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。多项研究报告了IBD期间上皮细胞中的线粒体功能障碍。受损的线粒体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。在IBD患者的粘膜活检和结肠炎动物模型中，一种线粒体蛋白--抑制素（PHB）的表达降低。我们以前的研究已经表明，使用基因操作（villin-PHB转基因小鼠）或通过纳米颗粒或腺病毒向结肠递送治疗剂来恢复结肠上皮PHB表达保护小鼠免受实验性结肠炎并降低氧化应激。在培养的肠上皮细胞中，基因沉默的PHB增加线粒体膜去极化，细胞内ROS，线粒体自噬和细胞凋亡，这表明，PHB参与维持线粒体的完整性和上皮细胞的稳态。此外，我们最近的数据表明，在结肠粘膜和培养的肠上皮细胞系中，PHB与STAT 3相互作用，并调节其下游的凋亡反应。除了其作为转录因子的活性外，STAT 3最近已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，该提议的中心假设是，PHB调节线粒体STAT 3以维持肠上皮细胞中的线粒体完整性和稳态。为了解决这一假设，将测试以下目标：1）表征 PHB-mediated mitochondrial STAT 3 modulation and its downstream effects on apoptosis and mitochondrial function and 2）使用肠上皮细胞特异性PHB-conditional knockout mouse作为体内模型，用于检查在基础条件和结肠炎期间PHB-mediated mitochondrial STAT 3 modulation and modulate mitochondrial STAT 3 during basal conditions and colitis中PHB-mediated mitochondrial STAT 3 modulation的作用。该提案的总体目标是确定PHB在维持上皮稳态和粘膜完整性中的作用。总之，这些研究将提供关于PHB和STAT 3参与肠道炎症特征性线粒体功能障碍的新的全面数据。我们相信，我们的研究结果将确定新的分子机制，采取行动，以保持上皮屏障的完整性基础和组织损伤的背景下，并将提供新的治疗目标。

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.