Mammalian PSP24s (alpha and beta isoforms) are not responsive to lysophosphatidic acid in mammalian expression systems

Xenopus PSP24 (xPSP24) is a G-protein-coupled receptor which was originally identified as a functional lysophosphatidic acid (LPA) receptor. We obtain ed two different types (alpha and beta) of mammalian homologues of xPSP24 a nd found that these receptors are highly expressed in the brain (Kawasawa c t al., Biochem. Biophys. Res. Commun. 276, 952-956, 2000), These receptor d id not respond to LPA by GTP gamma S binding assays, while Edg2 or Edg4 sho wed responses to LPA under the same assay conditions. Furthermore, a sensit ive reporter gene assay using PC12 cells with serum response element promot er failed to detect any response of mammalian PSP24s to various concentrati ons of LPA. Thus, unlike xPSP24, we conclude that PSP24s are not functional LPA receptors in mammalian systems. (C) 2000 Academic Press.