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标题：Voltage-activated calcium channels that must be phosphorylated to respond to membrane depolarization
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作者：D Armstrong ; R Eckert
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1987
卷号：84
期号：8
页码：2518-2522
DOI：10.1073/pnas.84.8.2518
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Two classes of calcium channels were activated by membrane depolarization in cell-free membrane patches from GH3 cells, an electrically excitable cell line derived from a mammalian pituitary tumor. One class had a conductance of approximately 10 pS in 90 mM barium, had a threshold of activation near -40 mV, and was inactivated rapidly at holding potentials more positive than -80 mV. The other class, with a conductance of approximately 23 pS and a threshold nearer -20 mV, did not inactivate in barium but stopped responding to depolarization altogether when the cytoplasmic side of the patch was exposed to a standard physiological saline solution. Buffering the concentration of calcium ions to less than 10 nM on the cytoplasmic side did not prevent this loss of activity. However, activity was restored and maintained for the duration of the patch when the catalytic subunit of cAMP-dependent protein kinase was added with MgATP to the cytoplasmic side of the membrane. Cell-free patch formation in the presence of the dihydropyridine, BAY K 8644, also delayed the loss of activity, but unlike the catalytic subunit plus ATP, BAY K 8644 alone did not restore activity when it was added after the channels no longer responded to depolarization. Evidently the dihydropyridine-sensitive class of voltage-activated calcium channels must be phosphorylated in order to open when the membrane is depolarized. That hypothesis provides a simple framework for understanding the modulation of calcium channel gating by neurotransmitters, calcium ions, and dihydropyridines.