CD22 associates with the human surface IgM-B-cell antigen receptor complex.
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.
Leprince
C
C
Department of Microbiology, University of Washington, Seattle 98195.
Draves
K E
KE
Geahlen
R L
RL
Ledbetter
J A
JA
Clark
E A
EA
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002051:Burkitt Lymphoma; D015815:Cell Adhesion Molecules / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000276:immunology / Q000378:metabolism; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007075:Immunoglobulin M / Q000302:isolation & purification / Q000378:metabolism*; D037102:Lectins; D051379:Mice; D008969:Molecular Sequence Data; D008970:Molecular Weight; D014066:Palatine Tonsil / Q000276:immunology; D011494:Protein Kinases / Q000302:isolation & purification / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000302:isolation & purification / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D051918:Sialic Acid Binding Ig-like Lectin 2; D014407:Tumor Cells, Cultured
D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; C497867:CD22 protein, human; C497868:Cd22 protein, mouse; D015815:Cell Adhesion Molecules; D007075:Immunoglobulin M; D037102:Lectins; D011947:Receptors, Antigen, B-Cell; D051918:Sialic Acid Binding Ig-like Lectin 2; D011494:Protein Kinases