Ｌ型Ｃ・lt;`ャネルの基本活動の維持におけるカルモジュリン依存性キナーゼIIとカルモジュリンの役割

抄録

We have previously reported that the basal activity of L-type Ca²⁺ channel is suppressed by the inhibitors of calmodulin (CaM)-dependent protein kinase II (CaMKII), and that CaMKII activated by CaM recovers Ca²⁺ channel activity after run-down. In this study, we have investigated how CaMKII and CaM play their roles in the maintenance of the basal activity of Ca²⁺ channel. [Method] Single Ca²⁺ channel activities were recorded with patch clamp technique in guinea-pig ventricular myocytes. CaMKIIα-T286D, a mutant recombinant CaMKIIα (presented by Dr. Miyamoto E. & Dr. Takeuchi Y.), was produced by site-directed mutagenesis and GST fusion protein purification. CaMKIIα-T286D had partial enzymatic activity in the absence of CaM and Ca²⁺, and was used as an activated CaMKII. [Results & Discussion] After the patches were excised into basic internal solution, the Ca²⁺ channel activity disappeared (run-down). Application of CaMKIIα-T286D (1, 3, 10, 30 μM) recovered the Ca²⁺ channel activity to only 0.5, 3, 5 and 4% of that recorded in the cell-attached mode. The effect of CaM to reverse run-down was time-dependent, but in the presence of CaMKIIα-T286D, it became time-independent. These results suggest that both of CaMKII and CaM are involved in the maintenance of the basal activity of Ca²⁺ channel. CaMKII may keep the channel in a state that can be reactivated by CaM. [Jpn J Physiol 54 Suppl:S67 (2004)]