title: LPS-induced formation of immunoproteasomes: TNF-α and nitric oxide production are regulated by altered composition of proteasome-active sites.
abstract: Stimulation of mouse macrophages with LPS leads to tumor necrosis factor (TNF-α) secretion and nitric oxide (NO) release at different times through independent signaling pathways. While the precise regulatory mechanisms responsible for these distinct phenotypic responses have not been fully delineated, results of our recent studies strongly implicate the cellular cytoplasmic ubiquitin-proteasome pathway as a key regulator of LPS-induced macrophage inflammatory responses. Our objective in this study was to define the relative contribution of specific proteasomal active-sites in induction of TNF-α and NO after LPS treatment of RAW 264.7 macrophages using selective inhibitors of these active sites. Our data provide evidence that LPS stimulation of mouse macrophages triggers a selective increase in the levels of gene and protein expression of the immunoproteasomes, resulting in a modulation of specific functional activities of the proteasome and a corresponding increase in NO production as compared to untreated controls. These findings suggest the LPS-dependent induction of immunoproteasome. In contrast, we also demonstrate that TNF-α expression is primarily dependent on both the chymotrypsin- and the trypsin-like activities of X, Y, Z subunits of the proteasome. Proteasome-associated post-acidic activity alone also contributes to LPS-induced expression of TNF-α. Taken together; our results indicate that LPS-induced TNF-α in macrophages is differentially regulated by each of the three proteasome activities. Since addition of proteasome inhibitors to mouse macrophages profoundly affects the degradation of proteins involved in signal transduction, we conclude that proteasome-specific degradation of several signaling proteins is likely involved in differential regulation of LPS-dependent secretion of proinflammatory mediators.
authors: Department of Basic Medical Science, Shock/Trauma Research Center, School of Medicine, University of Missouri, 2411 Holmes Street, Kansas City, MO 64108, USA.
authors: Julia
authors: J
authors: Reis
authors: Xiu Qin
authors: XQ
authors: Guan
authors: Alexei F
authors: AF
authors: Kisselev
authors: Christopher J
authors: CJ
authors: Papasian
authors: Asaf A
authors: AA
authors: Qureshi
authors: David C
authors: DC
authors: Morrison
authors: Charles W
authors: CW
authors: Van Way
authors: Stefanie N
authors: SN
authors: Vogel
authors: Nilofer
authors: N
authors: Qureshi
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D020134:Catalytic Domain; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D018836:Inflammation Mediators / Q000378:metabolism; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis*; D011070:Poly I-C / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
chemical_list: D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D021122:Protein Subunits; D014409:Tumor Necrosis Factor-alpha; C067713:lactacystin; C071313:LMP-2 protein; D009569:Nitric Oxide; D007371:Interferon-gamma; D003546:Cysteine Endopeptidases; C077436:LMP7 protein; D046988:Proteasome Endopeptidase Complex; C478802:Psmb5 protein, mouse; D011070:Poly I-C; D000111:Acetylcysteine