NF-κB activation by tumor necrosis factor α in the jurkat T cell line is independent of protein kinase A, protein kinase C, and Ca 2+-regulated kinases

Abstract

NF-κB is a DNA-binding regulatory factor able to control transcription of a number of genes, including human immunodeficiency virus (HIV) genes. In T cells, NF-κB is activated upon cellular treatment by phorbol esters and the cytokine tumor necrosis factor α (TNFα). In the present work, we investigated the molecular events leading to NF-κB activation by TNFα in a human T cell line (Jurkat) and its subclone JCT6, which presents a deficiency in the PKA transduction pathway. We found that in both cell lines, both phorbol ester and TNFα were able to activate NF-κB. Phorbol activation was positively modulated by CA 1+ influx while TNFα activation was not. Furthermore, while PMA activation was inhibited by the PKC inhibitor staurosporin, the TNFα effect was unchanged. TNFα did not activate cAMP production and its signal was not modulated by cAMP activators. Moreover, cAMP activators did not activate NF-κB in Jurkat cells. Thus, TNFα-induced NF-gkB activation was found to be mediated by none of the major signal-mediating kinases such as protein kinase C (PKC), protein kinase A, or Ca 2-regulated kinases. Furthermore, we found that cytoplasmic acidification facilitated NF-κB activation by both TNFα and PKC, by a mechanism that increases NF-κB/IκB dissociation without afflecting the NF-κB translocation step.