Physiological Regulation of Intestinal Epithelial Transport and Barrier Function

肠道运输缺陷是许多肠道疾病的中心组成部分。这种运输，在形式上 营养、离子和水分的吸收是由特定的细胞转运蛋白以及 被动的细胞旁运动穿过上皮紧密连接。一种新兴的观点是，个人 转运蛋白可以相互调节，也可以调节细胞旁的通透性，从而产生协调调节。 肠道运输的影响。这一概念得到了我们对钠-葡萄糖共转运依赖的TIME的研究的支持 连接调节显示顶端Na+-葡萄糖共转运体SGLT1激活了一种信号转导 依次触发NHE3递送到质膜的级联，NHE3是一种尖端的Na+-H+交换器， 增加心尖部Na+-H+交换，肌球蛋白轻链(MLC)激酶激活，MLC磷酸化， 肌动球蛋白收缩，并增加紧密连接通透性。尽管有这些和其他方面的进步，但 囊泡运输、蛋白质相互作用和肌动球蛋白收缩调节的机制 肠上皮转运和屏障功能的关系在很大程度上仍不清楚。这一关键差距限制了我们的 了解肠道转运和屏障功能障碍的疾病机制的能力，包括 感染性、炎症性和吸收不良的腹泻疾病。因此，本应用程序的目标是 确定激活膜交通和修饰的信号转导通路的机制 蛋白质相互作用参与肠道转运和屏障功能的调节。我们将完成 这些目标通过三个特定的目标：1.确定Ezrin在蛋白质的急性调节中的作用 传递到质膜，2.确定定义动态行为的机制 紧密连接的蛋白质，以及3.确定肌动球蛋白依赖的机制和意义 严密的连接维护和调节。这些研究将使用体外和体内模型进行。 包括在活细胞和组织中表达的荧光融合蛋白的成像和体内分析 紧密连接通透性转基因操作的继发性免疫激活。因此，我们将 极大地提高了我们对膜、蛋白质和细胞骨架 动力学有助于调节运输和屏障功能。除了提供新的基本原理之外 这一知识预计将对人类健康产生重大积极影响，因为它将使 合理开发运输或屏障功能缺陷疾病的新治疗策略。 摘要：肠上皮必须平衡营养物质的运输和对屏障的需要，以保持 肠道内容物与身体的其余部分分开。最近的数据表明，这些 职能是协调监管的，这与两者经常受到损害的事实相一致 在疾病中。拟议的研究将促进对这一协调规则和 因此可能导致开发治疗肠道疾病的新方法。

Defective intestinal transport is a central component of many intestinal diseases. Such transport, in the form of nutrient, ion, and water absorption, is accomplished by specific transcellular transporters as well as passive paracellular movement across the epithelial tight junction. An emerging view is that individual transporters can regulate one another as well as paracellular permeability, resulting in coordinate regulation of intestinal transport. This concept is supported by our studies of Na+-glucose cotransport-dependent tight junction regulation showing that SGLT1, the apical Na+-glucose cotransporter, activates a signal transduction cascade that sequentially triggers delivery of NHE3, an apical Na+-H+ exchanger, to the plasma membrane, increased apical Na+-H+ exchange, myosin light chain (MLC) kinase activation, MLC phosphorylation, actomyosin contraction, and increased tight junction permeability. Despite these and other advances, the mechanisms by which vesicular transport, protein interactions, and actomyosin contraction effect regulation of intestinal epithelial transport and barrier function remain largely undefined. This critical gap limits our ability to understand the mechanisms of diseases with intestinal transport and barrier dysfunction, including infectious, inflammatory, and malabsorptive diarrheal diseases. Thus, the objectives of this application are to define the mechanisms by which signal transduction pathways that activate membrane traffic and modify protein interactions are involved in regulation of intestinal transport and barrier function. We will accomplish these objectives through three specific aims: 1. To define the role of ezrin in acute regulation of protein delivery to the plasma membrane, 2. To identify the mechanisms that define the dynamic behavior of proteins at the tight junction, and 3. To define the mechanisms and significance of actomyosin-dependent tight junction maintenance and regulation. These studies will be performed using in vitro and in vivo models that include imaging of fluorescent fusion proteins expressed in living cells and tissues and in vivo analysis of immune activation secondary to transgenic manipulation of tight junction permeability. As a result we will significantly advance our understanding of the mechanisms by which membrane, protein, and cytoskeletal dynamics contribute to regulation of transport and barrier function. In addition to providing new fundamental knowledge this is expected to have significant positive effects on human health because it will allow the rational development of new therapeutic strategies for diseases with deficient transport or barrier function. SUMMARY: The intestinal epithelium must balance nutrient transport with the need for a barrier that keeps the intestinal contents separate from the remainder of the body. Recent data have shown that these functions are coordinately regulated, which is consistent with the fact that both are frequently compromised in disease. The proposed studies will advance mechanistic understanding of this coordinate regulation and may therefore lead to the development of novel approaches for treatment of intestinal disease.