Evidence that the tertiary structure of 20(S)-ginsenoside Rg(3) with tight hydrophobic packing near the chiral center is important for Na(+) channel regulation.
Ginsenosides are the active ingredients of Panax ginseng. Ginsenoside Rg(3) exists as two stereoisomers of carbon-20: 20-S-protopanaxatriol-3-[O-beta-d-glucopyranosyl (1-->2)-beta-glucopyranoside] (20(S)-Rg(3)) and 20-R-protopanaxatriol-3-[O-beta-d-glucopyranosyl (1-->2)-beta-glucopyranoside] (20(R)-Rg(3)). Recently, we reported that 20(S)-Rg(3) regulates voltage-dependent Ca(2+) channel activity and several types of ligand-gated ion channels, whereas 20(R)-Rg(3) does not have this activity. In this study, we investigated the structure-activity relationship of these two stereoisomers by NMR spectroscopy and by measurement of the current in Xenopus oocytes expressing the mouse cardiac voltage-dependent Na(+) channel (Na(v)1.5). We found that 20(S)-Rg(3) but not 20(R)-Rg(3) inhibited Na(+) channel current in a dose- and voltage-dependent manner. The difference between Rg(3) epimers in voltage-dependent ion channel regulation indicates that the structure of 20(S)-Rg(3) may be geometrically better aligned than that of 20(R)-Rg(3) for interaction with receptor regions in Na(+) channels. The (1)H and (13)C NMR chemical shifts, including all hydroxyl protons of 20(S)-Rg(3) and 20(R)-Rg(3), were completely assigned, and their tertiary structures were determined. 20(S)-Rg(3) has more tight hydrophobic packing near the chiral center than 20(R)-Rg(3). Tertiary structures and activities of 20(S)-Rg(3) and 20(R)-Rg(3) indicate that 20(S)-Rg(3) may have stronger interactions with the receptor region in ion channels than 20(R)-Rg(3). This may result in different stereoselectivity of Rg(3) stereoisomers in the regulation of voltage-dependent Na(+) channel activity. This is the first structural approach to ginsenoside action on ion channel.
Kang
Dong-Il
DI
Department of Chemistry and Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Republic of Korea.
Lee
Jee-Young
JY
Yang
Ji-Young
JY
Jeong
Sang Min
SM
Lee
Jun-Ho
JH
Nah
Seung-Yeol
SY
Kim
Yangmee
Y
D000818:Animals; D002478:Cells, Cultured; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D036145:Ginsenosides / Q000008:administration & dosage* / Q000032:analysis / Q000737:chemistry*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D008956:Models, Chemical; D008958:Models, Molecular; D009124:Muscle Proteins / Q000187:drug effects / Q000502:physiology*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D009865:Oocytes / Q000502:physiology*; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D036145:Ginsenosides; D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568321:Scn5a protein, mouse; D015222:Sodium Channels; C097367:ginsenoside Rg3