Identification and regional distribution of a type II calcium/calmodulin-dependent kinase in mouse brain

Abstract

A calcium/calmodulin-dependent protein kinase was partially purified from mouse brain cytosol and compared to a type II calcium/calmodulin-dependent protein kinase (CaM kinase II) previously purified from rat brain. The purification (approximately 200-fold) was followed by the ability of the kinase to phosphorylate the high molecular weight microtubule-associated protein, MAP-2. Approximately 40% of the mouse brain kinase was soluble, and it contained two subunits of 50 kD and 58–60 kD. Both subunits bound [ 125I]calmodulin in a calcium-dependent manner and demonstrated calmodulin-dependent autophosphorylation. The subunits from whole brain were present in a molar ratio of 3 1 . The apparent K m values of the kinase for ATP and calmodulin were 17 μM and 55 nM respectively. The time course, substrate specificity, and subunit phosphopeptide maps were comparable to CaM kinase II from rat brain. Regional distribution studies indicate that the enzyme activity was enriched in hippocampus, cerebral cortex and corpus striatum, whereas activity in cerebellum and pons/medulla was approximately 10-fold lower. All of these characteristics were shared with the rat brain enzyme, indicating that the kinase in mouse brain was a type II calcium/calmodulin-dependent kinase. The mouse may be useful for examining the neuronal localization of CaM kinase II in different brain regions, since this model offers a variety of genetic mutants with well-defined lesions in specific neuronal populations.