Figure 4
Skeletal-type EC coupling expressed by fs-α1S. A) Voltage-dependence of peak Ca2+ for 5 control myotubes expressing wt-α1S and 5 myotubes expressing fs-α1S. Ca2+transients for 15 non-transfected myotubes (NT) are included for reference. The sigmoidal lines are a Boltzmann fit with parameters ΔF/Fo max = 2.9, 1.4 ΔF/Fo; V1/2 = 11.7, 20 mV; k = 8.7, 13.2 mV, for wt-α1S and fs-α1S respectively. B) Line-scans (horizontal dimension is 2.05 seconds) and traces of integrated fluorescence in ΔF/Fo units for depolarizations to +30 mV. Top line-scans are for the same fs-α1S transfected myotube in standard external solution (10 mM CaCl2) and the same solution without added CaCl2 (0 Ca2+). Bottom line-scans show fs-α1S transfected KO myotubes lacking DHPR β1a or lacking RyR1 in standard external solution.