title: HOIL-1L interacting protein (HOIP) as an NF-kappaB regulating component of the CD40 signaling complex.
abstract: The tumor necrosis factor receptor (TNFR) superfamily mediates signals critical for regulation of the immune system. One family member, CD40, is important for the efficient activation of antibody-producing B cells and other antigen-presenting cells. The molecules and mechanisms that mediate CD40 signaling are only partially characterized. Proteins known to interact with the cytoplasmic domain of CD40 include members of the TNF receptor-associated factor (TRAF) family, which regulate signaling and serve as links to other signaling molecules. To identify additional proteins important for CD40 signaling, we used a combined stimulation/immunoprecipitation procedure to isolate CD40 signaling complexes from B cells and characterized the associated proteins by mass spectrometry. In addition to known CD40-interacting proteins, we detected SMAC/DIABLO, HTRA2/Omi, and HOIP/RNF31/PAUL/ZIBRA. We found that these previously unknown CD40-interacting partners were recruited in a TRAF2-dependent manner. HOIP is a ubiquitin ligase capable of mediating NF-kappaB activation through the ubiquitin-dependent activation of IKKgamma. We found that a mutant HOIP molecule engineered to lack ubiquitin ligase activity inhibited the CD40-mediated activation of NF-kappaB. Together, our results demonstrate a powerful approach for the identification of signaling molecules associated with cell surface receptors and indicate an important role for the ubiquitin ligase activity of HOIP in proximal CD40 signaling.
authors.affiliation: Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States of America. bruce-hostager@uiowa.edu
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Hostager
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Fox
authors.forename: Douglas
authors.initials: D
authors.lastname: Whitten
authors.forename: Curtis G
authors.initials: CG
authors.lastname: Wilkerson
authors.forename: Betty A
authors.initials: BA
authors.lastname: Eipper
authors.forename: Victor P
authors.initials: VP
authors.lastname: Francone
authors.forename: Paul B
authors.initials: PB
authors.lastname: Rothman
authors.forename: John D
authors.initials: JD
authors.lastname: Colgan
mesh_terms: D000818:Animals; D019013:CD40 Antigens / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D047468:Immunoprecipitation; D013058:Mass Spectrometry; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases
chemical_list: D019013:CD40 Antigens; D002352:Carrier Proteins; D016328:NF-kappa B; C000607389:Rbck1 protein, mouse; D044767:Ubiquitin-Protein Ligases