Early postnatal development of calmodulin-dependent protein kinase II in rat brain

The postnatal levels of the α- (M_r 50,000) and β- (M_r 58,000/60,000) subunits of type II calmodulin-dependent protein kinase were investigated in cytosolic, cytoskeletal and nuclear subfractions of rat brain. Substantial amounts of the β-subunit were present neonatally, especially in the cytoplasm; both subunits increased markedly during the subsequent three weeks with α-preponderance in the cortex and midbrain. The development of the α-subunit was attenuated in the cerebellum and brain stem, resulting in a relative excess of the β-subunit. Primary neuronal cultures from fetal brain initially displayed low enzyme content, followed by an increase in the levels of the β- but not α-subunit. Regulation of the cellular content of type II calmodulin-dependent protein kinase may be relevant to neuronal differentiation.