The PlA2 polymorphism of integrin β3 enhances outside-in signaling and adhesive functions

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Abstract
Genetic factors are believed to influence the development of arterial thromboses. Because integrin αIIbβ3 plays a crucial role in thrombus formation, we analyzed receptor adhesive properties using Chinese hamster ovary and human kidney embryonal 293 cells overexpressing the PlA1 or PlA2 polymorphic forms of αIIbβ3. Soluble fibrinogen binding was no different between PlA1 and PlA2 cells, either in a resting state or when αIIbβ3 was activated with anti-LIBS6. PlA1 and PlA2 cells bound equivalently to immobilized fibronectin. In contrast, significantly more PlA2 cells bound to immobilized fibrinogen in an αIIbβ3-dependent manner than did PlA1 cells. Disruption of the actin cytoskeleton by cytochalasin D abolished the increased binding of PlA2 cells. Compared with PlA1 cells, PlA2 cells exhibited a greater extent of polymerized actin and cell spreading, enhanced tyrosine phosphorylation of pp125FAK, and greater fibrin clot retraction. These adhesion differences appear to depend on a signaling mechanism sensitive to receptor occupancy. Thus, the PlA2 polymorphism altered integrin-mediated functions of adhesion, spreading, actin cytoskeleton rearrangement, and clot retraction.