Gintonin, a Ginseng-Derived Lysophosphatidic Acid Receptor Ligand, Potentiates ATP-Gated P2X1 Receptor Channel Currents

Abstract

Ginseng, the root of Panax ginseng C.A. Meyer, is used as a general tonic. Recently, we isolated a novel ginsengderived lysophosphatidic acid (LPA) receptor ligand, gintonin. Gintonin activates G protein-coupled LPA receptors with high affinity in cells endogenously expressing LPA receptors, e.g., Xenopus oocytes. P2X receptors are ligandgated ion channels activated by extracellular ATP, and 7 receptor subtypes (P2X 1 -P2X 7 ) have been identified. Most of the P2X 1 receptors are expressed in the smooth muscles of genitourinary organs involved in reproduction. A main characteristic of the P2X 1 receptor is rapid desensitization after repeated ATP treatment of cells or tissues expressing P2X 1 receptors. In the present study, we examined the effect of gintonin on P2X 1 receptor channel activity. P2X 1 receptors were heterologously expressed in Xenopus oocytes. ATP treatment of oocytes expressing P2X 1 receptors induced large inward currents (I ATP ), but repetitive ATP treatments induced a rapid desensitization of I ATP . Gintonin treatment after P2X 1 receptor desensitization potentiated I ATP in a concentration-dependent manner. We further examined the signaling transduction pathways involved in gintonin-mediated potentiation of I ATP . Gintonin-mediated I ATP potentiation was blocked by Ki16425, an LPA1/3 receptor antagonist, a PKC inhibitor, a PLC inhibitor, and a PI4-Kinase inhibitor but not by a calcium chelator. In addition, mutations of the phosphoinositide binding site of the P2X 1 receptor greatly attenuated the gintonin-mediated I ATP potentiation. These results indicate that G protein-coupled LPA receptor activation by gintonin is coupled to the potentiation of the desensitized P2X 1 receptor through a phosphoinositide-dependent pathway.

A brief method for preparation of gintonin-enriched fraction from ginseng

“…Gintonin induces intracellular Ca 2+ mobilization via the phospholipase C–IP 3 –Ca 2+ pathway in mammalian cells expressing endogenous LPA receptors [2] . Further studies demonstrated that gintonin-mediated transient mobilization of [Ca 2+ ] i is coupled with Ca 2+ -dependent in vitro regulations of ion channels, neurotransmitter release by enhancing synaptic transmission, and in vivo anti-Alzheimer's activity by activating nonamyloidogenic pathways [3] , [4] , [5] , [6] , [7] . We extracted ginseng with multiple procedures such as anion exchange chromatography and dialysis, yielding approximately 0.2% in the previous method ( Fig.…”

“…The transient elevation of intracellular Ca 2+ via LPA receptor activation is a key mediator of diverse gintonin-mediated in vitro and in vivo effects. For example, gintonin regulates various Ca 2+ -dependent ion channels [3] , [4] , [5] and modulates N -methyl- d -aspartic acid and P2X 1 receptors via Ca 2+ -dependent signaling pathways [6] , [7] . Gintonin-mediated ion channels and receptor regulations are linked to the increase of gastrointestinal contractility by stimulation of pacemaker activity in the gastrointestinal system [8] and enhancement of synaptic transmission in hippocampal slices in the brain [9] .…”

Characteristics of Gintonin-Mediated Membrane Depolarization of Pacemaker Activity in Cultured Interstitial Cells of Cajal

“…Currently, we are investigating the possibility that GLP151 binds to LPA and induces LPA to exhibit gintonin action. In previous studies, we demonstrated that gintonin regulates diverse Ca 2+ -dependent ion channels such as BK Ca , Ca 2+ -activated Cl - , and Kv1.2 channels, and receptors such as NMDA and P2X 1 receptors via endogenous LPA receptor activation [32,33,34,58,59]. In an in vivo study, gintonin showed anti-Alzheimer's disease effects by activating a non-amyloidogenic pathway via LPA receptors and reduced amyloid plaque formations in the cortex and hippocampus [60].…”

Gintonin, a novel ginseng-derived lysophosphatidic acid receptor ligand, stimulates neurotransmitter release

“…acid receptors with high affinity in cells expressing LPA receptors endogenously or heterologously. Gintonin-mediated LPA receptor activation is also accountable for diverse downstream events, including stimulation of phospholipase C, protein kinase C (PKC), mitogen-activated protein kinases, and phosphoinositide 4-kinase (PI4 kinase) through multiple G proteins, such as G␣ i/o , G␣ 12/13 , and G␣ q/11 [2,10,13,16]. In addition, gintonin has been reported to regulate various ion channels (e.g., Ca 2+ -activated Cl − , Ca 2+ -activated K + , and voltage-gated Kv1.2) and receptors (e.g., NMDA and P2X 1 ) through LPA receptor activation [9,10].…”