title: The B cell receptor promotes B cell activation and proliferation through a non-ITAM tyrosine in the Igalpha cytoplasmic domain.
abstract: In addition to the tyrosines of the Igalpha and beta immunoreceptor tyrosine-based activation motifs (ITAMs), the evolutionarily conserved Igalpha non-ITAM tyrosine 204 becomes phosphorylated upon antigen recognition by the B cell receptor (BCR). Here we demonstrate that splenic B cells from mice with a targeted mutation of Igalpha Y204 exhibited an isolated defect in T cell-independent B cell activation, proliferation, and antibody response upon BCR engagement, yet normal BCR capping, antigen internalization, antigen presentation, and T cell-dependent antibody production. Mutant B cells, present in normal numbers, exhibited unimpaired BCR-induced spleen tyrosine kinase (Syk) phosphorylation but reduced B cell linker protein (BLNK) phosphorylation, calcium flux, and nuclear factor kappaB (NFkappaB), c-jun N-terminal kinase (JNK), and extracellular signal-regulated kinase (ERK) activation. These results suggest that Igalpha non-ITAM tyrosine 204 promotes a distinct cellular response, namely T-independent B cell proliferation and differentiation via phosphorylation of the adaptor BLNK.
authors.affiliation: The CBR Institute for Biomedical Research, Boston, Massachusetts 02115, USA.
authors.forename: Heide Christine K
authors.initials: HC
authors.lastname: Patterson
authors.forename: Manfred
authors.initials: M
authors.lastname: Kraus
authors.forename: You-Me
authors.initials: YM
authors.lastname: Kim
authors.forename: Hidde
authors.initials: H
authors.lastname: Ploegh
authors.forename: Klaus
authors.initials: K
authors.lastname: Rajewsky
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D017951:Antigen Presentation / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002454:Cell Differentiation; D049109:Cell Proliferation; D003593:Cytoplasm / Q000378:metabolism*; D004789:Enzyme Activation; D007137:Immunoglobulin alpha-Chains / Q000737:chemistry* / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D016328:NF-kappa B / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000737:chemistry / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D000072377:Syk Kinase; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C113939:B cell linker protein; D002352:Carrier Proteins; D007137:Immunoglobulin alpha-Chains; D047908:Intracellular Signaling Peptides and Proteins; D016328:NF-kappa B; D010750:Phosphoproteins; D011947:Receptors, Antigen, B-Cell; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium