Tonicity signaling to TonEBP transcription factor

哺乳动物肾髓质的渗透压很高。高渗透压提供了水分重吸收和尿液浓缩的动力，这是肾脏维持适当体液量和血压的关键功能。盐和尿素是肾髓质内的主要溶质。不幸的是，高盐(高渗)会导致DNA损伤，而高尿素会导致细胞死亡。为了肾脏的成功功能，肾髓质细胞必须克服高渗透压的有害影响。细胞通过积累相容的渗透压来适应高渗。我们已经证明，TONEBP通过刺激基因在亲和渗透调节物质的积累中发挥核心作用，这些基因的产物可以主动运输或合成亲和渗透调节物质。此外，TONEBP刺激加压素调节的尿素转运体，该转运体在尿素在肾髓质中的逆流循环中发挥关键作用。我们的数据表明，TONEBP还刺激热休克蛋白70，该蛋白的功能是保护细胞免受高尿素的致命压力。因此，TONEBP控制着一个对肾髓质的功能和保护至关重要的基因网络。我们已经证明，在利水和抗利尿的生理条件下，核定位是TnEBP调节的主要部位。我们假设存在控制TONEBP核浆运输的信号通路，以响应环境张力的变化。目的1是定义TONEBP的结构域，这些结构域负责核定位中张力响应的变化。培养的细胞将与突变的TonEBPs的表达结合使用。我们希望定义对核进口、核出口和调节两种相反活动至关重要的氨基酸。这些结构域将提供关键试剂来揭示紧张性信号通路。TONEBP的磷酸化与核的重要性和出口都有时间上的相关性。目的2定义其磷酸化影响TONEBP核定位的氨基酸残基。目的I揭示蛋白质相互作用在核定位中的作用。我们将通过研究缺陷突变来研究TnEBP二聚体形成的作用。将确定TONEBP建筑群的其他组成部分，并调查它们的作用。这些研究可能会发现一种新的信号转导模式，这是肾髓质独有的。

Osmolality of the mammalian kidney medulla is very high. The high osmolality provides driving force for water reabsorption and urinary concentration, a key function of the kidney for maintaining proper body fluid volume and blood pressure. Salt and urea are major solutes in the renal medullary interstitium. Unfortunately, high salt (hypertonicity) causes DNA damage and high urea causes cell death. For the successful function of the kidney, the renal medullary cells have to overcome the deleterious effects of hyperosmolality. The cells adapt to the hypertonicity by accumulating compatible osmolytes. We have shown that TonEBP play a central role in the compatible osmolyte accumulation via stimulating genes whose products either actively transport or synthesize compatible osmolytes. In addition, TonEBP stimulates the vasopressin regulated urea transporters that play a critical role in the counter current recycling of urea in the renal medulla. Our data demonstrate that TonEBP also stimulates a heat shock protein 70 that functions to protect the cells from the deadly stress of high urea. Thus, TonEBP controls a network of genes that is essential for the function and protection of the renal medulla. We have shown that nuclear localization is the major site of TnEBP regulation under physiological conditions of water diuresis and antidiuresis. We hypothesize that there are signaling pathways that control nucleocytoplasmic trafficking of TonEBP in response to changes in ambient tonicity. Aim 1 is to define domains of TonEBP responsible for tonicity-responsive changes in nuclear localization. Cultured cells will be used in combination with expression of mutated TonEBPs. We expect to define amino acids critical for nuclear import, nuclear export, and modulation of the two opposing activities. These domains will provide key reagents to uncover the tonicity signaling pathways. Phosphorylation of TonEBP temporally correlates with both nuclear important and export. Aim 2 is to define amino acid residues whose phosphorylation affects nuclear localization of TonEBP. Aim I is to uncover the role of protein-protein interaction in nuclear localization. We will investigate the role of TnEBP dimer formation by studying defective mutants. Other components of the TonEBP complex will be identified and their role will also be investigated. These studies are likely to uncover a new paradigm of signal transduction unique to the kidney medulla.