title: Ca2+-dependent protein phosphorylation of purely cholinergic Torpedo synaptosomes.
abstract: Preincubation of intact, purely cholinergic Torpedo synaptosomes with [32P]Pi results in the incorporation of 32P into about 10 specific proteins. Depolarizing the Torpedo synaptosomes by a high K+ buffer or treatment with the Ca2+ ionophore A23187 result in Ca2+ uptake, in acetylcholine (ACh) release, and in a marked increase of 32P incorporation into a specific protein band with an apparent subunit molecular weight of 100,000 (band alpha). The kinetics of synaptosomal 45Ca2+ uptake, of 32P incorporation into band alpha, and of ACh release is similar and reach maximal values about 45 s after the synaptosomes have been treated. Sr2+ and Ba2+ can replace Ca2+ in evoking both K+ depolarization-dependent ACh release and 32P incorporation into band alpha. The effectiveness of these ions (Ca2+ greater than Sr2+ greater than Ba2+) is similar in both cases. The data presented suggest that Ca2+ accumulation by Torpedo synaptosomes leads to an increase in the phosphorylation of a specific protein and to ACh release. This phosphoprotein may be involved in the regulation of presynaptic processes which underly ACh release.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology*; D004557:Electric Organ / Q000378:metabolism*; D005399:Fishes; D007700:Kinetics; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
chemical_list: D009419:Nerve Tissue Proteins; D000001:Calcimycin; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium