Mutagenesis Studies Revealed Minimal Impact Of Human A120t Variant Of Protease-Activated Receptor 4 On Receptor Function Or Pharmacological Response To A Potent And Selective Antagonist.

Introduction: Protease-activated receptor 4 (PAR4) is a platelet thrombin receptor and a novel target for ischemic stroke treatment. Recent reports suggested a subtle racial difference in platelet responses to submaximal concentrations of PAR4 agonist peptide (PAR4-AP). One of the PAR4 variants, A120T, is more common in African American than white (63% vs. 19%, Edelstein et al., Blood 2014). It was suggested that this variant contributes to the difference in response to PAR4-AP and impacts the in vitro response to YD-3, a PAR4 antagonist. In this study, site-directed mutagenesis was used to evaluate the effect of the A120T variant on PAR4 function and response to a newly discovered potent and selective PAR4 antagonist, UDM-001651. Unlike YD-3, UDM-001651 inhibited thrombin-induced platelet aggregation and prevented thrombosis in a monkey model and thus served as a relevant PAR4 pharmacology tool. Methods: Human PAR4 cDNAs expressing A120 and T120 variants were stably expressed in HEK293 cells. Cell surfac...