Activation of Ca(2+)/calmodulin-dependent protein kinase II in cerebellar granule cells by N-methyl-d-aspartate receptor activation

Abstract

Cultured cerebellar granule cells were studied to determine if the excitatory neurotransmitter glutamate acting through the N-methyl-d-aspartate (NMDA) receptor could stimulate autophosphorylation of Ca(2+)/calmodulin-dependent protein kinase II (CaM-kinase II) to generate its Ca(2+)-independent form. Glutamate did elevate Ca(2+)-independent CaM-kinase II through autophosphorylation when granule cells were incubated in Mg(2+)-free buffer, and this response was potentiated by 1 muM glycine. Extracellular Ca(2+) was required, and specific antagonists of the NMDA receptor blocked the response. These results support the hypothesis that postsynaptic Ca(2+) influx through the NMDA receptor-gated ion channel, as occurs during induction of long-term potentiation, may convert CaM-kinase II to a constitutively active, Ca(2+)-independent form.