Assembling the presynaptic active zone: a characterization of an active one precursor vesicle.

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• The presynaptic active zone is crucial for neurotransmission, mediating synaptic vesicle docking and fusion.
• The precise mechanisms for assembling the active zone, particularly protein transport, remain incompletely understood.

Purpose of the Study:

• To investigate the cellular transport and recruitment mechanism of the active zone protein Piccolo to nascent synapses.
• To identify the vesicular carriers involved in delivering active zone components during synapse formation.

Main Methods:

• Immunocytochemistry and electron microscopy were used to visualize and characterize vesicles transporting active zone proteins.
• Proteomic analysis of the transport vesicles was performed to identify their molecular cargo.

Main Results:

• Piccolo is transported to nascent synapses on dense core granulated vesicles (approximately 80 nm in diameter).
• These vesicles co-transport other active zone proteins like Bassoon, Syntaxin, SNAP-25, and N-cadherin, along with chromogranin B.
• Synaptic vesicle proteins (e.g., VAMP 2, synaptophysin, synaptotagmin) and perisynaptic membrane proteins (e.g., GAT1) were notably absent from these transport vesicles.

Conclusions:

• The presynaptic active zone is partially assembled through the fusion of specialized active zone precursor vesicles with the presynaptic plasma membrane.
• This finding reveals a novel mechanism for the targeted delivery and assembly of essential synaptic machinery during synapse development.