Afadin regulates RhoA/Rho-associated protein kinase signaling to control formation of actin stress fibers in kidney podocytes.

The function of kidney podocytes is closely associated with actin cytoskeleton. Rho family small GTPase RhoA promotes stress fiber assembly through Rho-associated protein kinase (ROCK)-dependent myosin II phosphorylation and plays an important role in maintenance of actin stress fibers of podocytes. However, little is known how stress fiber assembly is regulated in podocytes. Here, we found that afadin, an actin filament-binding protein, is required for RhoA/ROCK-dependent formation of actin stress fibers in rat podocyte C7 cells. We show that depletion of afadin in C7 cells induced loss of actin stress fibers. Conversely, forced expression of afadin increased the formation of actin stress fibers. Depletion of afadin inactivated RhoA and reduced the phosphorylation of myosin II. Moreover, the DIL domain of afadin appears to be responsible for actin stress fiber formation. Thus, afadin mediates RhoA/ROCK signaling and contributes to the formation of actin stress fibers in podocyte cells.