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The structural mechanism of KCNH-channel regulation by the eag domain

Nature volume 501, pages 444–448 (2013)Cite this article

Abstract

The KCNH voltage-dependent potassium channels (ether-à-go-go, EAG; EAG-related gene, ERG; EAG-like channels, ELK) are important regulators of cellular excitability1,2,3 and have key roles in diseases such as cardiac long QT syndrome type 2 (LQT2)4, epilepsy5, schizophrenia6 and cancer7. The intracellular domains of KCNH channels are structurally distinct from other voltage-gated channels. The amino-terminal region contains an eag domain, which is composed of a Per-Arnt-Sim (PAS) domain and a PAS-cap domain8, whereas the carboxy-terminal region contains a cyclic nucleotide-binding homology domain (CNBHD), which is connected to the pore through a C-linker domain. Many disease-causing mutations localize to these specialized intracellular domains, which underlie the unique gating and regulation of KCNH channels9. It has been suggested that the eag domain may regulate the channel by interacting with either the S4–S5 linker or the CNBHD8,10. Here we present a 2 Å resolution crystal structure of the eag domain–CNBHD complex of the mouse EAG1 (also known as KCNH1) channel. It displays extensive interactions between the eag domain and the CNBHD, indicating that the regulatory mechanism of the eag domain primarily involves the CNBHD. Notably, the structure reveals that a number of LQT2 mutations at homologous positions in human ERG, in addition to cancer-associated mutations in EAG channels, localize to the eag domain–CNBHD interface. Furthermore, mutations at the interface produced marked effects on channel gating, demonstrating the important physiological role of the eag domain–CNBHD interaction. Our structure of the eag domain–CNBHD complex of mouse EAG1 provides unique insights into the physiological and pathophysiological mechanisms of KCNH channels.

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Figure 1: Structure of the eag domain–CNBHD complex of mEAG1.
Figure 2: The various interfaces between the eag domain and CNBHD, and different complex types in the asymmetric unit.
Figure 3: A salt bridge between the eag domain and the CNBHD.
Figure 4: PAS-cap interaction with the CNBHD, and predicted tetramer of the eag domain–CNBHD complex.

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Protein Data Bank

Data deposits

Atomic coordinates and structure factors for the reported crystal structures have been deposited with the Protein Data Bank under accession code 4LLO.

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Acknowledgements

We thank S. Cunnington and S. Camp for technical assistance. We thank the beamline staff at the Advanced Light Source (ALS). We also thank G. Flynn, J. Bankston, M. Puljung and S. Gordon for helpful discussions and critical reading of the manuscript. This work was supported by the National Institutes of Health (NIH) grant R01 EY010329 (W.N.Z.), The International Human Frontier Science Program Organization (HFSPO) long-term postdoctoral fellowship LT-001025/2011 (Y.H.), and NIH grant F32 HL095241 (A.E.C.). The Berkeley Center for Structural Biology is supported in part by the National Institutes of Health, National Institute of General Medical Sciences, and the Howard Hughes Medical Institute. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the US Department of Energy under Contract No. DE-AC02-05CH11231.

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Authors and Affiliations

  1. Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, 98195, Washington, USA

    Yoni Haitin, Anne E. Carlson & William N. Zagotta

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  1. Yoni Haitin
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  2. Anne E. Carlson
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Contributions

Y.H. and W.N.Z. conceived the experiments. Y.H. performed the biochemical and crystallographic experiments and data analysis. A.E.C. conceived the PAS-cap-related experiments and performed all the electrophysiology experiments and data analysis. Y.H. and W.N.Z. wrote the manuscript.

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Correspondence to William N. Zagotta.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Figures 1-7 and Supplementary Tables 1-4. (PDF 3384 kb)

Morph of the two confomers of the mEAG1 intracellular complex .

A 'type I' eag domain-CNBHD complex (chains A and B) was morphed with a 'type II' complex (chains C and D). Color-coding as in Fig. 1b. Distance measurement is shown between residues D47 of the eag domain and E578 of the CNBHD. Angle measurement was performed between S94 (eag domain), V706 (CNBHD) and H570 (CNBHD). (MOV 3451 kb)

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Haitin, Y., Carlson, A. & Zagotta, W. The structural mechanism of KCNH-channel regulation by the eag domain. Nature 501, 444–448 (2013). https://doi.org/10.1038/nature12487

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