Wischmeyer E, Lentes K U, Karschin A
Max-Planck-Institute for Biophysical Chemistry, Göttingen, Germany.
Pflugers Arch. 1995 Apr;429(6):809-19. doi: 10.1007/BF00374805.
The basophilic leucaemia cell line RBL-2H3 exhibits a robust inwardly rectifying potassium current, IKIR, which is likely to be modulated by G proteins. We examined the physiological and molecular properties of this KIR conductance to define the nature of the underlying channel species. The macroscopic conductance revealed characteristics typical of classical K+ inward rectifiers of the IRK type. Channel gating was rapid, first order (tau approximately 1 ms at -100 mV) and steeply voltage dependent. Both activation potential and slope conductance were dependent on extracellular K+ concentration ([K+]o) and inward rectification persisted in the absence of internal Mg2+. The current was susceptible to a concentration- and voltage-dependent block by extracellular Na+, Cs+ and Ba2+. Initial IKIR whole-cell amplitudes as well as current rundown were dependent on the presence of 1 mM internal ATP. Perfusion of intracellular guanosine 5'-Q-(3-thiotriphosphate) (GTP[gamma S]) suppressed IKIR with an average half-time of decline of approximately 400 s. It was demonstrated that the dominant IRK-type 25 pS conductance channel was indeed suppressed by 100 microM preloaded GTP[gamma S]. Reverse transcriptase-polymerase chain reactions (RT-PCR) with RBL cell poly(A)+ RNA identified a full length K+ inward rectifier with 94% base pair homology to the recently cloned mouse IRK1 channel. It is concluded that RBL cells express a classical voltage-dependent IRK-type K+ inward rectifier RBL-IRK1 which is negatively controlled by G proteins.
嗜碱性白血病细胞系RBL-2H3表现出强大的内向整流钾电流IKIR，该电流可能受G蛋白调节。我们研究了这种KIR电导的生理和分子特性，以确定潜在通道种类的性质。宏观电导显示出IRK型经典K⁺内向整流器的典型特征。通道门控快速，呈一级反应（在-100 mV时τ约为1 ms）且强烈依赖电压。激活电位和斜率电导均依赖于细胞外K⁺浓度（[K⁺]o），并且在没有内部Mg²⁺的情况下内向整流仍然存在。该电流易受细胞外Na⁺、Cs⁺和Ba²⁺的浓度和电压依赖性阻断。初始IKIR全细胞幅度以及电流衰减依赖于1 mM内部ATP的存在。细胞内灌注鸟苷5'-Q-(3-硫代三磷酸)（GTP[γS]）抑制IKIR，平均下降半衰期约为400 s。结果表明，主要的IRK型25 pS电导通道确实被100 μM预加载的GTP[γS]抑制。用RBL细胞多聚(A)⁺ RNA进行逆转录聚合酶链反应（RT-PCR）鉴定出一种全长K⁺内向整流器，与最近克隆的小鼠IRK1通道有94%的碱基对同源性。结论是，RBL细胞表达一种经典的电压依赖性IRK型K⁺内向整流器RBL-IRK1，它受G蛋白负调控。
