EFFECTS OF MASTOPARAN-B AND ITS ANALOGS ON THE PHOSPHOLIPASE-D ACTIVITY IN L1210 CELLS

Mastoparan B (MP-B), an amphiphilic alpha-helical peptide isolated fro m hornet venom, and its Ala-substituted analogs were examined for thei r effectiveness on phospholipase D (PLD) activity in L1210 cells. PLD activity was determined by measuring phosphatidylethanol produced from [H-3]myristate-labelled cells in the presence of ethanol. PLD activit y mas stimulated by MP-B, 4MP-B (Lys(4) --> Ala), and 12MP-B (Lys(12) --> Ala), but not by 3MP-B (Leu(3) --> Ala) and 9MP-B (Trp(9) --> Ala) . Other MPs including mastoparan 7 also stimulated the PLD activity, b ut inactive mastoparan 17 did not. The stimulatory effect of various M P analogs could be correlated with their alpha-helical contents. The P LD activity stimulated by MP-B was not affected by G-protein blocking chemicals. The extent of PLD stimulation by various MP-Bs, as sell as by digitonin and beta-escin, correlated with the permeability of the m embrane to ethidium bromide, These results suggest that the stimulatio n of PLD activity by RIP-B in L1210 cells is probably coupled with mem brane perturbation brought about by the peptide. (C) 1998 Federation o f European Biochemical Societies.