Glibenclamide blockade of CFTR chloride channels
Glibenclamide blockade of CFTR chloride channels
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DOI：
10.1152/ajplung.1996.271.2.l192
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发表时间：
1996-08-01
影响因子：
4.9
通讯作者：
Bridges, RJ
中科院分区：
文献类型：
--
作者：
Schultz, BD;DeRoos, ADG;Bridges, RJ
囊性纤维化跨膜传导调节因子（CFTR）是位于上皮细胞顶膜的蛋白激酶A和ATP调节的Cl-通道。先前Sheppard和Welsh（J.Gen.Physiol.100：573-591，1992）表明，格列本脲（一种结合磺酰脲受体并因此阻断核苷酸依赖性K+通道的化合物）降低CFTR全细胞电流。本研究的目的是确定在含有CFTR Cl-通道的无细胞膜贴片中这种抑制的机制。暴露于格列本脲导致CFTR携带的电流可逆性降低，通道开放概率（P-o）降低。P-o的降低是浓度依赖性的，半最大抑制（Ki）发生在30 μ M。波动分析表明，开放CFTR通道的闪烁型块。事件持续时间分析支持这一观点，显示格列本脲诱导的P-o降低伴随开放爆发的中断[即，脉冲串持续时间（τ（burst））的明显减少]而闭合时间（τ（c））仅略微减少。相应的开闭图（tau（爆发）（-1））和关闭-开放（tau（c）（-1））速率作为格列本脲浓度的函数与假一级开放-阻断机制一致，并提供了对开启速率（k（on）= 1.17 μ M（-1）s（-1）），关闭速率（k（off）= 16 s（-1）），和解离常数（Kd = 14 μ M）。K-i（30 μ M）和K-d（14 μ M）之间的差异是初始P-o为0.47的封闭-开放-阻断模型的预期结果。由于初始P-o为0.50 +/- 0.02（n = 12），我们可以得出结论，格列本脲通过闭合-开放-阻断机制阻断CFTR。
The cystic fibrosis transmembrane conductance regulator (CFTR) is a protein kinase A- and ATP-regulated Cl- channel located in the apical membranes of epithelial cells. Previously Sheppard and Welsh (J. Gen. Physiol. 100: 573-591, 1992) showed that glibenclamide, a compound which binds to the sulfonylurea receptor and thus blocks nucleotide-dependent K+ channels, reduced CFTR whole cell current. The aim of this study was to identify the mechanism underlying this inhibition in cell-free membrane patches containing CFTR Cl- channels. Exposure to glibenclamide caused a reversible reduction in current carried by CFTR which was paralleled by a decrease in channel open probability (P-o). The decrease in P-o was concentration dependent, and half-maximum inhibition (K-i) occurred at 30 mu M. Fluctuation analysis indicated a flickery-type block of open CFTR channels. Event duration analysis supported this notion by showing that the glibenclamide-induced decrease in P-o was accompanied by interruptions of open bursts [i.e., an apparent reduction in the burst duration (tau(burst))] With only a slight reduction in closed time (tau(c)). The plot of the corresponding open-to-closed (tau(burst)(-1)) and closed-to-open (tau(c)(-1)) rates as a function of glibenclamide concentration were consistent with a pseudo-first-order open-blocked mechanism and provided estimates of the on rate (k(on) = 1.17 mu M(-1)s(-1)), the off rate (k(off) = 16 s(-1)), and the dissociation constant (K-d = 14 mu M). The difference between the K-i (30 mu M) and the K-d (14 mu M) is the result expected for a closed-open-blocked model with an initial P-o of 0.47. Since the initial P-o was 0.50 +/- 0.02 (n = 12), we can conclude that glibenclamide blocks CFTR by a closed-open-blocked mechanism.