Separation and characterization of currents through store-operated CRAC channels and Mg2+-inhibited cation (MIC) channels.
Separation and characterization of currents through store-operated CRAC channels and Mg2+-inhibited cation (MIC) channels.
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DOI：
10.1085/jgp.20028551
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发表时间：
2002-05
期刊：
影响因子：
--
通讯作者：
Lewis RS
中科院分区：
文献类型：
--
作者：
Prakriya M;Lewis RS
尽管钙库操纵的钙释放激活的Ca 2+（CRAC）通道在生理离子条件下具有高度的Ca 2+选择性，但细胞外二价阳离子的去除使其对单价阳离子自由渗透。一些过去的研究已经得出结论，在这些条件下，CRAC通道传导Na+和Cs+，单位电导为1.40 pS，并且细胞内Mg 2+调节它们的活性和选择性。这些结果对于理解离子通过CRAC通道的渗透和筛选潜在的CRAC通道基因具有重要意义。我们发现观察到的40-pS通道不是CRAC通道，而是Mg 2+抑制的阳离子（MIC）通道，其随着Mg 2+从胞质溶胶中洗出而打开。MIC通道在几个关键方面不同于CRAC通道。外挂物消耗不会激活MIC通道，外挂物补充也不会使它们失效.与CRAC通道不同，MIC通道不被SKF 96365阻断，不被低剂量的2-APB增强，并且对高剂量药物的阻断不太敏感。通过应用8-10 mM细胞内Mg 2+抑制MIC通道，我们检测了通过CRAC通道的单价渗透。从20 mM Ca 2+到不含二价的细胞外溶液的快速切换通过开放的CRAC通道（Na+-ICRAC）引起Na+电流，其最初比先前的Ca 2+电流大8倍，并且在20 s内下降约80%。与MIC通道不同，CRAC通道在很大程度上不渗透Cs+（PC/PNa = 0.13对MIC的1.2）。Na+-ICRAC的下降及其低Cs+渗透性均不受细胞内Mg 2+（90 μM至10 mM）的影响。单价CRAC通道的单一开口在全细胞记录中检测不到，但从噪声分析估计为0.2 pS的单位电导。关于CRAC通道的选择性、电导和调节的新信息迫使CRAC通道的生物物理指纹的修订，并揭示了电压门控和存储操作的Ca 2+通道的渗透机制的有趣的相似性和差异。
Although store-operated calcium release–activated Ca2+ (CRAC) channels are highly Ca2+-selective under physiological ionic conditions, removal of extracellular divalent cations makes them freely permeable to monovalent cations. Several past studies have concluded that under these conditions CRAC channels conduct Na+ and Cs+ with a unitary conductance of ∼40 pS, and that intracellular Mg2+ modulates their activity and selectivity. These results have important implications for understanding ion permeation through CRAC channels and for screening potential CRAC channel genes. We find that the observed 40-pS channels are not CRAC channels, but are instead Mg2+-inhibited cation (MIC) channels that open as Mg2+ is washed out of the cytosol. MIC channels differ from CRAC channels in several critical respects. Store depletion does not activate MIC channels, nor does store refilling deactivate them. Unlike CRAC channels, MIC channels are not blocked by SKF 96365, are not potentiated by low doses of 2-APB, and are less sensitive to block by high doses of the drug. By applying 8–10 mM intracellular Mg2+ to inhibit MIC channels, we examined monovalent permeation through CRAC channels in isolation. A rapid switch from 20 mM Ca2+ to divalent-free extracellular solution evokes Na+ current through open CRAC channels (Na+-ICRAC) that is initially eightfold larger than the preceding Ca2+ current and declines by ∼80% over 20 s. Unlike MIC channels, CRAC channels are largely impermeable to Cs+ (PCs/PNa = 0.13 vs. 1.2 for MIC). Neither the decline in Na+-ICRAC nor its low Cs+ permeability are affected by intracellular Mg2+ (90 μM to 10 mM). Single openings of monovalent CRAC channels were not detectable in whole-cell recordings, but a unitary conductance of 0.2 pS was estimated from noise analysis. This new information about the selectivity, conductance, and regulation of CRAC channels forces a revision of the biophysical fingerprint of CRAC channels, and reveals intriguing similarities and differences in permeation mechanisms of voltage-gated and store-operated Ca2+ channels.
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DOI：
10.1085/jgp.88.3.293
发表时间：
1986-09
期刊：
The Journal of general physiology
影响因子：
--
作者：
Hess P;Lansman JB;Tsien RW
通讯作者：
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DOI：
10.1085/jgp.111.4.521
发表时间：
1998-04
期刊：
The Journal of general physiology
影响因子：
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作者：
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通讯作者：
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影响因子：
4.8
作者：
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5.5
作者：
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