Calcium channel agonists and antagonists regulate protein phosphorylation in intact synaptosomes

Area of Science:

• Neuroscience
• Molecular Biology
• Pharmacology

Background:

• Protein phosphorylation in synaptosomes is sensitive to calcium (Ca2+) fluxes.
• Calcium channel modulators are critical in neurological research and therapeutics.

Purpose of the Study:

• To investigate the mechanism of action of calcium channel agents BAY K 8644, verapamil, and nifedipine.
• To explore the impact of these agents on synaptosomal protein phosphorylation.

Main Methods:

• Intact synaptosomes were treated with calcium channel agonist BAY K 8644 and antagonists verapamil and nifedipine (1 microM).
• Basal and depolarization-dependent protein phosphorylation levels were analyzed.
• Protein kinase activity was assessed to rule out direct stimulation.

Main Results:

• All tested agents significantly increased basal phosphorylation of specific synaptosomal phosphoproteins (P139, P124, P96, P60).
• Depolarization-dependent protein phosphorylation remained unaltered by these agents.
• The observed increases in phosphorylation were not due to direct protein kinase stimulation.

Conclusions:

• Calcium channel modulators may exert effects through a novel mechanism involving basal protein phosphorylation.
• This finding suggests a potential new pathway for drugs interacting with calcium channels, distinct from their effects on neurotransmitter release.