Calcium-dependent protein phosphorylation and dephosphorylation in intact brain neurons in culture

Abstract

Preincubation of intact fetal rat brain neurons in culture with 32P i results in the incorporation of 32P i into about 20 specific proteins. Upon stimulation by electrical field stimulation or by K +-induced depolarization, highly significant calcium-dependent increase in phosphorylation of a protein of app. M r 43 000 and decrease in phosphorylation of an app. M r 55 000 protein occur. These changes can be attributed to the entry of Ca 2+ into the cellular cytoplasm since they can occur upon selective permeabilization of the cell membrane to Ca 2+ by the Ca 2+-ionophore A23187 and are not observed upon stimulation of the cells in the presence of the Ca 2+ channel blocker D-600. These data suggest that these phosphoproteins may be involved in the regulation of processes underlying neurotransmitter release.