The regulation of selective and nonselective Na+ conductances in H441 human airway epithelial cells
The regulation of selective and nonselective Na+ conductances in H441 human airway epithelial cells
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DOI：
10.1152/ajplung.00240.2007
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发表时间：
2008-05-01
影响因子：
4.9
通讯作者：
Wilson, Stuart M.
中科院分区：
文献类型：
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作者：
Brown, Sean G.;Gallacher, Michael;Wilson, Stuart M.
从去钠H441细胞记录的膜电流的分析表明，单细胞中的膜电位（V-m）（约-80 mV）不受降低[Na+]（o）或[Cl-]（o）的影响，表明细胞Na+和Cl-电导（分别为G（Na）和G（Cl））可忽略不计。尽管胰岛素（20 nM，类似于24 h）和地塞米松（0.2 μ M，类似于24 h）均使Vm去极化20 mV，但对胰岛素的反应反映了通过磷脂酰肌醇3-激酶（PI 3 K）介导的GCl升高，而地塞米松通过诱导GNa的血清和糖皮质激素调节激酶1（SGK 1）依赖性升高起作用。虽然胰岛素刺激/PI 3 K-P110 α表达并不直接增加G（Na），但这些操作增强了地塞米松诱导的电导。糖皮质激素/SGK 1诱导的GNa在单细胞中的Na+和K+之间的区别很差（P-Na/P-K类似于0.6），对阿米洛利（1 mM）不敏感，但被LaCl 3（La 3 +; 1 mM，类似于80%）、匹莫齐特（0.1 mM，类似于40%）和二氯苯扎明（15 μ M，类似于15%）部分阻断。另一方面，作为小群体生长的细胞表达了阿米洛利敏感性（10 μ M），选择性GNa，其显示与单细胞中的非选择性电导相同的激素调节模式。因此，这些数据1）证实H441细胞可以表达选择性或非选择性GNa（14，48），2）表明这些电导都是由糖皮质激素/SGK 1诱导的，并受到PI 3 K依赖性调节，3）确定细胞-细胞接触对Na+选择性和阿米洛利敏感性的发展至关重要。
Analysis of membrane currents recorded from hormone-deprived H441 cells showed that the membrane potential (V-m) in single cells ( approximately -80 mV) was unaffected by lowering [Na+](o) or [Cl-](o), indicating that cellular Na+ and Cl- conductances (G(Na) and G(Cl), respectively) are negligible. Although insulin ( 20 nM, similar to 24 h) and dexamethasone (0.2 mu M, similar to 24 h) both depolarized Vm by similar to 20 mV, the response to insulin reflected a rise in GCl mediated via phosphatidylinositol 3-kinase (PI3K) whereas dexamethasone acted by inducing a serum- and glucocorticoid-regulated kinase 1 (SGK1)-dependent rise in GNa. Although insulin stimulation/PI3K-P110 alpha expression did not directly increase G(Na), these maneuvers augmented the dexamethasone-induced conductance. The glucocorticoid/SGK1-induced GNa in single cells discriminated poorly between Na+ and K+ (P-Na/P-K similar to 0.6), was insensitive to amiloride ( 1 mM), but was partially blocked by LaCl3 (La3+; 1 mM, similar to 80%), pimozide ( 0.1 mM, similar to 40%), and dichlorobenzamil ( 15 mu M, similar to 15%). Cells growing as small groups, on the other hand, expressed an amiloride-sensitive ( 10 mu M), selective GNa that displayed the same pattern of hormonal regulation as the nonselective conductance in single cells. These data therefore 1) confirm that H441 cells can express selective or nonselective GNa ( 14, 48), 2) show that these conductances are both induced by glucocorticoids/SGK1 and subject to PI3K-dependent regulation, and 3) establish that cell-cell contact is vitally important to the development of Na+ selectivity and amiloride sensitivity.