RNA Editing of the Human Serotonin 5-HT2C Receptor Alters Receptor-mediated Activation of G13 Protein

Abstract

The recent completion of the human genome predicted the presence of only 30,000 genes, stressing the importance of mechanisms that increase molecular diversity at the post-transcriptional level. One such post-transcriptional event is RNA editing, which generates multiple protein isoforms from a single gene, often with profound functional consequences. The human serotonin 5-HT 2C receptor undergoes RNA editing that creates multiple receptor isoforms. One consequence of RNA editing of cell surface receptors may be to alter the pattern of activation of heterotrimeric G-proteins and thereby shift preferred intracellular signaling pathways. We examined the ability of the nonedited 5-HT2C receptor isoform (INI) and two extensively edited isoforms, VSV and VGV, to interact with various G-protein α subunits. Two functional assays were utilized: the cell-based functional assay, Receptor Selection/Amplification TechnologyTM, in which the pharmacological consequences of co-expression of 5HT2C receptor isoforms with G-protein α subunits in fibroblasts were studied, and 5HT2C receptor-mediated rearrangements of the actin cytoskeleton in stable cell lines. These studies revealed that the nonedited 5-HT2C receptor functionally couples to Gq and G13. In contrast, coupling to G13 was not detected for the extensively edited 5-HT2C receptors. Thus, RNA editing represents a novel mechanism for regulating the pattern of activation of heterotrimeric G-proteins, molecular switches that control an enormous variety of biological processes.