Conformational ensemble of the human TRPV3 ion channel

Abstract

Transient receptor potential vanilloid channel 3 (TRPV3), a member of the thermosensitive TRP (thermoTRPV) channels, is activated by warm temperatures and serves as a key regulator of normal skin physiology through the release of pro-inflammatory messengers. Mutations in trpv3 have been identified as the cause of the congenital skin disorder, Olmsted syndrome. Unlike other members of the thermoTRPV channel family, TRPV3 sensitizes upon repeated stimulation, yet a lack of structural information about the channel precludes a molecular-level understanding of TRPV3 sensitization and gating. Here, we present the cryo-electron microscopy structures of apo and sensitized human TRPV3, as well as several structures of TRPV3 in the presence of the common thermoTRPV agonist 2-aminoethoxydiphenyl borate (2-APB). Our results show α-to-π-helix transitions in the S6 during sensitization, and suggest a critical role for the S4-S5 linker π-helix during ligand-dependent gating.

Molecular mechanism of TRPV2 channel modulation by cannabidiol

“…Many previous TRPV cryo-EM maps have shown strong lipid densities in hydrophobic pockets in the TMD [15][16][17]21,22 . The "vanilloid" pocket of TRPV1 is occupied by phosphatidylinositol (PI) in the apo structure in nanodiscs 15 (Figure 5A), and TRPV5 16 and TRPV6 17 both report obvious densities for annular lipids in this pocket in proteins prepared in both detergents and nanodiscs.…”

“…The highly hydrophobic nature of CBD would have caused it to accumulate in the nanodiscs, effectively increasing its local concentration even further in the CBD-bound TRPV2 in nanodiscs sample. A recent paper from the Lee group 22 reported a similar situation for their structures of TRPV3 in the presence of 2-APB: although they were able to observe structural changes to the channel upon exposure to the activator, they were not able to identify density for the 2-APB 22 .…”

“…The density for CBD in this binding pocket in the CBD-bound TRPV2 in nanodiscs structure is prominent and clearly present in both half maps (Supplementary Figure 11). As of the time of writing this manuscript, no other TRPV channel structures [15][16][17][18][19][20][21][22][23] were reported to have lipid density in this pocket, so in combination with the good fit of the drug to the density, we are confident in assigning it to CBD. With the identification of the CBD binding pocket in the nanodisc structure, we re-examined the map of CBD-bound TRPV2 in detergent at the same pocket (Supplementary Figure 11).…”

“…This pocket has also been shown to be a drug binding site in some TRPV channels and different occupants of this pocket can transmit conformational changes into the pore which affect gating 15,16 . This "vanilloid" pocket does not have very strong lipid density in currently available structures of TRPV2 [18][19][20] , TRPV3 21,22 and TRPV4 23 channels, while annular or modulating lipids have strong density in this pocket in TRPV1 15 , TRPV5 16 and TRPV6 17 channels. One lipid of interest for this study is phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), which is a known modulator of all TRPV channels 14 , but it is uncertain whether the mechanisms of modulation are conserved among these closely related channels 14 .…”

“…Instead, Tyr525 forms a hydrogen bond with the backbone amide of Met640, as recently seen in the apo TRPV3 structure from the Lee group between the homologous residues Tyr575 and Met672 (PBD 6MHO) ( Supplementary Figure 12). As these bonds are broken in their 2-APB sensitized TRPV3 structure featuring a π-helix in S6 (PDB 6MHS), the Lee group 22 suggests that this interaction stabilizes the α-helix of S6 preventing it from forming a π-helix, which is implicated in channel opening 17,21,22 (Supplementary Figure 12).…”