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.
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.
Authors: Anna Lecchi; Eti A Femia; Silvia Paoletta; Arnaud Dupuis; Philippe Ohlmann; Christian Gachet; Kenneth A Jacobson; Katharina Machura; Gian M Podda; Barbara Zieger; Marco Cattaneo Journal: Hamostaseologie Date: 2016-08-04 Impact factor: 1.778
Authors: Anna Lecchi; Cristina Razzari; Silvia Paoletta; Arnaud Dupuis; Lea Nakamura; Philippe Ohlmann; Christian Gachet; Kenneth A Jacobson; Barbara Zieger; Marco Cattaneo Journal: Blood Date: 2014-11-26 Impact factor: 22.113
Authors: V C Leo; N V Morgan; D Bem; M L Jones; G C Lowe; M Lordkipanidzé; S Drake; M A Simpson; P Gissen; A Mumford; S P Watson; M E Daly Journal: J Thromb Haemost Date: 2015-01-27 Impact factor: 5.824
Authors: Matthew L Jones; Jane E Norman; Neil V Morgan; Stuart J Mundell; Marie Lordkipanidzé; Gillian C Lowe; Martina E Daly; Michael A Simpson; Sian Drake; Steve P Watson; Andrew D Mumford Journal: Thromb Haemost Date: 2015-01-08 Impact factor: 5.249
Authors: Marie Lordkipanidzé; Gillian C Lowe; Nicholas S Kirkby; Melissa V Chan; Martina H Lundberg; Neil V Morgan; Danai Bem; Shaista P Nisar; Vincenzo C Leo; Matthew L Jones; Stuart J Mundell; Martina E Daly; Andrew D Mumford; Timothy D Warner; Steve P Watson Journal: Blood Date: 2014-01-09 Impact factor: 22.113
Authors: Riyaad Aungraheeta; Alexandra Conibear; Mark Butler; Eamonn Kelly; Sven Nylander; Andrew Mumford; Stuart J Mundell Journal: Blood Date: 2016-09-30 Impact factor: 22.113