CaMKIIα不活性型ノックインマウスの神経活動異常

抄録

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) is one of the most abundant protein kinase in the central nervous system and a key mediator of intracellular Ca²⁺ in response to various stimuli. CaMKII is involved in many neuronal functions including the regulation of neuronal activity. Previous studies reported episodes of epileptic seizure in CaMKIIα knock-out mice and manifestation of epileptic discharges in cultured neurons treated with anti-sense oligonucleotide to CaMKIIα. However, which protein function of CaMKII, i.e., protein kinase activity, calmodulin-binding capacity or multimeric structure interacting with other proteins, is responsible for stabilizing neuronal activity remains to be elucidated yet. To clarify specifically the role of protein kinase activity of CaMKII, we engineered knock-in mice with the inactivated α subunit of CaMKII by replacing Lys-42 with Arg-42. CaMKIIα protein level was unchanged, but CaMKII activity was specifically decreased in these mutant mice. Spontaneous death rate was higher, and pentylenetetrazole injection resulted in higher seizure-induced mortality in homozygous mutants. Spontaneous seizure was sporadically observed in homozygous and heterozygous mutants, but rarely in wild type controls. Cytochrome oxidase staining revealed decreased neuronal activity in nucleus accumbens in homozygous mutants. These results indicate that protein kinase activity of CaMKII, i.e., protein phosphorylation by CaMKII, is important for maintaining basic and normal neuronal activity in vivo. [J Physiol Sci. 2006;56 Suppl:S63]