Synergistic activation of thrombin and angiotensin II receptors revealed by bioluminescence resonance energy transfer

We recently reported a physical interaction between the angiotensin II (AngII) receptor (AT1R) and thrombin receptor (PAR1) in HEK293 cells using bioluminescence resonance energy transfer (BRET) technology. This was characterized by thrombin trans-activating AT1R and the synergistic responses of the AT1R–PAR1 complex. Here, we investigated the other face of the coin by examining the effect of AT1R on PAR1 activity using BRET. AngII/AT1R did not promote PAR1 activation in the absence of thrombin. However, the combination of thrombin and AngII resulted in their synergistic/allosteric action. Moreover, AngII/AT1R potentiated the maximal thrombin responses, suggesting specific conformational changes within the AT1R–PAR1 complex. Overall, our data confirm the functional AT1R–PAR1 interplay and further support the implication of both AT1R and PAR1 protomers in their synergistic interaction as previously reported.