title: Gbetagamma acts at the C terminus of SNAP-25 to mediate presynaptic inhibition.
abstract: Presynaptic inhibition mediated by G protein-coupled receptors may involve a direct interaction between G proteins and the vesicle fusion machinery. The molecular target of this pathway is unknown. We demonstrate that Gbetagamma-mediated presynaptic inhibition in lamprey central synapses occurs downstream from voltage-gated Ca(2+) channels. Using presynaptic microinjections of botulinum toxins (BoNTs) during paired recordings, we find that cleavage of synaptobrevin in unprimed vesicles leads to an eventual exhaustion of synaptic transmission but does not prevent Gbetagamma-mediated inhibition. In contrast, cleavage of the C-terminal nine amino acids of the 25 kDa synaptosome-associated protein (SNAP-25) by BoNT A prevents Gbetagamma-mediated inhibition. Moreover, a peptide containing the region of SNAP-25 cleaved by BoNT A blocks the Gbetagamma inhibitory effect. Finally, removal of the last nine amino acids of the C-terminus of SNAP-25 weakens Gbetagamma interactions with soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complexes. Thus, the C terminus of SNAP-25, which links synaptotagmin I to the SNARE complex, may represent a target of Gbetagamma for presynaptic inhibition.
authors.affiliation: Department of Biological Sciences, University of Illinois at Chicago, 840 West Taylor, Chicago, Illinois 60607, USA.
authors.forename: Tatyana
authors.initials: T
authors.lastname: Gerachshenko
authors.forename: Trillium
authors.initials: T
authors.lastname: Blackmer
authors.forename: Eun-Ja
authors.initials: EJ
authors.lastname: Yoon
authors.forename: Cheryl
authors.initials: C
authors.lastname: Bartleson
authors.forename: Heidi E
authors.initials: HE
authors.lastname: Hamm
authors.forename: Simon
authors.initials: S
authors.lastname: Alford
mesh_terms: D000818:Animals; D000870:Anterior Horn Cells / Q000187:drug effects / Q000378:metabolism; D001905:Botulinum Toxins / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D004525:Efferent Pathways / Q000187:drug effects / Q000378:metabolism; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism*; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism*; D007798:Lampreys; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism; D018408:Patch-Clamp Techniques; D010782:Photolysis; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000502:physiology; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; D050857:Synaptotagmins; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D002135:Calcium-Binding Proteins; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D050683:R-SNARE Proteins; D050600:SNARE Proteins; D050825:Synaptosomal-Associated Protein 25; D050863:Synaptotagmin I; D033921:Vesicular Transport Proteins; D050857:Synaptotagmins; D001905:Botulinum Toxins