Presynaptic membrane protein phosphorylation modulates the release of GABA from preloaded synaptosomes

Incubation of rat cortical synaptosomes in the presence of 1 mM ATP markedly reduced Ca2+-dependent K+-induced release of preloaded 3H-GABA. This effect is probably dependent on phosphorylation of presynaptic membrane proteins. By contrast, the uptake of 3H-GABA by the nerve endings was not significantly affected by phosphorylation. These data suggest that membrane protein phosphorylation and dephosphorylation may form a mechanism for the presynaptic control of transmitter release.