Fig. 4.
STAC1 and STAC2 impede CDI of CaV1.2 currents. Representative normalized calcium and barium CaV1.2 currents in the presence of STAC1 (A) or STAC2 (B) using mild intracellular calcium buffering (0.5 mM EGTA). Significant differences in Ires250/Ipk in calcium and barium indicate CDI (****P < 0.0001, unpaired t test). (C) Analysis of the net CDI (−ICa/IBa) of CaV1.2 indicates that with 0.5 mM EGTA in the internal solution coexpression of STAC1 and STAC2 slows down CDI to different extents. ANOVA F(2, 24) = 7.44; P = 0.0029; P values in the figure are from Tukey post hoc analysis, **P = 0.002. (D) With strong intracellular calcium buffering (10 mM EGTA) coexpression of STAC1 resulted in loss of CDI, as the calcium and barium currents inactivated similarly and Ires250/Ipk were not significantly different (n.s., P = 0.70). (E) Coexpression of STAC2 strongly reduced CDI (*P = 0.02). (F) Representative normalized net CDI of CaV currents and relative Ires250/Ipk demonstrate that STAC1 abolishes and STAC2 severely reduces the CDI of CaV1.2. ANOVA F(2, 19) = 1.319; P < 0.0001; P values in the figure are from Tukey post hoc analysis, ****P < 0.0001.