Ginseng gintonin activates the human cardiac delayed rectifier K+ channel: involvement of Ca2+/calmodulin binding sites

Mol Cells. 2014 Sep;37(9):656-63. doi: 10.14348/molcells.2014.0087. Epub 2014 Sep 18.

Abstract

Gintonin, a novel, ginseng-derived G protein-coupled lysophosphatidic acid (LPA) receptor ligand, elicits [Ca(2+)]i transients in neuronal and non-neuronal cells via pertussis toxin-sensitive and pertussis toxin-insensitive G proteins. The slowly activating delayed rectifier K(+) (I(Ks)) channel is a cardiac K(+) channel composed of KCNQ1 and KCNE1 subunits. The C terminus of the KCNQ1 channel protein has two calmodulin-binding sites that are involved in regulating I(Ks) channels. In this study, we investigated the molecular mechanisms of gintonin-mediated activation of human I(Ks) channel activity by expressing human I(Ks) channels in Xenopus oocytes. We found that gintonin enhances IKs channel currents in concentration- and voltage-dependent manners. The EC50 for the I(Ks) channel was 0.05 ± 0.01 μg/ml. Gintonin-mediated activation of the I(Ks) channels was blocked by an LPA1/3 receptor antagonist, an active phospholipase C inhibitor, an IP3 receptor antagonist, and the calcium chelator BAPTA. Gintonin-mediated activation of both the I(Ks) channel was also blocked by the calmodulin (CaM) blocker calmidazolium. Mutations in the KCNQ1 [Ca(2+)]i/CaM-binding IQ motif sites (S373P, W392R, or R539W)blocked the action of gintonin on I(Ks) channel. However, gintonin had no effect on hERG K(+) channel activity. These results show that gintonin-mediated enhancement of I(Ks) channel currents is achieved through binding of the [Ca(2+)]i/CaM complex to the C terminus of KCNQ1 subunit.

Keywords: IKs channel; LPA receptor; ginseng; gintonin; heart.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites
  • Calcium / metabolism
  • Calcium Signaling / drug effects*
  • Calmodulin / metabolism
  • Delayed Rectifier Potassium Channels / metabolism*
  • Dose-Response Relationship, Drug
  • Gene Expression Regulation / drug effects
  • Guinea Pigs
  • Humans
  • Isoxazoles / pharmacology
  • KCNQ1 Potassium Channel / genetics
  • KCNQ1 Potassium Channel / metabolism*
  • Myocytes, Cardiac / drug effects*
  • Myocytes, Cardiac / physiology
  • Oocytes / drug effects
  • Oocytes / physiology
  • Panax / chemistry*
  • Plant Proteins / chemistry
  • Plant Proteins / pharmacology*
  • Propionates / pharmacology
  • Receptors, Lysophosphatidic Acid / metabolism
  • Xenopus laevis

Substances

  • 3-(4-(4-((1-(2-chlorophenyl)ethoxy)carbonyl amino)-3-methyl-5-isoxazolyl) benzylsulfanyl) propanoic acid
  • Calmodulin
  • Delayed Rectifier Potassium Channels
  • Isoxazoles
  • KCNQ1 Potassium Channel
  • KCNQ1 protein, human
  • MLP151 protein, Panax ginseng
  • Plant Proteins
  • Propionates
  • Receptors, Lysophosphatidic Acid
  • Calcium