The disulfide isomerase ERp57 mediates platelet aggregation, hemostasis, and thrombosis.
A close homologue to protein disulfide isomerase (PDI) called ERp57 forms disulfide bonds in glycoproteins in the endoplasmic reticulum and is expressed on the platelet surface. We generated 2 rabbit Abs to ERp57. One Ab strongly inhibited ERp57 in a functional assay and strongly inhibited platelet aggregation. There was minimal cross-reactivity of this Ab with PDI by Western blot or in the functional assay. This Ab substantially inhibited activation of the αIIbβ3 fibrinogen receptor and P-selectin expression. Furthermore, adding ERp57 to platelets potentiated aggregation. In contrast, adding a catalytically inactive ERp57 inhibited platelet aggregation. When infused into mice the inactive ERp57 prolonged the tail bleeding times. We generated 2 IgG2a mAbs that reacted with ERp57 by immunoblot. One of these Abs inhibited both ERp57 activity and platelet aggregation. The other Ab did not inhibit ERp57 activity or platelet aggregation. The inhibitory Ab inhibited activation of αIIbβ3 and P-selectin expression, prolonged tail bleeding times, and inhibited FeCl(3)-induced thrombosis in mice. Finally, we found that a commonly used mAb to PDI also inhibited ERp57 activity. We conclude that a glycoprotein-specific member of the PDI family, ERp57, is required for platelet aggregation, hemostasis, and thrombosis.
The Cyrus Tang Hematology Center, Jiangsu Institute of Hematology, First Affiliated Hospital, Soochow University, Suzhou, China.
Yi
Y
Wu
Syed S
SS
Ahmad
Junsong
J
Zhou
Lu
L
Wang
Matthew P
MP
Cully
David W
DW
Essex
D000818:Animals; D003545:Cysteine / Q000235:genetics; D006487:Hemostasis / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000494:pharmacology / Q000502:physiology; D010974:Platelet Aggregation / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D019704:Protein Disulfide-Isomerases / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D011817:Rabbits; D012694:Serine / Q000235:genetics; D013927:Thrombosis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism
D050505:Mutant Proteins; D012694:Serine; C513195:Pdia3 protein, mouse; D019704:Protein Disulfide-Isomerases; D003545:Cysteine