MESANGIAL CELL TYROSINE PHOSPHATASE IN RENAL DISEASE

我们克隆了一种新的受体样蛋白酪氨酸磷酸酶rPTP-GMC1 (Kidphos)，并对其进行了部分表征，该酶由在增殖性肾小球肾炎大鼠模型中迁移和增殖的系膜细胞表达。我们已经证明，Kidphos具有较低的酪氨酸磷酸酶活性，但可以催化肌醇3位的去磷酸化，以及PTEN（一种ptpase样蛋白，已被证明在体内肌醇磷酸信号传导中起重要作用）。我们假设Kidphos的3-磷酸酶活性在发育和疾病过程中调节周细胞和周细胞样（包括系膜细胞和肝星状细胞）的迁移和/或增殖中起作用，并且Kidphos的活性是通过调节表达水平以及通过结合配体/反受体到细胞外结构域来调节催化活性/特异性来决定的。我们将在以下具体目标中检验这一假设：目标1。确定Kidphos蛋白的结构、生物合成、加工和亚细胞定位。目标2。表征Kidphos肌醇磷酸酶活性及其通过磷脂酰肌醇调节信号传导的能力。我们将在体内验证Kidphos具有PIP3 3磷酸酶活性的假设，并且该活性可以调节p13激酶下游的信号传导，包括增殖、趋化和生存。目标3。验证Kidphos在发育和疾病过程中由活化的周细胞样细胞表达的假设。目标4。使用靶向基因破坏和定量嵌合体分析来验证Kidphos在发育和疾病期间调节系膜和周细胞样细胞的迁移和/或增殖中起重要作用的假设。目标5。鉴定假定的Kidphos配体/反受体。根据其推断的结构，我们假设Kidphos的胞外结构域与配体或反受体相互作用，并且这种相互作用调节细胞质磷酸酶结构域的活性或底物访问。在这个目标中，我们描述了我们将用于识别、克隆和使用这种假定配体的策略。

We have cloned and partially characterized a novel receptor-like protein tyrosine phosphatase, rPTP-GMC1 ( Kidphos ) that is expressed by mesangial cells that are migrating and proliferating in a rat model of proliferative glomerulonephritis. We have shown that Kidphos has low tyrosine phosphatase activity but can catalyze the dephosphorylation of the 3 position of inositol as well as can PTEN, a PTPase-like protein that has been demonstrated to play an important role in inositol phosphate signaling in vivo. We hypothesize that the 3-phosphatase activity of Kidphos plays a role in regulating the migration and/or proliferation of pericytes and pericyte-like (including mesangial cells and liver stellate cells) during development and in disease processes, and that the activity of Kidphos is determined through regulation of expression level as well as through regulation of catalytic activity/specificity by binding of a ligand/counter-receptor to the extracellular domain. We will test this hypothesis in the following specific aims: Aim 1. Determine the structure, biosynthesis, processing, and subcellular localization of Kidphos protein. Aim 2. Characterize the inositol phosphatase activity of Kidphos and its ability to regulate signaling through phosphatidylinositols. We will test the hypothesis that Kidphos has PIP3 3 phosphatase activity in vivo, and that this activity can regulate signaling downstream of P13Kinase, including proliferation, chemotaxis, and survival. Aim 3. Test the hypothesis that Kidphos is expressed by activated pericyte-like cells during development and in disease processes. Aim 4. Use targeted gene disruption and quantitative chimera analysis to test the hypothesis that Kidphos plays an important role in regulating the migration and/or proliferation of mesangial and pericyte-like cells during development and in disease. Aim 5. Identify the putative ligand/counter-receptor for Kidphos. Based on its deduced structure, we hypothesize that the extracellular domain of Kidphos interacts with a ligand or counter-receptor, and that this interaction regulates the activity or substrate access of the cytoplasmic phosphatase domain. In this aim, we describe the strategy we will use to identify, clone, and use this putative ligand.