Mechanisms of cellular osmosensing and osmotic stress induced damage repair

描述(申请人提供)：细胞渗透平衡是生命的基本要求。所有细胞都暴露在由细胞内溶质通量变化和/或细胞外渗透压扰动所带来的渗透挑战中。大多数哺乳动物细胞受到肾脏的保护，免受细胞外渗透的挑战，肾脏严格调节血液离子和渗透浓度。肾髓质细胞是这种泛化的一个重要例外，通常会受到肾脏浓缩机制的极端渗透压力。细胞通过严格控制盐和有机溶质的得失来维持渗透平衡，这种有机溶质称为有机渗透调节物质，并通过检测和修复渗透胁迫引起的损伤来维持渗透平衡。调节动物细胞渗透调节溶质通量的运输和代谢途径被很好地描述。然而，关于动物细胞检测渗透压扰动的信号机制，渗透压引起的细胞和分子损伤的类型，以及这种损伤是如何被检测、修复和预防的，人们知之甚少。DK61168支持的研究开发了线虫作为一种新的遗传易处理的模型系统，用于定义动物细胞渗透感知和渗透平衡的基本机制。在之前的资助期间，我们进行了一项新的观察，即破坏蛋白质合成激活了有机渗透调节物质积累所需的基因的表达。我们还首次证明了高渗会在体内引起快速和广泛的蛋白质损伤，蛋白质降解所需的基因是高渗应激期间生存所必需的。目前的提案建立在这些新发现的基础上，并解决了三个具有广泛生物学和病理生理学意义的问题。蛋白质合成受阻如何激活渗透敏感基因的表达？细胞利用什么质量控制机制来检测、降解和修复因高渗应激而受损的蛋白质？适应高渗应激抑制高渗诱导的蛋白质损伤的机制是什么？我们将利用细胞生物学、分子和生化方法的组合，首次详细描述高渗应激诱导的蛋白质损伤以及细胞用来应对和预防这种损伤的机制。我们还将开发线虫的遗传易感性，并开始定义信号和信号通路，这些信号和信号通路调节在高渗环境中生存所需基因的表达。我们的工作将为细胞渗透和信号转导以及保护高张应激细胞免受蛋白质损伤和相关损伤和死亡的机制提供新的见解。详细了解高张诱导的信号、细胞损伤和蛋白质损伤是了解肾脏生理学和病理生理学的基础，也直接关系到了解与衰老和许多遗传性疾病相关的病理生理学。

DESCRIPTION (provided by applicant): Cellular osmotic homeostasis is a fundamental requirement for life. All cells are exposed to osmotic challenges brought about by changes in intracellular solute flux and/or perturbations in extracellular osmolality. Most mammalian cells are protected from extracellular osmotic challenges by the kidney, which tightly regulates blood ionic and osmotic concentrations. Renal medullary cells are an important exception to this generalization and are subjected normally to extreme osmotic stress by the renal concentrating mechanism. Cells maintain osmotic homeostasis by the tightly regulated gain and loss of salt and organic solutes termed organic osmolytes, and by detecting and repairing osmotic stress induced damage. The transport and metabolic pathways that mediate animal cell osmoregulatory solute fluxes are well described. However, little is known about the signaling mechanisms by which animal cells detect osmotic perturbations, about the types of cellular and molecular damage induced by osmotic stress, and about how this damage is detected, repaired and prevented. DK61168 supported studies developed the nematode C. elegans as a novel genetically tractable model system for defining fundamental mechanisms of animal cell osmosensing and osmotic homeostasis. During the previous funding period, we made the novel observation that disruption of protein synthesis activates expression of genes required for organic osmolyte accumulation. We also demonstrated for the first time that hypertonicity causes rapid and extensive protein damage in vivo and that genes required for protein degradation are essential for survival during hypertonic stress. The current proposal builds on these new findings and addresses three questions with broad biological and pathophysiological significance. How does disruption of protein synthesis activate osmosensitive gene expression? What are the quality control mechanisms utilized by cells to detect, degrade and repair proteins damaged by hypertonic stress? What are the mechanisms by which acclimation to hypertonic stress suppresses hypertonicity induced protein damage? We will utilize a combination of cell biological, molecular and biochemical approaches to provide the first detailed characterization of hypertonic stress induced protein damage and the mechanisms that cells employ to cope with and prevent this damage. We will also exploit the genetic tractability of C. elegans and begin to define the signals and signaling pathways that regulate expression of genes required for survival in hypertonic environments. Our work will provide novel insights into cellular osmosensing and signal transduction and into the mechanisms that protect hypertonically stressed cells from protein damage and associated injury and death. Detailed understanding of hypertonicity induced signaling, cell injury and protein damage is essential for understanding renal physiology and pathophysiology, and is directly relevant to understanding pathophysiology associated with aging and numerous inherited diseases.