title: Dendritic cell IL-1α and IL-1β are polyubiquitinated and degraded by the proteasome.
abstract: IL-1α and β are key players in the innate immune system. The secretion of these cytokines by dendritic cells (DC) is integral to the development of proinflammatory responses. These cytokines are not secreted via the classical secretory pathway. Instead, 2 independent processes are required; an initial signal to induce up-regulation of the precursor pro-IL-1α and -β, and a second signal to drive cleavage and consequent secretion. Pro-IL-1α and -β are both cytosolic and thus, are potentially subject to post-translational modifications. These modifications may, in turn, have a functional outcome in the context of IL-1α and -β secretion and hence inflammation. We report here that IL-1α and -β were degraded intracellularly in murine bone marrow-derived DC and that this degradation was dependent on active cellular processes. In addition, we demonstrate that degradation was ablated when the proteasome was inhibited, whereas autophagy did not appear to play a major role. Furthermore, inhibition of the proteasome led to an accumulation of polyubiquitinated IL-1α and -β, indicating that IL-1α and -β were polyubiquitinated prior to proteasomal degradation. Finally, our investigations suggest that polyubiquitination and proteasomal degradation are not continuous processes but instead are up-regulated following DC activation. Overall, these data highlight that IL-1α and -β polyubiquitination and proteasomal degradation are central mechanisms in the regulation of intracellular IL-1 levels in DC.
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and Joseph.ainscough@postgrad.manchester.ac.uk.
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Ainscough
authors.affiliation: the Procter & Gamble Company Co., Cincinnati, Ohio 45253.
authors.forename: G
authors.initials: G
authors.lastname: Frank Gerberick
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and.
authors.forename: Maryam
authors.initials: M
authors.lastname: Zahedi-Nejad
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and.
authors.forename: Gloria
authors.initials: G
authors.lastname: Lopez-Castejon
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and.
authors.forename: David
authors.initials: D
authors.lastname: Brough
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and.
authors.forename: Ian
authors.initials: I
authors.lastname: Kimber
authors.affiliation: From the Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom and.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Dearman
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003713:Dendritic Cells / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D007375:Interleukin-1 / Q000235:genetics / Q000378:metabolism; D053582:Interleukin-1alpha / Q000235:genetics / Q000378:metabolism*; D053583:Interleukin-1beta / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008807:Mice, Inbred BALB C; D025821:Polyubiquitin / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D015853:Cysteine Proteinase Inhibitors; D007375:Interleukin-1; D053582:Interleukin-1alpha; D053583:Interleukin-1beta; D007976:Leupeptins; D008070:Lipopolysaccharides; D011498:Protein Precursors; C043830:interleukin 1 precursor; D025821:Polyubiquitin; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde
keywords: Dendritic Cell; IL-1α IL-1β; Inflammation; Interleukin 1 (IL-1); Proteasome; Ubiquitylation (Ubiquitination)