Heme is a carbon monoxide receptor for large-conductance Ca2+-activated K+ channels
Heme is a carbon monoxide receptor for large-conductance Ca2+-activated K+ channels
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DOI：
10.1161/01.res.0000186180.47148.7b
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发表时间：
2005-10-14
影响因子：
20.1
通讯作者：
Leffler, CW
中科院分区：
文献类型：
--
作者：
Jaggar, JH;Li, AL;Leffler, CW
一氧化碳（CO）是一种内源性旁分泌和自分泌的气体信使，调节各种组织的生理功能。CO通过激活动脉平滑肌大电导钙激活钾（BKCa）通道诱导血管舒张。然而，CO激活BKCa通道的机制仍不清楚。在这里，我们测试的假设，CO激活BKCa通道结合血红素，BKCa通道抑制剂，并改变血红素和保守的血红素结合域（HBD）的通道α亚基C端之间的相互作用。使用薄层色谱法，分光光度法，质谱法（MS），和MS-MS获得的数据表明，CO修改还原血红素的α亚基HBD的结合。相反，CO不改变HBD和氧化血红素（氯化血红素）之间的相互作用，CO不能结合。与这些研究结果一致，电生理学测量的本地和克隆（cbv）脑动脉平滑肌BKCa通道显示，CO逆转BKCa通道抑制血红素，但不是氯化血红素。cbv HBD从CKACH到CKASR的定点突变消除了血红素诱导的通道抑制和CO诱导的激活。此外，在结合CO时，血红素从通道抑制剂转变为激活剂。这些发现表明，还原血红素是BKCa通道的功能性CO受体，引入了CO调节靶蛋白活性的独特机制，并揭示了气体信使调节离子通道活性的新过程。
Carbon monoxide ( CO) is an endogenous paracrine and autocrine gaseous messenger that regulates physiological functions in a wide variety of tissues. CO induces vasodilation by activating arterial smooth muscle large conductance Ca2+-activated potassium ( BKCa) channels. However, the mechanism by which CO activates BKCa channels remains unclear. Here, we tested the hypothesis that CO activates BKCa channels by binding to channel-bound heme, a BKCa channel inhibitor, and altering the interaction between heme and the conserved heme-binding domain ( HBD) of the channel alpha subunit C terminus. Data obtained using thin-layer chromatography, spectrophotometry, mass spectrometry ( MS), and MS-MS indicate that CO modifies the binding of reduced heme to the alpha subunit HBD. In contrast, CO does not alter the interaction between the HBD and oxidized heme ( hemin), to which CO cannot bind. Consistent with these findings, electrophysiological measurements of native and cloned ( cbv) cerebral artery smooth muscle BKCa channels show that CO reverses BKCa channel inhibition by heme but not by hemin. Site-directed mutagenesis of the cbv HBD from CKACH to CKASR abolished both heme-induced channel inhibition and CO-induced activation. Furthermore, on binding CO, heme switches from being a channel inhibitor to an activator. These findings indicate that reduced heme is a functional CO receptor for BKCa channels, introduce a unique mechanism by which CO regulates the activity of a target protein, and reveal a novel process by which a gaseous messenger regulates ion channel activity.