Influence of point mutations on proton sensitivity.

<p>(A) Kinetic response in the Ca²⁺ flux assay. Although 12 cells were evaluated in the same experiment, the results are divided into two graphs for clarity. 50 μL of D-PBS (pH 5.5) solution was added to 100μL of cells in D-PBS (pH 7.4) solution at the 20-s time point. Data are expressed as the mean from n = 3 measurements. (B) Activation of wild-type and mutant TRPV1 channels by capsaicin and proton. Maximum response in the period after stimulation was used as the representative value. W549A did not respond to either 1 μM capsaicin (grey) or proton addition (pH5.5, black). Y511A showed diminished ligand sensitivity, but maintained proton sensitivity. The F587A, F591A and L670A mutations markedly decreased proton sensitivity. Data are expressed as the mean ± SEM from n = 3 measurements.