Synaptic vesicle recycling studied in transgenic mice expressing synaptopHluorin.
Synaptic vesicles are recycled locally within presynaptic specializations. We examined how vesicles are reused after endocytosis, using transgenic mice expressing the genetically encoded fluorescent indicator synaptopHluorin in subsets of neurons. At both excitatory and inhibitory synapses in cultured hippocampal neurons, newly endocytosed vesicles did not preferentially enter the releasable pool of vesicles. Rather, they entered the reserve pool first and subsequently the readily releasable pool over a period of several minutes. All vesicles in the recycling pool could be accessed by spaced stimuli, arguing against preferential local reuse of the readily releasable vesicles. Interestingly, nearly half the vesicles at excitatory synapses, and a third at inhibitory synapses, could not be recruited for release even by sustained stimuli. We conclude that, at presynaptic terminals in the hippocampus, most vesicles vacate release sites after exocytosis and are replaced by existing vesicles from the reserve pool, placing constraints on kiss-and-run recycling.
Li
Zhiying
Z
Department of Molecular and Cellular Biology, Harvard University, 16 Divinity Avenue, Cambridge, MA 02138, USA.
Burrone
Juan
J
Tyler
William J
WJ
Hartman
Kenichi N
KN
Albeanu
Dinu F
DF
Murthy
Venkatesh N
VN
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D004705:Endocytosis; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009419:Nerve Tissue Proteins / Q000235:genetics*; D009474:Neurons / Q000502:physiology; D018408:Patch-Clamp Techniques; D013569:Synapses / Q000502:physiology; D013572:Synaptic Vesicles / Q000502:physiology*
D009419:Nerve Tissue Proteins; C485184:enhanced green fluorescent protein; C485506:synapto-pHluorin protein, mouse; D049452:Green Fluorescent Proteins