FIGURE 5.

Polymerization of WT and mutant CASQ2s in living cells. (A) Pooled data for FRET efficiency in 3T3 fibroblasts coexpressing WT and mutant CASQ2 at 0 [Ca] (5 mM EGTA in the solution), or in the presence of 10 mM [Ca] (n from 18 to 28). Cells were exposed to 1 μM of ionomycin. (B) Pooled data for FRET efficiency in cells expressing WT CASQ2 CFP/YFP infected with adenoviral Ad-CASQ2^WT or Ad-CASQ2^DEL constructs at 10 mM [Ca] (n = 14 and 15 respectively). (C) Pooled data for efficiency of FRET between CASQ2^WT-CFP and CASQ2^WT-YFP or CASQ2^R33Q-YFP at different Ca concentrations. Data points (n from 18 to 24) were fitted using logistic functions with EC₅₀ values 509 and 51 μmol/L for FRET to CASQ2^WT and CASQ2^R33Q, respectively. (D) Time-dependent changes in FRET efficiency after application of 10 mM [Ca] (solid triangles) or 0 [Ca] (5 mM EGTA, open circles) to fibroblasts in the presence of 1 μM ionomycin. Data presented as mean ± SE; n from 14 to 23. Data for 0 [Ca] were fitted with a singe exponential function with time constant of 18.1 min.