Actin assembly at membranes controlled by ARF6

The small GTPase, ADP-ribosylation factor-6 (ARF6), has been implicated in regulating membrane traffic and remodeling cortical F-actin. Using real-tim e video analysis of actin assembly in living cells, we investigated the fun ction and mechanism of ARF6 in control of actin assembly. Expression of an activated form of ARF6 that mimicks the GTP-bound form of the GTPase induce d actin assembly resulting in the movement of vesicle-like particles, some of which contain markers for pinosomes. Activated ARF6 also stimulated acti n assembly at foci on the ventral surface of the cell and stimulated fluid phase pinocytosis, Particle motility induced by ARF6 involved Arp2/3 comple x, tyrosine kinase activity, phospholipase D (PLD) and D3-phosphoinositides . but not phosphatidylinositol 4,5-bisphosphate (PI(4,5)P-2). We conclude t hat ARF6 regulates actin assembly for pinosome motility and at foci on the ventral cell surface.