Upregulation of immunoproteasomes by nitric oxide: potential antioxidative mechanism in endothelial cells.
Nitric oxide (*NO) was shown to stimulate the proteasomal function and the ubiquitin-proteasome pathway and to ameliorate endothelial apoptotic signaling induced by oxidants. Understanding the regulatory mechanisms by which *NO stimulates proteasomes and affords cytoprotection in endothelial cells has therapeutic implications, as many vascular diseases are characterized by a deficiency in *NO. Here we report that *NO/cGMP/cAMP-induced immunoproteasome subunit expression is responsible for the increased proteasomal activities. Cells pretreated with protein kinase G and protein kinase A inhibitors markedly attenuated *NO-dependent proteasome activation. Results show that the *NO/cGMP/cAMP signaling mechanism enhanced the phosphorylation of the transcription factor cAMP-response element-binding protein, elevated the cAMP-response element-promoter activity and induced the expression of immunoproteasomal subunits (LMP2 and LMP7). *NO-dependent proteasomal activity was abrogated in cells transfected with antisense LMP2 and LMP7 oligonucleotides. Lower levels of LMP2 and LMP7 were detected in aorta of iNOS(-/-) mice compared to wild-type controls, suggesting that endogenous production of *NO is important in the basal regulation of immunoproteasome. The *NO/cGMP/cAMP signaling pathway mitigates transferrin-iron-mediated oxidative stress and apoptosis through induction of immunoproteasomes. These results provide new insights on the regulatory mechanisms by which the *NO-mediated immunoproteasome signaling pathway affords cytoprotection in endothelial cells.
Department of Biophysics and Free Radical Research Center, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
Srigiridhar
S
Kotamraju
Sadis
S
Matalon
Toshiyuki
T
Matsunaga
Tiesong
T
Shang
J M
JM
Hickman-Davis
B
B
Kalyanaraman
D000818:Animals; D000975:Antioxidants / Q000502:physiology*; D017209:Apoptosis / Q000187:drug effects; D002417:Cattle; D000242:Cyclic AMP / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D006152:Cyclic GMP / Q000502:physiology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009097:Multienzyme Complexes / Q000378:metabolism; D009569:Nitric Oxide / Q000494:pharmacology*; D052247:Nitric Oxide Synthase Type II / Q000172:deficiency; D018384:Oxidative Stress / Q000187:drug effects*; D046988:Proteasome Endopeptidase Complex / Q000187:drug effects* / Q000276:immunology / Q000502:physiology*; D015398:Signal Transduction; D015854:Up-Regulation
D000975:Antioxidants; D017362:Cyclic AMP Response Element-Binding Protein; D009097:Multienzyme Complexes; C071313:LMP-2 protein; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D000242:Cyclic AMP; D052247:Nitric Oxide Synthase Type II; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D003546:Cysteine Endopeptidases; C077436:LMP7 protein; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D006152:Cyclic GMP