Figure 2.

Data of Figure 1 were analyzed regarding rates of activation and inactivation. (A) Time course of normalized whole-cell current over 445 s, exemplarily depicted for [Ca²⁺]_i = 300 nM. Currents are given as means ± SEM. (B) Rate of activation was determined by fitting the Gompertz model to the development of current over time and calculating the maximum slope of the curve (slope_max). Rate of inactivation was determined by fitting the exponential decay model to the decline of current over time and employing the exponential decay constant (k). Determination exemplarily depicted for a single measurement at [Ca²⁺]i = 300 nM. Resulting rates of activation (C) and inactivation (D) for ADPR and 2dADPR. Data displayed log-normal distribution and were log-transformed to obtain normal distribution. They are presented on an anti-log scale. The bar denotes the mean. ns not significant, **p < 0.01, ****p < 0.0001 (multiple t test). (E) Ca²⁺ imaging experiments were performed with HEK293 cells stably expressing human TRPM2. 100 µM ATP/ADPR/2dADPR were extracellularly added 1 min after the start of the measurement (dashed line). Negative controls were left without addition (buffer). The bold line represents the mean Fura-2 fluorescence ratio of n=240 (buffer), n=173 (ATP), n=198 (ADPR) and n=166 (2dADPR) cells from 9-10 cell fields from 4 independent experiments. (F) The change in ratio from minimum to maximum within the first 2 min after addition was analyzed for each cell. Data displayed non-normal distribution. The bar denotes the median ± 95% CI. ns not significant, **** p < 0.0001 (Kruskal-Wallis test).