Quantitative analysis of the native presynaptic cytomatrix by cryoelectron tomography

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• The presynaptic terminal's filamentous network organization and function remain largely uncharacterized.
• Understanding these structures is key to elucidating mechanisms of neurotransmission.

Purpose of the Study:

• To investigate the role of presynaptic terminal filaments in synaptic vesicle release.
• To elucidate the structural organization and dynamics of filaments involved in exocytosis.

Main Methods:

• Cryoelectron tomography was employed to visualize the presynaptic terminal ultrastructure.
• Tetanus toxin and okadaic acid were used to probe the functional mechanisms.

Main Results:

• Synaptic vesicles are linked to the active zone by tethers, not direct membrane contact.
• Tether length varies, with longer tethers preceding shorter ones as vesicles enter the readily releasable pool.
• Tether formation is dependent on soluble N-ethyl-maleimide sensitive fusion protein attachment protein receptor (SNARE) complex assembly.
• Inter-vesicular connectors undergo significant rearrangements upon stimulation, suggesting roles in vesicle mobilization.

Conclusions:

• Presynaptic filaments, via variable-length tethers, mediate synaptic vesicle docking and release.
• SNARE complex assembly is essential for the formation of short tethers.
• Filamentous connectors play a dynamic role in regulating synaptic vesicle pools and neurotransmitter release.