Voltage-sensitive oxonol dyes are novel large-conductance Ca2+-activated K+ channel activators selective for β1 and β4 but not for β2 Subunits
Voltage-sensitive oxonol dyes are novel large-conductance Ca2+-activated K+ channel activators selective for β1 and β4 but not for β2 Subunits
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DOI：
10.1124/mol.106.031146
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发表时间：
2007-04-01
影响因子：
3.6
通讯作者：
Imaizumi, Yuji
中科院分区：
文献类型：
--
作者：
Morimoto, Takashi;Sakamoto, Kazuho;Imaizumi, Yuji
大电导 Ca2+ 激活的 K+ (BK) 通道通过细胞内 Ca2+ 浓度的增加和膜去极化而被激活。 BK 通道作为负反馈机制中的关键分子，在调节各种细胞类型的膜兴奋性和细胞 Ca2+ 中发挥着至关重要的作用。在这里，我们报道了一种广泛使用的慢响应电压敏感荧光染料双(1,3-二丁基巴比妥酸)三甲川氧杂菁[DiBAC(4)(3)]，是一种有效的BK通道激活剂。在表达大鼠 BK 通道 α 和 β 1 亚基（rBK α β 1）的人胚胎肾 293 细胞中，应用 10 nM 或更高浓度的 DiBAC(4)(3) 显着增加全细胞 BK 通道电流。在300 nM DiBAC(4)(3)存在下，BK通道电流的激活电压向负方向移动约30 mV，但单通道电导不受影响。 DiBAC(4)(3) 在相同浓度范围内激活全细胞 rBK α beta 1 和 rBK α beta 4 电流，但部分阻断 rBK α beta 2 电流。单独的 BK 通道 α 亚基和所检查的一些其他类型的 K+ 通道并未受到 1 μM DiBAC(4)(3) 的显着影响。构效关系分析表明，两个 1,3-二烷基巴比妥酸中的一组氧代和氧代阴离子部分（通过寡甲碱缀合）是 DiBAC(4)(3) 和相关 oxonol 化合物的 β 亚基选择性 BK 通道开放特性的新骨架。该共轭结构可以立体化学地位于一个平面内。这些发现为理解辅助β亚基对BK通道活性的调节机制提供了分子和结构基础，并且对于β选择性BK通道开放剂的开发至关重要。
The large-conductance Ca2+-activated K+ (BK) channel is activated by both the increase of intracellular Ca2+ concentration and membrane depolarization. The BK channel plays crucial roles as a key molecule in the negative feedback mechanism regulating membrane excitability and cellular Ca2+ in various cell types. Here, we report that a widely used slow-response voltage-sensitive fluorescent dye, bis(1,3-dibutylbarbituric acid) trimethine oxonol [DiBAC(4)(3)], is a potent BK channel activator. The application of DiBAC(4)(3) at concentrations of 10 nM and higher significantly increased whole-cell BK channel currents in human embryonic kidney 293 cells expressing rat BK channel alpha and beta 1 subunits (rBK alpha beta 1). In the presence of 300 nM DiBAC(4)(3), the activation voltage of the BK channel current shifted to the negative direction by approximately 30 mV, but the single-channel conductance was not affected. DiBAC(4)(3) activated whole-cell rBK alpha beta 1 and rBK alpha beta 4 currents in the same concentration range but partially blocked rBK alpha beta 2 currents. The BK channel alpha subunit alone and some other types of K+ channels examined were not markedly affected by 1 mu M DiBAC(4)(3). Structure-activity relationship analyses revealed that a set of oxo- and oxoanion-moieties in two 1,3-dialkylbarbituric acids, which are conjugated by oligomethine, is the novel skeleton for the beta-subunit-selective BK channel-opening property of DiBAC(4)(3) and related oxonol compounds. This conjugated structure may be located stereochemically in one plane. These findings provide a molecular and structural basis for understanding the regulatory mechanism of BK channel activity by an auxiliary beta subunit and will be fundamental to the development of beta-selective BK channel openers.