MESANGIAL CELL TYROSINE PHOSPHATASE IN RENAL DISEASE

我们已经克隆和部分特点的一种新的受体样蛋白酪氨酸磷酸酶，rPTP-GMC 1（Kidphos），是由系膜细胞表达的迁移和增殖的大鼠模型增生性肾小球肾炎。 我们已经表明，Kidphos具有低酪氨酸磷酸酶活性，但可以催化肌醇的3位去磷酸化，以及可以PTEN，一种已被证明在体内磷酸肌醇信号转导中发挥重要作用的PTPase-like蛋白。 我们推测Kidphos的3-磷酸酶活性在调节周细胞和周细胞样细胞的迁移和/或增殖中起作用。（包括系膜细胞和肝星状细胞）在发育和疾病过程中，并且Kidphos的活性通过调节表达水平以及通过结合配体/反配体调节催化活性/特异性来确定。受体的胞外结构域。 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的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。 我们将测试Kidphos在体内具有PIP 3 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、趋化性和存活。目标3.检验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检验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。确定Kidphos的假定配体/反受体。 基于其推导的结构，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胞质磷酸酶结构域的活性或底物进入。 在这个目标中，我们描述了我们将使用的策略来识别，克隆和使用这个假定的配体。

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.