Letter | Published:

Structural insights into the voltage and phospholipid activation of the mammalian TPC1 channel

Nature volume 556, pages 130134 (05 April 2018) | Download Citation

Abstract

The organellar two-pore channel (TPC) functions as a homodimer, in which each subunit contains two homologous Shaker-like six-transmembrane (6-TM)-domain repeats1. TPCs belong to the voltage-gated ion channel superfamily2 and are ubiquitously expressed in animals and plants3,4. Mammalian TPC1 and TPC2 are localized at the endolysosomal membrane, and have critical roles in regulating the physiological functions of these acidic organelles5,6,7. Here we present electron cryo-microscopy structures of mouse TPC1 (MmTPC1)—a voltage-dependent, phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2)-activated Na+-selective channel—in both the apo closed state and ligand-bound open state. Combined with functional analysis, these structures provide comprehensive structural insights into the selectivity and gating mechanisms of mammalian TPC channels. The channel has a coin-slot-shaped ion pathway in the filter that defines the selectivity of mammalian TPCs. Only the voltage-sensing domain from the second 6-TM domain confers voltage dependence on MmTPC1. Endolysosome-specific PtdIns(3,5)P2 binds to the first 6-TM domain and activates the channel under conditions of depolarizing membrane potential. Structural comparisons between the apo and PtdIns(3,5)P2-bound structures show the interplay between voltage and ligand in channel activation. These MmTPC1 structures reveal lipid binding and regulation in a 6-TM voltage-gated channel, which is of interest in light of the emerging recognition of the importance of phosphoinositide regulation of ion channels.

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Acknowledgements

We thank N. Nguyen for manuscript preparation and M. X. Zhu for providing clones of animal TPC genes. Single particle cryo-EM data were collected at the University of Texas Southwestern Medical Center (UTSW) Cryo-Electron Microscopy Facility that is funded by the CPRIT Core Facility Support Award RP170644. We thank D. Nicastro and Z. Chen for facility access and data acquisition. Negatively stained sample screening was performed at UTSW Electron Microscopy core. This work was supported in part by the Howard Hughes Medical Institute (Y.J.) and by grants from the National Institute of Health (GM079179 to Y.J.) and the Welch Foundation (Grant I-1578 to Y.J.). X.B. is supported by the Cancer Prevention and Research Initiative of Texas and Virginia Murchison Linthicum Scholar in Medical Research fund.

Author information

Author notes

    • Ji She
    • , Jiangtao Guo
    •  & Qingfeng Chen

    These authors contributed equally to this work.

Affiliations

  1. Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA

    • Ji She
    • , Qingfeng Chen
    • , Weizhong Zeng
    •  & Youxing Jiang
  2. Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8816, USA

    • Ji She
    • , Qingfeng Chen
    • , Weizhong Zeng
    • , Youxing Jiang
    •  & Xiao-chen Bai
  3. Department of Biophysics, Zhejiang University School of Medicine, Hangzhou 310058, China

    • Jiangtao Guo
  4. Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA

    • Qingfeng Chen
    • , Weizhong Zeng
    •  & Youxing Jiang
  5. Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9039, USA

    • Xiao-chen Bai

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Contributions

J.S., J.G. and Q.C. prepared the samples; J.S., J.G., Q.C. and X.B. performed data acquisition, image processing and structure determination; W.Z. performed electrophysiology; Y.J. supervised the project and revised the manuscript; all authors participated in research design, data analysis and manuscript preparation.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Youxing Jiang or Xiao-chen Bai.

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https://doi.org/10.1038/nature26139

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