Involvement of PKA, PKC, and Ca2+ in LPS-activated expression of the chicken lysozyme gene

The lysozyme gene is activated in myelomonocytic HD11 cells in response to LPS, In this study, we described the involvement of LPS-activated signal tr ansduction pathways in activation of the lysozyme gene. Pre-treatment of HD 11 cells with H-89, H-7, TMB-8, or KN-93 resulted in inhibition of the LPS- enhanced lysozyme expression, suggesting that PKA, PKC, and Ca2+-dependent protein kinases participate in the LPS activation. CaMKII seems to be requi red for the processing of lysozyme transcripts. TPA and calcium ionophore A 23187, when separately added to HD11 cells, stimulated the lysozyme express ion effectively, and forskolin was ineffective. It is interesting that simu ltaneous treatment of cells with forskolin and calcium ionophore A23187 res ulted in a potentiated increase in lysozyme mRNA expression, indicating a s ynergistic cooperation of PKA and Ca2+, This synergistic effect of PKA and Ca2+ was observed on the expression of a stably integrated CAT construct, c ontrolled by the lysozyme promoter and the -6.1-kb enhancer containing bind ing sites for C/EBP and NF-kappaB/Rel, Therefore, we discussed the role of C/EBP beta (NF-M), CREB, and NF-kappaB/Rel as possible targets for phosphor ylation mediated by PKA, PKC, and Ca2+.