Abstract 15768: Novel Role of Redox-sensitive SUMOylation of Cu Transport Protein Atox1 in Inflammation and Atherosclerosis
Background: Copper (Cu) is implicated in inflammation and atherosclerosis with unknown mechanism. Cu chaperone Atox1 is recently discovered to function as a Cu-dependent transcription factor for NADPH oxidase organizer p47phox to promote ROS-dependent inflammatory gene expression in endothelial cells (ECs). However, mechanism of Atox1 nuclear translocation and its role in atherosclerosis remain unknown. SUMOylation can alter localization and transcriptional activity of proteins.
Hypothesis: SUMOylation is involved in transcription factor function of Atox1 which promotes atherosclerosis.
Results: In human ECs, Atox1 knockdown with siRNA, or Cu-chelator BCS inhibited TNFα- induced early and late phase of ROS production (70±8.6%) and its downstream VCAM1/ICAM1 expression and monocyte adhesion. Mechanistically, TNFα promoted Atox1/p47phox binding, which stimulated p47phox membrane translocation to produce early ROS, which was required for Cys oxidation of Cu importer CTR1 that imports Cu to Atox1 as well as Atox1 SUMOylation. Concomitantly these events enhanced Atox1 binding to adaptor protein TRAF4 in p47phox- and CTR1/Cu-dependent manner, which promoted the Atox1 nuclear translocation and p47phox transcription-dependent ROS production at late phase. Of note, SUMOylation defective mutant Atox1-K3R or Cu bind defective mutant Atox1C12,15S blocked TNFα-induced Atox1/TRAF4 binding; Atox1 nuclear translocation (80±6.8%); and p47phox and adhesion molecules VCAM1/ICAM1 expression. Functional significance of these proinflammatory effects of Atox1 in vivo was demonstrated by using arterial carotid ligation with high-fat feeding for 3 weeks in apolipoprotein E(ApoE-/-) and ApoE-/-Atox1-/- mice. Atherosclerotic lesion (40±3.6%, Oil-O-red staining), inflammatory cell recruitment (50±7.8%, Mac3+) and extracellular matrix deposition (Masson’s Trichrome) were markedly decreased in ApoE-/-Atox1-/- compared to ApoE-/-.
Conclusions: Atox1 SUMOylation plays an important role in ROS mediated Cu-dependent Atox1/TRAF4 binding, which is required for Atox1 nuclear translocation to promote p47phox/ROS-dependent adhesion molecule expression in ECs, thereby accelerating inflammatory cell recruitment and atherosclerosis.
Author Disclosures: A. Das: None. S. Varadarajan: None. B. Surenkhuu: None. J. Kweon: None. J. Abe: None. M. Ushio-Fukai: None. T. Fukai: None.
- © 2016 by American Heart Association, Inc.