Mediatophore, a protein supporting quantal acetylcholine release.

Area of Science:

• Neuroscience
• Molecular Biology
• Biochemistry

Background:

• Calcium-dependent acetylcholine release is a fundamental process in neurotransmission.
• The molecular machinery responsible for this release has been partially characterized.
• Mediatophore, a protein from Torpedo electric organ, was previously identified for its role in acetylcholine release.

Purpose of the Study:

• To investigate the function of mediatophore in acetylcholine release.
• To determine if mediatophore alone can mediate calcium-dependent acetylcholine release.
• To explore the role of synaptic vesicles in synchronizing mediatophore activity.

Main Methods:

• Reconstitution of calcium-dependent acetylcholine release in artificial membranes.
• Purification of mediatophore from Torpedo electric organ nerve terminals.
• Transfection of cells deficient in acetylcholine release with a plasmid encoding Torpedo mediatophore.

Main Results:

• Transfected cells acquired the ability to release acetylcholine in quanta upon calcium influx.
• The observed acetylcholine release was attributed to mediatophores, as cells lacked endogenous synthesis and vesicular concentration mechanisms.
• Mediatophore activity is regulated by calcium concentration, being activated at high levels and desensitized at low levels.

Conclusions:

• Mediatophore is sufficient to mediate calcium-dependent acetylcholine release.
• Synchronization of mediatophore activity may depend on calcium microdomains influenced by synaptic vesicles.
• Vesicular docking and associated proteins could play a role in synchronizing mediatophore function during neurotransmission.