title: Endotoxin tolerance impairs IL-1 receptor-associated kinase (IRAK) 4 and TGF-beta-activated kinase 1 activation, K63-linked polyubiquitination and assembly of IRAK1, TNF receptor-associated factor 6, and IkappaB kinase gamma and increases A20 expression.
abstract: Endotoxin tolerance reprograms Toll-like receptor 4 responses by impairing LPS-elicited production of pro-inflammatory cytokines without inhibiting expression of anti-inflammatory or anti-microbial mediators. In septic patients, Toll-like receptor tolerance is thought to underlie decreased pro-inflammatory cytokine expression in response to LPS and increased incidence of microbial infections. The impact of endotoxin tolerance on recruitment, post-translational modifications and signalosome assembly of IL-1 receptor-associated kinase (IRAK) 4, IRAK1, TNF receptor-associated factor (TRAF) 6, TGF-β-activated kinase (TAK) 1, and IκB kinase (IKK) γ is largely unknown. We report that endotoxin tolerization of THP1 cells and human monocytes impairs LPS-mediated receptor recruitment and activation of IRAK4, ablates K63-linked polyubiquitination of IRAK1 and TRAF6, compromises assembly of IRAK1-TRAF6 and IRAK1-IKKγ platforms, and inhibits TAK1 activation. Deficiencies in these signaling events in LPS-tolerant cells coincided with increased expression of A20, an essential deubiquitination enzyme, and sustained A20-IRAK1 associations. Overexpression of A20 inhibited LPS-induced activation of NF-κB and ablated NF-κB reporter activation driven by ectopic expression of MyD88, IRAK1, IRAK2, TRAF6, and TAK1/TAB1, while not affecting the responses induced by IKKβ and p65. A20 shRNA knockdown abolished LPS tolerization of THP1 cells, mechanistically linking A20 and endotoxin tolerance. Thus, deficient LPS-induced activation of IRAK4 and TAK1, K63-linked polyubiquitination of IRAK1 and TRAF6, and disrupted IRAK1-TRAF6 and IRAK1-IKKγ assembly associated with increased A20 expression and A20-IRAK1 interactions are new determinants of endotoxin tolerance.
authors.affiliation: From the Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201 and.
authors.forename: Yanbao
authors.initials: Y
authors.lastname: Xiong
authors.affiliation: From the Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201 and.
authors.forename: Fu
authors.initials: F
authors.lastname: Qiu
authors.affiliation: From the Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201 and.
authors.forename: Wenji
authors.initials: W
authors.lastname: Piao
authors.affiliation: From the Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201 and.
authors.forename: Chang
authors.initials: C
authors.lastname: Song
authors.affiliation: NIDCR, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Larry M
authors.initials: LM
authors.lastname: Wahl
authors.affiliation: From the Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland 21201 and. Electronic address: amedvedev@som.umaryland.edu.
authors.forename: Andrei E
authors.initials: AE
authors.lastname: Medvedev
mesh_terms: D002460:Cell Line; D004268:DNA-Binding Proteins; D004351:Drug Resistance / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D009000:Monocytes / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000235:genetics; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D054875:Ubiquitination / Q000187:drug effects*; D000099151:MAP Kinase Kinase Kinase 7
chemical_list: D004268:DNA-Binding Proteins; D051550:I-kappa B Kinase; D053592:Interleukin-1 Receptor-Associated Kinases; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D020930:MAP Kinase Kinase Kinases; D053594:Myeloid Differentiation Factor 88; D009687:Nuclear Proteins; D048029:TNF Receptor-Associated Factor 6; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D000099151:MAP Kinase Kinase Kinase 7; C507779:MYD88 protein, human; C507768:IRAK1 protein, human; C507773:IRAK4 protein, human; C076529:TNFAIP3 protein, human