Gintonin: A Novel Ginseng-Derived Ligand that Targets G Protein- Coupled Lysophosphatidic Acid Receptors

Abstract

Ginseng, the root of Panax ginseng C.A. Meyer, is one of the oldest herbal medicines and induces a variety of physiological and pharmacological effects. Ginseng contains saponins called ginsenosides, which are considered as the biologically active ingredients in ginseng. Increasing evidences indicate that ginsenosides are non-selective in their actions and high concentrations are required for cellular effects. Crude ginseng total saponin (cGTS) fraction is about 50% ginsenoside in composition, but the remainder is not defined clearly. Biochemically, cGTS fraction triggers differing patterns of ginsenoside activity; for example, the cGTS fraction itself functions as an agent that activates a G protein-coupled receptor because it induces endogenous calcium (Ca2+)-activating chloride (Cl-) channel activations in Xenopus oocytes via the same signaling pathways used by Gαq/11 protein-coupled receptors. Recent reports have revealed that the cGTS fraction contains novel glycolipoproteins, designated the gintonin. It was discovered that gintonin, but not ginsenosides, interacts with unidentified membrane proteins to generate [Ca2+]i transient in mammalian cells and to activate endogenous Ca2+-activating Cl- channels in Xenopus oocytes. Further studies have shown that gintonin is a novel lysophosphatidic acids (LPAs)-ginseng protein complex and can selectively activate LPA receptors with an affinity greater than that of LPA. This review aims to characterize gintonin as an LPA receptor ligand, explain the reasons why gintonin remained unidentified for a long time, list the advantages of LPA-ginseng protein complexes over free LPAs, compare the activities of gintonin and ginsenoside, and describe the pharmacological applications of gintonin as a drug that targets LPA receptors.