Direct Interaction of GABABReceptors with M2Muscarinic Receptors Enhances Muscarinic Signaling

• DOI: 10.1523/jneurosci.4103-09.2009
• Publication Date: 2009-12-16T18:23:44Z
• Authors: Stephanie B. Boyer; Sinead M. Clancy; Miho Terunuma; Raquel Revilla-Sa...; Steven M. Thomas; Stephen J. Moss; Paul A. Slesinger
• Keywords: 0301 basic medicine; Receptor, Muscarinic M2; 03 medical and health sciences; Receptors, GABA-B; Cell Membrane; Animals; Humans; PC12 Cells; Protein Binding; Rats; Signal Transduction

Downregulation of G-protein-coupled receptors (GPCRs) provides an important mechanism for reducing neurotransmitter signaling during sustained stimulation. Chronic stimulation of M2muscarinic receptors (M2Rs) causes internalization of M2R and G-protein-activated inwardly rectifying potassium (GIRK) channels in neuronal PC12 cells, resulting in loss of function. Here, we show that coexpression of GABABR2 receptors (GBR2s) rescues both surface expression and function of M2R, including M2R-induced activation of GIRKs and inhibition of cAMP production. GBR2 showed significant association with M2R at the plasma membrane but not other GPCRs (M1R, μ-opioid receptor), as detected by fluorescence resonance energy transfer measured with total internal reflection fluorescence microscopy. Unique regions of the proximal C-terminal domains of GBR2 and M2R mediate specific binding between M2R and GBR2. In the brain, GBR2, but not GBR1, biochemically coprecipitates with M2R and overlaps with M2R expression in cortical neurons. This novel heteromeric association between M2R and GBR2 provides a possible mechanism for altering muscarinic signaling in the brain and represents a previously unrecognized role for GBR2.