Phosphatidylinositol 4-phosphate 5-kinase α is a downstream effector of the small G protein ARF6 in membrane ruffle formation

Synthesis of phosphatidylinositol 4,5-bisphosphate [Pl(4,5)P₂], a signaling phospholipid, is primarily carried out by phosphatidylinositol 4- phosphate 5-kinase [Pl(4)P5K], which has been reported to be regulated by RhoA and Rac1. Unexpectedly, we find that the GTPγ/S-dependent activator of Pl(4)P5Kα is the small G protein ADP-ribosylation factor (ARF) and that the activation strictly requires phosphatidic acid, the product of phospholipase D (PLD). In vivo, ARF6, but not ARF1 or ARF5, spatially coincides with Pl(4)P5Kα. This colocalization occurs in ruffling membranes formed upon AlF₄ and EGF stimulation and is blocked by dominant-negative ARF6. PLD2 similarly translocates to the ruffles, as does the PH domain of phospholipase Cδ1, indicating locally elevated Pl(4,5)P₂. Thus, Pl(4)P5Kα is a downstream effector of ARF6 and when ARF6 is activated by agonist stimulation, it triggers recruitment of a diverse but interactive set of signaling molecules into sites of active cytoskeletal and membrane rearrangement.