Sidekick proteins in HIV-associated nephropathy

描述(由申请人提供)： HIV相关肾病(HIVAN)是导致黑人肾功能衰竭的主要原因。HIVAN的主要病理特征是塌陷性肾小球病变，它是由HIV-1直接感染足细胞引起的。感染的足细胞表现出独特的表型变化，包括去分化，增殖增加，以及肌动蛋白细胞骨架的变化。我们已经克隆了一个在HIV-1转基因足细胞中高度上调的宿主基因SideKick-1(SDK-1)，它是免疫球蛋白超家族的一种跨膜蛋白，我们认为SDK-1在HIVAN的发病机制中起着关键作用。我们已经证明，SDK-1在HIV-1转基因小鼠和人类肾脏活检组织中的肾小球中都高度上调。我们的数据还表明，SDK-1及其同源伙伴2(SDK-2)在细胞中作为亲水性黏附分子发挥作用，使得每个伙伴更喜欢与自己的种类结合，我们已经开始绘制相关结构域的图谱。此外，其他研究表明，SDK-1和SDK-2作为神经元引导分子发挥作用，将轴突定位于特定的突触；这表明SDK-1和SDK-2可能在正常和疾病中确定和维持肾小球结构方面具有类似的关键作用。在这份提案中： 1.我们将确定：a)sdk-1和sdk-2的关键结构域(S)负责sdk-1和sdk-2的同型相互作用的特异性；b)靶向阻断该关键结构域在体外和体内的HIV-1足细胞中的功能是否可以阻止HIV-1诱导的表型变化。 2.我们将鉴定SDK-1表达引起的足细胞表型变化。我们将确定：a)在转基因小鼠的足细胞中靶向过表达SDK-1在多大程度上概括了HIVAN的病理生理学；b)在足细胞中过表达SDK-1如何影响它们与肾小球基底膜成分相互作用的能力；c)在体外，HIV-1感染诱导的SDK-1上调是否改变了足眼-足细胞的黏附？ 3.我们将表征SDK-1与肌动蛋白细胞骨架的相互作用。我们将确定：a)潜在的细胞内SDK-1相互作用蛋白，包括α-肌动蛋白-4；b)SDK-1表达对足细胞肌动蛋白细丝和微管组织以及其他肌动蛋白相关分子表达的影响。 4.我们将进一步研究SDK-1在正常肾脏、HIVAN和其他肾小球疾病中的表达模式，并检测HIVAN易感和耐药小鼠SDK-1和SDK-2的表达差异。 这些研究应该阐明SDK-1在HIVAN中促进足细胞功能障碍的机制。

DESCRIPTION (provided by applicant): HIV-associated nephropathy (HIVAN) is a leading cause of renal failure in Blacks. The main pathologic feature of HIVAN is collapsing glomerulopathy, which is caused by the direct infection of podocytes by HIV-1. Infected podocytes show unique phenotypic changes including dedifferentiation, increased proliferation, and changes in the actin cytoskeleton. We have cloned a host gene named sidekick-1 (sdk-1), a transmembrane protein of the immunoglobulin superfamily, as being highly upregulated in HIV-1 transgenic podocytes, and we believe sdk-1 to have a key role in HIVAN pathogenesis. We have shown that sdk-1 is highly upregulated in glomeruli in both HIV-1 transgenic mice and in human kidney biopsies. Our data also show that sdk-1 and its ortholog sidekick-2 (sdk-2) function as homophilic adhesion molecules in cells such that each sidekick prefers to bind to its own kind, and we have begun to map the domains responsible. Moreover, sdk-1 and sdk-2 were shown by others to function as neuronal guidance molecules, targeting axons to specific synapses; this suggests that sdk-1 and sdk-2 may analogously have a critical role in determining and maintaining glomerular architecture normally and in disease. In this proposal: 1. We will determine: a) the critical domain(s) of sdk-1 and sdk-2 responsible for the specificity of sdk-1 and sdk-2's homophilic interactions; b) whether targeted disruption of this critical domain's function in HIV-1 podocytes in vitro and in vivo can prevent HIV-1 induced phenotypic changes. 2. We will identify phenotypic changes in podocytes induced by sdk-1 expression. We will determine: a) to what extent does targeted overexpression of sdk-1 in podocytes in transgenic mice recapitulate HIVAN pathophysiology; b) how overexpression of sdk-1 in podocytes effects their ability to interact with glomerular basement membrane components; c) if sdk-1 upregulation induced by HIV-1 infection changes podocye-podocyte adhesion in vitro? 3. We will characterize the interaction of sdk-1 with the actin cytoskeleton. We will identify:a) the potential intracellular sdk-1 interacting proteins including alpha actinin-4; b) the effects of sdk-1 expression on organization of actin filaments and microtubules in podocytes and on expression of other actin-associated molecules. 4. We will better characterize expression patterns of sdk-1 in normal kidney, HIVAN and other glomerular diseases and examine differences in sdk-1 and sdk-2 expression between HIVAN susceptible and HIVAN resistant mouse strains. These studies should elucidate the mechanisms by which sdk-1 contributes to podocyte dysfunction in HIVAN.