CD3-zeta surface expression is required for CD4-p56lck-mediated upregulation of T cell antigen receptor-CD3 signaling in T cells

J Biol Chem. 1992 Apr 15;267(11):7871-9.


It has been proposed that during T cell receptor antigen recognition, CD4- or CD8-p56lck molecules interact with the T cell antigen receptor-CD3 complex (TCR-CD3) to phosphorylate various undefined substrates, which then initiate signal transduction through the TCR-CD3 complex. The ability of CD4 to modulate the TCR-CD3-induced increase in intracellular Ca2+, [Ca2+]i, and substrate tyrosine phosphorylation was studied in mutants of the human leukemic T cell line HPB-ALL characterized by their low expression of the TCR-CD3 complex on the cell surface. In TCR-CD3low cells, in which CD3-zeta was found to be associated with the TCR-CD3 complex, cross-linking CD3 with CD4 resulted in a profile of calcium mobilization, CD3-zeta, and phospholipase C-gamma 1 tyrosine phosphorylation similar to that observed in HPB-ALL cells, although the magnitude of generalized substrate tyrosine phosphorylation appeared to be smaller, as compared with wild-type cells. Responses were weak or absent when CD3 was cross-linked alone. In contrast, in a mutant in which association of CD3-zeta 2 with the TCR-CD3 was defective, cross-linking of CD3 with CD4 had a weaker effect on any of the activation parameters tested. These experiments showed that the presence of CD3-zeta 2 in the TCR-CD3 complex is of critical importance for the ability of CD4 to enhance early transducing signals inside the cell. The data also suggest that CD4-associated protein tyrosine kinase p56lck could up-regulate defective CD3-mediated induction of phospholipase C activity by increasing tyrosine phosphorylation of phospholipase C-gamma 1.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Antigens, Differentiation, T-Lymphocyte / metabolism*
  • Blotting, Western
  • CD3 Complex
  • CD4 Antigens / metabolism*
  • Calcium / metabolism
  • Cross-Linking Reagents
  • Electrophoresis, Gel, Two-Dimensional
  • Enzyme Activation
  • Isoenzymes / metabolism
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
  • Membrane Proteins / biosynthesis*
  • Membrane Proteins / metabolism
  • Molecular Sequence Data
  • Phosphorylation
  • Protein-Tyrosine Kinases / metabolism*
  • Receptors, Antigen, T-Cell / biosynthesis*
  • Receptors, Antigen, T-Cell / metabolism*
  • Signal Transduction*
  • T-Lymphocytes / metabolism*
  • Tumor Cells, Cultured
  • Type C Phospholipases / metabolism
  • Tyrosine / metabolism
  • Up-Regulation*


  • Antigens, Differentiation, T-Lymphocyte
  • CD3 Complex
  • CD4 Antigens
  • Cross-Linking Reagents
  • Isoenzymes
  • Membrane Proteins
  • Receptors, Antigen, T-Cell
  • antigen T cell receptor, zeta chain
  • Tyrosine
  • Protein-Tyrosine Kinases
  • Lymphocyte Specific Protein Tyrosine Kinase p56(lck)
  • Type C Phospholipases
  • Calcium