Regulation of Stellate Cell Contractility

描述(由申请人提供)：肝脏损伤的伤口愈合反应的特征是纤维形成和组织收缩增强。临床结果是肝硬变，是美国和世界范围内发病率和死亡率的主要原因。近来研究证实，肝间质细胞在肝损伤反应中起重要作用，又称肝窦周围星状细胞(Ito细胞或脂肪细胞)。在这一过程中的关键事件之一是星状细胞的激活，导致细胞外基质合成增加和从头开始的平滑肌(-肌动蛋白)表达，最近的平滑肌肌球蛋白亚型。星状细胞中平滑肌蛋白的表达与其增强收缩能力的潜力有关。进一步推测，在激活的星状细胞中发现的高度收缩的表型在受损的肝脏中具有重要的生理效应，因为它有助于增加肝内对血流的阻力，这是门静脉高压症的典型特征，可能是由于肝脏的物理扭曲所致。在这项建议中提出的初步研究表明，平滑肌g-肌动蛋白直接介导星状细胞收缩，并在介导门脉高压中发挥重要的生理作用。此外，应用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特性增强提供了可能的分子机制。 因此，该提案的总体目标是了解激活的星状细胞典型的收缩能力增强的分子基础，并确定阻断这种夸大的收缩表型是否对肝内门脉高压或伤口愈合反应本身有影响。为此，本申请建议研究正常和激活的星状细胞中肌球蛋白II的调节和肌球蛋白信号通路，后续研究将探索平滑肌蛋白(即平滑肌肌球蛋白和肌动蛋白)的调节机制以及这些蛋白质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的分子基础，而且与人类肝病有直接关系。

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.