Cold sensitivity of recombinant TRPA1 channels.
TRPM8 and TRPA1, members of the transient receptor potential (TRP) channel family, are candidates for cooling-activated receptors. It is accepted that TRPM8 responds to moderate cooling, although it is controversial whether TRPA1 responds to deep cooling. Here, using Ca(2+) imaging and/or patch-clamp recordings, we examined the thermal sensitivity of primary cultured dorsal root ganglion (DRG) neurons and mouse TRPA1-expressing human embryonic kidney (HEK) 293 cells. In a subset of cultured mouse DRG neurons, deep cooling (5-18 degrees C) and allyl isothiocyanate (AITC, agonist of TRPA1) induced increases in intracellular Ca(2+) level. Most AITC-sensitive (TRPA1-expressing) neurons responded to deep cooling. In TRPA1-expressing HEK293 cells, deep cooling and AITC-induced Ca(2+) responses and whole-cell currents. In inside-out patches excised from TRPA1-expressing HEK293 cells, deep cooling, and AITC activated the same channels, which were inhibited by camphor (antagonist for TRPA1). When temperature was decreased below 18 degrees C, unit conductance of the channel decreased but open probability of it increased. Deep cooling-induced increase of the open probability of TRPA1 may underlie the increase in whole-cell currents induced by deep cooling. It is concluded that TRPA1 is a deep cooling-activated channel, which supports the previous findings that TRPA1 responds to deep cooling.
Sawada
Yosuke
Y
Division of Biological Information, Department of Intelligence Science and Technology, Graduate School of Informatics, Kyoto University, Kyoto, Japan.
Hosokawa
Hiroshi
H
Hori
Aiko
A
Matsumura
Kiyoshi
K
Kobayashi
Shigeo
S
D000818:Animals; D000891:Anti-Infective Agents, Local / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002164:Camphor / Q000494:pharmacology; D002478:Cells, Cultured; D003080:Cold Temperature; D005727:Ganglia, Spinal / Q000166:cytology; D006801:Humans; D017879:Isothiocyanates / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism*; D018408:Patch-Clamp Techniques / Q000379:methods; D011994:Recombinant Proteins / Q000378:metabolism; D000074025:TRPA1 Cation Channel; D014162:Transfection; D050051:Transient Receptor Potential Channels / Q000235:genetics / Q000502:physiology*
D000891:Anti-Infective Agents, Local; D017879:Isothiocyanates; D011994:Recombinant Proteins; D000074025:TRPA1 Cation Channel; D050051:Transient Receptor Potential Channels; C475685:Trpa1 protein, mouse; C041942:2,3,4-tri-O-acetylarabinopyranosyl isothiocyanate; D002164:Camphor; D002118:Calcium