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A novel complex, p40/42, is constitutively associated with the B cell antigen receptor and phosphorylated upon receptor stimulation. 1996

Y J Lee, and P Luisiri, and M R Clark
Department of Medicine, University of Chicago, IL 60637, USA.

Stimulation of the B cell Ag receptor (BCR), a multimeric complex containing heterodimers of Ig-alpha and Ig-beta, initiates a cascade of tyrosine phosphorylation that results in cellular activation. One of the earliest substrates phosphorylated is Ig-alphabeta, and it appears that kinase activation emanates from this structure with the most proximal kinases themselves, and some of their immediate substrates, associating with the heterodimer. To identify other molecules that may be involved in proximal BCR signaling, we examined the substrates that were tyrosine phosphorylated following stimulation with either anti-IgG Abs or pervanadate in the murine B cell lymphoma A20 IIA1.6 and in resting splenic B cells. Immunoblotting with anti-phosphotyrosine Abs revealed that a doublet of 40 and 42 kDa was phosphorylated within 1 min of stimulation with either agonist. The phosphorylation of p40/42 in A20 cells induced by anti-IgG was rapid and transient, peaking at 2 min after stimulation and becoming almost undetectable after 10 min. Furthermore, at least 25% of phosphorylated p40/42 co-immunoprecipitated with Ig-alphabeta, but none precipitated with MHC II, CD40, Fc(gamma)RII, Fyn, HS-1, or Syk, suggesting that this protein complex specifically associates with the Ig-alphabeta heterodimer. p40/42 did not react with Abs to Ig-alpha, Ig-beta, mitogen-activated protein kinase, or Lnk. Furthermore, and in contrast to Ig-alphabeta, p40/42 was highly acidic and not part of a disulfide-linked complex. Finally, p40/42 was demonstrated to be a glycosylated surface protein that was constitutively associated with Ig-alphabeta. These results suggest that p40/42 is a novel constituent of the resting B cell Ag receptor complex.

UI MeSH Term Description Entries
D008562 Membrane Glycoproteins Glycoproteins found on the membrane or surface of cells. Cell Surface Glycoproteins,Surface Glycoproteins,Cell Surface Glycoprotein,Membrane Glycoprotein,Surface Glycoprotein,Glycoprotein, Cell Surface,Glycoprotein, Membrane,Glycoprotein, Surface,Glycoproteins, Cell Surface,Glycoproteins, Membrane,Glycoproteins, Surface,Surface Glycoprotein, Cell,Surface Glycoproteins, Cell
D010766 Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Phosphorylations
D011499 Protein Processing, Post-Translational Any of various enzymatically catalyzed post-translational modifications of PEPTIDES or PROTEINS in the cell of origin. These modifications include carboxylation; HYDROXYLATION; ACETYLATION; PHOSPHORYLATION; METHYLATION; GLYCOSYLATION; ubiquitination; oxidation; proteolysis; and crosslinking and result in changes in molecular weight and electrophoretic motility. Amino Acid Modification, Post-Translational,Post-Translational Modification,Post-Translational Protein Modification,Posttranslational Modification,Protein Modification, Post-Translational,Amino Acid Modification, Posttranslational,Post-Translational Amino Acid Modification,Post-Translational Modifications,Post-Translational Protein Processing,Posttranslational Amino Acid Modification,Posttranslational Modifications,Posttranslational Protein Processing,Protein Processing, Post Translational,Protein Processing, Posttranslational,Amino Acid Modification, Post Translational,Modification, Post-Translational,Modification, Post-Translational Protein,Modification, Posttranslational,Modifications, Post-Translational,Modifications, Post-Translational Protein,Modifications, Posttranslational,Post Translational Amino Acid Modification,Post Translational Modification,Post Translational Modifications,Post Translational Protein Modification,Post Translational Protein Processing,Post-Translational Protein Modifications,Processing, Post-Translational Protein,Processing, Posttranslational Protein,Protein Modification, Post Translational,Protein Modifications, Post-Translational
D011947 Receptors, Antigen, B-Cell IMMUNOGLOBULINS on the surface of B-LYMPHOCYTES. Their MESSENGER RNA contains an EXON with a membrane spanning sequence, producing immunoglobulins in the form of type I transmembrane proteins as opposed to secreted immunoglobulins (ANTIBODIES) which do not contain the membrane spanning segment. Antigen Receptors, B-Cell,B-Cell Antigen Receptor,B-Cell Antigen Receptors,Surface Immunoglobulin,Immunoglobulins, Membrane-Bound,Immunoglobulins, Surface,Membrane Bound Immunoglobulin,Membrane-Bound Immunoglobulins,Receptors, Antigen, B Cell,Surface Immunoglobulins,Antigen Receptor, B-Cell,Antigen Receptors, B Cell,B Cell Antigen Receptor,B Cell Antigen Receptors,Bound Immunoglobulin, Membrane,Immunoglobulin, Membrane Bound,Immunoglobulin, Surface,Immunoglobulins, Membrane Bound,Membrane Bound Immunoglobulins,Receptor, B-Cell Antigen,Receptors, B-Cell Antigen
D011993 Recombinant Fusion Proteins Recombinant proteins produced by the GENETIC TRANSLATION of fused genes formed by the combination of NUCLEIC ACID REGULATORY SEQUENCES of one or more genes with the protein coding sequences of one or more genes. Fusion Proteins, Recombinant,Recombinant Chimeric Protein,Recombinant Fusion Protein,Recombinant Hybrid Protein,Chimeric Proteins, Recombinant,Hybrid Proteins, Recombinant,Recombinant Chimeric Proteins,Recombinant Hybrid Proteins,Chimeric Protein, Recombinant,Fusion Protein, Recombinant,Hybrid Protein, Recombinant,Protein, Recombinant Chimeric,Protein, Recombinant Fusion,Protein, Recombinant Hybrid,Proteins, Recombinant Chimeric,Proteins, Recombinant Fusion,Proteins, Recombinant Hybrid
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001402 B-Lymphocytes Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B-Cells, Lymphocyte,B-Lymphocyte,Bursa-Dependent Lymphocytes,B Cells, Lymphocyte,B Lymphocyte,B Lymphocytes,B-Cell, Lymphocyte,Bursa Dependent Lymphocytes,Bursa-Dependent Lymphocyte,Lymphocyte B-Cell,Lymphocyte B-Cells,Lymphocyte, Bursa-Dependent,Lymphocytes, Bursa-Dependent
D014638 Vanadates Oxyvanadium ions in various states of oxidation. They act primarily as ion transport inhibitors due to their inhibition of Na(+)-, K(+)-, and Ca(+)-ATPase transport systems. They also have insulin-like action, positive inotropic action on cardiac ventricular muscle, and other metabolic effects. Decavanadate,Metavanadate,Orthovanadate,Oxyvanadium,Vanadyl,Monovanadate,Sodium Vanadate,Vanadate,Vanadate, Sodium
D015398 Signal Transduction The intracellular transfer of information (biological activation/inhibition) through a signal pathway. In each signal transduction system, an activation/inhibition signal from a biologically active molecule (hormone, neurotransmitter) is mediated via the coupling of a receptor/enzyme to a second messenger system or to an ion channel. Signal transduction plays an important role in activating cellular functions, cell differentiation, and cell proliferation. Examples of signal transduction systems are the GAMMA-AMINOBUTYRIC ACID-postsynaptic receptor-calcium ion channel system, the receptor-mediated T-cell activation pathway, and the receptor-mediated activation of phospholipases. Those coupled to membrane depolarization or intracellular release of calcium include the receptor-mediated activation of cytotoxic functions in granulocytes and the synaptic potentiation of protein kinase activation. Some signal transduction pathways may be part of larger signal transduction pathways; for example, protein kinase activation is part of the platelet activation signal pathway. Cell Signaling,Receptor-Mediated Signal Transduction,Signal Pathways,Receptor Mediated Signal Transduction,Signal Transduction Pathways,Signal Transduction Systems,Pathway, Signal,Pathway, Signal Transduction,Pathways, Signal,Pathways, Signal Transduction,Receptor-Mediated Signal Transductions,Signal Pathway,Signal Transduction Pathway,Signal Transduction System,Signal Transduction, Receptor-Mediated,Signal Transductions,Signal Transductions, Receptor-Mediated,System, Signal Transduction,Systems, Signal Transduction,Transduction, Signal,Transductions, Signal
D015703 Antigens, CD Differentiation antigens residing on mammalian leukocytes. CD stands for cluster of differentiation, which refers to groups of monoclonal antibodies that show similar reactivity with certain subpopulations of antigens of a particular lineage or differentiation stage. The subpopulations of antigens are also known by the same CD designation. CD Antigen,Cluster of Differentiation Antigen,Cluster of Differentiation Marker,Differentiation Antigens, Leukocyte, Human,Leukocyte Differentiation Antigens, Human,Cluster of Differentiation Antigens,Cluster of Differentiation Markers,Antigen Cluster, Differentiation,Antigen, CD,CD Antigens,Differentiation Antigen Cluster,Differentiation Marker Cluster,Marker Cluster, Differentiation

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