Transient degradation of NF-kappa B proteins in macrophages after interaction with mast cell granules

THE exposure of the macrophage cell line, J774 to mast cell granules (MCG) led to the formation of altered nuclear transcription factor proteins (NF-k appa Bx), which had faster electrophoretic mobility than the p50 homodimer of NF-kappa B, but retained comparable DNA binding capacity. Antibodies to N-terminal peptides of p50, p52, p65 or c-Rel supershifted only a fraction of NF-kappa Bx. Western blot analyses revealed that nuclear p65 and c-Rel w ere progressively degraded after exposure to MCG, whereas nuclear p50 appea red to be unaffected. In contrast, cytoplasmic p50, p65, c-Rel as well as I kB alpha remained intact after MCG treatment, although p52 was clearly degr aded In comparison to J774 cells, incubation of mouse peritoneal macrophage s with MCG resulted in more extensive alterations to NF-kappa B proteins. T he alterations in NF-kappa B proteins did not affect the expression of Indu cible nitric oxide synthase (iNOS) or TNF-alpha mRNA in J774 cells. These d ata indicate that exposure of J774 cells to MCG leads to generation of alte red nuclear p52, p65 and c-Rel, which retain intact N-terminal peptides, sp ecific oligonucleotide binding and transactivating activity. On the other h and, in peritoneal macrophages, MCG induce more extensive modifications to NF-kappa B proteins with associated inhibition of iNOS or TNF-alpha mRNA ex pression.