The extracellular Ero1α/PDI electron transport system regulates platelet function by increasing glutathione reduction potential

Protein disulfide isomerase (PDI), an oxidoreductase, possesses two vicinal cysteines in the -Cys-Gly-His-Cys-motif that either form a disulfide bridge (S-S) or exist in a sulfhydryl form (-SH), forming oxidized or reduced PDI, respectively. PDI has been proven to be critical for platelet aggregation, thrombosis, and hemostasis, and PDI inhibition is being evaluated as a novel antithrombotic strategy. The redox states of functional PDI during the regulation of platelet aggregation, however, remain to be elucidated. Endoplasmic reticulum (ER) oxidoreductin-1 alpha (Ero1 alpha) and PDI constitute the pivotal oxidative folding pathway in the ER and play an important role in ER redox homeostasis. Whether Ero1 alpha and PDI constitute an extracellular electron transport pathway to mediate platelet aggregation is an open question. Here, we found that oxidized but not reduced PDI promotes platelet aggregation. On the platelet surface, Ero1 alpha constitutively oxidizes PDI and further regulates platelet aggregation in a glutathione-dependent manner. The Ero1 alpha/PDI system oxidizes reduced glutathione (GSH) and establishes a reduction potential optimal for platelet aggregation. Therefore, platelet aggregation is mediated by the Ero1 alpha-PDI-GSH electron transport system on the platelet surface. We further showed that targeting the functional interplay between PDI and Ero1 alpha by small molecule inhibitors may be a novel strategy for antithrombotic therapy.

Automated summary

Protein disulfide isomerase (PDI) plays a critical role in platelet aggregation, thrombosis, and hemostasis, and inhibiting PDI may be a novel antithrombotic strategy. The interaction between endoplasmic reticulum oxidoreductin-1 alpha (Ero1 alpha) and PDI in mediating platelet aggregation through an extracellular electron transport pathway is investigated. The study reveals that oxidized PDI promotes platelet aggregation, and Ero1 alpha regulates platelet aggregation in a glutathione-dependent manner.