CD4-dependent and -independent association of protein tyrosine kinases to the T cell receptor/CD3 complex of CD4+ mouse T lymphocytes.
Tyrosine phosphorylation of different substrates is the earliest intracellular signal detected after T cell receptor (TcR) ligation. Several tyrosine kinases have been detected associated to the CD3-TcR complex in stimulated or unstimulated cells, including p56lck, p59fyn and ZAP-70. We have observed, in one mouse T helper CD4 T cell line, that most TcR- or CD3-associated tyrosine kinase activity comes from CD4:p56lck (Diez-Orejas, R., Ballester, S., Feito, M. J., Ronda, M., Ojeda, G., Criado, G., Portolés, P. and Rojo, J. M., EMBO J. 1994. 13: 90). To analyze whether this is a major way of tyrosine kinase association to the TcR in normal CD4+ T cells, we examined the nature and mode of association of tyrosine kinases to the TcR complex in normal spleen CD4+ T lymphocytes. Our results show that, in normal CD4+ T lymphocytes, as in CD4+ T cell lines, there is a stable and readily detectable association between CD4:p56lck and the TcR/CD3 complex, as determined by in vitro kinase activity in immunoprecipitates from cell lysates. However, TcR/CD3 complexes from nature CD4+ lymphocytes have detectable amounts of p56lck associated in a CD4-independent manner, as shown by immunodepletion of the lysates with anti-CD4 antibodies. In addition, TcR/CD3 also bind p59fyn regardless of the presence of CD4. Conversely, we have observed that CD4 co-precipitates small quantities of p56fyn in a TcR/CD3-independent manner. Overall, our data suggest the existence of different possible molecular complexes between TcR/CD3, CD4 and their attending kinases, as well as some quantitative and qualitative differences between CD4+ T cells and CD4+ T cell lines in kinase association to the TcR/CD3 complex.
Criado
G
G
Centro de Investigaciones Biológicas, C.S.I.C., Madrid, Spain.
Feito
M J
MJ
Rojo
J M
JM
D000818:Animals; D017252:CD3 Complex / Q000737:chemistry*; D015704:CD4 Antigens / Q000737:chemistry*; D015496:CD4-Positive T-Lymphocytes / Q000201:enzymology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D046911:Macromolecular Substances; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D011505:Protein-Tyrosine Kinases / Q000737:chemistry*; D011518:Proto-Oncogene Proteins / Q000737:chemistry; D051076:Proto-Oncogene Proteins c-fyn; D015398:Signal Transduction; D019061:src-Family Kinases / Q000737:chemistry
D017252:CD3 Complex; D015704:CD4 Antigens; D046911:Macromolecular Substances; D011518:Proto-Oncogene Proteins; D011505:Protein-Tyrosine Kinases; C494960:Fyn protein, mouse; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051076:Proto-Oncogene Proteins c-fyn; D019061:src-Family Kinases