Figure 6.

rIP₃R1^ND is poorly functional when expressed in HEK-3KO.A, multiple WT rIP3R1 and mutant rIP₃R1^ND cell lines were generated in the IP₃R-null HEK-3KO cells and Western blotted. B, representative traces show Ca²⁺ signals of IP3R-null HEK-3KO cells (blue), WT rIP₃R1 (green), and rIP₃R1^ND (red) in response to trypsin (500 nm) when loaded with Fura-2/AM. C, scatter plots summarizing change in amplitude (peak ratio – basal ratio: average of initial 5 ratio points) for experiments similar to those shown in B when treated with 0.5, 1, 10, and 500 nm trypsin. Boxes represent the 25th, 50th, and 75th percentiles, whereas whiskers represent 5th and 95th percentiles and mean is represented by colored circles. D, stacked bar graph summarizing the percentage of amplitudes from C, which fall into pre-determined ranges such that only those cells with an amplitude change greater than 0.1 ratio units (black portion of bars) are considered to be responding to the trypsin stimulus shown in B. E, dose-response curve showing Ca²⁺ response of Fura-2/AM-loaded WT rIP₃R1 and rIP₃R1^ND cells when treated with increasing concentrations (0.5 nm, 1 nm, 3 nm, 10 nm, 30 nm, 100 nm, 300 nm, 500 nm, 1 μm, 2.5 μm, and 5 μm) of trypsin using a Flexstation3 96-well–plate reader. Data are mean ± S.E. of three (n = 3) independent experiments. **, p < 0.01 and ***, p < 0.001 when compared with WT rIP₃R1 cell line and ###, p < 0.001 when compared with HEK-3KO cell line; one-way ANOVA with Tukey's test was performed in C (F_10,791 = 532.1, p < 0.0001) and D (F_10,22 = 108.6, p < 0.0001). Unless otherwise stated, all data above comes from at least n = 3 experiments.