In vitro characterization of major ligands for Src homology 2 domains derived from protein tyrosine kinases, from the adaptor protein SHC and from GTPase-activating protein in Ramos B cells.
Antigen receptors of B lymphocytes transmit their activation signal to the cell interior by associating with and activation of specific non-receptor tyrosine kinases. Most of these kinases as well as other cytoplasmic effectors contain at least one Src homology 2 (SH2) domain, known to bind tyrosine-phosphorylated proteins. We examined the binding specificity of SH2 domains from different signaling molecules in B cells and found that each of the SH2 domains tested bound distinct subsets of stimulation-dependent phosphoproteins in vitro. SH2 domains from Src-like tyrosine kinases bound predominantly to the HS1 phosphoprotein. The tandem SH2 domains of the ZAP-70 tyrosine kinase bound to phosphorylated Ig-beta but only weakly to Ig-alpha. Also the SHC-derived SH2 domain formed complexes with the tyrosine-phosphorylated Ig-alpha/beta heterodimer, while the C- and N-terminal SH2 domains of GTPase-activating protein displayed completely different binding preferences. These results suggest that cytoplasmic effector molecules can be recruited to the activated B cell receptor in an SH2-phosphotyrosine-mediated manner. The data also provide a possible explanation for the notion that Ig-alpha and Ig-beta might couple to different biochemical pathways.
Baumann
G
G
Sandoz Pharma Ltd., Preclinical Research, Basel, Germany.
Maier
D
D
Freuler
F
F
Tschopp
C
C
Baudisch
K
K
Wienands
J
J
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D001665:Binding Sites; D001798:Blood Proteins / Q000276:immunology; D020690:GTPase-Activating Proteins; D006801:Humans; D007136:Immunoglobulins / Q000276:immunology; D008024:Ligands; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000276:immunology; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000276:immunology*; D011506:Proteins / Q000276:immunology; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000276:immunology*; D011993:Recombinant Fusion Proteins / Q000276:immunology; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014407:Tumor Cells, Cultured; D051746:ZAP-70 Protein-Tyrosine Kinase
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D001798:Blood Proteins; D020690:GTPase-Activating Proteins; C061909:HCLS1 protein, human; D007136:Immunoglobulins; D008024:Ligands; D011506:Proteins; D011993:Recombinant Fusion Proteins; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D011505:Protein-Tyrosine Kinases; D016392:Proto-Oncogene Proteins pp60(c-src); D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human