Yakel J L
Laboratoire de Neurobiologie (URA 295 CNRS), Ecole Normale Supérieure, Paris, France.
Pflugers Arch. 1992 Apr;420(5-6):470-8. doi: 10.1007/BF00374621.
The rate of inactivation of the voltage-dependent Ba2+ current in dissociated neurons from the snail Helix aspersa was found to be modulated by phosphorylation. Conditions were chosen such that the most likely mechanism of inactivation of the Ba2+ current was a voltage-dependent/calcium-independent inactivation process. If adenosine-triphosphate (ATP) was not included in the patch electrode filling solution, or if alkaline phosphatase was added, the Ba2+ current rapidly ran down and the rate of inactivation greatly increased with time. Dialysis with either ATP gamma S or the phosphatase inhibitor okadaic acid (OA) either enhanced the amplitude or greatly reduced the rate of run-down of the Ba2+ current (depending upon the presence of ATP), as well as reducing the rate of inactivation. However, dialysis with either the catalytic subunit of the cyclic-adenosine-mono-phosphate-dependent protein kinase (cAMP-PK), a synthetic peptide inhibitor of this enzyme, or staurosporine (a potent inhibitor of protein kinase C), did not have any significant effect on the amplitude or kinetics of the Ba2+ current. Surprisingly, dialysis with a peptide inhibitor (CKIP) of the Ca2+/calmodulin-dependent protein kinase II (Ca(2+)-CaM-PK) significantly reduced the rate of inactivation of this current. These results suggest that phosphorylation may exert its effect by modulating the gating properties of the Ca2+ channels.
研究发现，蜗牛（Helix aspersa）离体神经元中电压依赖性Ba2+电流的失活速率受磷酸化作用调节。实验选取了合适的条件，使Ba2+电流最可能的失活机制是电压依赖性/钙非依赖性失活过程。如果膜片钳电极灌流液中不包含三磷酸腺苷（ATP），或者加入碱性磷酸酶，Ba2+电流会迅速衰减，且失活速率随时间大幅增加。用ATPγS或磷酸酶抑制剂冈田酸（OA）进行透析，要么增强Ba2+电流的幅度，要么极大降低其衰减速率（取决于ATP的存在情况），同时还降低失活速率。然而，用环磷酸腺苷依赖性蛋白激酶（cAMP-PK）的催化亚基、该酶的合成肽抑制剂或星形孢菌素（蛋白激酶C的有效抑制剂）进行透析，对Ba2+电流的幅度或动力学没有任何显著影响。令人惊讶的是，用钙/钙调蛋白依赖性蛋白激酶II（Ca(2+)-CaM-PK）的肽抑制剂（CKIP）进行透析，能显著降低该电流的失活速率。这些结果表明，磷酸化可能通过调节Ca2+通道的门控特性发挥作用。
