POLYCYSTIN MODULATION OF GLUCOCORTICOID RECEPTOR ACTIVITY

描述：（直接取自应用）多囊肾通常被描述为异常分化。我们的长期目标是了解PKD1突变如何导致这种异常分化状态并导致肾功能丧失。多囊蛋白-1是PKD1基因的蛋白产物，被认为是一种质膜受体，可介导信号转导事件，从而调节与肾上皮细胞获得和/或维持终末分化状态相关的基因表达。一个基因家族的肾脏表达与分化表型相关，其表达已被证明是异常的囊性肾是编码异种代谢谷胱甘肽s -转移酶（GST）酶。我们新的初步数据表明，在稳定转染的肾上皮细胞系中，糖皮质激素（GC）诱导的内源性GST-Ya基因的表达通过膜导向的多囊蛋白融合蛋白的表达而增强。GCs参与细胞生长和分化的调控。GCs的大部分作用是由配体激活的糖皮质激素受体（GR）介导的，GR是一种转录调节剂，其活性受磷酸化的影响。综上所述，多胱氨酸激活JNK并抑制GSK-3，这两种已知的磷酸化GR的激酶。这些数据表明，多胱氨酸可以调节调节GR活性的信号转导途径，从而增加gc诱导的GST-Ya基因的表达。多囊素介导的信号通路与GC反应通路之间的相互作用可能代表了多囊素影响肾上皮细胞分化状态的一般机制，并可能被证明与多囊肾病的一些发病机制特别相关。本项目将利用GST-Ya基因启动子及其gc诱导的表达作为模型系统，确定多囊蛋白在调节gr调控功能中的作用。这一目标将通过以下具体目标来解决：1)确定多胱氨酸调节gc诱导的GST-Ya基因表达的核机制；2)确定多囊蛋白表达对GR活性的影响；3)确定多囊素调控GR功能和gc诱导GST-Ya基因表达的信号转导途径及下游效应物。该项目有望为多囊素影响PKD肾小管分化和防止肾功能丧失的机制提供新的见解。

Description: (Taken directly from the application) Polycystic kidneys are generally described as abnormally differentiated. Our long term goal is to understand how mutations in PKD1 result in this abnormally differentiated state and lead to the loss of renal function. Polycystin-1, the protein product of the PKD1 gene, is thought to be a plasma membrane receptor that mediates signal transduction events and thereby regulates gene expression associated with the acquisition and/or maintenance of the terminally differentiated state of renal epithelial cells. One family of genes whose renal expression is associated with a differentiated phenotype and whose expression has been shown to be aberrant in cystic kidneys is that encoding the xenobiotic-metabolizing glutathione S-transferase (GST) enzymes. Our new preliminary data demonstrates that the glucocorticoid (GC)-inducible expression of the endogenous GST-Ya gene is enhanced by expression of a membrane-directed polycystin fusion protein in a stably transfected renal epithelial cell line. GCs are involved in the regulation of cell growth and differentiation. Most of the effects of GCs are mediated by the ligand-activated glucocorticoid receptor (GR) that functions as a transcriptional regulator whose activity is affected by phosphorylation. Polycystin activates JNK and inhibits GSK-3, two kinases known to phosphorylate GR Taken together, these data suggest that polycystin could regulate signal transduction pathways that modulate the activity of GR and thereby result in augmentation of the GC-induced expression of the GST-Ya gene. Cross-talk between polycystin-mediated signaling pathways and the GC response pathway may represent a general mechanism by which polycystin influences the differentiated state of renal epithelial cells and may prove to be particularly relevant to some of the pathogenetic mechanisms associated with polycystic kidney disease. This project will utilize the GST-Ya gene promoter and its GC-induced expression as a model system in which to determine the role of polycystin in modulating GR-regulated functions. This objective will be addressed by the following Specific Aims: 1) determine the nuclear mechanism(s) by which polycystin modulates GC-induced GST-Ya gene expression; 2) determine the effect(s) of polycystin expression on GR activity; and 3) determine the signal transduction pathways and downstream effectors involved in polycystin modulation of GR function and GC-induced GST-Ya gene expression. This project is anticipated to lead to new insight into the mechanisms by which polycystin affects renal tubular differentiation and prevents the loss of renal function in PKD.