Ca(v)3.2 T‐type calcium channel regulates mouse platelet activation and arterial thrombosis

BACKGROUND: Ca(v)3.2 is a T‐type calcium channel that causes low‐threshold exocytosis. T‐type calcium channel blockers reduce platelet granule exocytosis and aggregation. However, studies of the T‐type calcium channel in platelets are lacking. OBJECTIVE: To examine the expression and role of Ca(v)3.2 in platelet function. METHODS: Global Ca(v)3.2(−/−) and platelet‐specific Ca(v)3.2(−/−) mice and littermate controls were used for this study. Western blot analysis was used to detect the presence of Ca(v)3.2 and activation of the calcium‐responsive protein extracellular signal‐regulated kinase (ERK). Fura‐2 dye was used to assess platelet calcium. Flow cytometry and light transmission aggregometry were used to evaluate platelet activation markers and aggregation, respectively. FeCl(3)‐induced thrombosis and a microfluidic flow device were used to assess in vivo and ex vivo thrombosis, respectively. RESULTS: Ca(v)3.2 was expressed in mouse platelets. As compared with wild‐type controls, Ca(v)3.2(−/−) mouse platelets showed reduced calcium influx. Similarly, treatment with the T‐type calcium channel inhibitor Ni(2+) decreased the calcium influx in wild‐type platelets. As compared with controls, both Ca(v)3.2(−/−) and Ni(2+)‐treated wild‐type platelets showed reduced activation of ERK. ATP release, P‐selectin exposure, and α(IIb)β3 activation were reduced in Ca(v)3.2(−/−) and Ni(2+)‐treated wild‐type platelets, as was platelet aggregation. On in vivo and ex vivo thrombosis assay, Cav3.2 deletion caused delayed thrombus formation. However, tail bleeding assay showed intact hemostasis. CONCLUSION: These results suggest that Ca(v)3.2 is required for the optimal activation of platelets.