The Role of Presenilin-2 in the Control and Function of Polycystin-1

描述（申请人提供）：常染色体显性多囊肾病（ADPKD）的特征是囊肿的进行性发展，压迫和损害周围正常肾实质，最终导致肾功能下降。虽然有两个基因与ADPKD表型相关，PKD1和PKD2，但大多数病例是由于编码多囊蛋白-1 （PC1）的PKD1基因突变。为了开发针对ADPKD患者的治疗方法，有必要了解与PC1功能相关的信号机制。因此，本应用的目的是探索早老素-2 （PSEN2）在控制PC1信号传导中的新作用。PSEN2是分泌酶的催化亚基，分泌酶是一种裂解PC1，导致其c端尾部（CTT）释放的蛋白酶。由此产生的PC1 CTT切割片段似乎作为参与维持细胞稳态的信号分子。尽管与PC1 CTT切割相关的信号通路的各个方面已经被阐明，但激活PSEN2介导的PC1 CTT切割的刺激和PSEN2在膀胱发生中的潜在参与仍不清楚。我们之前已经确定，在HEK293细胞中PSEN2敲低可显著减少PC1 CTT切割。我们之前的研究还表明，PC1 CTT切割调节内质网（ER）应激相关基因的转录活性，并由肾损伤引起血流减少。我们假设PSEN2是PC1 CTT正常切割和信号传递所必需的，并且该功能参与防止膀胱发生。我们提出以下具体目标来支持或反驳我们的假设：1)目的1将建立psen2介导的PC1 CTT切割受到内质网应激刺激的概念，如果这一过程受到干扰，则会导致囊肿形成。我们将在PSEN2敲低和内质网应激的条件下，使用基于荧光素酶的测定来测量PC1 CTT的切割，并确定与这种反应相关的特定片段的大小；2) Aim 2将建立psen2介导的PC1裂解在PC1预防囊肿活性中起关键作用的概念，PC1 CTT的预防增强了肾损伤诱导囊肿形成的能力。为此，我们将对PSEN2-/-小鼠进行基线和缺血/再灌注引起的急性肾损伤的表型分析。我们期望这些分子和生理方法可能为ADPKD的治疗发展提供新的治疗靶点。

DESCRIPTION (provided by applicant): Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the progressive development of cysts that compress and damage the surrounding normal renal parenchyma, which in turn leads to an eventual decline in renal function. Although two genes have been linked to the ADPKD phenotype, PKD1 and PKD2, majority of cases are due to mutations in the PKD1 gene, which encodes for polycystin-1 (PC1). In order to develop treatments for ADPKD patients, it is necessary to understand the signaling mechanisms associated with PC1 function. Therefore, the goal of this application is to explore the novel role of presenilin-2 (PSEN2) in the control of PC1 signaling. PSEN2 is the catalytic subunit of ¿-secretase, a protease that cleaves PC1, leading to the release of its C-terminal tail (CTT). The resulting PC1 CTT cleavage fragments appear to act as signaling molecules that participate in maintaining cell homeostasis. Although aspects of the signaling pathways associated with cleavage of PC1 CTT have been elucidated, the stimuli that activate PSEN2-mediated PC1 CTT cleavage and the potential involvement of PSEN2 in cystogenesis remain unclear. We have previously determined that PSEN2 knockdown in HEK293 cells markedly reduces PC1 CTT cleavage. Our previous studies also suggest that PC1 CTT cleavage modulates the transcriptional activity of genes related to endoplasmic reticulum (ER) stress, and is induced by renal injuries associated with decreased flow. We hypothesize that PSEN2 is required for proper PC1 CTT cleavage and signaling, and that this function participates in preventing cystogenesis. We propose the following specific aims to support or refute our hypothesis: 1) Aim 1 will establish the concept that PSEN2-mediated PC1 CTT cleavage is stimulated by ER stress, a process that if perturbed has shown to lead to cyst formation. We will measure PC1 CTT cleavage using a luciferase-based assay in conditions of PSEN2 knockdown and ER stress, and identify the size of the particular fragment associated with this response; 2) Aim 2 will establish the concept that PSEN2-mediated cleavage of PC1 plays a critical role in the cyst-preventing activities of PC1, and that prevention of PC1 CTT enhances the capacity of renal injury to induce cyst formation. To do this, we will conduct phenotypic analyses on PSEN2-/- mice at baseline and in response to ischemia/reperfusion-induced acute renal injury. We expect that these molecular and physiological approaches may suggest new therapeutic targets for ADPKD treatment development.