Chad J, Kalman D, Armstrong D
Department of Biology, University of California, Los Angeles.
Soc Gen Physiol Ser. 1987;42:167-86.
The predominant class of voltage-activated Ca channels in molluscan neurons (Helix) and a mammalian cell line (GH3) do not respond to membrane depolarization under conditions that prevent cAMP-dependent phosphorylation when the cytoplasm is replaced with standard physiological saline solutions. Under normal conditions, inactivation of these channels results from Ca ion entry and accumulation inside the cell. In dialyzed neurons, inactivation is enhanced in the presence of an exogenous Ca-dependent phosphatase, and inactivated channels appear to be susceptible to Ca-dependent proteolysis. Rephosphorylation of the channels by a cAMP-dependent kinase removes inactivation and protects the channels from proteolysis. Thus, phosphorylation/dephosphorylation reactions appear to be an important means of modulating Ca channel activity and may underlie both Ca-dependent inactivation and the metabolic maintenance of the channels.
在软体动物神经元（螺旋蜗牛）和一种哺乳动物细胞系（GH3）中，当用标准生理盐溶液替代细胞质且阻止环磷酸腺苷（cAMP）依赖性磷酸化时，主要类型的电压激活钙通道对膜去极化无反应。在正常情况下，这些通道的失活是由钙离子进入并在细胞内积累导致的。在透析的神经元中，外源性钙依赖性磷酸酶的存在会增强失活，并且失活的通道似乎易受钙依赖性蛋白水解作用的影响。由cAMP依赖性激酶对通道进行再磷酸化可消除失活并保护通道免受蛋白水解。因此，磷酸化/去磷酸化反应似乎是调节钙通道活性的重要手段，并且可能是钙依赖性失活和通道代谢维持的基础。
