CD45 tyrosine phosphatase-activated p59fyn couples the T cell antigen receptor to pathways of diacylglycerol production, protein kinase C activation and calcium influx.
The role of the CD45 phosphotyrosine phosphatase in coupling the T cell antigen receptor complex (TCR) to intracellular signals was investigated. CD45- HPB-ALL T cells were transfected with cDNA encoding the CD45RA+B+C- isoform. The tyrosine kinase activity of p59fyn was found to be 65% less in CD45- cells than in CD45+ cells, whereas p56lck kinase activity was comparable in both sub-clones. In CD45- cells the TCR was uncoupled from protein tyrosine phosphorylation, phospholipase C gamma 1 regulation, inositol phosphate production, calcium signals, diacylglycerol production and protein kinase C activation. Restoration of TCR coupling to all these pathways correlated with the increased p59fyn activity observed in CD45-transfected cells. Co-aggregation of CD4- or CD8-p56lck kinase with the TCR in CD45- cells restored TCR-induced protein tyrosine phosphorylation, phospholipase C gamma 1 regulation and calcium signals. Receptor-mediated calcium signals were largely due (60-90%) to Ca2+ influx, and only a minor component (10-40%) was caused by Ca2+ release from intracellular stores. Maximal CD3-mediated Ca2+ influx occurred at CD3 mAb concentrations at which inositol phosphate production was non-detectable. These results indicate that CD45-regulated p59fyn plays a critical role in coupling the TCR to specific intracellular signalling pathways and that CD4- or CD8-p56lck can only restore signal transduction coupling in CD45- cells when brought into close association with the TCR.
Shiroo
M
M
Department of Immunology, Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, UK.
Goff
L
L
Biffen
M
M
Shivnan
E
E
Alexander
D
D
D001692:Biological Transport; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D004075:Diglycerides / Q000096:biosynthesis*; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006801:Humans; D007295:Inositol Phosphates / Q000096:biosynthesis; D017493:Leukocyte Common Antigens / Q000502:physiology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism*; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051076:Proto-Oncogene Proteins c-fyn; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D004075:Diglycerides; D007295:Inositol Phosphates; D011518:Proto-Oncogene Proteins; D011948:Receptors, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases; C494957:FYN protein, human; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D051076:Proto-Oncogene Proteins c-fyn; D011493:Protein Kinase C; D017493:Leukocyte Common Antigens; D017027:Protein Tyrosine Phosphatases; D002118:Calcium