A G0-LIKE PROTEIN IN DROSOPHILA-MELANOGASTER AND ITS EXPRESSION IN MEMORY MUTANTS

G proteins couple receptors for extracellular signals to several intracellular effector systems and play a key role in signalling transduction mechanisms. In particulate preparations of Drosophila melanogaster heads, only one substrate for pertussis toxin at 39-40 kd was detected. This substrate, which showed only one isoform when analysed by isoelectric focusing, was recognized by immunoblotting and immunoprecipitation techniques using a polyclonal antibody against the α subunit of the G(o) protein purified from bovine brain and can be thus considered as a G(o)-like protein. Antibodies obtained against a carboxy-terminal sequence of the α subunit of G(o) (but not of G(i1) or G(i2)) and against an internal sequence shared by all the α subunits, were also able to cross-react with the α subunit of this protein in insects. We have also studied that G(o)-like protein in several D. melanogaster mutants, primarily in memory and learning mutants. In these mutants there was a sex-dependent enhancement in pertussis toxin-catalysed ADP-ribosylation with respect to the wild-type. This increase could be attributed in part to an increase in the α subunit of the G(o)-like protein, as revealed by immunoblotting with anti-G(oα) polyclonal antibody. This report constitutes the first evidence for the participation of a G(o) protein in learning and memory.