Structural Basis of TRPV3 Activation and Inactivation

Abstract

The TRPV3 ion channel is critically involved in skin physiology and pathophysiology. Here we present cryo-EM structures of TRPV3 in lipid nanodiscs in distinct functional states representing the gating cycle. The ligand-free, closed conformation reveals a dual gating mechanism involving both the extracellular selectivity-filter gate and the intracellular helix bundle-crossing gate, and lipids are identified throughout the channel assembly. Both gates expand upon channel activation, accompanied by substantial structural rearrangements in the cytoplasmic domains. Sustained application of an agonist inactivates TRPV3 and results in a distinct non-conducting conformation, which is dramatically different from the apo, closed state. The pore-lining helix S6 maintains a π-helical segment upon activation but becomes entirely α-helical during inactivation. These results are in sharp contrast to recently reported TRPV3 structures determined in detergent micelles and in amphiphilic polymers that are devoid of lipids. Taken together, multiple distinct TRPV3 structures in a lipid membrane environment provide unique insights into physiological activation and inactivation.