GABA (gamma amino butyric acid) is an important neurotransmitter in C. elegans, Drosophila and all vertebrates. Now, Anjard and Loomis report that GABA has another role in intercellular communication – inducing sporulation in Dictyostelium (see ). This finding excitingly shows that GABA is not only an important neurotransmitter but also an ancient intercellular signal. Towards the end of Dictyostelium development, prespore cells migrate to the top of the fruiting body where they encapsulate in response to a secreted peptide SDF-2, which is generated from a precursor, AcbA, by a prestalk-specific protease. The researchers show that GABA triggers the release and processing of AcbA. By examining the Dictyostelium genome, they identified a putative receptor for GABA–GrlE. Dictyostelium cells that lack this G-protein-coupled receptor did not produce SDF-2 in response to GABA. Finally, the authors used pharmacological inhibitors and specific mutations to reveal that the effects of GABA on sporulation are mediated by PI3 kinase and a protein kinase B-related kinase,proteins that often act downstream of G-protein-coupled receptors.
