Role of Plakoglobin on Intestinal Mucosal Healing and Epithelial Barrier Regulation in Inflammatory Bowel Disease

炎症性肠病(IBD)表现出一种复杂的发病机制，目前尚不清楚。到目前为止，治疗的重点是调节IBD的异常免疫反应，这与大多数患者的高副作用和有限的临床反应有关。由于肠上皮屏障(IEB)的恢复和粘膜愈合是IBD治疗中的一个重要治疗目标，因此需要针对肠上皮细胞的特定方法。先前的研究指出桥粒蛋白桥粒蛋白-2(Dsg2)和桥粒蛋白-2(Dsc2)在肠道屏障稳定和伤口愈合中的相关性，特别是在IBD患者中，机制很不明确。这项建议的初步工作表明，桥粒斑块蛋白蛋白是桥粒完整性的关键调节因子：IBD患者产生的肠道标本和器官中的斑块球蛋白显著减少。在体外，siRNA诱导肠上皮细胞培养的蛋白表达下调，导致细胞边界的Dsg2丢失，细胞间黏附减少，肠上皮损伤愈合发生变化。在此基础上，我们假设白蛋白的丢失与肠道屏障功能的调节和粘膜愈合密切相关。在机制水平上，蛋白可能作为支架蛋白促进细胞运动、肠屏障功能和粘膜愈合等重要信号通路，这可能在IBD肠屏障功能的发生和延续中发挥重要作用。这项建议的目的是全面评估在小鼠肠道上皮细胞选择性诱导的蛋白基因敲除(VilCreERT2 JUP-/-)后，肠道蛋白在体内的作用。这个老鼠品系是为这个项目做准备而产生的。此外，来自IBD患者的小鼠肠样、人肠样和肠上皮细胞系将有助于阐明蛋白依赖屏障调节和粘膜愈合的机制。从长远来看，这将为IBD患者重建粘膜稳态的特定机制和潜在的新治疗靶点增加新的见解。

Inflammatory Bowel Diseases (IBD) display a complex pathogenesis that is poorly understood. To date, therapies focus on the modulation of the aberrant immune response in IBD which is associated with high rates of side effects and a limited clinical response in a majority of patients. Since restoration of the intestinal epithelial barrier (IEB) and mucosal healing is an important therapeutic aim in IBD treatment, specific approaches to target the intestinal epithelium are needed. Previous search pointed to the relevance of the desmosomal proteins Desmoglein-2 (Dsg2) and Desmocollin-2 (Dsc2) on barrier stabilization and wound healing in the gut and especially in IBD patients by largely undefined mechanisms. Preliminary work for this proposal suggests that the desmosomal plaque protein plakoglobin is a critical regulator for desomosomal integrity: in intestinal specimens and organoids generated from patients with IBD plakoglobin was significantly reduced. In vitro, siRNA-induced downregulation of plakoglobin in cell cultures of intestinal epithelial cells resulted in a loss of Dsg2 at cell borders, reduced intercellular adhesion and changes of intestinal epithelial wound healing. Based on this, we hypothesize that the loss of Plakoglobin is critically involved in the regulation of intestinal barrier function and mucosal healing. On a mechanistic level, Plakoglobin might act as a scaffold protein to facilitate signaling pathways important for cell motility, intestinal barrier function and mucosal healing which may play a relevant role for the onset and perpetuation of intestinal barrier function in IBD. The aim of this proposal is to comprehensively evaluate the role of intestinal plakoglobin in vivo following intestinal epithelial selective inducible knockout of Plakoglobin in mice (VilCreERT2 JUP-/-). This mouse strain has been generated in preparation for this project. In addition, murine enteroids, human enteroids from IBD patients and intestinal epithelial cell lines will serve to elucidate the mechanisms underlying plakoglobin-dependent barrier regulation and mucosal healing. On a long-term perspective, this will add novel insights into specific mechanisms and potential novel therapeutic targets to reconstitute mucosal homeostasis in patients with IBD.