ACTIVATION OF PHOSPHOLIPASE D1 BY DIRECT INTERACTION WITH ADP-RIBOSYLATION FACTOR-1 AND RALA

Phospholipase D1 (PLD1) is known to be activated by ADP-ribosylation f actor 1 (ARF1). We report here that ARF1 co-immunoprecipitates with PL D1 and that the ARF1-dependent PLD activation is induced hv the direct interaction between ARF1 and PLD1. We found that RalA, another member of the small GTP-binding proteins, synergistically enhances the ARF1- dependent PLD activity with an EC50 of about 30 nM. Using in vitro bin ding assay, we show that ARF1 and RalA directly interact with differen t sites of PLD1, The results suggest that the independent interactions of RalA and ARF1 with PLD1 are responsible for the synergistic activa tion, (C) 1998 Federation of European Biochemical Societies.