title: TRAF6 and A20 regulate lysine 63-linked ubiquitination of Beclin-1 to control TLR4-induced autophagy.
abstract: Autophagy delivers cytoplasmic constituents to autophagolysosomes and is linked to both innate and adaptive immunity. Toll-like receptor 4 (TLR4) signaling induces autophagy and recruits Beclin-1, the mammalian homolog of yeast Atg6, to the receptor complex. We found that tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6)-mediated, Lys(63) (K63)-linked ubiquitination of Beclin-1 is critical for TLR4-triggered autophagy in macrophages. Two TRAF6-binding motifs in Beclin-1 facilitated the binding of TRAF6 and the ubiquitination of Beclin-1. Lys(117), which is strategically located in the Bcl-2 homology 3 (BH3) domain of Beclin-1, was a major site for K63-linked ubiquitination. The deubiquitinating enzyme A20 reduced the extent of K63-linked ubiquitination of Beclin-1 and limited the induction of autophagy in response to TLR signaling. Treatment of macrophages with either interferon-gamma or interleukin-1 also triggered the K63-linked ubiquitination of Beclin-1 and the formation of autophagosomes. These results indicate that the status of K63-linked ubiquitination of Beclin-1 plays a key role in regulating autophagy during inflammatory responses.
authors.affiliation: B Cell Molecular Immunology Section, Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA. cshi@niaid.nih.gov
authors.forename: Chong-Shan
authors.initials: CS
authors.lastname: Shi
authors.forename: John H
authors.initials: JH
authors.lastname: Kehrl
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D000071186:Beclin-1; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D006801:Humans; D047468:Immunoprecipitation; D007371:Interferon-gamma / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008239:Lysine / Q000235:genetics / Q000378:metabolism; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism; D011485:Protein Binding; D034622:RNA Interference; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; C115010:Becn1 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; D009687:Nuclear Proteins; D048029:TNF Receptor-Associated Factor 6; D051197:Toll-Like Receptor 4; D007371:Interferon-gamma; D008239:Lysine