MESANGIAL CELL TYROSINE PHOSPHATASE IN RENAL DISEASE

我们已经克隆并部分鉴定了一种新的受体样蛋白酪氨酸磷酸酶，RPTP-GMC1(Kidphos)，它是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的。我们发现，Kidphos具有较低的酪氨酸磷酸酶活性，但可以催化肌醇和CaN PTEN 3位的去磷酸化，PTEN是一种PTPase样蛋白，已被证明在体内肌醇磷酸信号转导中发挥重要作用。我们假设Kidphos的3-磷酸酶活性在发育和疾病过程中对周细胞和周细胞样细胞(包括系膜细胞和肝星状细胞)的迁移和/或增殖起调控作用，并且Kidphos的活性是通过调节表达水平以及通过与细胞外域的配体/对受体结合来调节催化活性/特异性来确定的。我们将从以下几个方面对这一假说进行验证：目的1.确定Kidphos蛋白的结构、生物合成、加工和亚细胞定位。目的2.鉴定Kidphos的肌醇磷酸酶活性及其通过磷脂酰肌醇调节信号的能力。我们将验证这一假设，即Kidphos在体内具有PIP3-3磷酸酶活性，并且该活性可以调节P13Kinase下游的信号，包括增殖、趋化和存活。目的3.验证Kidphos在发育和疾病过程中由激活的周细胞样细胞表达的假说。目的4.利用靶向基因干扰和定量嵌合体分析来验证Kidphos在系膜细胞和周细胞样细胞的发育和疾病过程中发挥重要作用的假设。目的5.确定Kidphos可能的配体/对受体。根据其推导的结构，我们假设Kidphos的胞外区与配体或反受体相互作用，这种相互作用调节细胞质磷酸酶区域的活性或底物访问。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.