Figure 5
Greater activation of thin filament results in prolonged diastole. (A) To determine how each isoform regulates dynamic contraction, full-length MyBP-C adult rat ventricular myocytes (ARVM) were infected with adenoviral constructs (MOI 1000) overexpressing full-length, cMyc-tagged slow-skeletal, fast-skeletal, or cardiac MyBP-C, followed by 48 h culture. (B) Immunofluorescence (IF) imaging demonstrates localization of adenoviral-mediated expression of MyBP-C isoforms (green) within the sarcomere, as delineated by α-actinin (red). (C,D) Unloaded shortening was measured by changes in sarcomere length (SL) during dynamic contraction and relaxation (ARVM paced at 1 Hz, 20 V, 2 ms). (C) Relaxation kinetics was measured by time to % baseline, how fast the cell returns to 10, 50, and 90% of resting SL, and (D) relaxation constant tau, a logarithmic fit of the relaxation curve. (E) Changes in relaxation kinetics were evident by combined traces, and in silico simulations demonstrate that greater thin filament activation can contribute to relaxation kinetics. Graphs represented as mean ± SEM, *p < 0.05 vs. uninfected controls, #p < 0.05 vs. cMyBP-C.
