4f12
Crystal structure of the extracellular domain of human GABA(B) receptor GBR2
Structural highlights
FunctionGABR2_HUMAN Component of a heterodimeric G-protein coupled receptor for GABA, formed by GABBR1 and GABBR2. Within the heterodimeric GABA receptor, only GABBR1 seems to bind agonists, while GABBR2 mediates coupling to G proteins. Ligand binding causes a conformation change that triggers signaling via guanine nucleotide-binding proteins (G proteins) and modulates the activity of down-stream effectors, such as adenylate cyclase. Signaling inhibits adenylate cyclase, stimulates phospholipase A2, activates potassium channels, inactivates voltage-dependent calcium-channels and modulates inositol phospholipid hydrolysis. Plays a critical role in the fine-tuning of inhibitory synaptic transmission. Pre-synaptic GABA receptor inhibits neurotransmitter release by down-regulating high-voltage activated calcium channels, whereas postsynaptic GABA receptor decreases neuronal excitability by activating a prominent inwardly rectifying potassium (Kir) conductance that underlies the late inhibitory postsynaptic potentials. Not only implicated in synaptic inhibition but also in hippocampal long-term potentiation, slow wave sleep, muscle relaxation and antinociception.[1] [2] [3] [4] Publication Abstract from PubMedInhibitory neurotransmission is mediated primarily by GABA. The metabotropic GABA(B) receptor is a G protein-coupled receptor central to mammalian brain function. Malfunction of GABA(B) receptor has been implicated in several neurological disorders. GABA(B) receptor functions as a heterodimeric assembly of GBR1 and GBR2 subunits, where GBR1 is responsible for ligand-binding and GBR2 is responsible for G protein coupling. Here we demonstrate that the GBR2 ectodomain directly interacts with the GBR1 ectodomain to increase agonist affinity by selectively stabilizing the agonist-bound conformation of GBR1. We present the crystal structure of the GBR2 ectodomain, which reveals a polar heterodimeric interface. We also identify specific heterodimer contacts from both subunits, and GBR1 residues involved in ligand recognition. Lastly, our structural and functional data indicate that the GBR2 ectodomain adopts a constitutively open conformation, suggesting a structural asymmetry in the active state of GABA(B) receptor that is unique to the GABAergic system. Structure and functional interaction of the extracellular domain of human GABA(B) receptor GBR2.,Geng Y, Xiong D, Mosyak L, Malito DL, Kniazeff J, Chen Y, Burmakina S, Quick M, Bush M, Javitch JA, Pin JP, Fan QR Nat Neurosci. 2012 Jun 3;15(7):970-8. doi: 10.1038/nn.3133. PMID:22660477[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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