The Met268Pro mutation of mouse TRPA1 changes the effect of caffeine from activation to suppression.
The transient receptor potential A1 channel (TRPA1) is activated by various compounds, including isothiocyanates, menthol, and cinnamaldehyde. The sensitivities of the rodent and human isoforms of TRPA1 to menthol and the cysteine-attacking compound CMP1 differ, and the molecular determinants for these differences have been identified in the 5th transmembrane region (TM5) for menthol and TM6 for CMP1. We recently reported that caffeine activates mouse TRPA1 (mTRPA1) but suppresses human TRPA1 (hTRPA1). Here we aimed to identify the molecular determinant that is responsible for species-specific differences in the response to caffeine by analyzing the functional properties of various chimeras expressed in Xenopus oocytes. We initially found that the region between amino acids 231 and 287, in the distal N-terminal cytoplasmic region of mTRPA1, is critical. In a mutagenesis study of this region, we subsequently observed that introduction of a Met268Pro point mutation into mTRPA1 changed the effect of caffeine from activation to suppression. Because the region including Met-268 is different from other reported ligand-binding sites and from the EF-hand motif, these results suggest that the caffeine response is mediated by a unique mechanism, and confirm the importance of the distal N-terminal region for regulation of TRPA1 channel activity.
Division of Biophysics and Neurobiology, National Institute for Physiological Sciences, Graduate University for Advanced Studies, Aichi, Japan.
Katsuhiro
K
Nagatomo
Hiroshi
H
Ishii
Tomomi
T
Yamamoto
Koichi
K
Nakajo
Yoshihiro
Y
Kubo
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D051379:Mice; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D017354:Point Mutation / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D000074025:TRPA1 Cation Channel; D050051:Transient Receptor Potential Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D014981:Xenopus
D015220:Calcium Channels; D050505:Mutant Proteins; D009419:Nerve Tissue Proteins; D011994:Recombinant Proteins; D000074025:TRPA1 Cation Channel; C473350:TRPA1 protein, human; D050051:Transient Receptor Potential Channels; C475685:Trpa1 protein, mouse; D002110:Caffeine