Phospholipid signalling: Rho is only ARF the story

Small GTP-binding proteins act as switches that control diverse cellular processes. Those in the ADP-ribosylation factor (ARF) class direct key steps in intracellular protein traffic, whereas those in the Rho family regulate gene transcription as well as changes in cell motility and morphology [1,2]. Several groups have now produced evidence that these regulatory activities of Rho and ARF proteins may be mediated by phosphatidylcholine (PC)-specific phospholipase D (PLD). PLD generates phosphatidic acid (PA), which may be an intracellular mediator in its own right and which can be metabolized to form lipids with proven roles as both intercellular and intracellular messengers [3].