Calmodulin in neurotransmitter release and synaptic function.

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Calmodulin is a key calcium-binding protein in the brain.
• Calcium ions (Ca2+) play crucial roles in neuronal functions.
• Understanding calmodulin's role in synaptic activity is vital.

Purpose of the Study:

• To characterize calmodulin in presynaptic and synaptic vesicle fractions.
• To investigate calmodulin's regulation of Ca2+-stimulated protein phosphorylation in synaptic components.
• To elucidate the role of Ca2+-calmodulin in neurotransmitter release and synaptic plasticity.

Main Methods:

• Characterization of calmodulin in subcellular fractions (presynaptic cytoplasm, synaptic vesicles).
• Assessing Ca2+-stimulated protein phosphorylation in various synaptic fractions (vesicle, membrane, junction, postsynaptic density).
• Investigating neurotransmitter release and protein phosphorylation in synaptosomes and isolated vesicles.

Main Results:

• Calmodulin regulated Ca2+-stimulated phosphorylation of synaptic proteins.
• Depolarization-induced Ca2+ influx triggered synaptic protein phosphorylation.
• Ca2+-calmodulin mediated synaptic vesicle-membrane interactions, neurotransmitter release, and protein phosphorylation.
• A distinct synaptic tubulin kinase system, regulated by Ca2+-calmodulin, was identified.
• Calmodulin-regulated tubulin phosphorylation altered tubulin properties, leading to insoluble fibril formation.

Conclusions:

• Ca2+-calmodulin-regulated synaptic protein phosphorylation is implicated in neurotransmitter release.
• Calmodulin may convert Ca2+ signals into motor forces via tubulin phosphorylation.
• This pathway offers insights into Ca2+ regulation of synaptic activity and plasticity.