Journal Article

Structural mechanisms of phospholipid activation of the human TPC2 channel

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

2019

Overview

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.

• Publisher: eLife Science Publications, Ltd,eLife Sciences Publications Ltd,eLife Sciences Publications, Ltd
• Subject: Biophysics / Calcium Channels - chemistry / Channel gating / Conformation / cryo-EM / Cryoelectron Microscopy / Data processing / Endosomes - chemistry / HEK293 Cells / Humans / Ion Channel Gating / Ion channels / Ions / Ligands / Lipids / lysosome / Lysosomes - chemistry / Membrane potential / Phosphatidylinositol / phosphoinositide / Phospholipids / Phospholipids - chemistry / Physiological aspects / Physiology / Protein Binding / Protein Structure, Secondary / Structural Biology and Molecular Biophysics / two-pore channels / Voltage