The Met268Pro mutation of mouse TRPA1 changes the effect of caffeine from activation to suppression.

Abstract

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 those differences were 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 responsible for the species-specific difference 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.  By 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.  As the region including Met268 is different from other reported ligand binding sites and from the EF-hand motif, these results suggest the caffeine response is mediated by a unique mechanism and confirms the importance of the distal N-terminal region for regulation of TRPA1 channel activity.

Published Paper

The Met268Pro mutation of mouse TRPA1 changes the effect of caffeine from activation to suppression
Katsuhiro Nagatomo, Hiroshi Ishii, Tomomi Yamamoto, Koichi Nakajo and Yoshihiro Kubo
Biophysical Journal, 99: 3609-3618 (2010)

Figure 1

Design and characterization of chimeras between mouse TRPA1 and human TRPA1

(A) Comparison of amino acid sequence of mouse TRPA1 and human TRPA1 in the 231-287 region. (B) Analyses of caffeine response of various point mutants.  A value less than 1 indicates suppression.