Ki16425, a subtype-selective antagonist for EDG-Family lysophosphatidic acid receptors

Lysophosphatidic acid (LPA) exerts a variety of biological responses through specific receptors: three subtypes of the EDG-family receptors, LPA(1), LPA(2), and LPA(3) ( formerly known as EDG-2, EDG-4, and EDG-7, respectively), and LPA(4)/GPR23, structurally distinct from the EDG-family receptors, have so far been identified. In the present study, we characterized the action mechanisms of 3-(4-[4-([1-(2-chlorophenyl)ethoxy]carbonyl amino)-3-methyl-5-isoxazolyl] benzylsulfanyl) propanoic acid (Ki16425) on the EDG-family LPA receptors. Ki16425 inhibited several responses specific to LPA, depending on the cell types, without any appreciable effect on the responses to other related lipid receptor agonists, including sphingosine 1- phosphate. With the cells overexpressing LPA(1), LPA(2), or LPA(3), we examined the selectivity and mode of inhibition by Ki16425 against the LPA-induced actions and compared them with those of dioctyl glycerol pyrophosphate ( DGPP 8: 0), a recently identified antagonist for LPA receptors. Ki16425 inhibited the LPA-induced response in the decreasing order of LPA(1) greater than or equal to LPA(3) >> LPA(2), whereas DGPP 8: 0 preferentially inhibited the LPA(3)- induced actions. Ki16425 inhibited LPA-induced guanosine 5'-O-(3-thio)triphosphate binding as well as LPA receptor binding to membrane fractions with a same pharmacological specificity as in intact cells. The difference in the inhibition profile of Ki16425 and DGPP 8: 0 was exploited for the evaluation of receptor subtypes involved in responses to LPA in A431 cells. Finally, Ki16425 also inhibited LPA-induced long-term responses, including DNA synthesis and cell migration. In conclusion, Ki16425 selectively inhibits LPA receptor-mediated actions, especially through LPA(1) and LPA(3); therefore, it may be useful in evaluating the role of LPA and its receptor subtypes involved in biological actions.