Phosphonothioate and fluoromethylene phosphonate analogues of cyclic phosphatidic acid: Novel antagonists of lysophosphatidic acid receptors

Isoform-selective antagonists of the lysophosphatidic acid (LPA) G-protein coupled receptors (GPCRs) have important potential uses in cell biology and clinical applications. Novel phosphonothioate and fluoromethylene phosphonate analogues of carbacyclic phosphatidic acid (ccPA) were prepared by chemical synthesis. The pKa values of these amphilic phosphonolipids and the parent cyclic phosphonate were measured titrimetrically using the Yasuda-Shedlovsky extrapolation. The pharmacological properties of these and other ccPA analogues were characterized for LPA receptor (LPAR) subtype-specific agonist and antagonist activity using Ca2+-mobilization assays in RH7777 cells expressing the individual EDG-family GPCRs. In particular, the phosphonothioate ccPA analogue inhibited Ca2+ release through LPA(1)/LPA(3) activation and was an LPA(1)/LPA(3) antagonist. The monofluoromethylene phosphonate ccPA analogue was also a potent LPA(1)/LPA(3) antagonist. In contrast, the difluoromethylene phosphonate ccPA analogue was a weak LPAR agonist, while ccPA itself had neither agonist nor antagonist activity.