Regulation of the mTOR pathway in polycystic kidney disease

描述（由申请人提供）：常染色体显性（ADPKD）是最常见的危及生命的遗传性疾病。结节性硬化症（TSC）比ADPKD少10倍。这两种疾病都以肾囊肿为特征。目前还没有治疗方法可以减缓这两种疾病的发病或进展。我们最近发现，ADPKD中受影响的蛋白polycytin -1 （PC1）与TSC中受影响的蛋白tuberin相互作用，并调节激酶mTOR的活性。mTOR在细胞生长和增殖中起重要作用，已知可被tuberin抑制。我们提出了一种模型，其中PC1的c端胞质尾部可以诱导tuberin和mTOR以及其他调节蛋白之间形成复合物。该复合物的功能是抑制正常肾上皮细胞的mTOR活性。我们的研究结果表明，mTOR的抑制受根尖流体流动的调节。我们发现mTOR在ADPKD患者和多囊肾小鼠的肾脏中有不适当的活性。用mTOR抑制剂雷帕霉素治疗多囊肾小鼠可显著减小肾脏和囊肿大小，并保留肾功能。这强烈表明，ADPKD中mTOR异常激活对肾囊肿生长至关重要。我们现拟详细研究PC1抑制mTOR活性的机制。在Aim 1中，我们将研究PC1和mTOR之间的相互作用，并确定其他调节因子和该复合物的亚细胞定位。我们将测试该复合体在肾囊肿中是否被破坏。在目标2中，我们将测试流体流动如何调节mTOR活性。在Aim 3中，使用来自ADPKD肾脏的样本和具有条件失活PKD1基因的小鼠模型，我们将表征哪些已知的mTOR下游效应物和上游调节物在该疾病中受到影响。在Aim 4中，为了准备未来可能的临床试验，我们将研究雷帕霉素对PKD1小鼠模型的影响。我们将评估剂量和治疗方案，并研究对囊上皮细胞增殖和凋亡的影响。这些研究将对指导未来可能的临床试验具有重要意义。雷帕霉素已经是一种临床批准的药物，用于长期治疗肾移植患者的免疫抑制。基于我们的数据，我们对雷帕霉素有望成为减缓ADPKD疾病进展的第一种可用治疗方法持谨慎乐观态度。此外，本研究结果将增强我们对TSC中肾脏受累机制的理解。

DESCRIPTION (provided by applicant): Autosomal-dominant (ADPKD) is the most common life-threatening genetic disease. Tuberous Sclerosis Complex (TSC) is 10-times less common than ADPKD. Both diseases are characterized by renal cysts. No treatment is currently available to slow the onset or progression of either disease. We have recently found that polycystin-1 (PC1), the protein affected in ADPKD, interacts with tuberin, the protein affected in TSC, and regulates the activity of the kinase mTOR. mTOR plays an important role in cell growth and proliferation and is known to be inhibited by tuberin. We propose a model in which the C-terminal cytoplasmic tail of PC1 functions to induce the formation of a complex between tuberin and mTOR and other regulatory proteins. The function of this complex is to suppress mTOR activity in normal renal epithelial cells. Our results suggest that mTOR inhibition is regulated by apical fluid flow. We found that mTOR is inappropriately active in the kidneys of ADPKD patients and in mice with polycystic kidneys. Treatment of polycystic kidney mice with the mTOR inhibitor rapamycin results in the dramatic reduction of renal and cyst sizes and in the preservation of kidney function. This strongly suggests that aberrant mTOR activation in ADPKD is critical for renal cyst growth. We now propose to study in detail the mechanism of the suppression of mTOR activity by PC1. In Aim 1, we will investigate the interaction between PC1 and mTOR and identify additional regulatory factors and the subcellular localization of the complex. We will test whether this complex is disrupted in renal cysts. In Aim 2, we will test how fluid flow regulates mTOR activity. In Aim 3, using samples from ADPKD kidneys and a mouse model with a conditionally inactivated PKD1 gene we will characterize which of the known downstream effectors and upstream regulators of mTOR are affected in the disease. In Aim 4, in preparation for possible future clinical trials, we will investigate the effects of rapamycin on the PKD1 mouse model. We will assess dosage and treatment regimens and investigate the effects on proliferation and apoptosis of cystic epithelial cells. These investigations will be important to guide possible future clinical trials. Rapamycin is already a clinically approved drug, used for long-term treatment for immunosuppression in renal transplant patients. Based on our data, we are cautiously optimistic that rapamycin has promise to become the first available treatment to slow the disease progression in ADPKD. Furthermore, results from this research will enhance our understanding of the mechanisms underlying the renal involvement in TSC.