Figure 4: Site-Specific Phosphorylation of N2Bus Titin in Nonfailing Donor (Control) and AS Patient Hearts

(A) Representative WBs from 1.8% polyacrylamide/1% agarose gels, using antititin antibodies against phosphoserine P-S4185 within the N2Bus element. Coomassie-stained PVDF membrane is also shown to indicate protein load. (B and C) Summary of results of densitometric analysis for the P-S4185 phosphosite in N2Bus titin, which was the only phosphosite showing significant differences in AS versus nonfailing donor hearts. Titin phosphorylation was indexed to protein load. Shown are box plots (median [first quartile, third quartile]) with whiskers and individual data points (red circles). (B) Mann-Whitney U test revealed statistically significant differences between control hearts and all AS patients (p = 0.023). (C) Comparison was made between the control group and AS subgroups using the Kruskal-Wallis test, revealing significant differences within the study groups (p = 0.017). A post hoc test (pairwise Wilcoxon Mann-Whitney U test) suggested a significant difference between donor and ASrEF hearts (*p < 0.05). Abbreviations as in Figures 1 and 3.