The purpose of the current work is to understand the signaling function of the Gbeta5/R7-RGS/R7BP complex in humans. To this end we are first trying to identify and characterize the functions of the Gbeta5 complex that are evolutionarily conserved between the insect and mammalian nervous systems. Current work in our laboratory examines such shared functions using Drosophila melanogaster, cultured PC12 and SH-SY5Y cells, and primary rodent brain neurons as model systems. We are continuing to use an insect model system in which Drosophila Gbeta5 is transgenically over-expressed in the fly nervous system. Two independent Gbeta5 transgenic fly lines have a phenotype that is not evident in control lines lacking the transgene or lacking the """"""""driver"""""""" that is necessary for Gbeta5 expression from the transgenic promoter. Using these transgenic flies, and based on the observed phenotype, quantitative real-time PCR was used to estimate the levels of relevant transcripts. Certain fly transcripts were up-regulated in the Gbeta5 transgenic, but not control, fly lines. The effects on some of these fly transcripts were also observed on the homologous mammalian transcripts in PC12 cells in which mouse Gbeta5 was inducibly over-expressed by stable transfection. Immunoblot studies showed that the corresponding protein products were also up-regulated by Gbeta5 overexpression. The molecular mechanism of the observed changes, and the effect of Gbeta5 loss-of-function (to see if the phenotype is opposite to the over-expression models) such as in neurons and brain of Gbeta5 knockout mice, are currently being examined.
