Mitogen-activated protein kinase regulates early phosphorylation and delayed expression of Ca2+/calmodulin-dependent protein kinase II in long-term potentiation
Activation of mitogen-activated protein kinase (MAPK) and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) are required for numerous forms of neuronal plasticity, including long-term potentiation (LTP). We induced LTP in rat hippocampal area CA1 using theta-pulse stimulation (TPS) paired with beta-adrenergic receptor activation [isoproterenol (ISO)], a protocol that may be particularly relevant to normal patterns of hippocampal activity during learning. This stimulation resulted in a transient phosphorylation of p42 MAPK, and the resulting LTP was MAPK dependent. In addition, CaMKII was regulated in two, temporally distinct ways after TPS-ISO: a transient rise in the fraction of phosphorylated CaMKII and a subsequent persistent increase in CaMKII expression. The increases in MAPK and CaMKII phosphorylation were strongly colocalized in the dendrites and cell bodies of CA1 pyramidal cells, and both the transient phosphorylation and delayed expression of CaMKII were prevented by inhibiting p42/p44 MAPK. These results establish a novel bimodal regulation of CaMKII by MAPK, which may contribute to both post-translational modification and increased gene expression.