title: Calcium-dependent 4-aminopyridine stimulation of protein phosphorylation in squid optic lobe synaptosomes.
abstract: When intact synaptosomes were incubated with [gamma-32P]ATP, maximal protein phosphorylation was attained 2 min after the start of incubation. Protein phosphorylation under basal conditions was dependent on external Ca2+, and the dominant peak of phosphorylation was a 50-kd protein. Incubation of intact synaptosomes in the presence of 3-6 mM 4-aminopyridine (4-AP) caused a markedly enhanced phosphorylation of high molecular weight proteins of 90, 100, 130, and 180 kd, with no increase in the 50 or 38 kd proteins. This effect of 4-AP was dependent on external calcium ions in the incubation medium. The 4-AP effect on the high molecular weight proteins was also found in synaptosomal plasma membranes isolated from the synaptosomes. Tetraethylammonium (TEA) ions did not produce this enhancement of phosphorylation.
mesh_terms: D015761:4-Aminopyridine; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000631:Aminopyridines / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D049832:Decapodiformes; D004591:Electrophoresis, Polyacrylamide Gel; D004983:Ethanolamines / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects*; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009899:Optic Lobe, Nonmammalian / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D013574:Synaptosomes / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000631:Aminopyridines; D004983:Ethanolamines; D007473:Ion Channels; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D000255:Adenosine Triphosphate; C009546:triethanolamine; D015761:4-Aminopyridine; D002118:Calcium