Effects of alternative N termini on ANO2 channel properties. (A–D) Inside-out excised patch-clamp traces of ANO2 isoforms expressed individually in HEK293T cells. Dose–response traces were recorded ∼20 min after patch excision when the rundown phase was over. Patches were exposed to various concentrations of Ca2+ for 10 s as indicated in the figures. The current traces are color-coded to match their respective stimulus concentrations. (A and B) Typical currents from a patch expressing Isoform A at −40- and +40-mV holding potentials. (C and D) Currents from the expression of Isoform B. (E and F) Hill fits of the maximal currents from Isoform A (11 patches) and Isoform B (7 patches) at negative and positive holding potentials, respectively. (G) Inactivation properties of currents from Isoforms A and B are quantified using the ratio of current amplitudes at 10 s (I10s) after Ca2+ exposure to the peak I value (Imax). ns, no significant difference in inactivation between the isoforms at positive and negative holding potentials across all concentrations of Ca2+ (two-way ANOVA). Data are means of I10s/Imax values (±SEM) from 7–11 patches for the four Ca2+concentrations (0.75, 2.4, 11, and 67 µM Ca2+). (H) I-V relationship for the two isoforms in response to saturating Ca2+ (67 µM).
