PMID:21724853

Citation	Hannan, S, Wilkins, ME, Dehghani-Tafti, E, Thomas, P, Baddeley, SM and Smart, TG (2011) Gamma-aminobutyric acid type B (GABA(B)) receptor internalization is regulated by the R2 subunit. J. Biol. Chem. 286:24324-35
Abstract	γ-Aminobutyric acid type B (GABA(B)) receptors are important for slow synaptic inhibition in the CNS. The efficacy of inhibition is directly related to the stability of cell surface receptors. For GABA(B) receptors, heterodimerization between R1 and R2 subunits is critical for cell surface expression and signaling, but how this determines the rate and extent of receptor internalization is unknown. Here, we insert a high affinity α-bungarotoxin binding site into the N terminus of the R2 subunit and reveal its dominant role in regulating the internalization of GABA(B) receptors in live cells. To simultaneously study R1a and R2 trafficking, a new α-bungarotoxin binding site-labeling technique was used, allowing α-bungarotoxin conjugated to different fluorophores to selectively label R1a and R2 subunits. This approach demonstrated that R1a and R2 are internalized as dimers. In heterologous expression systems and neurons, the rates and extents of internalization for R1aR2 heteromers and R2 homomers are similar, suggesting a regulatory role for R2 in determining cell surface receptor stability. The fast internalization rate of R1a, which has been engineered to exit the endoplasmic reticulum, was slowed to that of R2 by truncating the R1a C-terminal tail or by removing a dileucine motif in its coiled-coil domain. Slowing the rate of internalization by co-assembly with R2 represents a novel role for GPCR heterodimerization whereby R2 subunits, via their C terminus coiled-coil domain, mask a dileucine motif on R1a subunits to determine the surface stability of the GABA(B) receptor.
Links	PubMed PMC3129212 Online version:10.1074/jbc.M110.220814
Keywords	Animals; Bungarotoxins/pharmacology; Endoplasmic Reticulum/genetics; Endoplasmic Reticulum/metabolism; Gene Expression Regulation/drug effects; Gene Expression Regulation/physiology; HEK293 Cells; Humans; Neurons/metabolism; Protein Multimerization/drug effects; Protein Multimerization/physiology; Protein Stability; Protein Structure, Tertiary; Protein Transport/drug effects; Protein Transport/physiology; Rats; Receptors, GABA-B/genetics; Receptors, GABA-B/metabolism; Signal Transduction/drug effects; Signal Transduction/physiology; Synaptic Transmission/drug effects; Synaptic Transmission/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
RAT:GABR2		GO:0002091: negative regulation of receptor internalization	ECO:0000315:		P		Figure 5.	complete CACAO 6636

References

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