Role of arrestin1 in regulation of GPCR signaling in platelet activation

Abstract

The arrestins are a class of soluble proteins that function in concert with the GPCR kinases to stop or arrest GPCR‐mediated intracellular signaling. Although β‐arrestins function in the desensitization of most GPCRs, the functional differences of β‐arrestin1 (arrestin2, BARR1) versus β‐arrestin2 (arrestin1, BARR2) in the regulation of GPCR signaling in platelets and the mechanisms of desensitization of platelets to GPCR agonists by β‐arrestins have not been understood. In this study, we identify the role of BARR2 in the regulation of platelet function and GPCR signaling in platelets. We used mice lacking BARR1 and BARR2 to evaluate the functional role of BARR2 in platelet activation. Platelet aggregation, dense‐granule secretion, and fibrinogen receptor activation induced by 2‐MeSADP, U46619, thrombin, and AYPGKF were significantly potentiated in BARR2 −/− platelets compared to WT platelets. In contrast to BARR2 −/− platelets, AYPGKF‐, thrombin‐, and U46619‐induced platelet aggregation and secretion were significantly inhibited in BARR1 −/− platelets compared to WT platelets, while 2‐MeSADP‐induced platelet aggregation and secretion were minimally affected in BARR1 −/−platelets. However, CRP‐induced platelet aggregation and secretion were not affected in both BARR1 −/− and BARR2 −/− platelets. These results suggest that BARR2 functions as the predominant regulator in the termination of GPCR signaling in platelets. In addition, platelet aggregation was restored in response to second challenge of 2‐MeSADP and AYPGKF in BARR2 −/− platelets whereas re‐stimulation of agonist failed to induce aggregation in WT and b‐arrestin1 −/− platelets, indicating BARR2 contributes to P2Y1, P2Y12, and PAR receptor desensitization. Furthermore, 2MeSADP‐ and AYPGKF‐induced Akt and ERK phosphorylations were significantly potentiated in BARR2 −/− platelets. Finally, BARR2 −/− mice show an enhanced and stable thrombus formation after FeCl3 injury to the carotid artery, indicating BARR2 is critical for thrombus formation in vivo. We conclude that BARR2 plays an important role in regulation of platelet function through selective GPCR desensitization.Support or Funding InformationThis work was supported by the National Research Foundation of Korea (NRF) Grant of the Korean government (NRF‐2016R1D1A1B01010310) and the Global Research and Development Center (GRDC) Program through the NRF funded by the Ministry of Education, Science and Technology (2017K1A4A3014959).