title: A Network of Three Types of Filaments Organizes Synaptic Vesicles for Storage, Mobilization, and Docking.
abstract: Synaptic transmission between neurons requires precise management of synaptic vesicles. While individual molecular components of the presynaptic terminal are well known, exactly how the molecules are organized into a molecular machine serving the storage and mobilization of synaptic vesicles to the active zone remains unclear. Here we report three filament types associated with synaptic vesicles in glutamatergic synapses revealed by electron microscope tomography in unstimulated, dissociated rat hippocampal neurons. One filament type, likely corresponding to the SNAREpin complex, extends from the active zone membrane and surrounds docked vesicles. A second filament type contacts all vesicles throughout the active zone and pairs vesicles together. On the third filament type, vesicles attach to side branches extending from the long filament core and form vesicle clusters that are distributed throughout the vesicle cloud and along the active zone membrane. Detailed analysis of presynaptic structure reveals how each of the three filament types interacts with synaptic vesicles, providing a means to traffic reserved and recycled vesicles from the cloud of vesicles into the docking position at the active zone.
  
  
  CONCLUSIONS
  The formation and release of synaptic vesicles has been extensively investigated. Explanations of the release of synaptic vesicles generally begin with the movement of vesicles from the cloud into the synaptic active zone. However, the presynaptic terminal is filled with filamentous material that would appear to limit vesicular diffusion. Here, we provide a systematic description of three filament types connecting synaptic vesicles. A picture emerges illustrating how the cooperative attachment and release of these three filament types facilitate the movement of vesicles to the active zone to become docked in preparation for release.
authors.affiliation: Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, and Department of Cellular and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611 cole.andy.a@gmail.com.
authors.forename: Andy A
authors.initials: AA
authors.lastname: Cole
authors.affiliation: Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, and.
authors.forename: Xiaobing
authors.initials: X
authors.lastname: Chen
authors.affiliation: Laboratory of Neurobiology, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, and.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Reese
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000648:ultrastructure; D055032:Electron Microscope Tomography; D004622:Embryo, Mammalian; D005614:Freeze Fracturing; D006624:Hippocampus / Q000166:cytology; D021621:Imaging, Three-Dimensional; D062105:Molecular Docking Simulation; D009474:Neurons / Q000166:cytology*; D051381:Rats; D050600:SNARE Proteins / Q000378:metabolism; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure*; D013572:Synaptic Vesicles / Q000145:classification* / Q000502:physiology* / Q000648:ultrastructure
chemical_list: D050600:SNARE Proteins
keywords: docking; presynaptic; storage; synaptic vesicles; tomography; vesicle mobilization