Activation of phospholipases A2 and D of a human neuroblastoma cell line (LA-N-2) by N-dodecyl-L-lysine amide (compound 24), a putative G protein activator:: Characteristics of inhibition by (-)-nicotine

Compound 24, an alkyl-substituted amino acid amide, previously found to activate pertussis toxin-sensitive G proteins in cell membranes and membrane protein fractions, was used as a tool to determine the mechanism/location of nicotine inhibition of amyloid beta peptide-stimulated phospholipase A(2) and D activities in a human neuroblastoma cell line, LA-N-2, in vitro. In contrast to our previous findings with amyloid beta peptide, these phospholipase activations by compound 24 were not inhibited by (-)-nicotine, cholera toxin or tetanus toxin pretreatment. The contrasting activation of these phospholipases by amyloid beta peptide and compound 24 are discussed.