Format

Send to

Choose Destination
Mol Pharmacol. 2017 Oct;92(4):437-450. doi: 10.1124/mol.117.108886. Epub 2017 Jul 13.

Molecular Basis of Altered hERG1 Channel Gating Induced by Ginsenoside Rg3.

Author information

1
Nora Eccles Harrison Cardiovascular Research and Training Institute (A.G., W.W., S.T., M.C.S.) and Division of Cardiovascular Medicine, Department of Internal Medicine, (M.C.S.), University of Utah, Salt Lake City, Utah; and Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria (E.-M.Z.-P., A.S.-W.).
2
Nora Eccles Harrison Cardiovascular Research and Training Institute (A.G., W.W., S.T., M.C.S.) and Division of Cardiovascular Medicine, Department of Internal Medicine, (M.C.S.), University of Utah, Salt Lake City, Utah; and Department of Pharmacology and Toxicology, University of Vienna, Vienna, Austria (E.-M.Z.-P., A.S.-W.) m.sanguinetti@utah.edu.

Abstract

Outward current conducted by human ether-à-go-go-related gene type 1 (hERG1) channels is a major determinant of action potential repolarization in the human ventricle. Ginsenoside 20(S)-Rg3 [Rg3; (2S,3R,4S,5S,6R)-2-[(2R,3R,4S,5S,6R)-4,5-dihydroxy-2-[[(3S,5R,8R,9R,10R,12R,13R,14R,17S)-12-hydroxy-17-[(2S)-2-hydroxy-6-methylhept-5-en-2-yl]-4,4,8,10,14-pentamethyl-2,3,5,6,7,9,11,12,13,15,16,17-dodecahydro-1H-cyclopenta[a]phenanthren-3-yl]oxy]-6-(hydroxymethyl)oxan-3-yl]oxy-6-(hydroxymethyl)oxane-3,4,5-triol], 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 the deactivation rate of mutant channel currents were characterized using the two-microelectrode voltage clamp technique. 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.

PMID:
28705808
PMCID:
PMC5588553
[Available on 2018-10-01]
DOI:
10.1124/mol.117.108886
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center