title: Negative regulation of CD40-mediated B cell responses by E3 ubiquitin ligase Casitas-B-lineage lymphoma protein-B.
abstract: It has been documented that CD40 is essential for B cell function. Casitas-B-lineage lymphoma protein-b (Cbl-b), an adapter protein and ubiquitin ligase, has been shown to regulate the activation of T and B cells through their Ag receptors. In this study, we report that CD40-induced B cell proliferation is significantly augmented in mice lacking Cbl-b. Furthermore, Cbl-b(-/-) mice display enhanced thymus-dependent Ab responses and germinal center formation, whereas introduction of CD40 deficiency abolishes these effects. Hyper thymus-dependent humoral response in Cbl-b(-/-) mice is in part due to an intrinsic defect in B cells. Mechanistically, Cbl-b selectively down-modulates CD40-induced activation of NF-kappaB and JNK. Cbl-b associates with TNF receptor-associated factor 2 upon CD40 ligation, and inhibits the recruitment of TNF receptor-associated factor 2 to the CD40. Together, our data suggest that Cbl-b attenuates CD40-mediated NF-kappaB and JNK activation, thereby suppressing B cell responses.
authors: Section of Nephrology, Department of Medicine, University of Chicago, Chicago, IL 6063, USA.
authors: Guilin
authors: G
authors: Qiao
authors: Minxiang
authors: M
authors: Lei
authors: Zhenping
authors: Z
authors: Li
authors: Yonglian
authors: Y
authors: Sun
authors: Andrew
authors: A
authors: Minto
authors: Yang-Xin
authors: YX
authors: Fu
authors: Haiyan
authors: H
authors: Ying
authors: Richard J
authors: RJ
authors: Quigg
authors: Jian
authors: J
authors: Zhang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D019013:CD40 Antigens / Q000276:immunology / Q000378:metabolism*; D023201:CD40 Ligand / Q000276:immunology / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D015536:Down-Regulation; D008213:Lymphocyte Activation / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D011485:Protein Binding; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D050721:Proto-Oncogene Proteins c-cbl / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D047992:TNF Receptor-Associated Factor 2 / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019013:CD40 Antigens; C118387:Cblb protein, mouse; D016328:NF-kappa B; D047992:TNF Receptor-Associated Factor 2; D025801:Ubiquitin; D023201:CD40 Ligand; D050721:Proto-Oncogene Proteins c-cbl; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases