The in Vivo Specificity of Synaptic G[beta] and G[gamma] Subunits to the [alpha]2a Adrenergic Receptor at CNS Synapses
Abstract: G proteins are major transducers of signals from G-protein coupled receptors (GPCRs). They are made up of [alpha], [beta], and [gamma] subunits, with 16 G[alpha], 5 G[beta] and 12 G[gamma] subunits. Though much is known about the specificity of G[alpha] subunits, the specificity of G[beta][gamma]s activated by a given GPCR and that activate each effector in vivo is not known. Here, we examined the in vivo G[beta][gamma] specificity of presynaptic [alpha]2a-adrenergic receptors ([alpha]2aARs) in both adrenergic (auto-[alpha]2aARs) and non-adrenergic neurons (hetero-[alpha]2aARs) for the first time. With a quantitative MRM proteomic analysis of neuronal G[beta] and G[gamma] subunits, and co-immunoprecipitation of tagged [alpha]2aARs from mouse models including transgenic FLAG-[alpha]2aARs and knock-in HA-[alpha]2aARs, we investigated the in vivo specificity of G[beta] and G[gamma] subunits to auto-[alpha]2aARs and hetero-[alpha]2aARs activated with epinephrine to understand the role of G[beta][gamma] specificity in diverse physiological functions such as anesthetic sparing, and working memory enhancement. We detected G[beta]2, G[gamma]2, G[gamma]3, and G[gamma]4 with activated auto [alpha]2aARs, whereas we found G[beta]4 and G[gamma]12 preferentially interacted with activated hetero-[alpha]2aARs. Further understanding of in vivo G[beta][gamma] specificity to various GPCRs offers new insights into the multiplicity of genes for G[beta] and G[gamma], and the mechanisms underlying GPCR signaling through G[beta][gamma] subunits