Sidekick proteins in HIV-associated nephropathy

描述（由申请人提供）： HIV 相关肾病 (HIVAN) 是黑人肾衰竭的主要原因。 HIVAN的主要病理特征是塌陷性肾小球病，是由HIV-1直接感染足细胞引起的。受感染的足细胞表现出独特的表型变化，包括去分化、增殖增加和肌动蛋白细胞骨架的变化。我们克隆了一个名为 sidekick-1 (sdk-1) 的宿主基因，它是免疫球蛋白超家族的一种跨膜蛋白，在 HIV-1 转基因足细胞中高度上调，我们相信 sdk-1 在 HIVAN 发病机制中发挥关键作用。我们已经表明，HIV-1 转基因小鼠和人肾活检的肾小球中 sdk-1 高度上调。我们的数据还表明，sdk-1 及其直系同源 si​​dekick-2 (sdk-2) 在细胞中充当同源粘附分子，因此每个 sidekick 更喜欢与自己的同类结合，我们已经开始绘制负责的域。此外，其他人证明 sdk-1 和 sdk-2 可以作为神经元引导分子，将轴突靶向特定的突触；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。在此提案中： 1. 我们将确定： a) sdk-1 和 sdk-2 负责 sdk-1 和 sdk-2 同亲相互作用特异性的关键域； b) 在体外和体内有针对性地破坏 HIV-1 足细胞中这一关键结构域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 表达诱导的足细胞表型变化。我们将确定：a) 转基因小鼠足细胞中 sdk-1 的靶向过度表达在多大程度上概括了 HIVAN 病理生理学； b) 足细胞中 sdk-1 的过度表达如何影响其与肾小球基底膜成分相互作用的能力； c) HIV-1 感染诱导的 sdk-1 上调是否会改变体外足细胞粘附？ 3. 我们将描述 sdk-1 与肌动蛋白细胞骨架的相互作用。我们将鉴定：a) 潜在的细胞内 sdk-1 相互作用蛋白，包括 α actinin-4； b) sdk-1表达对足细胞中肌动蛋白丝和微管的组织以及其他肌动蛋白相关分子表达的影响。 4. 我们将更好地表征正常肾脏、HIVAN 和其他肾小球疾病中 sdk-1 的表达模式，并检查 HIVAN 易感和 HIVAN 耐药小鼠品系之间 sdk-1 和 sdk-2 表达的差异。 这些研究应阐明 sdk-1 导致 HIVAN 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.