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DOI: 10.1160/TH13-08-0672
A novel thromboxane A2 receptor N42S variant results in reduced surface expression and platelet dysfunction
Financial support: This work was supported by the British Heart Foundation and the Wellcome Trust (BHF; PG/06/038 and RG/09/007/27917, Wellcome Trust ref 093994). SJM is a BHF Senior Research Fellow and SPW holds a BHF Chair. ML is supported by the Canadian Institute of Health Research (MFE-107592) and the British Heart Foundation (PG/11/31/28835). GL holds a Wellcome Trust fellowship.Publikationsverlauf
Received:
16. August 2013
Accepted after major revision:
19. Januar 2013
Publikationsdatum:
30. November 2017 (online)
![](https://www.thieme-connect.de/media/10.1055-s-00035024/201405/lookinside/thumbnails/10-1160-th13-08-0672-1.jpg)
Summary
A small number of thromboxane receptor variants have been described in patients with a bleeding history that result in platelet dysfunction. We have identified a patient with a history of significant bleeding, who expresses a novel heterozygous thromboxane receptor variant that predicts an asparagine to serine substitution (N42S). This asparagine is conserved across all class A GPCRs, suggesting a vital role for receptor structure and function. We investigated the functional consequences of the TP receptor heterozygous N42S substitution by performing platelet function studies on platelet-rich plasma taken from the patient and healthy controls. We investigated the N42S mutation by expressing the wild-type (WT) and mutant receptor in human embryonic kidney (HEK) cells. Aggregation studies showed an ablation of arachidonic acid responses in the patient, whilst there was right-ward shift of the U46619 concentration response curve (CRC). Thromboxane generation was unaffected. Calcium mobilisation studies in cells lines showed a rightward shift of the U46619 CRC in N42S–expressing cells compared to WT. Radioligand binding studies revealed a reduction in BMax in platelets taken from the patient and in N42S–expressing cells, whilst cell studies confirmed poor surface expression. We have identified a novel thromboxane receptor variant, N42S, which results in platelet dysfunction due to reduced surface expression. It is associated with a significant bleeding history in the patient in whom it was identified. This is the first description of a naturally occurring variant that results in the substitution of this highly conserved residue and confirms the importance of this residue for correct GPCR function.
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