Protein disulfide isomerase capture during thrombus formation in vivo depends on the presence of β3 integrins

Extracellular protein disulfide isomerase (PDI) is required for platelet thrombus formation and fibrin generation after arteriolar wall injury in live mice. PDI is secreted from platelets and endothelial cells on cellular activation, but the mechanism of capture of secreted PDI within the injured vasculature is unknown. We establish that, like the endothelial beta 3 integrin alpha(V)beta(3), the platelet integrin alpha(IIb)beta(3) binds PDI. PDI also binds to recombinant beta 3. Using intravital microscopy, we demonstrate that PDI accumulation at the site of laser-induced arteriolar wall injury is markedly reduced in beta 3-null (beta 3(-/-)) mice, and neither a platelet thrombus nor fibrin is generated at the vessel injury site. The absence of fibrin after vascular injury in beta 3(-/-) mice is because of the absence of extracellular PDI. To evaluate the relative importance of endothelial alpha(V)beta(3) versus platelet alpha(IIb)beta(3) or alpha(V)beta(3), we performed reciprocal bone marrow transplants on wildtype and beta 3(-/-) mice. PDI accumulation and platelet thrombus formation were markedly decreased after vessel injury in wild-type mice transplanted with beta 3(-/-) bone marrow or in beta 3(-/-) mice transplanted with wild-type bone marrow. These results indicate that both endothelial and platelet beta 3 integrins contribute to extracellular PDI binding at the vascular injury site. (Blood. 2012;120(3):647-655)