Heat Shock Protein 90α–Dependent Translocation of Annexin II to the Surface of Endothelial Cells Modulates Plasmin Activity in the Diabetic Rat Aorta

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Abstract
The goals of this article were (1) to identify cell surface proteins whose expression was regulated by diabetes and (2) to assess their contribution to diabetic complications. We purified heat shock protein 90α (Hsp90α) from the membrane fraction of high glucose–treated endothelial cells (ECs) as a binding partner for a diabetes-specific phage. Further investigation revealed that high glucose elevated cell surface Hsp90α in cultured cells, and that diabetes increased the amount of Hsp90α on the luminal surface of the aorta. We also found that high glucose or diabetes promoted the association of Hsp90α with annexin II and increased the expression of annexin II on the surface of aortic ECs. Finally, plasmin activity was increased by high glucose or diabetes, and this change was partially reversed with an annexin II antibody. These findings reveal a novel glucose-regulated interaction between Hsp90α and annexin II, and raise the possibility that increased expression of annexin II, which promotes the generation of plasmin, is linked to clotting abnormalities associated with the diabetic state.