Arkett S A, Dixon J, Yang J N, Sakai D D, Minkin C, Sims S M
Department of Physiology, University of Western Ontario, London, Canada.
Recept Channels. 1994;2(4):281-93.
Previous studies have revealed that expression of K+ channels in osteoclasts correlates with cell morphology and is influenced by interaction with the extracellular matrix. In this study, we investigated the electrophysiological properties of an outwardly rectifying K+ channel in rat and mouse osteoclasts using patch-clamp techniques. Cell-attached patch recordings revealed a channel of approximately 14 pS conductance that opened upon depolarization, and had a reversal potential close to that predicted for a K+ channel. Channel activity was transient; inactivation of ensemble currents, like that of whole-cell currents, occurred as a single exponential process. Both single-channel and macroscopic currents exhibited use-dependent inactivation in response to repetitive depolarizations. Two scorpion toxins, margatoxin and charybdotoxin, blocked this transient K+ channel, with half-maximal inhibition at 200 pM and 5 nM, respectively. In contrast, dendrotoxin (500 nM) had little effect. In summary, the outwardly rectifying K+ channel in osteoclasts resembles the Shaker-related K+ channel, Kv1.3. When membrane potential was recorded in whole-cell configuration, charybdotoxin (50 nM) caused a depolarization of 5 to 10 mV from resting levels of -50 mV or more positive; therefore this K+ channel contributes to the membrane potential of osteoclasts under some conditions. To investigate the molecular nature of osteoclast K+ channels, we performed RT-PCR on osteoclast RNA using primers for Kv1.3 and the inward rectifier, IRK1. mRNA encoded by Kv1.3 and IRK1 was detected and message identity confirmed by restriction enzyme digestion and sequence analysis. We conclude that osteoclasts exhibit, in addition to the previously described inward rectifier, an outwardly rectifying K+ conductance with properties of the Kv1.3. channel.
先前的研究表明，破骨细胞中钾离子通道的表达与细胞形态相关，并受细胞与细胞外基质相互作用的影响。在本研究中，我们使用膜片钳技术研究了大鼠和小鼠破骨细胞中一种外向整流钾离子通道的电生理特性。细胞贴附式膜片钳记录显示，存在一种电导约为14 pS的通道，该通道在去极化时开放，其反转电位接近钾离子通道的预测值。通道活性是瞬时的；总体电流的失活，与全细胞电流一样，呈单指数过程。单通道电流和宏观电流在重复去极化时均表现出使用依赖性失活。两种蝎毒素，玛格毒素和卡律蝎毒素，可阻断这种瞬时钾离子通道，半数最大抑制浓度分别为200 pM和5 nM。相比之下，树眼镜蛇毒素（500 nM）几乎没有作用。总之，破骨细胞中的外向整流钾离子通道类似于与Shaker相关的钾离子通道Kv1.3。当以全细胞模式记录膜电位时，卡律蝎毒素（50 nM）可使静息电位为-50 mV或更正电位时产生5至10 mV的去极化；因此，在某些条件下，这种钾离子通道有助于破骨细胞的膜电位。为了研究破骨细胞钾离子通道的分子特性，我们使用Kv1.3和内向整流钾离子通道IRK1的引物对破骨细胞RNA进行了逆转录聚合酶链反应（RT-PCR）。检测到了由Kv1.3和IRK1编码的mRNA，并通过限制性内切酶消化和序列分析确认了信息的一致性。我们得出结论，破骨细胞除了先前描述的内向整流钾离子通道外，还表现出具有Kv1.3通道特性的外向整流钾离子电导。
