Mapping human protease-activated receptor 4 (PAR4) homodimer interface to transmembrane helix 4.

Thrombin activates platelets by binding and cleaving protease-activated receptors 1 and 4 (PAR1 and PAR4). Because of the importance of PAR4 activation on platelets in humans and mice and emerging roles for PAR4 in other tissues, experiments were done to characterize the interaction between PAR4 homodimers. Bimolecular fluorescence complementation and bioluminescence resonance energy transfer (BRET) were used to examine the PAR4 homodimer interface.