生物学和遗传研究以进一步探索生物学特性和潜在的肿瘤抑制作用这些有趣的新蛋白质。具体来说，这个项目包括生化研究以定义潜在的Calimodulin调节的GTPase 调节IQGAP1和2的活动，表达研究以确定这些蛋白质执行的精确组织和细胞类型功能，细胞生物学分析以测试IQGAP1和2是否形成瞬态刺激细胞中的蛋白质复合物，正如出乎意料的观察钙离子团依赖性核易位，并观察到探索潜在的肿瘤抑制作用的遗传研究。超越 NF1和P120GAP都在特定的癌症中突变的事实，后者还提出了研究，因为IQGAP1和IQGAP2是异质的在肺和肝癌细胞系中表达，因为在肺肿瘤中使用IQGAP1探针检测到杂合性，并且因为IQGAP1基因映射到涉及重复肺的区域腺癌染色体易位。除了提供线索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与钙调蛋白之间经常有可疑联系的结构基础 - 介导的信号转导。