Rab family small G proteins in regulation of epithelial apical junctions.

Tight junctions (TJs) and adherens junctions (AJs) comprise epithelial apical junctions that adhere neighboring epithelial cells and determine tissue organization. They are highly dynamic structures that undergo continuous remodeling during physiological morphogenesis and under pathological conditions. The assembly and disassembly of epithelial apical junctions is regulated by the interplay between a variety of cellular processes, such as the remodeling of actin cytoskeletons and the endocytic recycling of apical junctional proteins, and coordinated by many signaling pathways. Accumulating evidences demonstrate that Rab family small G proteins are crucially involved in the regulation of epithelial apical junctions. Rab proteins localized both at endosomes and apical junctions can influence the assembly and disassembly of epithelial apical junctions. In this review, we summarize how Rab proteins influence epithelial apical junctions and describe the role of Rab8/13-a junctional Rab13-binding protein (JRAB)/molecule interacting with CasL-like 2 (MICAL-L2) complexes in the regulation of epithelial apical junctions.