Role of PACS proteins in polycystin-2 trafficking and ADPKD

描述（由申请人提供）：本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在肾脏中形成许多囊肿，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发挥作用的钙渗透性离子通道。我们最近发现的分子运输机PACS-1和PACS-2-管理的多囊蛋白-2之间的内质网（ER），高尔基体和细胞表面的逐步运动。此外，我们发现PACS-1和PACS-2整合蛋白运输与细胞凋亡和细胞分化。我们假设PACS-1和PACS-2是多功能分选蛋白，控制多囊蛋白-2在正常肾脏中的亚细胞定位，并且PACS-1和PACS-2的失调有助于在多囊肾中观察到的囊肿形成和过度凋亡。我们确定PACS-2作为第一个COPI连接器，目标1中的实验将确定PACS-2和COPI如何联合收割机将多囊蛋白-2定位于ER-该离子通道的主要细胞库。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trans-Golgi网络（TGN）。目标2中的研究将确定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。尽管多囊蛋白-2突变和ADPKD之间存在因果关系，但从通道功能障碍到囊肿发生和疾病的步骤仍知之甚少。我们最近发现，PACS-1的表达在ADPKD肾脏中严重减少，而PACS-2的表达相对变化不大，这一组合有利于培养细胞的凋亡。目的3中的研究将确定PACS-1和PACS-2在ADPKD肾脏中的细胞表达，并将使用多囊肾疾病的小鼠模型测试PACS-2的缺失是否抑制囊肿形成。成功完成我们提出的研究将首次阐明多功能运输机制- PACS-1和PACS-2-调节多囊蛋白-2在多个细胞器中传导钙电流的能力，以及PACS-1和PACS-2表达的失调如何导致ADPKD中发现的囊形成和过度凋亡。

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.