Constricting membranes at the nano and micro scale

摘要

Dynamin GTPases regulate membrane traffic, in part, by constricting nanometer-sized membrane tubes to form vesicles by fission. In this issue of PNAS, Chua et al. (1) report that dynamin2 remodels membranes on a much grander scale by influencing the contractile activity of actomyosin encircling epithelial cells at their apical cell-cell junctions. Using a simple epithelial cell system, Madin-Darby canine kidney (MDCK) epithelial cells, Chua et al. found that apical junctional complexes that contain the cytoskeletal linker protein, ZO-1, and elements of the basolat-eral F-actin cytoskeleton, were missing or poorly organized in cells depleted of dynamin2. Notably, in MDCK cells expressing the GTP-binding-defective mutant protein, dynamin2-K44A, polarized membrane domains defined by ZO-1-containing apical junctions formed, but the circumferential actomyosin network associated with junctional complexes was constricted > 2-fold over that in cells expressing wild-type dynamin2 (Fig. 1).