A novel mutation in the P2Y12 receptor and a function-reducing polymorphism in protease-activated receptor 1 in a patient with chronic bleeding

J Thromb Haemost. 2014 May;12(5):716-25. doi: 10.1111/jth.12539.


Background: The study of patients with bleeding problems is a powerful approach in determining the function and regulation of important proteins in human platelets. We have identified a patient with a chronic bleeding disorder expressing a homozygous P2RY(12) mutation, predicting an arginine to cysteine (R122C) substitution in the G-protein-coupled P2Y(12) receptor. This mutation is found within the DRY motif, which is a highly conserved region in G-protein-coupled receptors (GPCRs) that is speculated to play a critical role in regulating receptor conformational states.

Objectives: To determine the functional consequences of the R122C substitution for P2Y(12) function.

Patient/methods: We performed a detailed phenotypic analysis of an index case and affected family members. An analysis of the variant R122C P2Y(12) stably expressed in cells was also performed.

Results: ADP-stimulated platelet aggregation was reduced as a result of a significant impairment of P2Y(12) activity in the patient and family members. Cell surface R122C P2Y(12) expression was reduced both in cell lines and in platelets; in cell lines, this was as a consequence of agonist-independent internalization followed by subsequent receptor trafficking to lysosomes. Strikingly, members of this family also showed reduced thrombin-induced platelet activation, owing to an intronic polymorphism in the F2R gene, which encodes protease-activated receptor 1 (PAR-1), that has been shown to be associated with reduced PAR-1 receptor activity.

Conclusions: Our study is the first to demonstrate a patient with deficits in two stimulatory GPCR pathways that regulate platelet activity, further indicating that bleeding disorders constitute a complex trait.

Keywords: P2Y12 purinoceptor; bleeding disorder due to P2RY12 defect; blood platelets; point mutation; receptors, G-protein-coupled.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs
  • Blood Platelets / cytology*
  • Cell Line, Tumor
  • Chronic Disease
  • Female
  • Hemorrhage / enzymology*
  • Homozygote
  • Humans
  • Male
  • Mutation*
  • Phenotype
  • Platelet Activation / drug effects
  • Platelet Aggregation / drug effects
  • Point Mutation
  • Polymorphism, Genetic*
  • Protein Conformation
  • Receptor, PAR-1 / genetics*
  • Receptor, PAR-1 / physiology
  • Receptors, G-Protein-Coupled / metabolism
  • Receptors, Purinergic P2Y12 / genetics*
  • Sequence Analysis, DNA


  • P2RY12 protein, human
  • Receptor, PAR-1
  • Receptors, G-Protein-Coupled
  • Receptors, Purinergic P2Y12