Mode shifts in the voltage gating of the mouse and human HCN2 and HCN4 channels

被引:51
作者
Elinder, Fredrik [1 ]
Mannikko, Roope
Pandey, Shilpi
Larsson, H. Peter
机构
[1] Linkoping Univ, Div Cell Biol, Dept Biomed & Surg, SE-58185 Linkoping, Sweden
[2] Oregon Hlth & Sci Univ, Inst Neurol Sci, Beaverton, OR 97006 USA
[3] Karolinska Inst, Nobel Inst Neurophysiol, Dept Neurosci, S-10401 Stockholm, Sweden
[4] Oregon Hlth & Sci Univ, Inst Neurol Sci, Beaverton, OR USA
来源
JOURNAL OF PHYSIOLOGY-LONDON | 2006年 / 575卷 / 02期
关键词
D O I
10.1113/jphysiol.2006.110437
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Hyperpolarization-activated, cyclic-nucleotide-gated (HCN) channels regulate pacemaker activity in the heart and the brain. Previously, we showed that spHCN and HCN1 channels undergo mode shifts in their voltage dependences, shifting the conductance versus voltage curves by more than +50 mV when measured from a hyperpolarized potential compared to a depolarized potential. In addition, the kinetics of the ionic currents changed in parallel to these voltage shifts. In the studies reported here, we tested whether slower cardiac HCN channels also display similar mode shifts. We found that HCN2 and HCN4 channels expressed in oocytes from the frog Xenopus laevis do not display the activation kinetic changes that we observed in spHCN and HCN1. However, HCN2 and HCN4 channels display changes in their tail currents, suggesting that these channels also undergo mode shifts and that the conformational changes underlying the mode shifts are due to conserved aspects of HCN channels. With computer modelling, we show that in channels with relatively slow opening kinetics and fast mode-shift transitions, such as HCN2 and HCN4 channels, the mode shift effects are not readily observable, except in the tail kinetics. Computer simulations of sino-atrial node action potentials suggest that the HCN2 channel, together with the HCN1 channel, are important regulators of the heart firing frequency and that the mode shift is an important property to prevent arrhythmic firing. We conclude that although all HCN channels appear to undergo mode shifts - and thus may serve to prevent arrhythmic firing - it is mainly observable in ionic currents from HCN channels with faster kinetics.
引用
收藏
页码:417 / 431
页数:15
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