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

Antigen receptor signaling is known to activate NF-kappaB in lymphocytes. W hile T-cell-receptor-indticed NF-kappaB activation critically depends on no vel protein kinase C theta (PKC theta), the role of novel PKCs in B-cell st imulation has not been elucidated. In primary murine splenic B cells, we fo und high expression of the novel PKCs delta and epsilon but only weak expre ssion of the theta isoform. Rottlerin blocks phorbol ester (phorbol myrista te acetate [PMA])or B-cell receptor (BCR)-mediated NF-kappaB and c-Jun N-te rminal kinase (JNK) activation in primary B and T cells to a similar extent , suggesting that novel PKCs are positive regulators of signaling in hemato poietic 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 cel ls, 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 activ ation due to the lack of the I kappaB kinase (IKK gamma) protein. Ectopic e xpression of IKK gamma can rescue NF-kappaB activation in response to lipop olysaccharides (LPS) and interleukin-1 beta (IL-1 beta), but not to PMA. In addition, PMA-induced activation of the mitogen-activated protein kinase J NK is blocked in 1.3E2 cells, suggesting that an upstream component common to both pathways is either missing or mutated. Analysis of various PKC isof orms revealed that exclusively PKC theta was absent in 1.3E2 cells while it was expressed in 70Z/3 cells. Stable expression of either novel PKC theta or -delta but not classical PKC beta II in 1.3E2 IKK gamma -expressing cell s rescues PMA activation of NF-kappaB and JNK signaling, demonstrating a cr itical role of novel PKCs for B-cell activation.