Wallner M, Meera P, Ottolia M, Kaczorowski G J, Latorre R, Garcia M L, Stefani E, Toro L
Department of Anesthesiology, UCLA, 90095, USA.
Recept Channels. 1995;3(3):185-99.
cDNAs encoding functional maxi KCa channel alpha-subunits (hslo) were cloned from human myometrium. Northern blot analysis revealed a high abundance of mRNA in human uterine smooth muscle. Calcium- and voltage-activated K+ currents were recorded from Xenopus laevis oocytes injected with hslo cRNA and compared with currents after reconstitution of oocyte membranes expressing cloned maxi KCa channels. The expressed channels displayed characteristics of native maxi KCa channels, including large conductance (280 pS in symmetrical 110 mM K+), calcium sensitivity, kinetics and pharmacology. Currents were activated by niflumic acid; blocked by tetraethylammonium, charybdotoxin and iberiotoxin; and were insensitive to lemakalim, pinacidil, apamin and 4-aminopyridine. Coexpression with the beta-subunit, cloned from bovine trachea smooth muscle, dramatically increased the apparent calcium sensitivity as evident from a leftward shift of the voltage-activation curves. Half maximal activation (V1/2), measured in 10 microM Ca2+, was 12 +/- 18 mV (+/- SD, n = 62) for the alpha-subunit alone and -87 +/- 10 mV (+/- SD, n = 39) in presence of the beta-subunit.
从人子宫肌层克隆出编码功能性大电导钙激活钾通道α亚基（hslo）的互补脱氧核糖核酸（cDNA）。Northern印迹分析显示，人子宫平滑肌中该信使核糖核酸（mRNA）含量很高。从注射了hslo互补核糖核酸（cRNA）的非洲爪蟾卵母细胞中记录钙激活和电压激活的钾电流，并与表达克隆的大电导钙激活钾通道的卵母细胞膜重构后的电流进行比较。所表达的通道表现出天然大电导钙激活钾通道的特性，包括大电导（在对称的110 mM钾中为280皮安）、钙敏感性、动力学和药理学特性。电流可被尼氟酸激活；被四乙铵、蝎毒素和iberiotoxin阻断；对瑞替加滨、匹那地尔、蜂毒明肽和4-氨基吡啶不敏感。与从牛气管平滑肌克隆的β亚基共表达，可显著提高表观钙敏感性，电压激活曲线向左移位即可明显看出。在10微摩尔/升钙离子中测得的半数最大激活电位（V1/2），单独α亚基时为12±18毫伏（±标准差，n = 62），存在β亚基时为-87±10毫伏（±标准差，n = 39）。
