Protein tyrosine kinase p56(lck) is required for ceramide-induced but not tumor necrosis factor-induced activation of NF-kappa B, AP-1, JNK, and apoptosis

Ceramide has been implicated as an intermediate in the signal transduction of several cytokines including tumor necrosis factor (TNF), Both ceramide a nd TNF activate a wide variety of cellular responses, including NF-kappa B, AP-1, JNK, and apoptosis, Whether ceramide transduces these signals throug h the same mechanism as TNF is not known. In the present study we investiga ted the role of the T cell-specific tyrosine kinase p56(lck) in ceramide- a nd TNF-mediated cellular responses by comparing the responses of Jurkat T c ells with JCaM1 cells, isogeneic Lck-deficient T cells. Treatment with cera mide activated NF-kappa B, degraded I kappa B alpha, and induced NF-kappa B -dependent reporter gene expression in a time-dependent manner in jurkat ce lls but not in JCaM1 cells, suggesting the critical role of p56(lck) kinase , These effects were specific to ceramide, as activation of NF-kappa B by p horbol 12-myristate 13-acetate, lipopolysaccharide, H2O2, and TNF was minim ally affected. p56(lck) was also found to be required for ceramide-induced but not TNF-induced AP-1 activation. Similarly, ceramide activated the prot ein kinases JNK and mitogen-activated protein kinase kinase in Jurkat cells but not in JCaM1 cells. Ceramide also induced cytotoxicity and activated c aspases and reactive oxygen intermediates in Jurkat cells but not in JCaM1 cells. Ceramide activated p56(lck) activity in Jurkat cells. Moreover, the reconstitution of JCaM1 cells with p56(lck) tyrosine kinase reversed the ce ramide-induced NF-kappa B activation and cytotoxicity, Overall our results demonstrate that p56(lck) plays a critical role in the activation of NF-kap pa B, AP-1, JNK, and apoptosis by ceramide but has minimal or no role in ac tivation of these responses by TNF.