Tonicity signaling to TonEBP transcription factor

描述（由申请人提供）： 摘要 转录激活因子TonEBP对肾髓质的发育和功能至关重要。TonEBP在高渗盐条件下被激活，通过刺激水通道蛋白-2水通道和UT-A尿素转运蛋白的转录，成为尿浓度的关键调节因子。此外，TonEBP是通过刺激有机渗透压物质和分子伴侣的细胞积累来保护肾髓质细胞免受高渗和尿素的有害影响的主要调节剂。缺乏肾脏TonEBP的转基因小鼠由于大量细胞死亡而显示出严重的髓质萎缩，并且由于浓缩尿液的能力受损而显示出危及生命的体积减少。在患者中，TonEBP与包括糖尿病肾病、炎症和癌症转移在内的疾病有关。尽管TonEBP在健康和疾病中的重要性，但很少有人了解张力变化是如何识别的，以及信息是如何传递给TonEBP的。我们在前一时期获得的数据揭示了TonEBP本身是一个张力传感器的线索，它控制着核贩运，以响应环境张力的变化。这些数据还表明，TonEBP是共价修饰的乙酰基和小泛素样修饰剂（SUMO），以响应高渗。在这项提案中，我们将继续这些令人兴奋的发现，以了解分子水平上TonEBP的细胞信号传导。我们将探讨高渗信号的两种模型。内在模型指出TonEBP本身是张力传感器（目的1）。外在模型指出，传感器通过涉及乙酰基和SUMO的翻译后修饰（Aim 2和Aim 3）向TonEBP发出信号。在目的1中，我们将通过研究TonEBP的核定位信号与执行核输入的细胞机器之间的相互作用中的张力响应变化来揭示张力感测的分子基础。目的2是了解组蛋白去乙酰化酶SIRT 1如何以张力响应的方式控制TonEBP的核输出。乙酰化位点和低渗调节将被描绘出来。目的3是通过检测转录抑制和蛋白质稳定性来了解SUMO缀合如何调节TonEBP的活性。张力依赖性SUMO修饰的细胞机制将被描述。 项目叙述 拟议中的研究可能会从根本上揭示关于TonEBP分子是如何控制的新信息-打开或关闭。这些信息将为开发糖尿病肾病和急性肾功能衰竭等肾脏疾病的治疗提供新的机会。

DESCRIPTION (provided by applicant): Abstract The transcriptional activator TonEBP is essential for the development and function of the renal medulla. Activated by hypertonicity (hyperosmotic salinity), TonEBP is a key regulator for the urinary concentration via stimulating transcription of aquaporin-2 water channel and UT-A urea transporters. In addition, TonEBP is the master regulator for protecting the renal medullary cells from the deleterious effects of hypertonicity and urea via stimulating cellular accumulation of organic osmolytes and molecular chaperone. Genetically modified mice deficient in the renal TonEBP display severe medullary atrophy due to massive cell death, and life threatening volume depletion due to impaired ability to concentrate the urine. In patients, TonEBP is implicated in diseases including diabetic nephropathy, inflammation, and cancer metastasis. Despite the importance of TonEBP in health and disease, little is understood how changes in tonicity is recognized and the information is conveyed to TonEBP. Our data obtained in the previous period reveal clues that TonEBP itself is a tonicity sensor that controls the nuclear trafficking in response to changes in ambient tonicity. The data also demonstrate that TonEBP is covalently modified with acetyl groups and small ubiquitin-like modifiers (SUMO) in response to hypertonicity. In this proposal, we will pursue these exciting findings to understand the cellular signaling to TonEBP at the molecular level. We will explore two models of hypertonicity signaling. The intrinsic model states that TonEBP itself is a tonicity sensor (Aim 1). The extrinsic model states that a sensor signals to TonEBP via posttranslational modifications involving acetyl group and SUMO (Aim 2 and Aim 3). In Aim 1, we will uncover molecular basis of the tonicity sensing by investigating tonicity-responsive changes in the interaction between the nuclear localization signal of TonEBP and the cellular machinery carrying out the nuclear import. Aim 2 is to understand how the histone deaceytlase SIRT1 control the nuclear export of TonEBP in a tonicity-responsive manner. Sites of acetylation and regulation by hypotonicity will be delineated. Aim 3 is to understand how SUMO conjugation modulates the activity of TonEBP by examining transcriptional repression and protein stability. Cellular mechanism of the tonicity-dependent SUMO modification will be delineated. Project Narrative The proposed studies are likely to uncover fundamentally new information about how the TonEBP molecule is controlled -turned on or off. This information will provide new opportunity to develop therapy for renal diseases such as diabetic nephropathy and acute renal failure.