title: Compartmentalization of the GABAB receptor signaling complex is required for presynaptic inhibition at hippocampal synapses.
abstract: Presynaptic inhibition via G-protein-coupled receptors (GPCRs) and voltage-gated Ca(2+) channels constitutes a widespread regulatory mechanism of synaptic strength. Yet, the mechanism of intermolecular coupling underlying GPCR-mediated signaling at central synapses remains unresolved. Using FRET spectroscopy, we provide evidence for formation of spatially restricted (<100 Å) complexes between GABA(B) receptors composed of GB(1a)/GB(2) subunits, Gα(o)β(1)γ(2) G-protein heterotrimer, and Ca(V)2.2 channels in hippocampal boutons. GABA release was not required for the assembly but for structural reorganization of the precoupled complex. Unexpectedly, GB(1a) deletion disrupted intermolecular associations within the complex. The GB(1a) proximal C-terminal domain was essential for association of the receptor, Ca(V)2.2 and Gβγ, but was dispensable for agonist-induced receptor activation and cAMP inhibition. Functionally, boutons lacking this complex-formation domain displayed impaired presynaptic inhibition of Ca(2+) transients and synaptic vesicle release. Thus, compartmentalization of the GABA(B1a) receptor, Gβγ, and Ca(V)2.2 channel in a signaling complex is required for presynaptic inhibition at hippocampal synapses.
authors: Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, 69978 Tel Aviv, Israel.
authors: Tal
authors: T
authors: Laviv
authors: Irena
authors: I
authors: Vertkin
authors: Yevgeny
authors: Y
authors: Berdichevsky
authors: Hilla
authors: H
authors: Fogel
authors: Inbal
authors: I
authors: Riven
authors: Bernhard
authors: B
authors: Bettler
authors: Paul A
authors: PA
authors: Slesinger
authors: Inna
authors: I
authors: Slutsky
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001418:Baclofen / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020864:Calcium Channels, N-Type / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004558:Electric Stimulation; D018756:GABA Antagonists / Q000494:pharmacology; D058786:GABA-B Receptor Agonists / Q000494:pharmacology; D044387:GTP-Binding Protein beta Subunits / Q000235:genetics / Q000378:metabolism; D044388:GTP-Binding Protein gamma Subunits / Q000235:genetics / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology*; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D009154:Mutation / Q000235:genetics; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009943:Organophosphorus Compounds / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D010852:Picrotoxin / Q000494:pharmacology; D017729:Presynaptic Terminals / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D018080:Receptors, GABA-B / Q000172:deficiency / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism
chemical_list: D001418:Baclofen; D002118:Calcium; D020864:Calcium Channels, N-Type; D000242:Cyclic AMP; D018756:GABA Antagonists; D058786:GABA-B Receptor Agonists; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D008164:Luminescent Proteins; D009943:Organophosphorus Compounds; D037342:Pertussis Toxin; D010852:Picrotoxin; D018080:Receptors, GABA-B; C500963:Cacna1b protein, mouse; C107353:CGP 54626