Figure 7

Involvement of the N-terminal cysteine residues of mouse TRPA1 in its activation by polysulfide. (A) The Na₂S₃ (10 μM)-induced [Ca²⁺]_i increase was inhibited by dithiothreitol (DTT) (a) 2 min before and during 4 min application of Na₂S₃, (b) after 4 min in HEK 293 cells expressing mouse TRPA1 (mTRPA1-HEK). The upper panels show [Ca²⁺]_i responses to Na₂S₃ without DTT, and the lower ones those in the presence of DTT. (B) Summarized effects of DTT. (a) Open and filled columns show the increases of [Ca²⁺]_i responses to Na₂S₃ in the absence (Control) and presence of DTT, respectively. (b) Times required for half-decline of [Ca²⁺]_i responses to Na₂S₃ (T_1/2) in the absence (Control) and presence of DTT. T_1/2 was calculated by subtracting the value of the time when the Na₂S₃-induced [Ca²⁺]_i increase was reduced by half from that when Na₂S₃-induced [Ca²⁺]_i increase peaked. Columns with vertical lines show mean ± SEM (a; n = 23–32, b; n = 55–63, from three different transfections). **P < 0.01. (C) The [Ca²⁺]_i increments induced by Na₂S₃ (10 μM and 30 μM) and 2APB (100 μM and 300 μM) in mTRPA1-HEK (left columns) and HEK293 cells expressing mouse TRPA1 mutant (mTRPA1-2C, right columns). Columns with vertical lines show mean ± SEM (wild-type mTRPA1; n = 55–72, mTRPA1-2C; n = 46–63, from three separate transfections). **P, < 0.01 vs. ∆[Ca²⁺]_i in mTRPA1-HEK.