title: TNF-alpha induced c-IAP1/TRAF2 complex translocation to a Ubc6-containing compartment and TRAF2 ubiquitination.
abstract: Signaling through tumor necrosis factor receptor 2 (TNF-R2) results in ubiquitination of TRAF2 by the E3 c-IAP1. In this report, we confirm that TRAF2 translocates to a Triton X-100 (TX)-insoluble compartment upon TNF-R2 engagement. Moreover, TRAF2 ubiquitination occurs in this compartment, from which TRAF2 is degraded in a proteasome-dependent manner. Confocal microscopy demonstrated that the TX-insoluble compartment is perinuclear and co-localizes with endoplasmic reticulum (ER) markers. The ER transmembrane Ubc6 bound to c-IAP1 and served as a cognate E2 for c-IAP1's E3 activity in vitro. Furthermore, Ubc6 co-localized with translocated TRAF2/c-IAP1 in the ER-associated compartment in vivo, and a catalytically inactive Ubc6 mutant inhibited TNF-alpha-induced, TNF-R2-dependent TRAF2 degradation. These results indicate that upon TNF-R2 signaling, translocation of TRAF2 and c-IAP1 to an ER-associated, Ubc6-containing perinuclear compartment is required for the ubiquitination of TRAF2 by c-IAP1. Therefore, the ER plays a key role in the TNF-R-mediated signal transduction cascade by acting as a site of assembly for E2/E3/substrate complexes.
authors.affiliation: Laboratory of Immune Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Chuan-Jin
authors.initials: CJ
authors.lastname: Wu
authors.forename: Dietrich B
authors.initials: DB
authors.lastname: Conze
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Li
authors.forename: Sai-Xia
authors.initials: SX
authors.lastname: Ying
authors.forename: John A
authors.initials: JA
authors.lastname: Hanover
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Ashwell
mesh_terms: D000818:Animals; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins; D019169:Jurkat Cells; D011506:Proteins / Q000378:metabolism*; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000378:metabolism; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D011506:Proteins; D047889:Receptors, Tumor Necrosis Factor, Type II; D047992:TNF Receptor-Associated Factor 2; D014409:Tumor Necrosis Factor-alpha; D025801:Ubiquitin; D044763:Ubiquitin-Conjugating Enzymes; C494833:BIRC2 protein, human; D044767:Ubiquitin-Protein Ligases