INTRACELLULAR PROTEIN-PHOSPHORYLATION IN MURINE PERITONEAL-MACROPHAGES IN RESPONSE TO BACTERIAL LIPOPOLYSACCHARIDE (LPS) - EFFECTS OF KINASE-INHIBITORS AND LPS-INDUCED TOLERANCE

Intracellular protein phosphorylation is thought to be the initial ste p in cell activation. Bacterial lipopolysaccharide (LPS) induces a spe cial set of the protein phosphorylation in the murine peritoneal macro phages, including p65 (molecular mass of 65 kDa) which is a substrate of serine kinase and the most dominant phosphorylated cytosolic protei n. This article deals with the relation between the LPS-induced protei n phosphorylation in the murine peritoneal macrophages and their produ ctions of IL-1beta and TNF-alpha. LPS-induced p65 phosphorylation seem s to be dependent on protein kinase C (PKC) and calmodulin (CaM), beca use it diminishes in the presence of inhibitors to PKC or CaM. Tyrosin e kinase inhibitors do not affect the p65 phosphorylation. The PKC inh ibitors also affect the mRNA expressions and the productions of active molecules of IL-1beta and TNF-alpha. Though the CaM inhibitor inhibit s the mRNA expression and the active molecule production of IL-1beta, it does not affect those of TNF-alpha. These results suggest that LPS- induced p65 phosphorylation is closely related to PKC and CaM, and tha t IL-1beta production depends on PKC and CaM, while the TNF-alpha prod uction is not dependent on CaM. These findings indicate the existances of multiple pathways and different regulatory mechanisms for transduc tion of LPS signal in the macrophages. Furthermore, LPS-induced phosph orylation is not observed in endotoxin tolerant macrophages after re-s timulation with LPS, suggesting that the LPS-stimulus signal is blocke d at a site in the signal transduction-pathway before the point of pho sphorylation of proteins in the tolerant macrophages.