title: Synapsin dispersion and reclustering during synaptic activity.
abstract: Presynaptic modulation of synaptic transmission provides an important basis for control of synaptic function. The synapsins, a family of highly conserved proteins associated with synaptic vesicles, have long been implicated in the regulation of neurotransmitter release. However, direct physiological measurements of the molecular mechanisms have been lacking. Here we show that in living hippocampal terminals, green fluorescent protein (GFP)-labeled synapsin Ia dissociates from synaptic vesicles, disperses into axons during action potential (AP) firing, and reclusters to synapses after the cessation of synaptic activity. Using various mutated forms of synapsin Ia that prevent phosphorylation at specific sites, we performed simultaneous FM 4-64 measurements of vesicle pool mobilization along with synapsin dispersion kinetics. These studies indicate that the rate of synapsin dispersion is controlled by phosphorylation, which in turn controls the kinetics of vesicle pool turnover. Thus synapsin acts as a phosphorylation-state-dependent regulator of synaptic vesicle mobilization, and hence, neurotransmitter release.
authors.affiliation: Department of Biochemistry, Weill Medical College of Cornell University, 1300 York Avenue, New York, New York 10021, USA.
authors.forename: P
authors.initials: P
authors.lastname: Chi
authors.forename: P
authors.initials: P
authors.lastname: Greengard
authors.forename: T A
authors.initials: TA
authors.lastname: Ryan
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D005822:Genetic Vectors; D049452:Green Fluorescent Proteins; D006624:Hippocampus / Q000378:metabolism / Q000648:ultrastructure; D007150:Immunohistochemistry; D007202:Indicators and Reagents / Q000378:metabolism; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010766:Phosphorylation; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D016704:Synapsins / Q000235:genetics / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D016708:Synaptophysin / Q000378:metabolism; D013997:Time Factors
chemical_list: D007202:Indicators and Reagents; D008164:Luminescent Proteins; D018377:Neurotransmitter Agents; D016704:Synapsins; D016708:Synaptophysin; D049452:Green Fluorescent Proteins; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium