Distribution of two GABA receptor-like subunits in the Drosophila CNS.

Previously we have described the distribution of the Rdl GABA receptor subunit in the Drosophila CNS. Knowing that Rdl can coassemble with LCCH3 (a Drosophila GABA receptor-like subunit showing sequence similarity to vertebrate beta subunit GABAA receptors) in baculovirus infected insect cells, we compared the localization of these two receptor subunits in order to identify any potential overlap in their spatial or temporal distribution. The two subunits show very different patterns of localization. Early in development LCCH3 is found in the majority of developing neuroblasts and later is localized to the cell bodies of the embryonic nerve cord and brain, and the neuronal cell bodies surrounding the adult brain. In contrast, Rdl receptor subunits appear confined to the neuropil in all developmental stages. These results have two important implications. Firstly, they suggest that although these two subunits can coassemble in heterologous expression systems, they may not be found in the same tissues in the nervous system. Secondly, production of LCCH3 before neuronal differentiation leads us to speculate on the role of that LCCH3 containing receptors in the developing nervous system.