eLife (Mar 2019)

Structural mechanisms of phospholipid activation of the human TPC2 channel

  • Ji She,
  • Weizhong Zeng,
  • Jiangtao Guo,
  • Qingfeng Chen,
  • Xiao-chen Bai,
  • Youxing Jiang

DOI
https://doi.org/10.7554/eLife.45222
Journal volume & issue
Vol. 8

Abstract

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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.

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