Evidence that Llck-mediated phosphorylation of p56dok and p62dok may play a role in CD2 signaling.
The Lck tyrosine kinase is involved in signaling by T cell surface receptors such as TCR/CD3, CD2, and CD28. As other downstream protein-tyrosine kinases are activated upon stimulation of these receptors, it is difficult to assign which tyrosine-phosphorylated proteins represent bona fide Lck substrates and which are phosphorylated by other tyrosine kinases. We have developed a system in which Lck can be activated independently of TCR/CD3. We have shown that activation of an epidermal growth factor receptor/Lck chimera leads to the specific phosphorylation of Ras GTPase-activating protein (RasGAP) and two RasGAP-associated proteins, p56(dok) and p62(dok). Activation of the chimeric protein correlates with an increase in cellular Ca(2+) in the absence of ZAP-70 and phospholipase Cgamma1 phosphorylation. Furthermore, we have found that p62(dok) co-immunoprecipitates with the activated epidermal growth factor receptor/LckF505 and that phosphorylated Dok proteins bind to the Src homology 2 domain of Lck in vitro. In addition, we have shown that activation via the CD2 but not the TCR/CD3 receptor leads to the phosphorylation of p56(dok) and p62(dok). Using JCaM1.6 cells, we have demonstrated that Lck is required for CD2-mediated phosphorylation of Dok proteins. We propose that phosphorylation and Src homology 2-mediated association of p56(dok) and p62(dok) with Lck play a selective function in accessory receptor signal transduction mechanisms.
Némorin
J G
JG
Institut National de la Recherche Scientifique, Institut Armand-Frappier, Université du Québec, Laval, Québec H7V 1B7, Canada.
Duplay
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D048868:Adaptor Proteins, Signal Transducing; D018801:CD2 Antigens / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins; D066246:ErbB Receptors / Q000378:metabolism; D006801:Humans; D019169:Jurkat Cells; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D020703:ras GTPase-Activating Proteins / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D018801:CD2 Antigens; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C489560:DOK1 protein, human; C115089:DOK2 protein, human; C074561:GAP-associated protein p62; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D020703:ras GTPase-Activating Proteins; D066246:ErbB Receptors; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)