title: E3 ubiquitin ligase NKLAM positively regulates macrophage inducible nitric oxide synthase expression.
abstract: Stimulated macrophages generate potent anti-microbial reactive oxygen and nitrogen species within their phagosomes. Previous studies have shown that the E3 ubiquitin ligase natural killer lytic-associated molecule (NKLAM) is a macrophage phagosomal protein that plays a role in macrophage anti-bacterial activity. In vivo, NKLAM-knockout (KO) mice produce less nitric oxide (NO) upon exposure to lipopolysaccharide (LPS) than wild type (WT) mice. In vitro, we found that NO production and inducible nitric oxide synthase (iNOS) protein were diminished in LPS-stimulated NKLAM-KO bone marrow-derived and splenic macrophages. Additionally, LPS-stimulated NKLAM-KO macrophages displayed defects in STAT1 tyrosine phosphorylation and production of interferon beta (IFNβ). The JAK/STAT pathway is critical for the production of IFNβ, which augments iNOS protein expression in mice. iNOS protein expression is also regulated by the transcription factor NFκB, thus we investigated whether NKLAM influences NFκB function. LPS-stimulated NKLAM-KO macrophages showed evidence of delayed nuclear translocation of the NFκB subunit p65. This was associated with a reduction in p65/DNA colocalization. The defect in p65 translocation was independent of IKBα degradation. NKLAM-KO macrophages also expressed less p65 and showed evidence of defective p65 phosphorylation at serine 536. Importantly, LPS-stimulated NKLAM-KO macrophages have diminished NFκB transcriptional activity as assessed by transfection of a luciferase reporter plasmid. Collectively, our data implicate NKLAM as a novel modulator of macrophage iNOS expression.
authors.affiliation: Department of Pathology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States.
authors.forename: Donald W
authors.initials: DW
authors.lastname: Lawrence
authors.affiliation: Department of Pathology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States.
authors.forename: Gail
authors.initials: G
authors.lastname: Gullickson
authors.affiliation: Department of Pathology, Saint Louis University School of Medicine, St. Louis, MO 63104, United States; Veterans Administration Medical Center, St. Louis, MO 63106, United States. Electronic address: kornblut@slu.edu.
authors.forename: Jacki
authors.initials: J
authors.lastname: Kornbluth
mesh_terms: D000818:Animals; D002467:Cell Nucleus; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D016899:Interferon-beta / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D021381:Protein Transport; D059748:Proteolysis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000378:metabolism; D051996:Transcription Factor RelA / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D008070:Lipopolysaccharides; D008565:Membrane Proteins; C120864:NK lytic-associated molecule; D012333:RNA, Messenger; D050794:STAT1 Transcription Factor; D051996:Transcription Factor RelA; D009569:Nitric Oxide; D016899:Interferon-beta; D052247:Nitric Oxide Synthase Type II
keywords: Innate immunity; Macrophage; NFκB; NKLAM; Nitric oxide; iNOS; p65