Maintenance of intestinal epithelial cell homeostasis by prohibitin

描述（由申请人提供）：肠上皮细胞稳态紊乱是炎症性肠病（IBD）的一个关键特征。多项研究报道了IBD期间上皮细胞线粒体功能障碍。线粒体损伤是呼吸链功能障碍导致细胞内活性氧（ROS）增加的关键来源，可导致细胞死亡。禁止蛋白（PHB）是一种线粒体蛋白，在IBD患者和结肠炎动物模型的粘膜活检中表达降低。我们之前的研究表明，通过基因操作（绒毛蛋白-PHB转基因小鼠）或通过纳米颗粒或腺病毒给药到结肠可以恢复结肠上皮PHB的表达，保护小鼠免受实验性结肠炎并减少氧化应激。在培养的肠上皮细胞中，PHB基因沉默增加了线粒体膜去极化、细胞内ROS、线粒体自噬和凋亡，表明PHB参与维持线粒体完整性和上皮细胞稳态。此外，我们最近的数据表明，PHB在结肠黏膜和培养的肠上皮细胞系中与STAT3相互作用，并调节其下游凋亡反应。除了作为转录因子的活性外，STAT3最近被证明存在于细胞的线粒体中，并促进最佳的电子传递链活性。基于这些数据，本提案的中心假设是PHB调节线粒体STAT3以维持肠上皮细胞线粒体的完整性和稳态。为了解决这一假设，将测试以下目标：1)表征

DESCRIPTION (provided by applicant): Disturbed intestinal epithelial cell homeostasis is a key feature of inflammatory bowel disease (IBD). Multiple studies have reported mitochondrial dysfunction in epithelial cells during IBD. Damaged mitochondria are a key source of increased intracellular reactive oxygen species (ROS) from respiratory chain dysfunction that can result in cell death. Expression of prohibitin (PHB), a mitochondrial protein, is decreased in mucosal biopsies from IBD patients and in animal models of colitis. Our previous studies have shown that restoration of colonic epithelial PHB expression using genetic manipulation (villin-PHB transgenic mice) or therapeutic delivery to the colon via nanoparticle or adenovirus protects mice from experimental colitis and reduces oxidative stress. Gene silencing of PHB in cultured intestinal epithelial cells increases mitochondrial membrane depolarization, intracellular ROS, mitophagy, and apoptosis, suggesting that PHB is involved in maintaining mitochondrial integrity and epithelial cell homeostasis. Furthermore, our recent data show that PHB interacts with STAT3 in colon mucosa and cultured intestinal epithelial cell lines and modulates its downstream apoptotic responses. In addition to its activities as a transcription factor, STAT3 has recently been shown to reside in the mitochondria of cells and promote optimal electron transport chain activity. Based on these data, the central hypothesis of this proposal is that PHB modulates mitochondrial STAT3 to maintain mitochondrial integrity and homeostasis in intestinal epithelial cells. To address this hypothesis, the following Aims will be tested: 1) to characterize PHB-mediated mitochondrial STAT3 modulation and its downstream effects on apoptosis and mitochondrial function and 2) to use an intestinal epithelial cell-specific PHB conditional knockout mouse as an in vivo model for examining the role of PHB in maintaining intestinal epithelium homeostasis and modulating mitochondrial STAT3 during basal conditions and colitis. The overall objective of this proposal integrated across the two Aims is to determine the role of PHB in maintaining epithelial homeostasis and mucosal integrity. Together, these studies will provide novel comprehensive data on the involvement of PHB and STAT3 in mitochondrial dysfunction characteristic of intestinal inflammation. We believe our findings will identify novel molecular mechanisms that act to preserve epithelial barrier integrity basally and in the context of tissue injury and will provide new therapeutic targets.