Abstract
The B-cell surface molecule CD22, when cross-linked, modulates signaling through the surface IgM (sIgM)-B-cell receptor (BCR) complex. Here we analyzed the basis of this interaction between CD22 and the human sIgM complex. After lysis of B cells or B-cell lines in digitonin, CD22 coimmunoprecipitated a kinase activity that in vitro-phosphorylated two polypeptides of 150 and 130 kDa on tyrosine residues. By immunoblot analysis with a rabbit anti-serum specific for a synthetic peptide of CD22, we found these proteins to be CD22 itself. Furthermore, the phosphorylated 150-kDa CD22 was found in the sIgM-BCR complex maintained by digitonin, along with Ig alpha/mb-1, Ig beta/B29, and a 75-kDa polypeptide precipitated by an antiserum specific to protein-tyrosine kinase PTK72. CD22 is likely to be an important signaling partner in the sIgM-BCR complex since it is very rapidly and strikingly phosphorylated after sIgM is cross-linked and since it contains the antigen recognition homology I (ARHI) motif, present in other antigen receptor molecules.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Animals
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Antigens, CD / genetics
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Antigens, CD / isolation & purification
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Antigens, CD / metabolism*
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Antigens, Differentiation, B-Lymphocyte / genetics
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Antigens, Differentiation, B-Lymphocyte / isolation & purification
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Antigens, Differentiation, B-Lymphocyte / metabolism*
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B-Lymphocytes / immunology*
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B-Lymphocytes / metabolism
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Burkitt Lymphoma
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Cell Adhesion Molecules / isolation & purification
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Cell Adhesion Molecules / metabolism*
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Cell Membrane / immunology
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Cell Membrane / metabolism
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Cells, Cultured
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Electrophoresis, Polyacrylamide Gel
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Humans
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Immunoglobulin M / isolation & purification
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Immunoglobulin M / metabolism*
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Lectins*
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Mice
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Molecular Sequence Data
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Molecular Weight
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Palatine Tonsil / immunology
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Protein Kinases / isolation & purification
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Protein Kinases / metabolism*
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Receptors, Antigen, B-Cell / isolation & purification
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Receptors, Antigen, B-Cell / metabolism*
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Sequence Homology, Amino Acid
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Sialic Acid Binding Ig-like Lectin 2
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Tumor Cells, Cultured
Substances
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Antigens, CD
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Antigens, Differentiation, B-Lymphocyte
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CD22 protein, human
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Cd22 protein, mouse
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Cell Adhesion Molecules
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Immunoglobulin M
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Lectins
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Receptors, Antigen, B-Cell
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Sialic Acid Binding Ig-like Lectin 2
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Protein Kinases