Bacterial regulation of intestinal antimicrobial defense

描述(申请人提供)：哺乳动物宿主面临的一个主要挑战是与寄生在肠道中的大量细菌群落保持共生关系。肠上皮是肠道微生物区系和内部宿主组织之间的主要屏障，然而，关于肠上皮细胞如何控制细菌与粘膜表面的相互作用以及限制微生物对肠道屏障的渗透，人们知之甚少。填补这一知识空白是至关重要的，因为人类的许多胃肠道疾病起源于对肠道上皮的病理性入侵，或者涉及共生微生物区系和上皮细胞之间的失调相互作用。在之前的项目期间，我们表明肠上皮细胞自噬限制了机会性侵袭性共生体和侵袭性肠道病原体鼠伤寒沙门氏菌对组织的侵袭。我们发现，鼠伤寒沙门氏菌的自噬激活需要先天免疫信号转接子MyD88，并受抗自噬因子BCL2和必需的自噬蛋白Beclin 1之间的相互作用调节。因此，我们的初步发现确定自噬是一种重要的上皮细胞自主抗菌机制，并表明上皮自噬激活受到严格调控。在下一个项目期间，我们建议在这些发现的基础上，更深入地了解肠道上皮细胞中抗菌自噬是如何调节的，并阐明上皮自噬对于维持与微生物区系的动态平衡的生理意义。在目标1中，我们将使用活体小鼠模型来进一步描述bcl2在调节肠道上皮细胞抗菌自噬中的作用。在目标2中，我们将使用体内方法来确定MyD88如何调节肠道上皮细胞中的抗菌自噬。在目标3中，我们将使用具有上皮细胞特异性自噬缺陷的小鼠来测试自噬促进机会性入侵共生细菌清除的假设。这些研究将极大地促进我们对肠道上皮细胞如何促进肠道内不同细菌群落的动态平衡的理解。此外，我们的发现应该建议新的策略，以增强肠道上皮细胞自噬，以防止肠道感染和炎症性疾病。

DESCRIPTION (provided by applicant): A major challenge for mammalian hosts is to maintain symbiotic relationships with the vast bacterial communities that colonize the intestines. The intestinal epithelium is the primary barrier between the intestinal microbiota and internal host tissues, yet little is known about how epithelial cells control bacterial interactions with the mucosal surface and limit microbial penetration of the intestinal barrier. Filling this knowledge gap is crucial, as many gastrointestinal diseases of humans originate with pathogenic invasions of the intestinal epithelium, or involve dysregulated interactions between the commensal microbiota and epithelial cells. In the previous project period, we showed that intestinal epithelil cell autophagy limits tissue invasion by opportunistically invasive commensals and the invasive intestinal pathogen, Salmonella typhimurium. We found that autophagy activation by S. typhimurium requires the innate immune signaling adaptor MyD88, and is regulated by interactions between the anti-autophagy factor BCL2 and the essential autophagy protein Beclin 1. Our initial findings thus identify autophagy as an important epithelial cell-autonomous mechanism of antibacterial defense and indicate that epithelial autophagy activation is tightly regulated. During the next project period, we propose to build upon these findings to gain a deeper understanding of how antibacterial autophagy is regulated in the intestinal epithelium, and to elucidate the physiological significance of epithelial autophagy for maintaining homeostasis with the microbiota. In Aim 1, we will use in vivo mouse models to further delineate the role of BCL2 in regulating antibacterial autophagy in the intestinal epithelium. In Aim 2, we will use in vivo approaches to determine how MyD88 regulates antibacterial autophagy in intestinal epithelial cells. In Aim 3, we will use mice harboring epithelial cell-specific autophag defects to test the hypothesis that autophagy promotes the clearance of opportunistically-invasive commensal bacteria. These studies will significantly advance our understanding of how intestinal epithelial cells promote homeostasis with the diverse bacterial community in the intestine. Further, our findings should suggest novel strategies for enhancing intestinal epithelia cell autophagy to protect against intestinal infections and inflammatory diseases.