Figure 4. Effect of p.Asp219Val mutation on hERG channel inactivation.

A) Data traces show a family of whole cell current recordings of WT hERG, 50/50 mix or p.Asp219Val hERG undergoing a protocol for steady-state inactivation (protocol is below traces). Stably transfected WT-hERG and p.Asp219Val hERG HEK cells were used, and HEK cells transiently transfected with WT hERG and p.Asp219Val hERG plasmids were used for the 50/50 mix electrophysiology. Peak current was measured at the depolarization to +20 mV after the test pulses (indicated by the arrowhead), and was graphed against voltage. Summary data is displayed graphically in the panel to the right. The 50/50 mix and p.Asp219Val hERG steady-state of inactivation was right-shifted, and was significantly different than WT hERG (p= <0.0001). B) Families of whole cell current recordings demonstrating onset of inactivation are shown for WT, 50/50 mix or p.Asp219Val hERG. The lines were fitted by a single exponential curve to determine time of inactivation onset, and time constant was graphed against each respective voltage. The graph demonstrates a trend that p.Asp219Val hERG and the 50/50 mix have a longer onset of inactivation, with significantly different points at 40 and 60 mV mV (p=<0.05). C) Whole cell traces of WT, 50/50 mix or p.Asp219Val hERG demonstrating recovery from inactivation. Peak current at each time was obtained, and a single exponential curve was fitted to these data (to the peak, indicated by the curved arrow). The resulting time constant was plotted against the voltage. This protocol was repeated at -60 mV, -50 mV, -40 mV and -30 mV. There was a significant difference between the time constants for recovery from inactivation at -60- -50 (p<0.05) and between -40 - -30 mV (p=<0.001) for WT, 50/50 mix and and p.Asp219Val hERG. N=5 for WT hERG, 4 for 50/50 mix and 6 for p.Asp219Val.