Podocalyxin in the renal filtration apparatus

描述(申请人提供)：肾病综合征影响两端 儿童和成人，并可能导致肾功能衰竭和死亡。不正常的 肾病相关的足细胞结构和肾小球聚阴离子 综合症是公认的。根尖表面上的阴离子电荷 足细胞是维持足细胞结构和功能所必需的。足叶乙素 唾液酸糖蛋白是存在于尿液间隙表面的主要糖蛋白吗？ 足细胞，含有肾小球蛋白结合的唾液酸。 肾小球蛋白唾液酸化减少会导致蛋白尿， 实验动物的足突消退和肾病综合征。我们 已经克隆并鉴定了兔、人和 小鼠，并已克隆了小鼠的Podocalysin基因。Podocalyin基因敲除小鼠 出生时肾小球滤过装置有重大缺陷，没有 足细胞足突形成。我们假设需要用足叶乙素 用于形成和维持功能性肾小球滤器，以及用于 足细胞足突的发育。要明确足叶蛋白的功能 我们已经搜索并分离出一种可能的连接蛋白，它与 胡萝卜素的C-末端。这种连接物蛋白有可能将 Podocalyx对含eznn和eznn的蛋白质复合体中肌动蛋白细胞骨架的影响 调节酶。我们将在此定义Podocalysin的相互作用 蛋白复合体和确定Podocalysin-Linker复合体的功能 活着。验证足部需要足细胞的假说 过程形成我们将确定足细胞表达的兔足突蛋白 转基因将恢复足细胞足突的形成 基因敲除老鼠。确定Podocalyin C-末端结合基序的作用 在Podocalyin功能中，我们检测了Podocalyin基因敲除小鼠的足细胞 缺失Podocalyin C-末端的兔Podocalysin转基因表达 有约束力的主题。这些研究将促进我们对 Podocalyin在肾小球的发育、结构和维持中的作用 过滤。

DESCRIPTION (provided by applicant): The nephrotic syndrome affects both children and adults and may lead to renal failure and death. Abnormalities of podocyte structure and the glomerular polyanion associated with nephrotic syndrome are wellrecognized. The anionic charges on the apical surface of the podocyte are required to maintain podocyte structure and function. Podocalyxin is the major sialoglycoprotein present on the urinary space surface of podocytes and contains most of the protein bound sialic acid of the glomerulus. A reduction in the sialylation of glomerular proteins results in proteinuria, foot process effacement, and nephrotic syndrome in experimental animals. We have cloned and characterized the podocalyxin cDNAs from rabbit, human, and mouse and have cloned the mouse podocalyxin gene. Podocalyxin knockout mice have major defects in the glomerular filtration apparatus at birth with no podocyte foot process formation. We hypothesize that podocalyxin is required for the formation and maintenance of a functional glomerular filter and for the development of podocyte foot processes. To define the function of podocalyxin we have searched for and isolated a putative linker protein that binds to the C-terminal of podocalyxin. This linker protein has the potential to link podocalyxin to the actin cytoskeleton in a protein complex containing eznn and regulatory enzymes. We will define the interactions of podocalyxin in this protein complex and determine the function of the podocalyxin-linker complex in vivo. To test the hypothesis that podocyte podocalyxin is required for foot process formation we will determine if a podocyte-expressed rabbit podocalyxin transgene will restore podocyte foot process formation in the podocalyxin knockout mice. To define the role of the podocalyxin C-terminal binding motif in podocalyxin function we examine the podocytes of podocalyxin knockout mice expressing a rabbit podocalyxin transgene lacking the podocalyxin C-terminal binding motif. These studies will advance our understanding of the role of podocalyxin in the development, structure, and maintenance of the glomerular filter.