Ero1α is expressed on blood platelets in association with protein-disulfide isomerase and contributes to redox-controlled remodeling of αIIbβ3

Abstract

Recent evidence supports a role of protein-disulfide isomerase (PDI) in redox-controlled remodeling of the exofacial domains of α IIbβ3 in blood platelets. The aim of this study was to explain whether Ero1α can be responsible for extracellular reoxidation of the PDI active site. We showed that Ero1α can be found on platelets and is rapidly recruited to the cell surface in response to platelet agonists. It is physically associated with PDI and αIIbβ3, as suggested by colocalization analysis in confocal microscopy and confirmed by immunoprecipitation experiments. Apart from monomeric oxidized Ero1α, anti-αIIbβ3 immunoprecipitates showed the presence of several Ero1α-positive bands that corresponded to the complexes αIIbβ3-PDI-Ero1α, PDI-Ero1α, and Ero1α-Ero1α dimers. It binds more efficiently to the activated αIIbβ3 conformer, and its interaction is inhibited by RGD peptides. Ero1α appears to be involved in the regulation of αIIbβ3 receptor activity because of the following: (a) blocking the cell surface Ero1α by antibodies leads to a decrease in platelet aggregation in response to agonists and a decrease in fibrinogen and PAC-1 binding, and (b) transfection of MEG01 with Ero1α increases αIIbβ3 receptor activity, as indicated by increased binding of fibrinogen. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.