Figure 4. Depletion of Calstabin2 causes intracellular Ca²⁺ leakage, activation of calcineurin and AKT-mTOR pathway.

(A), Resting Ca²⁺ determined by the ratio of F340/F380 fluorescence in WT and KO mice at different ages. At 48 weeks, resting [Ca²⁺]_i was 20% higher in KO cells than in WT controls. Numbers in the bars indicate the number of the analyzed cells isolated from five to six mice. (B), Calcineurin activity was 48% higher in aged KO mice than in the age-matched WT mice and 1.8-fold higher than in young KO mice. Immunoblots for proteins involved in AKT-mTOR signaling pathway in hearts from 12-week-old (C) and 48-week-old (D) mice. The graphs indicate the relative expression levels of p-AKT, p-p70S6K and p-mTOR. n = 5 per group. Quantitative data are shown as means ± SEM. *P<0.05, **P<0.01 vs WT.