Lipopolysaccharide-unresponsive mutant pre-B-cell lines blocked in NF-kappa B activation

B-cell receptor- and phorbol ester-induced NF-kappaB and c-Jun N-terminal kinase activation in B cells requires novel protein kinase C's

Antigen receptor signaling is known to activate NF-kappaB in lymphocytes. While T-cell-receptor-induced NF-kappaB activation critically depends on novel protein kinase C theta (PKCtheta), the role of novel PKCs in B-cell stimulation has not been elucidated. In primary murine splenic B cells, we found high expression of the novel PKCs delta and epsilon but only weak expression of the theta isoform. Rottlerin blocks phorbol ester (phorbol myristate acetate [PMA])- or B-cell receptor (BCR)-mediated NF-kappaB and c-Jun N-terminal kinase (JNK) activation in primary B and T cells to a similar extent, suggesting that novel PKCs are positive regulators of signaling in hematopoietic cells. Mouse 70Z/3 pre-B cells have been widely used as a model for NF-kappaB activation in B cells. Similar to the situation in splenic B cells, rottlerin inhibits BCR and PMA stimulation of NF-kappaB in 70Z/3 cells. A derivative of 70Z/3 cells, 1.3E2 cells, are defective in NF-kappaB activation due to the lack of the IkappaB kinase (IKKgamma) protein. Ectopic expression of IKKgamma can rescue NF-kappaB activation in response to lipopolysaccharides (LPS) and interleukin-1beta (IL-1beta), but not to PMA. In addition, PMA-induced activation of the mitogen-activated protein kinase JNK is blocked in 1.3E2 cells, suggesting that an upstream component common to both pathways is either missing or mutated. Analysis of various PKC isoforms revealed that exclusively PKCtheta was absent in 1.3E2 cells while it was expressed in 70Z/3 cells. Stable expression of either novel PKCtheta or -delta but not classical PKCbetaII in 1.3E2 IKKgamma-expressing cells rescues PMA activation of NF-kappaB and JNK signaling, demonstrating a critical role of novel PKCs for B-cell activation.

Staphylococcus aureus and derived exotoxins induce nuclear factor kappa B-like activity in murine bone marrow macrophages

Heat-killed gram-positive Staphylococcus aureus as well as S. aureus-derived exotoxins B and toxic shock syndrome toxin 1 can induce nuclear factor kappa B (NF-kappa B)-like activity in murine bone marrow macrophages. The induction of NF-kappa B-like activity in murine macrophages by S. aureus was as effective as induction by tumor necrosis factor alpha (TNF-alpha) or lipopolysaccharides (LPS) and was observed in macrophages derived from LPS-sensitive and LPS-resistant mice. Stimulation of macrophages with S. aureus but not with the exotoxins resulted in the accumulation of TNF-alpha in the culture medium. The induction of NF-kappa B-like activity by S. aureus, however, clearly preceded TNF-alpha secretion and was not inhibited by a neutralizing serum against TNF-alpha. In addition, pretreatment of macrophages with the protein synthesis inhibitor cycloheximide or dexamethasone, which prevented the secretion of TNF-alpha from macrophages, did not interfere with the induction of NF-kappa B-like activity by S. aureus. This findings reveal the existence of bacterial components other than LPS which can induce NF-kappa B-like activity in susceptible cells.

The plasmacytoma J558L lacks constitutively active NF-kappa B and is deficient in early response gene activation

In mature B cells the nuclear factor NF-kappa B which binds within the kappa enhancer is constitutively present in the nucleus. However, the lambda light chain producing myeloma J558L has been found to lack constitutively functional NF-kappa B. Deoxycholate released functional NF-kappa B from cytoplasmic extracts and functional NF-kappa B was present in J558L following cycloheximide but not phorbol ester treatment. J558L was also unable to respond to phorbol ester stimulation with synthesis of mRNA from the early response gene TIS11. J558L differs from S107, another myeloma which was found to be deficient in the synthesis of NF-kappa B but not in the activation of TIS11. Somatic cell hybrids were used to further define the defect in J558L; hybrids were made with the myelomas S107 and S194 and the pre-B cell line 70Z/3. In general, complementation of the defect in J558L was observed; however there was not a direct correlation between the levels of TIS11 mRNA and NF-kappa B expression in the somatic cell hybrids, suggesting that the pathways of activation of these genes, while possibly sharing common elements, are not identical. The defect in J558L was surprising given that it has frequently been used for the expression of transfected light chain genes.