Structure and Function of Guanine Nucleotide Dissociation Inhibitor

描述(由申请人提供)：鸟嘌呤核苷酸解离抑制物(GDI)在Rab蛋白的循环中起着至关重要的作用，Rab蛋白是一种调节膜泡运输的小GTP酶。我们已经确定RAB回收涉及Hsp90-GDI伴侣系统。这项建议的主要重点是了解Hsp90伴侣复合体在Rab循环过程中介导GDI-Rab蛋白相互作用的生化和分子基础。我们提出了3个特定的目标，以提供对GDI、Rab及其与Hsp90伴侣机制组件之间的结构/功能关系的结构、分子和生化方面的洞察。我们将探索这样的一般假设，即在循环过程中，Rab从脂质双层转移到GDI涉及Hsp90伴侣复合体，其方式类似于类固醇激素受体(SHR)复合体与类固醇激素结合的Hsp90伴侣复合体。具体目标1将继续扩大我们的结构研究，以确定GDI功能的分子基础。这些研究将包括确定β和βGDI异构体的结构，确定从牛脑中分离的天然αGDI-Rab3A-GG复合体的结构，以及确定αGDI-Hsp90伴侣复合体的结构(S)。具体目标2将应用生化方法来鉴定和表征GDI与Hsp90伴侣复合体成分相互作用的基础。这些研究将利用对Hsp90伴侣复合体在调节SHR和信号通路中的作用的广泛知识。具体目标3将采用分子方法来确定GDI、Rab和Hsp90伴侣复合体之间蛋白质相互作用的基础。这三个目标将极大地促进我们对GDI和Rab GTP酶在膜运输中的一般作用的基本理解，这是当代细胞生物学高度感兴趣的领域。他们将提供对广泛的疾病的洞察，因为GDI和Rab在智力低下、造血系疾病、眼病和与Hsp90调节的信号通路变化相关的细胞增殖(癌症)中所起的作用。

DESCRIPTION (provided by applicant): Guanine nucleotide dissociation inhibitor (GDI) plays an essential role in the recycling of Rab proteins, small GTPases that regulate membrane vesicle traffic. We have established that Rab recycling involves a Hsp90-GDI chaperone system. The principle focus of this proposal is to understand the biochemical and molecular basis for the function of the Hsp90 chaperone complex in mediating GDI-Rab protein interaction during Rab recycling.We propose 3 specific aims to provide structural, molecular and biochemical insight into the structure/function relationships between GDI, Rab and their sequential physiological protein interactions with components of the Hsp90 chaperone machinery. We will explore the general hypothesis that transfer of Rab from the lipid bilayer to GDI during recycling involves a Hsp90 chaperone complex in an analogous fashion to the manner in which steroid hormone receptors (SHR) complexes are primed for steroid hormone binding by the Hsp90 chaperone complex. Specific Aim 1 will continue to expand our structural studies to determine the molecular basis of GDI function. These studies will include determining the structure of beta and delta GDI isoforms, determining the structure of the native alpha GDI-Rab3A-GG complex isolated from bovine brain, and determining structure(s) of alpha GDI-Hsp90 chaperone complexes. Specific Aim 2 will apply biochemical approaches to identify and characterize the basis for the interaction of GDI with components of the Hsp90 chaperone complex. These studies will take advantage of the extensive knowledge of the role of the Hsp90 chaperone complexes in regulation of SHR and signaling kinase pathways. Specific Aim 3 will take a molecular approach to identify the basis for protein interactions between GDI, Rab and the Hsp90 chaperone complex. These three aims will contribute significantly to advancing our basic understanding of the general role of GDI and Rab GTPases in membrane transport, an area of high interest to contemporary cell biology. They will provide insight into a broad spectrum of diseases given the role of GDI and Rab in mental retardation, diseases of hematopoietic lineage, eye disease and cell proliferation (cancer) related to changes in Hsp90 regulated signaling pathways.