title: The Pore Loop Domain of TRPV1 Is Required for Its Activation by the Volatile Anesthetics Chloroform and Isoflurane.
abstract: The environmental irritant chloroform, a naturally occurring small volatile organohalogen, briefly became the world's most popular volatile general anesthetic (VGA) before being abandoned because of its low therapeutic index. When chloroform comes in contact with skin or is ingested, it causes a painful burning sensation. The molecular basis for the pain associated with chloroform remains unknown. In this study, we assessed the role of transient receptor potential (TRP) channel family members in mediating chloroform activation and the molecular determinants of VGA activation of TRPV1. We identified the subpopulation of dorsal root ganglion (DRG) neurons that are activated by chloroform. Additionally, we transiently expressed wild-type or specifically mutated TRP channels in human embryonic kidney cells and used calcium imaging or whole-cell patch-clamp electrophysiology to assess the effects of chloroform or the VGA isoflurane on TRP channel activation. The results revealed that chloroform activates DRG neurons via TRPV1 activation. Furthermore, chloroform activates TRPV1, and it also activates TRPM8 and functions as a potent inhibitor of the noxious chemical receptor TRPA1. The results also indicate that residues in the outer pore region of TRPV1 previously thought to be required for either proton or heat activation of the channel are also required for activation by chloroform and isoflurane. In addition to identifying the molecular basis of DRG neuron activation by chloroform and the opposing effects chloroform has on different TRP channel family members, the findings of this study provide novel insights into the structural basis for the activation of TRPV1 by VGAs.
authors.affiliation: Department of Biological Structure, University of Washington, Seattle, Washington (C.K., A.D.); and The Center for the Study of Itch, Washington University Pain Center, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (J.L., S.Y., H.H.).
authors.forename: Corinna
authors.initials: C
authors.lastname: Kimball
authors.affiliation: Department of Biological Structure, University of Washington, Seattle, Washington (C.K., A.D.); and The Center for the Study of Itch, Washington University Pain Center, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (J.L., S.Y., H.H.).
authors.forename: Jialie
authors.initials: J
authors.lastname: Luo
authors.affiliation: Department of Biological Structure, University of Washington, Seattle, Washington (C.K., A.D.); and The Center for the Study of Itch, Washington University Pain Center, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (J.L., S.Y., H.H.).
authors.forename: Shijin
authors.initials: S
authors.lastname: Yin
authors.affiliation: Department of Biological Structure, University of Washington, Seattle, Washington (C.K., A.D.); and The Center for the Study of Itch, Washington University Pain Center, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (J.L., S.Y., H.H.).
authors.forename: Hongzhen
authors.initials: H
authors.lastname: Hu
authors.affiliation: Department of Biological Structure, University of Washington, Seattle, Washington (C.K., A.D.); and The Center for the Study of Itch, Washington University Pain Center, Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri (J.L., S.Y., H.H.) dhaka@uw.edu.
authors.forename: Ajay
authors.initials: A
authors.lastname: Dhaka
mesh_terms: D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D015220:Calcium Channels / Q000378:metabolism; D002211:Capsaicin / Q000494:pharmacology; D002478:Cells, Cultured; D002725:Chloroform / Q000494:pharmacology*; D005727:Ganglia, Spinal / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D057809:HEK293 Cells; D006358:Hot Temperature; D006801:Humans; D007530:Isoflurane / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D000074025:TRPA1 Cation Channel; D050053:TRPM Cation Channels / Q000378:metabolism; D050916:TRPV Cation Channels / Q000737:chemistry* / Q000378:metabolism*; D050051:Transient Receptor Potential Channels / Q000378:metabolism
chemical_list: D018685:Anesthetics, Inhalation; D015220:Calcium Channels; D009419:Nerve Tissue Proteins; D000074025:TRPA1 Cation Channel; C473350:TRPA1 protein, human; D050053:TRPM Cation Channels; C425966:TRPM8 protein, human; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D050051:Transient Receptor Potential Channels; D002725:Chloroform; D007530:Isoflurane; D002211:Capsaicin