Concurrent inactivation of calcium dependent phosphorylation and neurotransmitter release in cultured rat brain neurons.
Depolarization of cultured rat brain neurons preloaded with 3H-dopamine provokes a transient (t 1/2 = 9.6 sec), Ca(2+)-dependent release of the labeled neurotransmitter from cells. In parallel, the amount of 32Pi incorporated into a protein of apparent molecular weight of 43,000 increased whereas the phosphorylation of a protein with an apparent molecular weight of 55,000 daltons decreased. The time course of the change in phosphorylation pattern was examined. The depolarization-induced phosphorylation of the 45,000 protein and dephosphorylation of the 55,000 dalton protein consisted of an initial, rapidly terminating phase (t 1/2 = 5 sec), and of a slow, Ca(2+)-independent phosphorylation of both proteins which persisted during maintained depolarization. The depolarization-evoked changes in the neuronal protein phosphorylation were dependent on the extracellular Ca2+ concentration (half saturation at 0.4-0.5 mM Ca2+). These data indicate that the entry of Ca2+ into the depolarized cells induces rapid phosphorylation-dephosphorylation activities. These processes terminate within 10 sec, concurrently with the depression of neurotransmitter release.
Zurgil
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Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Israel.
Zisapel
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N
D000818:Animals; D001921:Brain / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology*; D002478:Cells, Cultured; D004298:Dopamine / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000502:physiology; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats
D009419:Nerve Tissue Proteins; D018377:Neurotransmitter Agents; D002118:Calcium; D004298:Dopamine