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The isoforms generated by alternative translation initiation adopt similar conformation in the selectivity filter in TREK-2

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Abstract

TREK-2 (TWIK-related K+ channel-2), a member of two-pore domain potassium (K2P) channel family, tunes cellular excitability via conducting leak or background currents. In TREK-2, the isoforms generated by alternative translation initiation (ATI) mechanism exhibit large divergence in unitary conductance, but similar in selectivity to K+. Up to now, the structural basis for this similarity in ion selectivity is unknown. Here, we report that externally applied Ba2+ inhibits the currents of TREK-2 in a concentration- and time-dependent manner. The blocking effect is blunted by elevated extracellular K+ or mutation of S4 K+ binding site, which suggests that the inhibitory mechanism of Ba2+ is due to its competitive docking properties within the selectivity filter (SF). Next, we demonstrate that all the ATI isoforms exhibit analogous behaviors upon the application of Ba2+ and alteration of extracellular pH (pHo), which acts on the outer position of the SF. These results strongly support the notion that all the ATI isoforms of TREK-2 possess resembled SF conformation in S4 site and the position defined by pHo, which implicates that neither the role of N-terminus (Nt) nor the unitary conductance is associated with SF conformation. Our findings might help to understand the detail gating mechanism of TREK-2 and K2P channels.

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Abbreviations

TREK:

TWIK-related K+ channel

K2P:

Two-pore domain potassium channel

SF:

Selectivity filter

ATI:

Alternative translation initiation

Nt:

N-terminus

pHo :

Extracellular pH

KcsA:

Potassium channels from S. lividans

Kv channel:

Voltage-gated K+ channel

WT:

Wild type

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Acknowledgments

We thank Professor Gail Robertson (University of Wisconsin-Madison Medical School, Madison, WI) for the pGH-19 plasmid.

Grants

This work was supported by grants from National Major Scientific and Technological Special Project for “Significant New Drug Development” (2014ZX09507-003), National Integrated Drug Discovery Technology Platform Foundation of China (2012ZX09301003-001), and the National Science Foundation of China Grants (31200797).

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Authors and Affiliations

  1. State Key Laboratory of Toxicology and Medical Countermeasures, Department of Biochemical Pharmacology, Beijing Institute of Pharmacology and Toxicology, 27 Taiping Road, Beijing, 100850, China

    Ren-Gong Zhuo, Peng Peng, Xiao-Yan Liu, Shu-Zhuo Zhang, Jian-Quan Zheng, Xiao-Li Wei & Xiao-Yun Ma

  2. Chinese PLA General Hospital, 28 Fuxing Street, Beijing, 100853, China

    Peng Peng

  3. Department of Neuropharmacology, School of Pharmaceutical Sciences, Southern Medical University, No.1838, North Guangzhou Avenue, Guangzhou, 510515, China

    Jiang-Ping Xu

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  1. Ren-Gong Zhuo
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Correspondence to Xiao-Li Wei or Xiao-Yun Ma.

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Zhuo, RG., Peng, P., Liu, XY. et al. The isoforms generated by alternative translation initiation adopt similar conformation in the selectivity filter in TREK-2. J Physiol Biochem 71, 601–610 (2015). https://doi.org/10.1007/s13105-015-0422-z

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  • DOI: https://doi.org/10.1007/s13105-015-0422-z

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