Mechanisms of Cell Volume Regulation in Liver

调节体积的能力对于细胞的存活至关重要。这在肝脏中尤其如此， 由于其在营养物加工、代谢和代谢中的作用， 胆汁形成紊乱的体积控制导致不可逆的细胞肿胀，这是急性和慢性炎症的标志。 慢性肝损伤鉴于这个问题的重要性，本项目的目标是了解如何 在渗透压应激期间维持了肝细胞体积，并进而维持了器官功能。已知 这种压力会使细胞结构发生巨大变化，质膜离子通道 这对肝细胞肿胀后的体积恢复至关重要。该实验室最近的工作表明， 酪氨酸激酶Src在协调这些行动中的新作用。这项提案将检验这一假设 Src就像一个分子开关，将信号从体积敏感的传感器传递到下游， 重组细胞骨架并通过钾激活液体和电解质运动的效应物 和氯离子通道。这将细胞体积维持在生理状态内。具体目标是：（1） 建立容量敏感性Src激活的动力学和细胞定位，（2）确定 Src在体积敏感性细胞骨架重组中的作用，以及（3）阐明Src如何调节 体积敏感离子通道。目标1中的研究将确定Src如何影响体积敏感性 整合素、粘着斑激酶（FAK）和Src效应子的细胞定位和调节功能 Vav和磷脂酶C（PLC）γ。还将检测Src或其效应物的表达是否与细胞凋亡有关。 在人类肝脏疾病中发生改变，表现为肝细胞气球样变。目标2中的研究将测试 Src效应物的抑制改变了肿胀诱导的肌动蛋白动力学， 减弱容量恢复。目标3中的研究将确定Src依赖性细胞外信号是否 ERK受体（ERK）激酶在肿胀时由PLC γ和/或Vav调节，并且ERK是否 效应磷脂酶A2调节容量敏感性钾和氯通道。拟议 研究有望提供一个综合的图片的机制，细胞体积是调节在 肝脏由于细胞体积控制对维持器官水平功能至关重要，因此了解 这些机制将提供新的方法来预防肝脏疾病中的器官功能障碍。

The ability to regulate volume is critical for the survival of cells. This is particularly true in the liver, which is subjected to dynamic changes in osmotic load as a result of its role in nutrient processing, metabolism, and bile formation. Disordered volume control leads to irreversible cell swelling that is a hallmark of acute and chronic liver injury. Given the importance of this problem, the goals of this project are to understand how hepatocellular volume, and by extension organ function, are maintained during osmotic stress. It is known that such stress imposes dramatic changes in cell architecture, and that plasma membrane ion channels are crucial to volume restoration after hepatocellular swelling. Recent work from this laboratory has suggested a novel role for the tyrosine kinase Src in coordinating these actions. This proposal will test the hypothesis that Src serves as a molecular switch that relays signals from volume-sensitive sensors to downstream effectors that reorganize the cytoskeleton and activate fluid and electrolyte movement through potassium and chloride channels. This maintains cell volume within a physiological state. The Specific Aims are: (1) to establish the kinetics and cellular localization of volume-sensitive Src activation, (2) to determine the role of Src in volume-sensitive cytoskeletal reorganization, and (3) to elucidate how Src regulates the activation of volume-sensitive ion channels. Studies in Aim 1 will determine how Src influences the volume-sensitive cellular localization and regulatory function of integrins, focal adhesion kinase (FAK), and the Src effectors Vav and phospholipase C (PLC) gamma. It will also be tested whether the expression of Src or its effectors is altered in human liver diseases manifested by hepatocyte ballooning. Studies in Aim 2 will test whether inhibition of Src effectors modifies swelling-induced actin dynamics, and whether inhibition of these dynamics attenuates volume recovery. Studies in Aim 3 will determine whether Src-dependent extracellular signal receptor (ERK) kinases are regulated upon swelling by PLC gamma and/or Vav, and whether the ERK effector phospholipase A2 regulates volume-sensitive potassium and chloride channels. The proposed studies are expected to provide an integrated picture of mechanisms by which cell volume is regulated in the liver. Since cell volume control is essential to the maintenance of organ level function, an understanding of these mechanisms will provide new ways to prevent organ dysfunction in the setting of liver disease.