Presence of calcium/calmodulin-dependent protein kinase II in nerve terminals of rat brain.

Calcium/calmodulin-dependent protein kinase type II, a multimeric 550-650 kilodalton enzyme composed of major alpha (50 kilodalton) and beta/beta' (60/58 kilodalton) subunits, is present in high concentrations in mammalian brain. Previous immunocytochemical studies indicated that the enzyme is enriched in cell bodies and dendrites, but did not show a clear-cut localization in nerve terminals. The present study presents evidence, using lesion-induced degenerations of pre- and postsynaptic neuronal populations in the neostriatum and substantia nigra, that calcium/calmodulin-dependent protein kinase II, as measured both by autophosphorylation of enzyme subunits and by synapsin I kinase activity, is present in high concentrations in several populations of presynaptic terminals. Lesions of the corticostriatal tract decreased the amount of enzyme by 30-40% in the neostriatum, a decrease similar to that seen in the same region of synapsin I, a general nerve terminal marker. Lesions of the striatonigral tract induced an even more pronounced decrease of the enzyme in the substantia nigra; this decrease was larger than the lesion-induced change of synapsin I seen in the same region. Our data therefore indicate that certain nerve terminal populations in the rat brain contain high levels of calcium/calmodulin-dependent protein kinase II.