Symmetry transitions during gating of the TRPV2 ion channel in lipid membranes

Abstract

The Transient Receptor Potential Vanilloid 2 (TRPV2) channel is a member of the temperature-sensing thermoTRPV family. Recent advances in cryo-electronmicroscopy (cryo-EM) and X-ray crystallography have provided many important insights into the gating mechanisms of thermoTRPV channels. Interestingly, crystallographic studies of ligand-dependent TRPV2 gating have shown that the TRPV2 channel adopts two-fold symmetric arrangements during the gating cycle. However, it was unclear if crystal packing forces played a role in stabilizing the two-fold symmetric arrangement of the channel. Here, we employ cryo-EM to elucidate the structure of full-length rabbit TRPV2 in complex with the agonist resiniferatoxin (RTx) in nanodiscs and amphipol. We show that RTx induces two-fold symmetric conformations of TRPV2 in both environments. However, the two-fold symmetry is more pronounced in the native-like lipid environment of the nanodiscs. Our data offers insights into a gating pathway in TRPV2 involving symmetry transitions.

Visualizing structural transitions of ligand-dependent gating of the TRPM2 channel

“…Therefore, the flexible elements in the S4b and the S4–S5 linker lead to a two-fold symmetric configuration of the TMD. Notably, a similar two-fold symmetric TMD arrangement induced by a conformational change in the S4–S5 linker was recently observed in the TRPV2 channel 21,22 . Also, a ligand-dependent α-to-3 10 change in the secondary structure of S4b was observed in TRPM8 33 , which is in contrast to the 3 10 -to-α transition in TRPM2.…”

“…We consider the possibility that the amphipol polymers used for the reconstitution of TRPM2 DR in the presence of ADPR and Ca 2+ might tightly encircle the transmembrane regions and restrain transmission of structural rearrangements from the CD to the TMD, thereby preventing a two-fold- to four-fold-symmetric conformational rearrangement of the TMD. Recently, a similar hindrance to conformational changes in the TMD imposed by amphipol was discussed in the structural study of RTx-mediated activation of the TRPV2 channel 22 .…”

“…Interestingly, a comparison of our structures with the recently published four-fold symmetric TRPM2 closed and TRPM2 open structures reveals that protomers A and C of TRPM2 DR_Ca2+ resemble the closed conformation, while protomers B and D approximate the open conformation, indicating that the homo-tetramer can accommodate a hybrid of structural arrangements that are representative of the closed and the open states. This study effectively emphasizes the necessity of carefully examining the symmetry states of 3D reconstructions and applying symmetry in a conservative manner during cryo-EM data processing, a strategy that has also been employed in the published studies of the magnesium channel CorA, TRPV2, and TRPV3 channels for capturing intermediate states 22,23,34 and of the mitochondrial calcium uniporter (MCU) 35–38 . It is noteworthy that among the published TRPM2 structures to date, either the C4 symmetry was imposed to the ab-initio map reconstructions from the beginning of data processing 28 , or detailed descriptions of the stage for C4 symmetry imposition during data processing were lacking in the methods 20,27 .…”

“…In spite of this progress toward understanding ligand-dependent activation of TRPM2, it remains unclear whether these drastic quaternary structural rearrangements occur in a concerted, four-fold symmetric manner. We recently reported that the transient receptor potential vanilloid 2 (TRPV2) channel adopts two-fold symmetric conformations upon resiniferatoxin (RTx)-mediated activation 21,22 , and that two-fold symmetric states appear to be associated with ligand-dependent gating of the TRPV3 channel 23 . It is presently unclear if reduced symmetry is associated with gating in other TRP channel families.…”

Molecular mechanism of TRPV2 channel modulation by cannabidiol

“…Recently, the TRPV2 channel has been the subject of several cryo-EM studies that offered thought-provoking insights on TRPV2 channel gating (Huynh et al, 2016; Zubcevic et al, 2019a; Zubcevic et al, 2016; Dosey et al, 2019). Constructs used in these studies varied from the pore turret deletion mutant (Zubcevic et al, 2016) to the full-length engineered resiniferatoxin (RTx)-sensitive channel (Zubcevic et al, 2019a) and full-length wild-type channel (Huynh et al, 2016; Dosey et al, 2019).…”