Figure 5.

A representative activator that decreases FRET and uncouples Ca²⁺-ATPase activity from Ca²⁺-uptake activity. (A) Chemical structure of DS26418355 (Compound 8). (B) CRC of normalized FRET E in 2CS biosensor in live HEK cells shows decreasing FRET response with increasing [compound]. (C) CRC shows Ca²⁺-ATPase activation in pCSR vesicles at both [Ca²⁺]_MAX (black) and [Ca²⁺]_MID (red). (D) Activation was less for Ca²⁺-uptake of SERCA2a in pCSR vesicles. ΔF_MAX, ΔF_MID, C₁₀, and EC₅₀ are defined and reported in Table 1 for panels B, C, and D. Data is presented as mean ± SEM, n = 3, *p < 0.05.