A novel mutation in the P2Y12 receptor and a function‐reducing polymorphism in protease‐activated receptor 1 in a patient with chronic bleeding. (May 2014)

• Record Type: Journal Article
• Authors: Patel, Y. M.; Lordkipanidzé, M.; Lowe, G. C.; Nisar, S. P.; Garner, K.; Stockley, J.; Daly, M. E.; Mitchell, M.; Watson, S. P.; Austin, S. K.; Mundell, S. J.
• Is Part Of: Journal of thrombosis and haemostasis. Volume 12:Number 5(2014:May)
• Page Start: 716
• Page End: 725
• Publication Date: 2014-05
• Subjects: Thrombosis -- Periodicals; Hemostasis -- Periodicals; Blood coagulation disorders -- Periodicals; 616.1
• DOI: 10.1111/jth.12539
• Languages: English
• ISSNs: 1538-7933

Abstract

<abstract abstract-type="main" id="jth12539-abs-0001"> <title>Summary</title> <sec id="jth12539-sec-0001" sec-type="section"> <title>Background</title> <p>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 <italic>P2RY12</italic> mutation, predicting an arginine to cysteine (R122C) substitution in the G‐protein‐coupled P2Y<sub>12</sub> 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.</p> </sec> <sec id="jth12539-sec-0002" sec-type="section"> <title>Objectives</title> <p>To determine the functional consequences of the R122C substitution for P2Y<sub>12</sub> function.</p> </sec> <sec id="jth12539-sec-0003" sec-type="section"> <title>Patient/methods</title> <p>We performed a detailed phenotypic analysis of an index case and affected family members. An analysis of the variant R122C P2Y<sub>12</sub> stably expressed in cells was also performed.</p> </sec> <sec id="jth12539-sec-0004" sec-type="section"> <title>Results</title> <p>ADP‐stimulated platelet aggregation was reduced as a result of a significant impairment of P2Y<sub>12</sub> activity in the patient and family members. Cell surface R122C P2Y<sub>12</sub> 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 <italic>F2R</italic> gene, which encodes protease‐activated receptor 1 (PAR‐1), that has been shown to be associated with reduced PAR‐1 receptor activity.</p> </sec> <sec id="jth12539-sec-0005" sec-type="section"> <title>Conclusions</title> <p>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.</p> </sec> </abstract>