Figure 5.

SR Ca²⁺-ATPase (Serca2a) and phospholamban (PLB) expression, phosphorylation and function in Ctl and pAF-patients. A. Representative Western blots (top) for total Serca2a and total PLB protein-expression, as well as Ser16-PLB phosphorylation, Thr17-PLB phosphorylation, and calsequestrin (CSQ) expression. Bottom panel shows quantification of total Serca2a and PLB expression, and relative Ser16/Thr17 PLB phosphorylation-levels. Group data are normalized to CSQ. B. Representative example of a caffeine experiment, highlighting the decay rate of the systolic (I_Ca,L-triggered) Ca²⁺-transient (k_syst) and the decay rate of the caffeine-induced Ca²⁺-transient (k_caff). C. Respective rate-constants k_syst (left), k_caff (middle) and k_Serca (right, obtained as the difference between k_syst and k_caff) in Ctl and pAF-patients. Numbers indicate tissue samples per group (panel A) or myocytes/patients (panel C). *P<0.05 vs. Ctl. Comparisons using one-way ANOVA (A) or multi-level mixed-effects models (C).