Lechuga Susana, Baranwal Somesh, Ivanov Andrei I
Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia;
Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia; Virginia Institute of Molecular Medicine, Virginia Commonwealth University, Richmond, Virginia; VCU Massey Cancer Center, Virginia Commonwealth University, Richmond, Virginia
Am J Physiol Gastrointest Liver Physiol. 2015 May 1;308(9):G745-56. doi: 10.1152/ajpgi.00446.2014. Epub 2015 Mar 19.
Adherens junctions (AJs) and tight junctions (TJs) are crucial regulators of the integrity and restitution of the intestinal epithelial barrier. The structure and function of epithelial junctions depend on their association with the cortical actin cytoskeleton that, in polarized epithelial cells, is represented by a prominent perijunctional actomyosin belt. The assembly and stability of the perijunctional cytoskeleton is controlled by constant turnover (disassembly and reassembly) of actin filaments. Actin-interacting protein (Aip) 1 is an emerging regulator of the actin cytoskeleton, playing a critical role in filament disassembly. In this study, we examined the roles of Aip1 in regulating the structure and remodeling of AJs and TJs in human intestinal epithelium. Aip1 was enriched at apical junctions in polarized human intestinal epithelial cells and normal mouse colonic mucosa. Knockdown of Aip1 by RNA interference increased the paracellular permeability of epithelial cell monolayers, decreased recruitment of AJ/TJ proteins to steady-state intercellular contacts, and attenuated junctional reassembly in a calcium-switch model. The observed defects of AJ/TJ structure and functions were accompanied by abnormal organization and dynamics of the perijunctional F-actin cytoskeleton. Moreover, loss of Aip1 impaired the apico-basal polarity of intestinal epithelial cell monolayers and inhibited formation of polarized epithelial cysts in 3-D Matrigel. Our findings demonstrate a previously unanticipated role of Aip1 in regulating the structure and remodeling of intestinal epithelial junctions and early steps of epithelial morphogenesis.
黏着连接（AJs）和紧密连接（TJs）是肠道上皮屏障完整性和修复的关键调节因子。上皮连接的结构和功能取决于它们与皮质肌动蛋白细胞骨架的关联，在极化上皮细胞中，皮质肌动蛋白细胞骨架表现为一条突出的连接周肌动球蛋白带。连接周细胞骨架的组装和稳定性由肌动蛋白丝的持续周转（拆卸和重新组装）控制。肌动蛋白相互作用蛋白（Aip）1是一种新兴的肌动蛋白细胞骨架调节因子，在细丝拆卸中起关键作用。在本研究中，我们研究了Aip1在调节人肠道上皮中AJs和TJs的结构和重塑中的作用。Aip1在极化的人肠道上皮细胞和正常小鼠结肠黏膜的顶端连接处富集。通过RNA干扰敲低Aip1可增加上皮细胞单层的细胞旁通透性，减少AJ/TJ蛋白向稳态细胞间接触的募集，并减弱钙切换模型中的连接重新组装。观察到的AJ/TJ结构和功能缺陷伴随着连接周F-肌动蛋白细胞骨架的异常组织和动态变化。此外，Aip1的缺失损害了肠道上皮细胞单层的顶-基极性，并抑制了三维基质胶中极化上皮囊肿的形成。我们的研究结果证明了Aip1在调节肠道上皮连接的结构和重塑以及上皮形态发生早期步骤中具有先前未预料到的作用。
