Role of PACS proteins in polycystin-2 trafficking and ADPKD

描述(申请人提供)：该项目的长期目标是确定分选蛋白PACS-1和PACS-2在常染色体显性遗传性多囊肾病(ADPKD)中的作用。这种遗传性疾病表现为在肾脏内形成大量的囊肿，最终导致过度的细胞凋亡和正常组织的破坏。ADPKD通常是由多囊蛋白-2突变引起的，多囊蛋白-2是一种在多个亚细胞细胞器中起作用的钙离子通道。我们最近发现了调控多囊蛋白-2在内质网、高尔基体和细胞表面之间逐步移动的分子运输机制--PACS-1和PACS-2。此外，我们还发现PACS-1和PACS-2将蛋白质转运与细胞凋亡和细胞分化结合在一起。我们推测PACS-1和PACS-2是控制多囊蛋白-2在正常肾脏的亚细胞定位的多功能分选蛋白，PACS-1和PACS-2的错误调控导致了多囊肾的囊变和过度的细胞凋亡。我们确定PACS-2是第一个COPI连接器，目标1中的实验将确定PACS-2和COPI如何结合将多囊蛋白-2定位到内质网-该离子通道的主要细胞库。此外，我们还证明了PACS-1是一种AP-1连接蛋白，它将多囊蛋白-2定位于反式高尔基体网络(TGN)。AIM 2的研究将确定PACS-1和PACS-2分选活性的调节如何影响多个亚细胞隔室中的多囊蛋白-2钙尖峰。尽管多囊蛋白-2突变与ADPKD之间存在因果关系，但从通道功能障碍到囊变和疾病的步骤还知之甚少。我们最近发现，PACS-1在ADPKD肾脏中的表达严重减少，而PACS-2的表达变化相对较小-这一组合有利于培养细胞的凋亡。AIM 3的研究将确定PACS-1和PACS-2在ADPKD肾脏中的细胞表达，并将使用多囊肾病的小鼠模型测试PACS-2的缺失是否抑制囊变。我们建议的研究的成功完成将首次阐明多功能转运机制-PACS-1和PACS-2-调控多囊蛋白-2在多个细胞器中传导钙电流的能力，以及PACS-1和PACS-2表达的错误调控如何导致ADPKD的囊变和过度凋亡。

DESCRIPTION (provided by applicant): The long-term goal of this project is to determine the role of the sorting proteins PACS-1 and PACS-2 in autosomal dominant polycystic kidney disease (ADPKD). This inherited disorder manifests in formation of numerous cysts in the kidney, culminating in excessive apoptosis and destruction of normal tissue. ADPKD is frequently caused by mutation of polycystin-2, a calcium-permeable ion channel that functions in multiple subcellular organelles. We recently identified the molecular trafficking machinery-PACS-1 and PACS-2- governing the stepwise movement of polycystin-2 between the endoplasmic reticulum (ER), Golgi and the cell surface. In addition, we discovered that PACS-1 and PACS-2 integrate protein trafficking with apoptosis and cell differentiation. We hypothesize that PACS-1 and PACS-2 are multifunctional sorting proteins that control the subcellular localization of polycystin-2 in the normal kidney, and that misregulation of PACS-1 and PACS-2 contributes to the cystogenesis and excess apoptosis observed in the polycystic kidney. We identified PACS-2 as the first COPI connector, and experiments in Aim 1 will determine how PACS-2 and COPI combine to localize polycystin-2 to the ER-the principle cellular reservoir for this ion channel. Also, we showed that PACS-1 is an AP-1 connector that localizes polycystin-2 to the trans-Golgi network (TGN). Studies in Aim 2 will determine how regulation of PACS-1 and PACS-2 sorting activity effects polycystin-2 calcium spikes in multiple subcellular compartments. Despite the causal relationship between polycystin-2 mutations and ADPKD, the steps leading from channel dysfunction to cystogenesis and disease are poorly understood. We recently found that PACS-1 expression is severely reduced in the ADPKD kidney, while PACS-2 expression is relatively little changed-a combination that favors apoptosis in cultured cells. Studies in Aim 3 will determine the cellular expression of PACS-1 and PACS-2 in the ADPKD kidney and will test whether loss of PACS-2 inhibits cystogenesis using a mouse model of polycystic kidney disease. Successful completion of our proposed studies will illuminate for the first time the multifunctional trafficking machinery- PACS-1 and PACS-2-that regulates the ability of polycystin-2 to conduct calcium currents in multiple organelles, and how misregulation of PACS-1 and PACS-2 expression contributes to the cystogenesis and excess apoptosis found in ADPKD.