C560Rβ3 caused platelet integrin αII b β3 to bind fibrinogen continuously, but resulted in a severe bleeding syndrome and increased murine mortality. J Thromb Haemost 2013 Jun;11(6):1163-71
Date
04/05/2013Pubmed ID
23551977Pubmed Central ID
PMC3702628DOI
10.1111/jth.12209Scopus ID
2-s2.0-84883256631 (requires institutional sign-in at Scopus site) 17 CitationsAbstract
BACKGROUND AND OBJECTIVES: β(3)-Deficient megakaryocytes were modified by human β(3)-lentivirus transduction and transplantation to express sufficient levels of a C560Rβ(3) amino acid substitution, for investigation of how an activated αII b β(3) conformation affects platelets in vivo in mice.
PATIENT/METHODS: As in our previous report of an R560β(3) mutation in a patient with Glanzmann thrombasthenia, R560β(3) murine platelets spontaneously bound antibody that only recognizes activated αII b β3 bound to its ligand, fibrinogen.
RESULTS: With this murine model, we showed that αII b -R560β3 mutation-mediated continuous binding of fibrinogen occurred in the absence of P-selectin surface expression, indicating that the integrin was in an active conformation, although the platelets circulated in a quiescent manner. Remarkably, only 35% of R560β(3) 'mutant' mice survived for 6 months after transplantation, whereas 87% of C560β(3) 'wild-type' mice remained alive. Pathologic examination revealed that R560β(3) mice had enlarged spleens with extramedullary hematopoiesis and increased hemosiderin, indicating hemorrhage. R560β(3) megakaryocytes and platelets showed abnormal morphology and irregular granule distribution. Interestingly, R560β(3) washed platelets could aggregate upon simultaneous addition of fibrinogen and physiologic agonists, but aggregation failed when platelets were exposed to fibrinogen before activation in vitro and in vivo.
CONCLUSIONS: The results demonstrate that continuous occupancy of αIIb β3 with fibrinogen disrupts platelet structure and function, leading to hemorrhagic death consistent with Glanzmann thrombasthenia rather than a thrombotic state.
Author List
Fang J, Nurden P, North P, Nurden AT, Du LM, Valentin N, Wilcox DAAuthors
Paula E. North MD, PhD Professor in the Pathology department at Medical College of WisconsinDavid A. Wilcox PhD Professor in the Pediatrics department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
AnimalsBlood Platelets
Bone Marrow Cells
Fibrinogen
Hemorrhage
Humans
Integrin beta3
Lentivirus
Megakaryocytes
Mice
Mutation
P-Selectin
Platelet Aggregation
Platelet Glycoprotein GPIIb-IIIa Complex
Protein Binding
Protein Conformation
Syndrome
Thrombasthenia
Thrombosis
