Structural mechanisms of phospholipid activation of the human TPC2 channel

• DOI: 10.7554/elife.45222
• Publication Date: 2019-03-12T13:00:28Z
• Authors: Ji She; Weizhong Zeng; Jiangtao Guo; Qingfeng Chen; Xiao-chen Bai; Youxing Jiang
• Keywords: QH301-705.5; Science; Structural Biology and Molecular Biophysics; Endosomes; Ligands; Protein Structure, Secondary; 03 medical and health sciences; Humans; Biology (General); Phospholipids; Ions; 0303 health sciences; two-pore channels; Q; Cryoelectron Microscopy; R; phosphoinositide; HEK293 Cells; lysosome; cryo-EM; Medicine; Calcium Channels; Lysosomes; Ion Channel Gating; Protein Binding

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.