Effects of KCNE2 on HCN isoforms: distinct modulation of membrane expression and single channel properties
Effects of KCNE2 on HCN isoforms: distinct modulation of membrane expression and single channel properties
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DOI：
10.1152/ajpheart.00154.2009
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发表时间：
2009-07-01
影响因子：
4.8
通讯作者：
Hoppe, Uta C.
中科院分区：
文献类型：
--
作者：
Brandt, Mathias C.;Endres-Becker, Jeannette;Hoppe, Uta C.
Brandt MC，Endres-Becker J，Zagidullin N，Motloch LJ，Er F，Rottlaender D，Michels G，Herzig S，Hoppe UC. KCNE 2对HCN亚型的影响：膜表达和单通道特性的不同调节。Am J Physiol Heart Circ Physiol 297：H355-H363，2009.首次发表于2009年5月8日; doi：10.1152/ajpheart.00154.2009。超极化激活阳离子（HCN）通道产生的内向电流与起搏电流（I-f）相比具有相似但不相同的特征，表明HCN通道功能受天然组织中调节β亚基的调节。KCNE 2被认为是HCN通道的β亚基，然而，现有的数据仍然相互矛盾。为了进一步阐明这种情况，我们分析了KCNE 2对CHO细胞系统中所有心脏HCN亚型的全细胞电流、单通道特性和膜蛋白表达的影响。在整个细胞水平上，所有HCN亚型的电流密度显着增加KCNE 2不改变电压依赖性或电流反转。虽然这些结果与KCNE 2介导的HCN 2和HCN 4的膜蛋白水平分别增加2.2倍和1.6倍相关，但没有获得KCNE 2对HCN 1表达的影响。所有HCN亚型与KCNE 2共表达后均表现出更快的激活动力学。最重要的是，我们首次证明了KCNE 2对单通道功能的调节，从而支持与HCN亚基的直接功能相互作用。在KCNE 2的存在下，HCN 1，HCN 2和HCN 4的单通道幅度和电导与对照记录相比显著增加。与单独的相应HCN亚基相比，共表达HCN 2 + KCNE 2的细胞的平均开放时间显着增加，而HCN 1 + KCNE 2共转染的细胞的平均开放时间不受影响，而HCN 4 + KCNE 2共转染的细胞的平均开放时间减少。因此，我们证明了KCNE 2介导的HCN膜表达和HCN亚型的直接功能调节的独特作用，进一步支持KCNE 2作为HCN通道的调节β亚基存活。
Brandt MC, Endres-Becker J, Zagidullin N, Motloch LJ, Er F, Rottlaender D, Michels G, Herzig S, Hoppe UC. Effects of KCNE2 on HCN isoforms: distinct modulation of membrane expression and single channel properties. Am J Physiol Heart Circ Physiol 297: H355-H363, 2009. First published May 8, 2009; doi: 10.1152/ajpheart.00154.2009.-Hyperpolarization-activated cation (HCN) channels give rise to an inward current with similar but not identical characteristics compared with the pacemaker current (I-f), suggesting that HCN channel function is modulated by regulatory beta-subunits in native tissue. KCNE2 has been proposed to serve as a beta-subunit of HCN channels; however, available data remain contradictory. To further clarify this situation, we therefore analyzed the effect of KCNE2 on whole cell currents, single channel properties, and membrane protein expression of all cardiac HCN isoforms in the CHO cell system. On the whole cell level, current densities of all HCN isoforms were significantly increased by KCNE2 without altering voltage dependence or current reversal. While these results correlated well with the KCNE2-mediated 2.2-fold and 1.6-fold increases of membrane protein levels of HCN2 and HCN4, respectively, no effect of KCNE2 on HCN1 expression was obtained. All HCN subtypes displayed faster activation kinetics upon coexpression with KCNE2. Most importantly, for the first time, we demonstrated modulation of single channel function by KCNE2, thus supporting direct functional interaction with HCN subunits. In the presence of KCNE2, the single channel amplitudes and conductance of HCN1, HCN2, and HCN4 were significantly increased versus control recordings. Mean open time was significantly increased in cells coexpressing HCN2 + KCNE2, whereas it was unaffected in HCN1 + KCNE2 cotransfected cells and reduced in HCN4 + KCNE2 cotransfected cells compared with the respective HCN subunits alone. Thus, we demonstrate KCNE2-mediated distinct effects on HCN membrane expression and direct functional modulation of HCN isoforms, further supporting that KCNE2 surves as a regulatory beta-subunit of HCN channels.