Synaptic vesicle depletion correlates with attenuated synaptic responses to prolonged repetitive stimulation in mice lacking alpha-synuclein.
Although the mutation of alpha-synuclein, a protein associated with presynaptic vesicles, is implicated in the etiology and pathogenesis of Parkinson's disease, the biological function of the normal protein is unknown. Mice that lack alpha-synuclein have been generated by homologous recombination in embryonic stem cells. Electron microscopic examination of hippocampal synapses revealed a striking selective deficiency of undocked vesicles without affecting docked vesicles. Field recording of CA1 synapses in hippocampal slices from the mutant mice demonstrated normal basal synaptic transmission, paired-pulse facilitation, and response to a brief train of high-frequency stimulation (100 Hz, 40 pulses) that exhausts only docked vesicles. In contrast, the alpha-synuclein knock-out mice exhibited significant impairments in synaptic response to a prolonged train of repetitive stimulation (12.5 Hz, 300 pulses) capable of depleting docked as well as reserve pool vesicles. Moreover, the replenishment of the docked vesicles by reserve pool vesicles after depletion was slower in the mutant synapses. Thus, alpha-synuclein may be required for the genesis and/or maintenance of a subset of presynaptic vesicles, those in the "reserve" or "resting" pools. These results reveal, for the first time, the normal function of endogenous alpha-synuclein in regulating synaptic vesicle mobilization at nerve terminals.
Cabin
Deborah E
DE
Genetic Diseases Research Branch, National Human Genome Research Institute, Bethesda, Maryland 20892-4472, USA.
Shimazu
Kazuhiro
K
Murphy
Diane
D
Cole
Nelson B
NB
Gottschalk
Wolfram
W
McIlwain
Kellie L
KL
Orrison
Bonnie
B
Chen
Amy
A
Ellis
Christopher E
CE
Paylor
Richard
R
Lu
Bai
B
Nussbaum
Robert L
RL
D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D003433:Crosses, Genetic; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D006579:Heterozygote; D006624:Hippocampus / Q000648:ultrastructure; D015151:Immunoblotting; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism*; D013574:Synaptosomes / Q000737:chemistry / Q000378:metabolism; D051843:Synucleins; D051844:alpha-Synuclein
D009419:Nerve Tissue Proteins; C497605:Snca protein, mouse; D051843:Synucleins; D051844:alpha-Synuclein; D000661:Amphetamine; D002118:Calcium