Role of PACS proteins in polycystin-2 trafficking and ADPKD

描述（由申请人提供）：该项目的长期目标是确定分选蛋白PACS-1和PACS-2在常染色体显性多囊肾病（ADPKD）中的作用。这种遗传性疾病表现为肾脏中形成大量囊肿，最终导致过度细胞凋亡和正常组织的破坏。ADPKD通常由多囊蛋白-2突变引起，多囊蛋白-2是一种在多个亚细胞器中起作用的钙渗透离子通道。我们最近发现了一种分子运输机制- pacs -1和PACS-2-控制多囊蛋白-2在内质网（ER）、高尔基体和细胞表面之间的逐步运动。此外，我们发现PACS-1和PACS-2将蛋白质转运与细胞凋亡和细胞分化结合起来。我们假设PACS-1和PACS-2是控制多囊素-2在正常肾脏中亚细胞定位的多功能分选蛋白，并且PACS-1和PACS-2的错误调节有助于多囊肾中观察到的囊发生和过度凋亡。我们确定PACS-2是第一个COPI连接器，Aim 1中的实验将确定PACS-2和COPI如何结合以将多囊蛋白-2定位到er， er是该离子通道的主要细胞储存库。此外，我们发现PACS-1是一个AP-1连接器，将多囊蛋白-2定位到反式高尔基网络（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区室中的多囊蛋白-2钙峰值。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膀胱发生和疾病的步骤尚不清楚。我们最近发现，在ADPKD肾脏中，PACS-1的表达严重降低，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，并将使用多囊肾病小鼠模型测试PACS-2的缺失是否会抑制囊生成。我们所提出的研究的成功完成将首次阐明调节多囊蛋白-2在多个细胞器中传导钙电流的多功能运输机制- PACS-1和PACS-2，以及PACS-1和PACS-2表达的错误调节如何导致ADPKD中膀胱发生和过度凋亡。

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.