TCR-induced T cell activation leads to simultaneous phosphorylation at Y505 and Y394 of p56(lck) residues

Cytometry A. 2012 Sep;81(9):797-805. doi: 10.1002/cyto.a.22070. Epub 2012 Jun 6.


Biochemical studies have demonstrated that phosphorylation of lymphocyte cell kinase (p56(lck) ) is crucial for activation of signaling cascades following T cell receptor (TCR) stimulation. However, whether phosphorylation/dephosphorylation of the activating or inhibitory tyrosine residues occurs upon activation is controversial. Recent advances in intracellular staining of phospho-epitopes and cytometric analysis, requiring few cells, have opened up novel avenues for the field of immunological signaling. Here, we assessed p56(lck) phosphorylation, using a multiparameter flow-cytometric based detection method following T cell stimulation. Fixation and permeabilization in conjunction with zenon labeling technology and/or fluorescently labeled antibodies against total p56(lck) or cognate phospho-tyrosine (pY) residues or surface receptors were used for detection purposes. Our observations showed that activation of Jurkat or primary human T cells using H(2) O(2) or TCR-induced stimulation led to simultaneous phosphorylation of the activating tyrosine residue, Y394 and the inhibitory tyrosine residue, Y505 of p56(lck) . This was followed by downstream calcium flux and expression of T cell activation markers; CD69 and CD40 ligand (CD40L). However, the extent of measurable activation readouts depended on the optimal stimulatory conditions (temperature and/or stimuli combinations). Treatment of cells with a p56(lck) -specific inhibitor, PP2, abolished phosphorylation at either residue in a dose-dependent manner. Taken together, these observations show that TCR-induced stimulation of T cells led to simultaneous phosphorylation of p56(lck) residues. This implies that dephosphorylation of Y505 is not crucial for p56(lck) activity. Also, it is clear that cytometric analysis provides for a rapid, sensitive, and quantitative method to supplement biochemical studies on p56(lck) signaling pathways in T cells at single cell level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Amino Acid Motifs
  • Antigens, CD / metabolism
  • Antigens, Differentiation, T-Lymphocyte / metabolism
  • CD4-Positive T-Lymphocytes / immunology*
  • CD4-Positive T-Lymphocytes / metabolism
  • CD40 Ligand / metabolism
  • Calcium Signaling
  • Humans
  • Hydrogen Peroxide / pharmacology
  • Jurkat Cells
  • Lectins, C-Type / metabolism
  • Lymphocyte Activation
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / antagonists & inhibitors
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / chemistry
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / metabolism*
  • Middle Aged
  • Phosphorylation
  • Protein Processing, Post-Translational*
  • Pyrimidines / pharmacology
  • Receptors, Antigen, T-Cell / metabolism*
  • Tyrosine / metabolism*
  • Young Adult


  • AG 1879
  • Antigens, CD
  • Antigens, Differentiation, T-Lymphocyte
  • CD69 antigen
  • Lectins, C-Type
  • Pyrimidines
  • Receptors, Antigen, T-Cell
  • CD40 Ligand
  • Tyrosine
  • Hydrogen Peroxide
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)