Evidence that Llck-mediated phosphorylation of p56dok and p62dok may play a role in CD2 signaling

J Biol Chem. 2000 May 12;275(19):14590-7. doi: 10.1074/jbc.275.19.14590.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing*
  • CD2 Antigens / metabolism*
  • Carrier Proteins / metabolism*
  • DNA-Binding Proteins*
  • ErbB Receptors / metabolism
  • Humans
  • Jurkat Cells
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / metabolism*
  • Phosphoproteins / metabolism*
  • Phosphorylation
  • RNA-Binding Proteins*
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction*
  • ras GTPase-Activating Proteins / metabolism


  • Adaptor Proteins, Signal Transducing
  • CD2 Antigens
  • Carrier Proteins
  • DNA-Binding Proteins
  • DOK1 protein, human
  • DOK2 protein, human
  • GAP-associated protein p62
  • Phosphoproteins
  • RNA-Binding Proteins
  • Recombinant Fusion Proteins
  • ras GTPase-Activating Proteins
  • ErbB Receptors
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)