Ultraviolet light-induced stimulation of the JNK mitogen-activated proteinkinase in the absence of Src family tyrosine kinase activation

In T cells, the JNK mitogen-activated protein kinase is activated by simult aneous stimulation of the T-cell receptor and CD28 or by a number of stress stimuli including ultraviolet light, hydrogen peroxide, and anisomycin, Lc k, a Src family kinase, is essential for T-cell receptor-mediated activatio n of JNK, We asked whether Lck was also involved in stress-mediated activat ion of JNK, JNK was activated by ultraviolet light irradiation in all of th e four T-cell lines we examined, but Lck was not. Additionally, JNK activat ion by ultraviolet light, hydrogen peroxide, and anisomycin was completely normal in T cells lacking Lck, These data suggest that Lck is not activated by ultraviolet light irradiation, nor is it required for JNK activation in T cells by any of the stress stimuli we tested. We also examined JNK activ ation by ultraviolet light in mouse fibroblasts expressing no known Src kin ases, The activation of JNK by ultraviolet light was completely normal in t hese cells. Finally, treatment of lymphoid and epithelial cells with a Src kinase family inhibitor PPB-reduced tyrosine phosphorylation of cellular pr oteins markedly without affecting ultraviolet light-induced activation of J NK, These results suggest that Src kinases are not essential for ultraviole t light-induced activation of JNK in a diverse variety of cell types.