β1-subunit of MaxiK channel in smooth muscle:: a key molecule which tunes muscle mechanical activity
β1-subunit of MaxiK channel in smooth muscle:: a key molecule which tunes muscle mechanical activity
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DOI：
10.1254/jphs.94.339
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发表时间：
2004-04-01
影响因子：
3.5
通讯作者：
Toro, L
中科院分区：
文献类型：
--
作者：
Tanaka, Y;Koike, K;Toro, L
MaxiK通道是一种大电导、电压依赖性和钙离子激活的钾通道。该通道几乎普遍分布于包括平滑肌在内的哺乳动物组织中。MaxiK作为一种微调膜电位和细胞内钙离子的变阻器的能力使其能够介导相反的功能：它促进收缩，但也作为一种负反馈机制在收缩周期后恢复张力。MaxiK的激活介导对多种生理物质的舒张作用，而其抑制在收缩反应中起重要作用。在分子水平上，MaxiK是一种由至少两个不同的完整膜亚基组成的蛋白质复合物，即形成孔道的α亚基和一个调节性的β亚基。在平滑肌中，β1是主要的亚基，大多数MaxiK似乎由α亚基和β1亚基组装而成。β1亚基的存在使MaxiK具有更高的钙离子/电压敏感性，这使得该通道在生理条件下成为平滑肌功能的有效调节器。缺乏β1亚基基因的小鼠平滑肌机械活动增强，这支持了该通道分子成分在组织和整体动物功能中的主要作用。在这篇综述中，我们讨论了MaxiK通道作为平滑肌收缩性调节器的作用，尤其关注调节性的β1亚基。
The MaxiK channel is the large-conductance, voltage-dependent, and Ca2+-activated K channel. This channel is almost ubiquitously distributed among mammalian tissues including smooth muscles. The ability of MaxiK to work as a rheostat fine tuning membrane potential and intracellular Ca2+ enables it to mediate opposite functions: it facilitates contraction, but also acts as a negative feedback mechanism to restore tone after a contraction cycle. MaxiK activation mediates relaxations to a variety of physiological substances, whereas its inhibition plays a significant role in contractile responses. At the molecular level, MaxiK is a protein complex formed by at least two integral dissimilar membrane subunits, the pore-forming a-subunit and a regulatory beta-subunit. In smooth muscles, beta1 is the predominant subunit and most MaxiK seem to be assembled of alpha- and beta1-subunits. The presence of the beta1-subunit confers MaxiK with higher Ca2+/voltage sensitivity, which makes this channel an efficient tuner of smooth muscle functions in physiological conditions. The enhanced smooth muscle mechanical activities in mice lacking the beta1-subunit gene support the principal role of this channel molecular component in tissue and whole animal functions. In this review, we discuss MaxiK channel roles as a tuner of smooth muscle contractility, especially focusing attention on the modulatory beta1-subunit.