These authors contributed equally to this work.
Platelet dysfunction associated with the novel Trp29Cys thromboxane A2 receptor variant
Article first published online: 13 MAR 2013
© 2012 International Society on Thrombosis and Haemostasis
Journal of Thrombosis and Haemostasis
Volume 11, Issue 3, pages 547–554, March 2013
How to Cite
The UK GAPP Study Group. Platelet dysfunction associated with the novel Trp29Cys thromboxane A2 receptor variant. J Thromb Haemost 2012; 11: 547–554., , , , , , , , , ,
- Issue published online: 13 MAR 2013
- Article first published online: 13 MAR 2013
- Accepted manuscript online: 29 DEC 2012 09:48AM EST
- Manuscript Accepted: 23 DEC 2012
- Manuscript Received: 30 OCT 2012
- platelet function disorder;
- TBXA2R gene;
- thromboxane A2 receptor;
- transmembrane domain 1
Genetic variations that affect the structure of the thromboxane A2 receptor (TP receptor) provide insights into the function of this key platelet and vascular receptor, but are very rare in unselected populations.
To determine the functional consequences of the TP receptor Trp29Cys (W29C) substitution.
We performed a detailed phenotypic analysis of an index case (P1) with reduced platelet aggregation and secretion responses to TP receptor pathway activators, and a heterozygous TP receptor W29C substitution. An analysis of the variant W29C TP receptor expressed in heterologous cells was performed.
Total TP receptor expression in platelets from P1 was similar to that of controls, but there was reduced maximum binding and reduced affinity of binding to the TP receptor antagonist [3H]SQ29548. HEK293 cells transfected with W29C TP receptor cDNA showed similar total TP receptor expression to wild-type (WT) controls. However, the TP receptor agonist U46619 was less potent at inducing rises in cytosolic free Ca2+ in HEK293 cells expressing the W29C TP receptor than in WT controls, indicating reduced receptor function. Immunofluorescence microscopy and cell surface ELISA showed intracellular retention and reduced cell surface expression of the W29C TP receptor in HEK293 cells. Consistent with the platelet phenotype, both maximum binding and the affinity of binding of [3H]SQ29548 to the W29C TP receptor were reduced compared to WT controls.
These findings extend the phenotypic description of the very rare disorder TP receptor deficiency, and show that the W29C substitution reduces TP receptor function by reducing surface receptor expression and by disrupting ligand binding.