PT  - JOURNAL ARTICLE
AU  - Seok Choi
AU  - Se-Yeon Jung
AU  - Yoo-Seung Ko
AU  - Seong-Ryong Koh
AU  - Hyewhon Rhim
AU  - Seung-Yeol Nah
TI  - Functional Expression of a Novel Ginsenoside Rf Binding Protein from Rat Brain mRNA in <em>Xenopus laevis</em> Oocytes
AID  - 10.1124/mol.61.4.928
DP  - 2002 Apr 01
TA  - Molecular Pharmacology
PG  - 928--935
VI  - 61
IP  - 4
4099  - http://molpharm.aspetjournals.org/content/61/4/928.short
4100  - http://molpharm.aspetjournals.org/content/61/4/928.full
SO  - Mol Pharmacol2002 Apr 01; 61
AB  - We have shown that ginsenoside Rf (Rf) regulates voltage-dependent Ca2+ channels through pertussis toxin (PTX)-sensitive G proteins in rat sensory neurons. These results suggest that Rf can act through a novel G protein-linked receptor in the nervous system. In the present study, we further examined the effect of Rf on G protein-coupled inwardly rectifying K+(GIRK) channels after coexpression with size-fractionated rat brain mRNA and GIRK1 and GIRK4 (GIRK1/4) channel cRNAs in Xenopus laevis oocytes using two-electrode voltage-clamp techniques. We found that Rf activated GIRK channel in a dose-dependent and reversible manner after coexpression with subfractions of rat brain mRNA and GIRK1/4 channel cRNAs. This Rf-evoked current was blocked by Ba2+, a potassium channel blocker. The size of rat brain mRNA responding to Rf was about 6 to 7 kilobases. However, Rf did not evoke GIRK current after injection with this subfraction of rat brain mRNA or GIRK1/4 channel cRNAs alone. Other ginsenosides, such as Rb1 and Rg1, evoked only slight induction of GIRK currents after coexpression with the subfraction of rat brain mRNA and GIRK1/4 channel cRNAs. Acetylcholine and serotonin almost did not induce GIRK currents after coexpression with the subfraction of rat brain mRNA and GIRK1/4 channel cRNAs. Rf-evoked GIRK currents were not altered by PTX pretreatment but were suppressed by intracellularly injected guanosine-5′-(2-O-thio) diphosphate, a nonhydrolyzable GDP analog. These results indicate that Rf activates GIRK channel through an unidentified G protein-coupled receptor in rat brain and that this receptor can be cloned by the expression method demonstrated here.