title: Protons stabilize the closed conformation of gain-of-function mutants of the TRPV1 channel.
abstract: The vanilloid transient receptor potential channel TRPV1 is a molecular integrator of noxious stimuli, including capsaicin, heat and protons. Despite clear similarities between the overall architecture of TRPV1 and voltage-dependent potassium (Kv) channels, the extent of conservation in the molecular logic for gating is unknown. In Kv channels, a small contact surface between S1 and the pore-helix is required for channel functioning. To explore the function of S1 in TRPV1, we used tryptophan-scanning mutagenesis and characterized the responses to capsaicin and protons. Wild-type-like currents were generated in 9 out of 17 mutants; three mutants (M445W, A452W, R455W) were non-functional. The conservative mutation R455K in the extracellular extent of S1 slowed down capsaicin-induced activation and prevented normal channel closure. This mutant was neither activated nor potentiated by protons, on the contrary, protons promoted a rapid deactivation of its currents. Similar phenotypes were found in two other gain-of-function mutants and also in the pore-helix mutant T633A, known to uncouple proton activation. We propose that the S1 domain contains a functionally important region that may be specifically involved in TRPV1 channel gating, and thus be important for the energetic coupling between S1-S4 sensor activation and gate opening. Analogous to Kv channels, the S1-pore interface might serve to stabilize conformations associated with TRPV1 channel gating.
authors.affiliation: Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague 4, Czech Republic.
authors.forename: Stepana
authors.initials: S
authors.lastname: Boukalova
authors.forename: Jan
authors.initials: J
authors.lastname: Teisinger
authors.forename: Viktorie
authors.initials: V
authors.lastname: Vlachova
mesh_terms: D002478:Cells, Cultured; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D015640:Ion Channel Gating; D007668:Kidney / Q000166:cytology / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D018408:Patch-Clamp Techniques; D017433:Protein Structure, Secondary; D011522:Protons; D050916:TRPV Cation Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D011522:Protons; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human