A new kinetic framework for synaptic vesicle trafficking tested in synapsin knock-outs

Area of Science:

• Neuroscience
• Cell Biology
• Biophysics

Background:

• Vesicle trafficking at synapses involves rate-limiting steps, but their molecular identities remain unclear.
• Existing models struggle to explain supply rate depression under high synaptic activity.

Purpose of the Study:

• To develop a new theoretical model for rate-limiting vesicle trafficking mechanisms.
• To propose a physical interpretation of these rate-limiting steps.

Main Methods:

• Developed a novel theoretical model for vesicle trafficking kinetics.
• Proposed a physical model of local reserve pools (4 vesicles) replenishing stochastically.
• Utilized synapsin knock-out mice and optical imaging experiments.

Main Results:

• The new model accurately predicts kinetic measurements of neurotransmission.
• Synapsin knock-outs exhibit faster supply rate depression, explained by altered local pool sizes.
• Optical imaging data refutes alternative interpretations involving general trafficking inhibition.

Conclusions:

• Local reserve pools of four vesicles, replenished stochastically, are key to vesicle supply regulation.
• Synapsin's role in vesicle trafficking is linked to the size of these local reserve pools.
• This framework aids in identifying rate-limiting mechanisms for synaptic modulation.