Small GTP Binding Proteins in Gastrointestinal Mucosa

顶端转运蛋白和酶的运输到肠细胞刷状缘对于建立 从肠腔吸收正常的液体、营养和电解质。同样，建立常态 细胞间紧密连接和粘连连接的蛋白质组成决定了上皮细胞的完整性 屏障功能。根尖运输或连接完整性的异常会导致肠道病理 包括腹泻、便秘和肠道屏障功能障碍。过去十年的调查显示 建立了依赖Rab11a和Rab8a的膜循环系统的组件调节 顶膜和连接蛋白的运输是维持适当的顶端极性所必需的。 功能性肌球蛋白VB(MYO5B)的丢失导致继发性心尖转运蛋白丢失导致严重腹泻 伴有微绒毛夹杂的新生儿中观察到的Rab11a和Rab8a依赖的根尖转运缺陷 疾病(MVID)。同时，Rab11a相互作用的蛋白Rab11-FIP1和Rab11-FIP2调节 连接结构和功能，部分通过它们被关键的极性相关激酶磷酸化 Mark2/Par1b。所有这些研究都使人们认识到，心尖极性的协调调节 而根尖循环系统各组成部分的转运是肠细胞生理学和 病理生理学。我们假设，通过回收系统的各个方面的路径提供 特定货物运输到顶膜和细胞间连接处的特异性。顶端 循环系统是干预破坏心尖的病理生理的关键靶点 膜运输到灌木丛边缘并建立功能连接的完整性。要分析这一点 假设，我们将追求两个具体目标：第一，我们将确定顶端元素的作用 将离子转运体和酶运输到肠细胞根尖刷状边缘的循环系统。这些 研究将检测内源性肠细胞顶端蛋白在人类肠小肠中的命运 在可渗透膜上的二维单层培养上分化。第二，我们将研究 Rab11-FIP1B及其被Mark2/Par1b磷酸化在肠道细胞调节中的作用 连接功能。这些研究将使我们更好地理解Rab11-FIP1B的磷酸化 管制贩运至各路口及维持这些路口。 影响：这些研究将确定可能调节心尖循环系统的组件 贩运特定灌木边界和交界处的货物。根尖多径路的确定 将货物贩运到灌木丛边界和交界处将提供对特定路径如何中断的洞察 可能会改变生理以及如何通过改变路线来恢复贩运的病理生理损失 蛋白质通向根尖膜的替代途径。

Trafficking of apical transporters and enzymes to the enterocyte brush border is critical for the establishment of normal fluid, nutrient and electrolyte absorption from the gut lumen. Similarly, establishment of the normal compendium of proteins at the intercellular tight and adherens junctions determines the integrity of epithelial barrier function. Aberrations in either apical trafficking or junctional integrity lead to enteric pathologies including diarrhea, constipation and intestinal barrier dysfunction. Investigations over the past decade have established that components of the Rab11a and Rab8a-dependent membrane recycling systems regulate trafficking of apical membrane and junctional proteins required for the maintenance of proper apical polarity. Loss of functional Myosin Vb (MYO5B) leads to severe diarrhea due to loss of apical transporters secondary to deficits in Rab11a and Rab8a-dependent apical trafficking as observed in neonates with Microvillus Inclusion Disease (MVID). At the same time, the Rab11a-interacting proteins, Rab11-FIP1 and Rab11-FIP2, regulate junctional structure and function, in part through their phosphorylation by the critical polarity-related kinase MARK2/Par1b. All of these studies have led to the recognition that the coordinated regulation of apical polarity and trafficking by components of the apical recycling system lies at the heart of enterocyte physiology and pathophysiology. We have hypothesized that pathways through aspects of the recycling system provide for specificity of trafficking of particular cargoes to the apical membrane and the intercellular junctions. The apical recycling system represents a critical target for intervention in pathophysiologies that undermine apical membrane trafficking to the brush border and establishment of functional junctional integrity. To analyze this hypothesis, we will pursue two specific aims: First, we will determine the roles of elements of the apical recycling system in trafficking of ion transporters and enzymes to the enterocyte apical brush border. These studies will examine the fates of endogenous enterocyte apical proteins in human intestinal enteroids differentiated on two-dimensional monolayer cultures on permeable membranes. Second, we will examine the role of Rab11-FIP1B and its phosphorylation by MARK2/Par1b in the regulation of intestinal enterocyte junctional function. These studies will allow a greater understanding of how phosphorylation of Rab11-FIP1B regulates trafficking to and maintenance of junctions. Impact: These studies will identify components of the apical recycling system that may regulate apical trafficking of particular brush border and junctional cargoes. Definition of the multiple pathways for apical cargo trafficking to the brush border and junctions will provide insights into how disruption of specific pathways may alter physiology and how pathophysiological loss of trafficking may be restored through rerouting of proteins to alternative routes to the apical membrane.!