Resting state structure of the hyperdepolarization activated two-pore channel 3

• DOI: 10.1073/pnas.1915144117
• Publication Date: 2020-01-11T00:59:17Z
• Authors: Miles Sasha Dicki...; Alexander Myasnikov; Jacob Eriksen; Nicole Poweleit; Robert M. Stroud
• Keywords: Models, Molecular; 0301 basic medicine; 570; Biomedical and Clinical Sciences; Protein Conformation; 1.1 Normal biological development and functioning; Medical Physiology; Cryoelectron Microscopy; Sodium; Neurosciences; Molecular; Action Potentials; voltage sensors; Voltage-Gated Sodium Channels; Zebrafish Proteins; electrophysiology; cryoEM; 03 medical and health sciences; HEK293 Cells; Models; ion channel; Humans; structure; Ion Channel Gating

Voltage-gated ion channels endow membranes with excitability and the means to propagate action potentials that form the basis of all neuronal signaling. We determined the structure of a voltage-gated sodium channel, two-pore channel 3 (TPC3), which generates ultralong action potentials. TPC3 is distinguished by activation only at extreme membrane depolarization (V 50 ∼ +75 mV), in contrast to other TPCs and Na V channels that activate between −20 and 0 mV. We present electrophysiological evidence that TPC3 voltage activation depends only on voltage sensing domain 2 (VSD2) and that each of the three gating arginines in VSD2 reduces the activation threshold. The structure presents a chemical basis for sodium selectivity, and a constricted gate suggests a closed pore consistent with extreme voltage dependence. The structure, confirmed by our electrophysiology, illustrates the configuration of a bona fide resting state voltage sensor, observed without the need for any inhibitory ligand, and independent of any chemical or mutagenic alteration.