A liquid phase of synapsin and lipid vesicles

Area of Science:

• Neuroscience
• Cell Biology
• Biophysics

Background:

• Synaptic vesicles (SVs) cluster at synapses, forming a reservoir for sustained neurotransmission.
• Synapsin is a known component involved in SV clustering.

Purpose of the Study:

• To investigate the physical properties of synapsin and its role in SV clustering.
• To explore the potential application of liquid-liquid phase separation principles in synaptic organization.

Main Methods:

• In vitro experiments demonstrating synapsin's ability to form liquid phases.
• Co-assembly studies with other scaffolding proteins.
• Lipid vesicle capture assays.
• Phosphorylation assays using calcium/calmodulin-dependent protein kinase II.

Main Results:

• Synapsin forms a distinct liquid phase in aqueous solutions.
• This synapsin condensate can capture small lipid vesicles.
• The synapsin phase undergoes rapid disassembly upon phosphorylation by CaMKII.

Conclusions:

• Synapsin's liquid phase behavior provides a mechanism for synaptic vesicle clustering.
• Liquid-liquid phase separation may underlie the dynamic organization of SVs at presynaptic terminals.
• Synapsin phosphorylation regulates SV clustering and release dynamics.