The purpose of the current work is to understand the cell biology of the Gbeta5/R7-RGS/R7BP complex in the human neuroendocrine system. In a related project (DK043304-14) we are trying to identify and characterize the functions of the Gbeta5 complex that are evolutionarily conserved between the insect and mammalian nervous systems. In that project we are using 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. In this project our current work examines a) whether, and where within the cell, the Gbeta5/R7-RGS/ R7BP complex is expressed in neuroendocrine cells and tissues such as the pituitary and pancreatic islets, and b) whether the phenotype observed by Gbeta5 over-expression in PC12 and SH-SY5Y cells provides valid insight into its possible natural (or endogenous) function in the pituitary and pancreatic islets. Model systems employed include pituitary- and pancreatic islet beta-cell-derived cell lines, as well as wild-type and Gbeta5 knockout mice.
