RIM determines Ca²+ channel density and vesicle docking at the presynaptic active zone

Area of Science:

• Neuroscience
• Cell Biology
• Synaptic Plasticity

Background:

• Neurotransmitter release relies on voltage-gated Ca²+ channels at presynaptic active zones.
• Mechanisms concentrating Ca²+ channels at active zones are poorly understood due to synapse accessibility limitations.

Purpose of the Study:

• To investigate the function of RIM proteins in presynaptic Ca²+ channel targeting and neurotransmitter release.
• To elucidate the role of RIM proteins in regulating active zone organization and synaptic vesicle dynamics.

Main Methods:

• Utilized a Cre-lox based conditional knockout system in the calyx of Held synapse.
• Assessed the impact of RIM protein removal on Ca²+ channel density, vesicle pools, and Ca²+-vesicle coupling.

Main Results:

• Complete removal of RIM1/2 isoforms significantly reduced presynaptic Ca²+ channel density.
• RIM protein deficiency led to a smaller readily releasable pool and fewer docked vesicles.
• The coupling between Ca²+ channels and vesicles was diminished upon RIM protein removal.

Conclusions:

• RIM proteins play a vital role in targeting Ca²+ channels to presynaptic active zones.
• RIM proteins are essential for maintaining high Ca²+ channel density and promoting vesicle docking.
• RIM proteins coordinately regulate critical aspects of fast neurotransmitter release, including Ca²+ channel-vesicle coupling.