An isolated pool of vesicles recycles at rest and drives spontaneous neurotransmission.
Spontaneous synaptic vesicle fusion is a common property of all synapses. To trace the origin of spontaneously fused vesicles in hippocampal synapses, we tagged vesicles with fluorescent styryl dyes, antibodies against synaptotagmin-1, or horseradish peroxidase. We could show that synaptic vesicles recycle at rest, and after spontaneous exo-endocytosis, they populate a reluctantly releasable pool of limited size. Interestingly, vesicles in this spontaneously labeled pool were more likely to re-fuse spontaneously compared to vesicles labeled with activity. We found that blocking vesicle refilling at rest selectively depleted neurotransmitter from spontaneously fusing vesicles without significantly altering evoked transmission. Furthermore, in the absence of the vesicle SNARE protein synaptobrevin (VAMP), activity-dependent and spontaneously recycling vesicles could mix, suggesting a role for synaptobrevin in the separation of the two pools. Taken together these results suggest that spontaneously recycling vesicles and activity-dependent recycling vesicles originate from distinct pools with limited cross-talk with each other.
Sara
Yildirim
Y
Center for Basic Neuroscience, Department of Physiology, The University of Texas, Southwestern Medical Center, Dallas, Texas 75390, USA.
Virmani
Tuhin
T
Deák
Ferenc
F
Liu
Xinran
X
Kavalali
Ege T
ET
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002478:Cells, Cultured; D003952:Diagnostic Imaging / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation / Q000379:methods; D004594:Electrophysiology / Q000379:methods; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D018942:Macrolides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission / Q000379:methods; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D050683:R-SNARE Proteins; D051381:Rats; D013569:Synapses / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D013572:Synaptic Vesicles / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D050863:Synaptotagmin I; D050857:Synaptotagmins; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors
D002135:Calcium-Binding Proteins; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D018942:Macrolides; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050683:R-SNARE Proteins; D050863:Synaptotagmin I; C494311:Syt1 protein, mouse; C494312:Syt1 protein, rat; D050857:Synaptotagmins; D013779:Tetrodotoxin; C036978:concanamycin A; D006735:Horseradish Peroxidase; D011188:Potassium