A complementary role for tetraspanin superfamily member TSSC6 and ADP purinergic P2Y₁₂ receptor in platelets

Tumor-suppressing subchromosomal transferable fragment cDNA 6 (TSSC6) expression is restricted to hematopoietic organs and tissues where it plays a role in hematopoietic-cell function. The ADP purinergic receptor P2Y₁₂ is mainly expressed by platelets with important clinical significance as a target for several clinically approved antithrombotic agents. We have previously shown a physical association between P2Y₁₂ and TSSC6 in platelets. Hence our aim was to investigate whether this physical association is translated to functional effects. To investigate this possibility, we used wild-type or TSSC6 knockout (KO) mice treated with either PBS or 50 mg/kg clopidogrel. TSSC6 KO mice treated with clopidogrel exhibited synergy in delayed kinetics of clot retraction, reduced collagen-mediated platelet aggregation, and platelet spreading on fibrinogen. Platelets derived from TSSC6 mice with P2Y₁₂ blockade form smaller thrombi when perfused over a collagen matrix under arterial flow. Clopidogrel treated TSSC6 KO arterioles showed smaller and less stable thrombi with increased tendency to embolise in vivo. These studies demonstrate a complementary role between TSSC6 and P2Y₁₂ receptor in platelets in regulating ‘outside in’ integrin α_IIbβ₃ signalling thrombus growth and stability.