Tonicity signaling to TonEBP transcription factor

哺乳动物肾髓质的渗透压非常高。高渗透压为水的再吸收和尿液浓度提供动力，这是肾脏维持适当的体液量和血压的关键功能。盐和尿素是肾髓质间质中的主要溶质。不幸的是，高盐（高渗）会导致DNA损伤，高尿素会导致细胞死亡。为了肾脏的正常功能，肾髓细胞必须克服高渗的有害影响。细胞通过积累相容的渗透细胞来适应高渗性。我们已经证明，TonEBP通过刺激基因在相容性渗透物积累中发挥核心作用，其产物主动运输或合成相容性渗透物。此外，TonEBP刺激抗利尿激素调节的尿素转运蛋白，这些转运蛋白在肾髓质尿素逆流循环中起关键作用。我们的数据表明，TonEBP还能刺激热休克蛋白70，保护细胞免受高尿素的致命压力。因此，TonEBP控制着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，在水利尿和抗利尿的生理条件下，核定位是TnEBP调控的主要位点。我们假设有信号通路控制核细胞质转运TonEBP以响应环境张力的变化。目的1是定义负责核定位中张力响应变化的TonEBP结构域。培养的细胞将与突变的tonebp的表达结合使用。我们期望定义对核进口、核出口和两种相反活动的调节至关重要的氨基酸。这些结构域将为揭示强直性信号通路提供关键试剂。TonEBP的磷酸化在时间上与核重要和出口相关。目的2是确定磷酸化影响TonEBP核定位的氨基酸残基。目的一是揭示蛋白-蛋白相互作用在核定位中的作用。我们将通过研究缺陷突变体来研究TnEBP二聚体形成的作用。TonEBP复合物的其他组分将被确定，它们的作用也将被研究。这些研究很可能揭示肾髓质独有的信号转导的新范式。

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.