title: Traf6 and A20 differentially regulate TLR4-induced autophagy by affecting the ubiquitination of Beclin 1.
abstract: Toll-like receptor 4 (TLR4) signaling triggers autophagy, which has been linked to both adaptive and innate immunity. Engagement of TLR4 recruits to the receptor complex Beclin 1, a key component of a class III phosphatidylinositol 3-kinase complex (PI3KC3) that initiates autophagosome formation. Recently, we found that tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6)-mediates Lys(63) (K63)- linked ubiquitination of Beclin 1 is crucial for TLR4-triggered autophagy in macrophages. We identified two TRAF6-binding motifs in Beclin 1 that facilitate the binding of TRAF6 and the ubiquitination of Beclin 1. A lysine located in the Bcl-2 homology 3 (BH3) domain of Beclin 1 serves as a major site for K63-linked ubiquitination. Opposing TRAF6, the deubiquitinating enzyme A20 reduces the extent of K63-linked ubiquitination of Beclin 1 and limits the induction of autophagy in response to TLR4 signaling. Furthermore, treatment of macrophages with either interferonγ or interleukin-1 triggers 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, USA.
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 / Q000502:physiology*; D000071186:Beclin-1; D002460:Cell Line; D004268:DNA-Binding Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3; D054875:Ubiquitination
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D048029:TNF Receptor-Associated Factor 6; D051197:Toll-Like Receptor 4; C076529:TNFAIP3 protein, human; D000072598:Tumor Necrosis Factor alpha-Induced Protein 3
references.citation: Sci Signal. 2010 May 25;3(123):ra42
references.pmid: 20501938