Ginseng Gintonin Activates the Human Cardiac Delayed Rectifier K+ Channel: Involvement of Ca2+/Calmodulin Binding Sites

  • Choi, Sun-Hye (Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center) ;
  • Lee, Byung-Hwan (Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center) ;
  • Kim, Hyeon-Joong (Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center) ;
  • Jung, Seok-Won (Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center) ;
  • Kim, Hyun-Sook (Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center) ;
  • Shin, Ho-Chul (Department of Pharmacology and Toxicology, College of Veterinary Medicine, Konkuk University) ;
  • Lee, Jun-Hee (Department of Physical Therapy, College of Health Science, Cheongju University) ;
  • Kim, Hyoung-Chun (Neuropsychopharmacology and Toxicology Program, College of Pharmacy, Kangwon National University) ;
  • Rhim, Hyewhon (Life Science Division, Korea Institute of Science and Technology) ;
  • Hwang, Sung-Hee (Department of Pharmaceutical Engineering College of Health Sciences Sangji University) ;
  • Ha, Tal Soo (Department of Biomedical Science, Daegu University) ;
  • Kim, Hyun-Ji (Department of Physiology and Samsung Biomedical Research Institute, School of Medicine, Sungkyunkwan University) ;
  • Cho, Hana (Department of Physiology and Samsung Biomedical Research Institute, School of Medicine, Sungkyunkwan University) ;
  • Nah, Seung-Yeol (Department of Physiology, College of Veterinary Medicine and Bio/Molecular Informatics Center)
  • Received : 2014.04.11
  • Accepted : 2014.08.11
  • Published : 2014.09.30


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 $I_{Ks}$ channel currents in concentration- and voltage-dependent manners. The $EC_{50}$ for the $I_{Ks}$ channel was $0.05{\pm}0.01{\mu}g/ml$. Gintonin-mediated activation 1 of the $I_{Ks}$ channels was blocked by an LPA1/3 receptor antagonist, an active phospholipase C inhibitor, an $IP_3$ 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.


Supported by : National Research Foundation of Korea (NRF)


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