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Voltage-sensing mechanism is conserved among ion channels gated by opposite voltages


Hyperpolarization-activated cyclic-nucleotide-gated (HCN) ion channels are found in rhythmically firing cells in the brain and in the heart1, where the cation current through HCN channels (called Ih or If) causes these cells to fire repeatedly2. These channels are also found in non-pacing cells, where they control resting membrane properties, modulate synaptic transmission, mediate long-term potentiation, and limit extreme hyperpolarizations3,4,5,6,7. HCN channels share sequence motifs with depolarization-activated potassium (Kv) channels, such as the fourth transmembrane segment S48,9. S4 is the main voltage sensor of Kv channels, in which transmembrane movement of S4 charges triggers the opening of the activation gate10,11,12,13,14,15,16,17. Here, using cysteine accessibility methods10,11,12, we investigate whether S4 moves in an HCN channel. We show that S4 movement is conserved between Kv and HCN channels, which indicates that S4 is also the voltage sensor in HCN channels. Our results suggest that a conserved voltage-sensing mechanism operates in the oppositely voltage-gated Kv and HCN channels, but that there are different coupling mechanisms between the voltage sensor and activation gate in the two different channels.

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Figure 1: Basic features of spHCN channels.
Figure 2: State-dependent accessibility of S338C.
Figure 3: MTSET modification locks activation gate and S4.
Figure 4: S4 movement is conserved between Shaker and spHCN channels.


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We thank U. B. Kaupp for providing the spHCN clone; A. Broomand, H. Sjölander and S. Pandey for help with some of the recordings; P. Århem for comments on the manuscript; and S. Oster for editing the manuscript. This study was supported by the Swedish Research Council, Åke Wibergs Stiftelse, Magn. Bergvalls Stiftelse, The Swedish Society of Medicine, and Jeanssons Stiftelser and start-up funds from Oregon Health & Science University. F.E. has a junior research position at the Swedish Research Council. R.M. is supported by a pre-doctoral grant from the National Network in Neuroscience in Sweden.

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Correspondence to H. Peter Larsson.

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Männikkö, R., Elinder, F. & Larsson, H. Voltage-sensing mechanism is conserved among ion channels gated by opposite voltages. Nature 419, 837–841 (2002).

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