CD3-zeta surface expression is required for CD4-p56lck-mediated upregulation of T cell antigen receptor-CD3 signaling in T cells.
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.
Sancho
J
J
Division of Immunology, Beth Israel Hospital, Boston, Massachusetts 02215.
Ledbetter
J A
JA
Choi
M S
MS
Kanner
S B
SB
Deans
J P
JP
Terhorst
C
C
D000595:Amino Acid Sequence; D000945:Antigens, Differentiation, T-Lymphocyte / Q000378:metabolism*; D015153:Blotting, Western; D017252:CD3 Complex; D015704:CD4 Antigens / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D003432:Cross-Linking Reagents; D015180:Electrophoresis, Gel, Two-Dimensional; D004789:Enzyme Activation; D007527:Isoenzymes / Q000378:metabolism; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D008565:Membrane Proteins / Q000096:biosynthesis* / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000096:biosynthesis* / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D010738:Type C Phospholipases / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation
D000945:Antigens, Differentiation, T-Lymphocyte; D017252:CD3 Complex; D015704:CD4 Antigens; D003432:Cross-Linking Reagents; D007527:Isoenzymes; D008565:Membrane Proteins; D011948:Receptors, Antigen, T-Cell; C054979:antigen T cell receptor, zeta chain; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010738:Type C Phospholipases; D002118:Calcium