A nonsynonymous SNP in the ITGB3 gene disrupts the conserved membrane-proximal cytoplasmic salt bridge in the αIIbβ3 integrin and cosegregates dominantly with abnormal proplatelet formation and macrothrombocytopenia
| Autor: | Cedric Ghevaert, Michael Laffan, Stephen F. Garner, Elisabeth Schaffner-Reckinger, Nicholas A. Watkins, Nelly Kieffer, Jonathan Stephens, Philip G. de Groot, Najet Debili, William Vainchenker, Alexandre Salsmann, James A. Huntington, Graham A. Smith, Angela Rankin, Willem H. Ouwehand |
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| Rok vydání: | 2008 |
| Předmět: |
Adult
Blood Platelets Male Immunology Integrin Mutation Missense Gene Expression CHO Cells Platelet Glycoprotein GPIIb-IIIa Complex Transfection medicine.disease_cause Fibrinogen Polymorphism Single Nucleotide Biochemistry Conserved sequence Cricetulus Von Willebrand factor Cricetinae von Willebrand Factor medicine Animals Humans Platelet Thrombopoiesis Mutation biology Integrin beta3 Fibrinogen binding Cell Biology Hematology Thrombocytopenia Molecular biology Pedigree Platelet Glycoprotein GPIb-IX Complex biology.protein Female Megakaryocytes Protein Binding medicine.drug |
| Zdroj: | Blood. 111:3407-3414 |
| ISSN: | 1528-0020 0006-4971 |
| DOI: | 10.1182/blood-2007-09-112615 |
| Popis: | We report a 3-generation pedigree with 5 individuals affected with a dominantly inherited macrothrombocytopenia. All 5 carry 2 nonsynonymous mutations resulting in a D723H mutation in the beta3 integrin and a P53L mutation in glycoprotein (GP) Ibalpha. We show that GPIbalpha-L53 is phenotypically silent, being also present in 3 unaffected pedigree members and in 7 of 1639 healthy controls. The beta3-H723 causes constitutive, albeit partial, activation of the alphaIIbbeta3 complex by disruption of the highly conserved cytoplasmic salt bridge with arginine 995 in the alphaIIb integrin as evidenced by increased PAC-1 but not fibrinogen binding to the patients' resting platelets. This was confirmed in CHO alphaIIbbeta3-H723 transfectants, which also exhibited increased PAC-1 binding, increased adhesion to von Willebrand factor (VWF) in static conditions and to fibrinogen under shear stress. Crucially, we show that in the presence of fibrinogen, alphaIIbbeta3-H723, but not wild-type alphaIIbbeta3, generates a signal that leads to the formation of proplatelet-like protrusions in transfected CHO cells. Abnormal proplatelet formation was confirmed in the propositus's CD34+ stem cell-derived megakaryocytes. We conclude that the constitutive activation of the alphaIIbbeta3-H723 receptor causes abnormal proplatelet formation, leading to incorrect sizing of platelets and the thrombocytopenia observed in the pedigree. |
| Databáze: | OpenAIRE |
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