title: Inducible nitric oxide synthase aggresome formation is mediated by nitric oxide.
abstract: Nitric oxide (NO) generated by inducible NO synthase (iNOS) contributes critically to inflammatory injury and host defense. While previously thought as a soluble protein, iNOS was recently reported to form aggresomes inside cells. But what causes iNOS aggresome formation is unknown. Here we provide evidence demonstrating that iNOS aggresome formation is mediated by its own product NO. Exposure to inflammatory stimuli (lipopolysaccharide and interferon-γ) induced robust iNOS expression in mouse macrophages. While initially existing as a soluble protein, iNOS progressively formed protein aggregates as a function of time. Aggregated iNOS was inactive. Treating the cells with the NOS inhibitor N-nitro-L-arginine methyl ester (L-NAME) blocked NO production from iNOS without affecting iNOS expression. However, iNOS aggregation in cells was prevented by L-NAME. The preventing effect of NO blockade on iNOS aggresome formation was directly observed in GFP-iNOS-transfected cells by fluorescence imaging. Moreover, iNOS aggresome formation could be recaptured by adding exogenous NO to L-NAME-treated cells. These studies demonstrate that iNOS aggresome formation is caused by NO. The finding that NO induces iNOS aggregation and inactivation suggests aggresome formation as a feedback inhibition mechanism in iNOS regulation.
authors.affiliation: Davis Heart and Lung Research Institute, Division of Cardiovascular Medicine, Department of Molecular and Cellular Biochemistry, The Ohio State University College of Medicine, 473 West 12th Avenue, Columbus, OH 43210, USA.
authors.forename: Tingting
authors.initials: T
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Xia
mesh_terms: D000818:Animals; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D025461:Feedback, Physiological; D057809:HEK293 Cells; D006801:Humans; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology; D051379:Mice; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D019331:NG-Nitroarginine Methyl Ester