Inhibition of neurotransmitter release by peptides that mimic the N-terminal domain of SNAP-25.
Botulinum neurotoxin serotypes A and E (BoNT/A and BoNT/E) block neurotransmitter release by cleaving the 206-amino-acid SNARE protein, SNAP-25. For each BoNT serotype, cleavage of SNAP-25 results in the loss of intact protein, the production of an N-terminal truncated protein, and the generation of a small C-terminal peptide. Peptides that mimic the C-terminal fragments of SNAP-25 following BoNT/A or BoNT/E cleavage were shown to depress transmitter release in bovine chromaffin cells and in Aplysia buccal ganglion cells. Similarly, the N-terminal-truncated SNAP-25 resulting from BoNT/A or BoNT/E cleavage has been found to inhibit transmitter exocytosis in various systems. With one exception, however, the inhibitory action of truncated SNAP-25 has not been demonstrated at a well-defined cholinergic synapse. The goal of the current study was to determine the level of inhibition of neurotransmitter release by N-terminal BoNT/A- or BoNT/E-truncated SNAP-25 in two different neuronal systems: cholinergically coupled Aplysia neurons and rat hippocampal cell cultures. Both truncated SNAP-25 products inhibited depolarization-dependent glutamate release from hippocampal cultures and depressed synaptic transmission in Aplysia buccal ganglion cells. These results suggest that truncated SNAP-25 can compete with endogenous SNAP-25 for binding with other SNARE proteins involved in transmitter release, thus inhibiting neurotransmitter exocytosis.
Apland
James P
JP
Neurotoxicology Branch, Pharmacology Division, USAMRICD, Aberdeen Proving Ground, Maryland 21010-5400, USA. James.Apland@apg.amedd.army.mil
Adler
Michael
M
Oyler
George A
GA
D000818:Animals; D001048:Aplysia / Q000187:drug effects; D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A; D002478:Cells, Cultured; D005971:Glutamates / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018377:Neurotransmitter Agents / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D013569:Synapses / Q000187:drug effects; D050825:Synaptosomal-Associated Protein 25
D005971:Glutamates; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D011993:Recombinant Fusion Proteins; C494210:Snap25 protein, rat; D050825:Synaptosomal-Associated Protein 25; D001905:Botulinum Toxins; D019274:Botulinum Toxins, Type A; C096326:botulinum toxin type E