Maintenance of intestinal epithelial cell homeostasis by prohibitin

描述(申请人提供)：肠上皮细胞动态平衡紊乱是炎症性肠病(IBD)的一个重要特征。已有多项研究报道IBD时上皮细胞线粒体功能障碍。线粒体受损是呼吸链功能障碍导致细胞内活性氧物种(ROS)增加的关键来源，而呼吸链功能障碍可导致细胞死亡。禁止蛋白(PHB)是一种线粒体蛋白，在IBD患者的粘膜活检组织和结肠炎动物模型中的表达减少。我们以前的研究表明，通过基因操作(Villin-PHB转基因小鼠)恢复结肠上皮PHB的表达，或者通过纳米颗粒或腺病毒将治疗性药物输送到结肠，可以保护小鼠免受实验性结肠炎的影响，并减少氧化应激。在培养的肠上皮细胞中，PHB的基因沉默增加了线粒体膜去极化、细胞内ROS、有丝分裂和细胞凋亡，提示PHB参与维持线粒体的完整性和上皮细胞的动态平衡。此外，我们最近的数据显示，PHB在结肠粘膜和培养的肠上皮细胞系中与STAT3相互作用，并调控其下游的凋亡反应。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输链活性。基于这些数据，这一建议的中心假设是PHB调节线粒体STAT3，以维持肠上皮细胞线粒体的完整性和动态平衡。为了解决这一假设，将测试以下目标：1)表征 PHB介导的线粒体STAT3调控及其下游对细胞凋亡和线粒体功能的影响；2)使用肠上皮细胞特异性PHB条件性基因敲除小鼠作为活体模型，研究PHB在基础状态和结肠炎期间维持肠上皮动态平衡和调控线粒体STAT3的作用。综合这两个目标的总体目标是确定PHB在维持上皮内稳态和粘膜完整性方面的作用。总之，这些研究将为PHB和STAT3参与肠道炎症的线粒体功能障碍提供新的全面数据。我们相信，我们的发现将确定新的分子机制，在组织损伤的基础上和背景下保护上皮屏障的完整性，并将提供新的治疗靶点。

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.