Structural mechanisms of phospholipid activation of the human TPC2 channel
- University of Texas Southwestern Medical Center, United States
- Zhejiang University School of Medicine, China
Abstract
Mammalian two-pore channels (TPCs) regulate the physiological functions of the endolysosome. Here we present cryo-EM structures of human TPC2 (HsTPC2), a phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2)-activated, Na+ selective channel, in the ligand-bound and apo states. The apo structure captures the closed conformation, while the ligand-bound form features the channel in both open and closed conformations. Combined with functional analysis, these structures provide insights into the mechanism of PI(3,5)P2-regulated gating of TPC2, which is distinct from that of TPC1. Specifically, the endolysosome-specific PI(3,5)P2 binds at the first 6-TM and activates the channel - independently of the membrane potential - by inducing a structural change at the pore-lining inner helix (IS6), which forms a continuous helix in the open state but breaks into two segments at Gly317 in the closed state. Additionally, structural comparison to the voltage-dependent TPC1 structure allowed us to identify Ile551 as being responsible for the loss of voltage dependence in TPC2.
Data availability
The cryo-EM density maps of the human TPC2 have been deposited in the Electron Microscopy Data Bank under accession numbers EMD-0478 for the apo state, EMD-0479 for the PI(3,5)P2-bound closed state and EMD-0477 for the PI(3,5)P2-bound open state. Atomic coordinates have been deposited in the Protein Data Bank under accession numbers 6NQ1 for the apo state, 6NQ2 for the PI(3,5)P2-bound closed state and 6NQ0 for the PI(3,5)P2-bound open state.
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Cryo-EM density map of the human TPC2 (apo state)Electron Microscopy Data Bank, EMD-0478.
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Cryo-EM density map of the human TPC2 (PI(3,5)P2-bound closed state)Electron Microscopy Data Bank, EMD-0479.
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Cryo-EM density map of the human TPC2 (PI(3,5)P2-bound open state)Electron Microscopy Data Bank, EMD-0477.
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Atomic coordinates of the human TPC2 (apo state)Protein Data Bank, 6NQ1.
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Atomic coordinates of the human TPC2 (PI(3,5)P2-bound closed state)Protein Data Bank, 6NQ2.
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Atomic coordinates of the human TPC2 (PI(3,5)P2-bound open state)Protein Data Bank, 6NQ0.
Article and author information
Author details
Funding
Howard Hughes Medical Institute
- Youxing Jiang
National Institute of General Medical Sciences (GM079179)
- Youxing Jiang
Welch Foundation (I-1578)
- Youxing Jiang
Cancer Prevention and Research Initiative of Texas
- Xiaochen Bai
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, She et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Structural mechanisms of phospholipid activation of the human TPC2 channel
eLife 8:e45222.
https://doi.org/10.7554/eLife.45222
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