Phosphorylation of murine CD8 alpha is not essential for responses of T cell hybridomas to antigen.
CD8 T cell differentiation antigens, expressed on class I-restricted T cells, have a key role in the control of recognition and response of these cells to antigen. It has been suggested that these molecules function as co-receptors together with antigen-specific T cell receptors to regulate T cell responses. We have addressed the question of whether cytoplasmic serine phosphorylation, which occurs on CD8 molecules after activation by antigen or phorbol esters, is relevant to its co-receptor function. By mutagenesis, we show that phorbol ester-induced phosphorylation occurs exclusively on CD8 alpha serine residue 216. However, inhibition of CD8 polypeptide phosphorylation does not appear to have a detrimental effect on several responses of CD8-dependent transfectants to antigen. This is in contrast to results reported with CD4 (N.Glaichenhaus, N.Shastri, D.R. Littmann and J.M.Turner. 1991. Cell, 64:511), suggesting that CD4 and CD8 molecules may play somewhat different roles in the control of T cell activation.
Williams
O
O
Imperial Cancer Research Fund Tumour Immunology Unit, Biology Department, University College London, UK.
Vukmanovic
S
S
Zamoyska
R
R
D000818:Animals; D000941:Antigens / Q000276:immunology*; D015704:CD4 Antigens / Q000502:physiology; D016827:CD8 Antigens / Q000378:metabolism*; D016923:Cell Death; D006825:Hybridomas / Q000276:immunology*; D051379:Mice; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*
D000941:Antigens; D015704:CD4 Antigens; D016827:CD8 Antigens; D012694:Serine