ARF1(2–17) does not specifically interact with ARF1-dependent pathways Inhibition by peptide of phospholipases Cβ, D and exocytosis in HL60 cells

AbstractThe small GTP-binding protein ARF has been shown recently to regulate phospholipase D (PLD). In order to investigate the role of ARF proteins in regulated exocytosis, we have used the N-terminal peptide ARF1(2–17) of the ARF1 protein. ARF1 reconstituted PLD activity in cytosol-depleted HL60 cells was inhibited by ARF1(2–17). In the presence of endogenous cytosol, ARF1(2–17) also inhibited GTP-γ-S-stimulated PLD activity and exocytosis. Mastoparan Politses jadwagae and mastoparan Vespula lewisii which exhibit similar structural properties to ARF1(2–17) also inhibited GTP-γ-S-stimulated PLD and exocytosis. GTP-γ-S-stimulated phospholipase C-β (PLC-β) was also inhibited by ARF(2–17) and mastoparan. In cytosol-depleted HL60 cells, the ARF(2–17) inhibited the reconstitution of GTP-γ-S-stimulated PLC-β activity with exogenously-added PLC-β1 and phosphatidylinositol transfer protein. We conclude that the widely-used ARF1(2–17) peptide inhibits both ARF-independent (i.e. PLC-β) and ARF-dependent pathways (i.e. PLD) and therefore cannot be regarded as a specific inhibitor of ARF function