Single Residues in the Outer Pore of TRPV1 and TRPV3 Have Temperature-Dependent Conformations

Abstract

Thermosensation is mediated by ion channels that are highly temperature-sensitive. Several members of the family of transient receptor potential (TRP) ion channels are activated by cold or hot temperatures and have been shown to function as temperature sensors in vivo. The molecular mechanism of temperature-sensitivity of these ion channels is not understood. A number of domains or even single amino acids that regulate temperature-sensitivity have been identified in several TRP channels. However, it is unclear what precise conformational changes occur upon temperature activation. Here, we used the cysteine accessibility method to probe temperature-dependent conformations of single amino acids in TRP channels. We screened over 50 amino acids in the predicted outer pore domains of the heat-activated ion channels TRPV1 and TRPV3. In both ion channels we found residues that have temperature-dependent accessibilities to the extracellular solvent. The identified residues are located within the second predicted extracellular pore loop. These residues are identical or proximal to residues that were shown to be specifically required for temperature-activation, but not chemical activation. Our data precisely locate conformational changes upon temperature-activation within the outer pore domain. Collectively, this suggests that these specific residues and the second predicted pore loop in general are crucial for the temperature-activation mechanism of these heat-activated thermoTRPs.

Role of the Outer Pore Domain in Transient Receptor Potential Vanilloid 1 Dynamic Permeability to Large Cations

“…As discussed above, although a structure of TRPV1 occupied by RTX alone has not yet been reported, there were substantial disparities in conformational changes induced by capsaicin versus the RTX/DkTx combination, including differential effects on the selectivity filter and opposing rotations of the Ile-679 residue in the lower pore gate (4). A similar theme recently emerged from the finding that heat and capsaicin exert different conformational effects at the rat TRPV1-Y653 residue (21,47). Moreover, capsaicin and RTX were previously shown to differentially alter TRPV1 calcium permeability (10) and to…”

Elephantid Genomes Reveal the Molecular Bases of Woolly Mammoth Adaptations to the Arctic

“…The mammothspecific TRPV4 V658I substitution occurred at the first site in the S6 helix ( Figure 5A), which is part of the outer pore region important for activation of the channel in response to heat (Figure 5B). Indeed, we found that site 658 is located within a cluster of sites that mediate heat activation in the related TRPV3 channel (Grandl et al, 2008), and it is homologous to a site in TRPV3 that adopts temperature-dependent conformations (Figures 5C and 5D; Kim et al, 2013). Site 658 also mediates the interaction between TRPV channels and the agonist vanillotoxin DkTx ( Figure 5E; Cao et al, 2013;Liao et al, 2013).…”

In the Heat of the Night: Thermo-TRPV Channels in the Salmonid Pineal Photoreceptors and Modulation of Melatonin Secretion

“…A further support to the idea that trout TRPV1 is a temperature receptor comes from the analysis of the rat and trout sequences. Both possess conserved aa sequences in the pore and C-terminal regions of the channel (33,45,48); Supplemental Figure 1). These include a tyrosine residue Y637, located in the pore region, which corresponding residue Y652 in rat is specifically required for temperature activation; this tyrosine is located close to other residues required for temperature and chemical activation (48).…”