mTORC1 activation and alcoholic liver injury

描述（由申请人提供）：mTORC 1激活和酒精性肝损伤关键词：酒精性脂肪肝，mTORC 1，DEPTOR，ER应激和SREBP-1酒精中毒是西方社会肝病的主要原因。肝脏脂肪变性（脂肪肝）是酒精性肝病的早期和可逆阶段。然而，未经检查的肝脂肪变性可发展成不可逆的脂肪性肝炎、纤维化、肝硬化，并最终发展成肝细胞癌。酒精性脂肪性肝病（AFLD）是由内质网（ER）应激信号激活引起的。然而，AFLD中肝ER应激的分子机制尚未完全清楚。虽然在鉴定哺乳动物雷帕霉素靶蛋白复合物1（mTORC 1）通路组分方面取得了很大进展，但对mTORC 1通路在酒精性肝病理生理学中的体内作用知之甚少。我们最近的研究表明，NAD依赖性脱乙酰酶SIRT 1对mTORC 1的肝脏抑制作用抑制了肝脏ER应激，下调了脂肪生成，从而改善了糖尿病小鼠的肝脏脂肪变性。令人兴奋的初步数据显示，肝脏mTORC 1在慢性酗酒喂养的小鼠中被激活，这伴随着ER应激的诱导、脂肪生成的激活和肝脏脂肪变性。重要的是，新的研究表明，与mTORC 1激活一致，酒精喂养小鼠中DEPTOR（一种新发现的mTORC 1内源性抑制剂）的肝脏水平降低。为了更好地了解酒精性肝病的发病机制并开发该疾病的替代治疗策略，我们的中心假设是mTORC 1通过促进肝脏ER应激和刺激脂肪生成在酒精性脂肪性肝病中发挥关键作用。提出了两个具体的目标：1）表征mTORC 1在酒精诱导的ER应激和肝细胞脂肪生成中的功能和机制作用; 2）确定mTORC 1抑制是否改善酒精性脂肪肝小鼠的肝脂肪变性和ER应激。为响应NIAAA项目（PA-10-094）“酒精诱导的器官损伤和保护中的应激途径”，拟定的研究将确定长期酒精暴露是否会通过mTORC 1组分（如DEPTOR、TSC 1/2或Raptor）导致mTORC 1激活，从而加速肝脂肪变性和ER应激的发展。将利用基于细胞的体外机制研究以及操纵肝脏mTORC 1活性的体内药理学和遗传学方法。这些研究的创新点包括：（1）对mTORC 1作为酒精诱导的内质网应激通路和脂肪肝的新调节剂的新认识;（2）DEPTOR依赖性抑制mTORC 1通过缓解内质网应激和抑制脂肪生成来改善酒精性脂肪肝和肝损伤的新概念;（3）DEPTOR/mTORC 1作为AFLD和ER应激相关肝病如癌症的治疗干预的新靶点。我们的长期目标是阐明AFLD的病理机制，确定在酒精性肝病的早期和可逆阶段进行干预的新分子靶点，并开发AFLD的潜在标志物以帮助早期诊断和预后。

DESCRIPTION (provided by applicant): mTORC1 activation and alcoholic liver injury Key words: alcohol fatty liver, mTORC1, DEPTOR, ER stress, and SREBP-1 Alcoholism is a leading cause of liver disease in Western societies. Hepatic steatosis (fatty liver) is an early and reversible stage of alcoholic liver disease. However, unchecked hepatic steatosis can develop into irreversible steatohepatitis, fibrosis, cirrhosis, and ultimately hepatocellular carcinoma. Alcoholic fatty liver disease (AFLD) is attributed to the activation of endoplasmic reticulum (ER) stress signaling. However, the molecular mechanisms underlying hepatic ER stress in AFLD are not fully understood. Although great progress has been made in the identification of mammalian target of rapamycin complex 1 (mTORC1) pathway components, relatively little is known about the in vivo role of the mTORC1 pathway in alcoholic liver pathophysiology. Our recent studies demonstrate that hepatic inhibition of mTORC1 by the NAD-dependent deacetylase SIRT1 suppresses hepatic ER stress, downregulates lipogenesis, and thereby ameliorates hepatic steatosis in diabetic mice. Exciting preliminary data show that hepatic mTORC1 is activated in chronic binge alcohol-fed mice, which is accompanied by induction of ER stress, activation of lipogenesis, and hepatic steatosis. Importantly, new studies suggest that consistent with mTORC1 activation, hepatic levels of DEPTOR, a newly identified endogenous inhibitor of mTORC1, are reduced in alcohol-fed mice. To better understand the pathogenesis of alcoholic liver disease and develop alternative therapeutic strategies for the disease, our CENTRAL HYPOTHESIS is that mTORC1 plays a key role in alcoholic fatty liver disease by promoting hepatic ER stress and stimulating lipogenesis. Two specific aims are proposed: 1) To characterize the functional and mechanistic role of mTORC1 in alcohol-induced ER stress and lipogenesis in hepatocytes; 2) To determine whether mTORC1 inhibition ameliorates hepatic steatosis and ER stress in mice with alcoholic fatty liver. In response to the NIAAA program (PA-10-094) entitled "stress pathways in alcohol induced organ injury and protection", the proposed studies will determine whether chronic alcohol exposure results in mTORC1 activation via mTORC1 components such as DEPTOR, TSC1/2 or Raptor and thereby accelerates the development of hepatic steatosis and ER stress. In vitro cell-based mechanistic studies as well as in vivo pharmacologic and genetic approaches of manipulating hepatic mTORC1 activity will be utilized. Innovative aspects of these proposed studies include: (1) new insight into mTORC1 as a novel regulator of alcohol-induced ER stress pathways and fatty liver; (2) the novel concept that DEPTOR-dependent inhibition of mTORC1 ameliorates alcoholic fatty liver and liver injury by relieving ER stress and inhibiting lipogenesis; (3) DEPTOR/mTORC1 as new targets for the therapeutic interventions of AFLD and ER stress-related liver diseases such as cancer. Our long-term objective is to elucidate the pathological mechanisms of AFLD, to identify novel molecular targets for intervention at this early and reversible stage of alcoholic liver disease, and to develop a potential marker of AFLD to aid early diagnosis and prognosis.