Gβγ and the C terminus of SNAP-25 are necessary for long-term depression of transmitter release

PLoS One. 2011;6(5):e20500. doi: 10.1371/journal.pone.0020500. Epub 2011 May 25.


Background: Short-term presynaptic inhibition mediated by G protein-coupled receptors involves a direct interaction between G proteins and the vesicle release machinery. Recent studies implicate the C terminus of the vesicle-associated protein SNAP-25 as a molecular binding target of Gβγ that transiently reduces vesicular release. However, it is not known whether SNAP-25 is a target for molecular modifications expressing long-term changes in transmitter release probability.

Methodology/principal findings: This study utilized two-photon laser scanning microscopy for real-time imaging of action potential-evoked [Ca(2+)] increases, in single Schaffer collateral presynaptic release sites in in vitro hippocampal slices, plus simultaneous recording of Schaffer collateral-evoked synaptic potentials. We used electroporation to infuse small peptides through CA3 cell bodies into presynaptic Schaffer collateral terminals to selectively study the presynaptic effect of scavenging the G-protein Gβγ. We demonstrate here that the C terminus of SNAP-25 is necessary for expression of LTD, but not long-term potentiation (LTP), of synaptic strength. Using type A botulinum toxin (BoNT/A) to enzymatically cleave the 9 amino acid C-terminus of SNAP-25 eliminated the ability of low frequency synaptic stimulation to induce LTD, but not LTP, even if release probability was restored to pre-BoNT/A levels by elevating extracellular [Ca(2+)]. Presynaptic electroporation infusion of the 14-amino acid C-terminus of SNAP-25 (Ct-SNAP-25), to scavenge Gβγ, reduced both the transient presynaptic inhibition produced by the group II metabotropic glutamate receptor stimulation, and LTD. Furthermore, presynaptic infusion of mSIRK, a second, structurally distinct Gβγ scavenging peptide, also blocked the induction of LTD. While Gβγ binds directly to and inhibit voltage-dependent Ca(2+) channels, imaging of presynaptic [Ca(2+)] with Mg-Green revealed that low-frequency stimulation only transiently reduced presynaptic Ca(2+) influx, an effect not altered by infusion of Ct-SNAP-25.

Conclusions/significance: The C-terminus of SNAP-25, which links synaptotagmin I to the SNARE complex, is a binding target for Gβγ necessary for both transient transmitter-mediated presynaptic inhibition, and the induction of presynaptic LTD.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Amino Acid Sequence
  • Animals
  • Botulinum Toxins, Type A / pharmacology
  • Calcium / metabolism
  • Calcium / pharmacology
  • GTP-Binding Protein beta Subunits / chemistry
  • GTP-Binding Protein beta Subunits / metabolism*
  • GTP-Binding Protein gamma Subunits / chemistry
  • GTP-Binding Protein gamma Subunits / metabolism*
  • Hippocampus / cytology
  • Hippocampus / drug effects
  • Hippocampus / metabolism
  • In Vitro Techniques
  • Long-Term Potentiation / drug effects
  • Long-Term Potentiation / physiology
  • Long-Term Synaptic Depression / drug effects
  • Long-Term Synaptic Depression / physiology*
  • Microscopy, Confocal / methods
  • Neural Inhibition / drug effects
  • Neural Inhibition / physiology
  • Neuromuscular Agents / pharmacology
  • Peptides / metabolism
  • Peptides / pharmacology
  • Protein Binding
  • Pyramidal Cells / drug effects
  • Pyramidal Cells / metabolism
  • Pyramidal Cells / physiology
  • Rats
  • Rats, Sprague-Dawley
  • Synaptic Transmission / drug effects
  • Synaptic Transmission / physiology
  • Synaptosomal-Associated Protein 25 / metabolism*


  • GTP-Binding Protein beta Subunits
  • GTP-Binding Protein gamma Subunits
  • Neuromuscular Agents
  • Peptides
  • Synaptosomal-Associated Protein 25
  • Botulinum Toxins, Type A
  • Calcium