Control of Epithelial Proliferation by the Microbiota

描述（由申请人提供）：我们对肠道微生物群在胃肠道癌症发生和进展期间影响上皮细胞周期调节和干细胞动力学的分子机制的认识存在重大差距。这一差距是科学进步的障碍，因为在解决这一问题之前，肠道微生物群和宿主之间生态失调所导致的状况的解释将继续超出我们的理解。我们的长期目标是确定细胞信号传导途径，细菌群落结构和介导微生物群对人类健康影响的微生物产物。该提案的目的是确定微生物群的扰动如何影响肠道干细胞（ISC）的周转，并通过扩展肿瘤的启动或进展-以及最终，微生物群的故意操纵如何提供治疗策略。基于我们的初步数据，我们的中心假设是高度适应宿主的微生物群的特定成员（特别是乳酸杆菌）已经共同进化，以通过诱导ROS的产生来促进肠细胞增殖，ROS然后调节细胞增殖。 肠道上皮细胞的信号。鉴于微生物群的一个子集具有有效的促增殖潜力，我们进一步假设微生物的绝对或相对数量的改变将对上皮细胞生长动力学产生后续影响，特别是在肠损伤的情况下，可能在肠肿瘤的发生和进展中发挥作用。这一假说的基本原理是公认的概念，即通过宿主NADPH氧化酶在不同亚细胞结构域中的作用生理产生低水平的ROS，在多个信号网络中充当关键的第二信使。此外，我们发表的和初步的数据确定了由细菌诱导的ROS产生调节的充分表征的致癌细胞信号传导途径。此外，已经确定的是，在不同的亚细胞结构域中生理产生的低水平ROS由于其可逆氧化低pKa半胱氨酸（“硫开关”）的能力而在多个信号传导网络中充当关键的第二信使。 特定的传感器靶蛋白。基于我们的研究小组产生的这些令人信服的初步数据，中心假设将在三个特定目标中进行测试：1）表征介导微生物群诱导的干细胞增殖的信号通路，2）确定模型上皮早期瘤形成中操纵的微生物群的影响，以及3）确定诱导氧化还原依赖性细胞信号传导的共生细菌和细菌群落。我们的方法将采用，离体肠模型，基因敲除小鼠，一种新的氧化还原I-CAT蛋白质组学技术，和一个高度创新的遗传听话的果蝇模型，其生物学可以操纵到更大的程度比哺乳动物模型。这些研究的结果将对公共卫生产生重要的积极影响，因为它们直接影响到特发性肠癌。这项调查也与的使命有关 NIDDK/NIH通过解决这些条件的预防性干预措施。

DESCRIPTION (provided by applicant): There is a critical gap in our knowledge regarding the molecular mechanisms by which the intestinal microbiota influence epithelial cell cycle regulation and stem cell dynamics during the initiation and progression of GI cancers. This gap represents a barrier to scientific progress because, until it is addressed, an explanation for conditions resulting from dysbiosis between the gut microbiota and the host will continue to be beyond our understanding. Our long-term goal is to identify the cellular signaling pathways, the bacterial community structure, and the microbial products that mediate the influences of the microbiota on human health. The objective of this proposal is to identify how perturbations to the microbiota influence intestinal stem cell (ISC) turnover, and by extension tumor initiation or progression -and ultimately, how deliberate manipulation of the microbiota may offer a therapeutic strategy. Based on our preliminary data, our central hypothesis is that specific members of the highly host adapted microbiota (particularly lactobacilli) have co-evolved to facilitate intestinal cell proliferation by inducing the generation of ROS which then regulate cell signaling in the gut epithelium. Given that a subset of the microbiota possess potent pro-proliferative potential, we further hypothesize that altered, absolute or relative numbers of the microbes will have consequent effects on epithelia growth dynamics, and particularly in cases of intestinal injury, may play a role in intestinal tumor initiation and progression. The rationale fo this hypothesis is the well-established notion that physiological generation of low levels of ROS by the action of host NADPH oxidases in distinct subcellular domains act as critical second messengers in multiple signaling networks. In addition, our published and preliminary data identify well- characterized oncogenic cell signaling pathways that are modulated by bacterial-induced ROS generation. Furthermore, it is well-established that physiological generation of low levels of ROS in distinct subcellular domains act as critical second messengers in multiple signaling networks due to their ability to reversibly oxidize low pKa cysteines ("sulfur switches") of specific sensor target proteins. Based on these compelling preliminary data generated by our research group, the central hypothesis will be tested in three specific aims; 1) Characterize the signaling pathways that mediate microbiota-induced stem cell proliferation, 2) Identify the influence of manipulated microbiota in model epithelial early neoplasia, and 3) Identify symbiotic bacteria and bacterial communities that induce redox dependent cell signaling. Our approach will employ, ex-vivo enteroid model, knockout mice, a novel redox I-CAT proteomic technique, and a highly innovative genetically tractable Drosophila model whose biology can be manipulated to a far greater extent than mammalian models. The outcomes of these investigations will have an important positive impact on public health because of direct implications to idiopathic intestinal cancers. The investigation is also relevant to the mission of NIDDK/NIH by addressing preventative interventions for these conditions.