RT Journal Article
SR Electronic
T1 Molecular basis of altered hERG1 channel gating induced by ginsenoside Rg3
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.117.108886
DO 10.1124/mol.117.108886
A1 Alison Gardner
A1 Wei Wu
A1 Steven Thomson
A1 Eva-Maria Zangerl-Plessl
A1 Anna Stary-Weinzinger
A1 Michael Sanguinetti
YR 2017
UL http://molpharm.aspetjournals.org/content/early/2017/07/13/mol.117.108886.abstract
AB Outward current conducted by human ether-a-g-go-related gene type 1 (hERG1) channels is a major determinant of action potential repolarization in the human ventricle. Ginsenoside 20(S)-Rg3 (Rg3), an alkaloid isolated from the root of Panax ginseng slows the rate of hERG1 deactivation, induces channels to open at more negative potentials than normal and increases current magnitude. The onset of Rg3 action is extremely fast, suggesting that it binds to an extracellular accessible site on the channel to alter its gating. Here we used a scanning mutagenesis approach to identify residues in the extracellular loops and transmembrane segments of hERG1 that might interact with Rg3. Single or multiple residues of hERG1 were mutated to Ala or Cys and the resulting mutant channels were heterologously expressed in Xenopus oocytes. The effects of Rg3 on the voltage dependence of activation and deactivation rate of mutant channel currents were characterized using two-microelectrode voltage clamp. Mutation to Ala of specific residues in the S1 (Tyr420), S2 (Leu452, Phe463) and S4 (Ile521, Lys525) segments partially inhibited the effects of Rg3 on hERG1. The double mutant Y420A/L452A nearly eliminated the effects of Rg3 on voltage dependent channel gating, but did not prevent the increase in current magnitude. These findings together with molecular modeling suggest that Rg3 alters the gating of hERG1 channels by interacting with and stabilizing the voltage sensor domain in an activated state.