Xenopus PSP24 (xPSP24) is a G-protein-coupled receptor which was originally identified as a functional lysophosphatidic acid (LPA) receptor. We obtained two different types (alpha and beta) of mammalian homologues of xPSP24 and found that these receptors are highly expressed in the brain (Kawasawa ct al., Biochem. Biophys. Res. Commun. 276, 952-956, 2000), These receptor did not respond to LPA by GTP gamma S binding assays, while Edg2 or Edg4 showed responses to LPA under the same assay conditions. Furthermore, a sensitive reporter gene assay using PC12 cells with serum response element promoter failed to detect any response of mammalian PSP24s to various concentrations of LPA. Thus, unlike xPSP24, we conclude that PSP24s are not functional LPA receptors in mammalian systems.