Tumor necrosis factor (TNF) is one of the few physiological inducers of the pleiotropic transcription factor NF kappa B. NF kappa B may play a central role in mediating TNF's gene regulatory action; however, the molecular mechanisms of TNF-induced NF kappa B activation are poorly understood. In this study, we demonstrate with two human leukemic cell lines, K562 and Jurkat, that TNF induces rapid and transient activation and translocation of protein kinase C (PK-C) from the cytosol to the membranes, which is followed by the emergence of kappa B-binding activity. In order to investigate whether TNF-mediated PK-C activation can be linked to induction of NF kappa B, we tried to block TNF action by use of various protein kinase C inhibitors as well as down-regulation of PK-C. Preincubation of Jurkat cells with protein kinase inhibitor H7 or staurosporine blocked PK-C activation by either TNF or phorbol 12-myristate 12-acetate (PMA). This pretreatment regimen completely inhibited NF kappa B activation by PMA. In contrast, TNF's ability to induce NF kappa B remained unaffected. In addition, NF kappa B was TNF-inducible in Jurkat cells depleted for PK-C by long-term exposure to high dose phorbol ester. The data indicate that PK-C is not required for NF kappa B activation by TNF and imply a novel, PK-C-independent mechanism of physiological NF kappa B activation.