Direct Interaction of GABA_BReceptors with M₂Muscarinic Receptors Enhances Muscarinic Signaling

Abstract

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.

Novel Mechanism of Voltage-Gated N-type (Cav2.2) Calcium Channel Inhibition Revealed through α-Conotoxin Vc1.1 Activation of the GABAB Receptor

“…The rat Ca v 2.2 channel, a 1B splice variant e37a, and auxiliary subunit b 3 were provided by Dr. Diane Lipscombe (Brown University), and the auxiliary subunit a 2 d 1 was provided by Dr. Gerald W. Zamponi (University of Calgary). Rat wild-type GABA B R and the mutant GABA B1a -ΔPCT, GABA B1a -Δ887, GABA B1a -Δ863 (Laviv et al, 2011), and GABA B2 -R576D (Binet et al, 2007;Boyer et al, 2009) constructs have been described previously. Site-directed mutagenesis on GABA B1a was carried out using the GENEART Site-Directed Mutagenesis System Kit (Invitrogen/Life Technologies, Mulgrave, VIC, Australia) with the following primers:…”

Cockroach GABAB receptor subtypes: Molecular characterization, pharmacological properties and tissue distribution

“…Here, the C-terminus of GB2 interacts, for example, with M 2 muscarinic receptors (Boyer et al 2009). …”

Compartmentalization of the GABABReceptor Signaling Complex Is Required for Presynaptic Inhibition at Hippocampal Synapses

“…Nontagged GB 1a -⌬103 was created by PCR and then subcloned into BamHI/NotI sites of peYFP-N1-GB 1a -WT. Nontagged GB 1a -⌬74 and GB 1a -⌬39 were described previously (Boyer et al, 2009).…”