Regulation of Stellate Cell Contractility

描述（由申请方提供）：对肝损伤的伤口愈合反应的特征在于增强的纤维形成以及组织收缩。临床结果肝硬化是美国和世界范围内发病率和死亡率的主要原因。最近已经确定，常驻肝间充质细胞，称为窦周星状细胞（Ito细胞或脂细胞），在肝损伤反应中起关键作用。这一过程中的关键事件之一是星状细胞的“活化”，导致细胞外基质合成增加和平滑肌β-肌动蛋白表达以及最近的平滑肌肌球蛋白同种型。平滑肌蛋白在星状细胞中的表达与其增强收缩性的潜力相关联。此外，据推测，在激活的星状细胞中发现的高度收缩表型通过增加门静脉高压症典型的肝内血流阻力以及可能通过肝脏的物理变形，对受损肝脏具有重要的生理作用。在这个提议中提出的初步研究中，表明平滑肌g-肌动蛋白直接介导星状细胞收缩，并且在介导门静脉高压中起重要的生理作用。此外，本申请中提供的初步数据表明，肌球蛋白马达在损伤和激活过程中上调，为激活的星状细胞的收缩性特征增强提供了推定的分子机制。 因此，该提案的总体目标是了解活化星状细胞典型的增强收缩性的分子基础，并确定这种夸张的收缩表型的中断是否对肝内门脉高压或伤口愈合反应本身有影响。为此，本申请提出在正常和活化的星状细胞中检查肌球蛋白II调节和肌球蛋白信号传导途径。随后的研究将探索平滑肌蛋白（即，平滑肌肌球蛋白和肌动蛋白）调节以及这些蛋白质中的每一种在肝脏中的体内功能。生理终点将是一个重要的焦点。拟议的研究将阐明星状细胞收缩性的分子基础，而且与人类肝脏疾病直接相关。

DESCRIPTION (provided by applicant): The wound healing response to liver injury is characterized by enhanced fibrogenesis as well as tissue contraction. The clinical result, cirrhosis, is a major cause of morbidity and mortality in the United States and worldwide. It has recently been established that resident hepatic mesenchymal cells, termed perisinusoidal stellate cells (Ito cells or lipocytes), play a critical role in the hepatic wounding response. One of the key events in this process is the "activation" of stellate cells, resulting in increased extracellular matrix synthesis and de novo smooth muscle (-actin expression, and recently smooth muscle myosin isoforms. Expression of smooth muscle proteins in stellate cells has been coupled to their potential for enhanced contractility. Further, it is postulated that the highly contractile phenotype found in activated stellate cells has important physiologic effects in the injured liver by contributing to increased intrahepatic resistance to blood flow typical of portal hypertension and perhaps by physical distortion of the liver. In preliminary studies presented in this proposal, it is shown that smooth muscle g- actin directly mediates stellate cell contraction and that it plays an important physiologic role in mediating portal hypertension. Further, preliminary data presented in the application indicate that myosin motors are upregulated during the injury and activation process, providing a putative molecular mechanism for enhanced contractility characteristic of activated stellate cells. The overall aim of the proposal is therefore to understand the molecular basis for enhanced contractility typical of activated stellate cells and to determine whether interruption of this exaggerated contractile phenotype has effects on intrahepatic portal hypertension or the wound healing response itself. Toward this end, the application proposes to examine myosin II regulation and the myosin signaling pathway in normal and activated stellate cells Subsequent studies will explore mechanisms of smooth muscle protein (i.e., smooth muscle myosin and actin) regulation as well as the in vivo function of each of these proteins in the liver. Physiologic endpoints will be an important focus. The proposed studies will shed light on the molecular basis of stellate cell contractility and moreover have direct relevance to human liver disease.