Pharmacological rescue of hERG currents carried out by G604S and wide type hERG co‐expression

Mutations in human ether-a-go-go-related gene (hERG) can lead to type 2 long-QT syndrome (LQT2). The authors previously identified the hERG mutation G604S results in a loss of function and obviously decreased current amplitude and impaired channel protein trafficking when co-expressed with WT-hERG. The present study further investigates the biological and electrophysiological consequences of pharmacologic chaperones in HEK293 cells expressing G604S-hERG or co-expressing G604S-hERG and WT-hERG. It was found that a low temperature (27°C), thapsigargin, NS1643 and E-4031 fail to rescue the G604S mutation. Interestingly, only E-4031 treatment resulted in a significant increase in hERG currents in cells co-expressing G604S-hERG and WT-hERG, correspondingly more mature protein band at 155 kDa by Western blotting and an increased membrane staining by confocal microscopy. In addition, E-4031 treatment shifted the steady-state half maximal activation voltage (V1/2 ) of the inactivation curve by +8 mV in cells co-expressing G604S-hERG and WT-hERG. The present experimental results suggest that a G604S mutation is resistant to pharmacological rescue. E-4031 treatment resulted in a significant increase in hERG currents by promoting the hERG channel processing and trafficking in cells co-expressing G604S-hERG and WT-hERG.