Podocalyxin in the renal filtration apparatus

描述（由申请人提供）：肾病综合征同时影响 儿童和成人，并可能导致肾衰竭和死亡。异常 足细胞结构和肾小球多聚阴离子与肾病综合征 综合征是公认的。表面上的阴离子电荷 需要足细胞来维持足细胞结构和功能。Podocalyxin 是主要的唾液酸糖蛋白存在于泌尿空间表面上， 足细胞并含有肾小球的大部分蛋白质结合唾液酸。 肾小球蛋白唾液酸化的减少导致蛋白尿， 足突消失和实验动物肾病综合征。我们 克隆并鉴定了来自兔、人和 并克隆了小鼠足糖萼蛋白基因。足糖萼蛋白基因敲除小鼠 出生时肾小球滤过装置有重大缺陷， 足细胞足突形成。我们假设足糖萼蛋白是必需的 用于功能性肾小球过滤器的形成和维持以及用于 足细胞足突的发育。为了明确足糖萼蛋白的功能 我们已经寻找并分离了一种假定的连接蛋白， podocalyxin的C末端。这种连接蛋白有可能连接 podocalyxin的肌动蛋白细胞骨架在一个蛋白质复合物含有eznn和 调节酶我们将定义足糖萼蛋白的相互作用， 蛋白质复合物，并确定足糖萼蛋白-接头复合物在 vivo.为了验证足细胞足萼蛋白是足发育所必需的假设， 我们将确定足细胞表达的兔足糖萼蛋白是否 转基因将恢复足细胞足突的形成 敲除小鼠为了确定足糖萼蛋白C-末端结合基序的作用， 在足糖萼蛋白功能中，我们检测了足糖萼蛋白敲除小鼠的足细胞， 表达缺乏足糖萼蛋白C-末端的兔足糖萼蛋白转基因， 结合基序这些研究将促进我们对 足糖萼蛋白在肾小球的发育、结构和维持中的作用 滤波

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.