An intact PDZ motif is essential for correct P2Y12 purinoceptor traffic in human platelets

The platelet P2Y(12) purinoceptor (P2Y(12)R), which plays a crucial role in hemostasis, undergoes internalization and subsequent recycling to maintain receptor responsiveness, processes that are essential for normal platelet function. Here, we observe that P2Y(12)R function is compromised after deletion or mutation of the 4 amino acids at the extreme C-terminus of this receptor (ETPM), a putative postsynaptic density 95/disc large/zonula occludens-1 (PDZ)-binding motif. In cell line models, removal of this sequence or mutation of one of its core residues (P341A), attenuates receptor internalization and receptor recycling back to the membrane, thereby blocking receptor resensitization. The physiologic significance of these findings in the regulation of platelet function is shown by identification of a patient with a heterozygous mutation in the PDZ binding sequence of their P2Y(12)R (P341A) that is associated with reduced expression of the P2Y(12)R on the cell surface. Importantly, platelets from this subject showed significantly compromised P2Y(12)R recycling, emphasizing the importance of the extreme C-terminus of this receptor to ensure correct receptor traffic.