Mechanisms of cellular osmosensing and osmotic stress induced damage repair

描述（由申请人提供）：细胞渗透平衡是生命的基本要求。所有细胞都暴露于细胞内溶质通量的变化和/或细胞外渗透压的扰动所带来的渗透挑战。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。肾髓质细胞是这种概括的一个重要例外，通常受到肾浓缩机制的极端渗透应激。细胞通过严格调节盐和有机溶质（称为有机渗透物）的获得和损失，以及通过检测和修复渗透应激引起的损伤来维持渗透稳态。介导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扰动的信号机制，关于渗透胁迫引起的细胞和分子损伤的类型，以及如何检测、修复和预防这种损伤，人们知之甚少。DK61168支持的研究发展了秀丽隐杆线虫作为一种新的遗传可处理的模型系统，用于定义动物细胞渗透传感和渗透稳态的基本机制。在之前的资助期间，我们进行了新的观察，即蛋白质合成的破坏激活了有机渗透物积累所需的基因表达。我们也首次证明了高渗性在体内引起快速和广泛的蛋白质损伤，并且蛋白质降解所需的基因对于高渗应激下的生存是必不可少的。目前的建议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。蛋白质合成的破坏如何激活渗透敏感基因的表达？细胞检测、降解和修复高渗应激损伤蛋白的质量控制机制是什么？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、分子和生化方法的结合，首次详细描述高渗应激诱导的蛋白质损伤以及细胞应对和预防这种损伤的机制。我们还将利用秀丽隐杆线虫的遗传易感性，并开始定义在高渗环境中生存所需的调节基因表达的信号和信号通路。我们的工作将为细胞渗透传感和信号转导以及保护高渗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。详细了解高渗性诱导的信号、细胞损伤和蛋白质损伤对于理解肾脏生理和病理生理至关重要，并且与理解与衰老和许多遗传性疾病相关的病理生理直接相关。

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. Public Health Relevance: Cellular osmotic homeostasis is a fundamental requirement for life. Studies described in this application will define the signals and signaling pathways that regulate expression of genes required for survival of cells in hypertonic environments and will provide the first detailed characterization of hypertonic stress induced protein damage and the mechanisms that cells employ to cope with and prevent this damage. Detailed understanding of osmotic stress 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.