Determination of second messengers and protein kinase C in bone marrow derived macrophages stimulated with a bacterial lipopeptide.

The synthetic lipopeptide Pam3Cys-Ala-Gly, an analogue of the N-terminal part of bacterial lipoprotein, constitutes a potent macrophage activator. The role of protein kinase C (PKC) in lipopeptide induced signal transduction was investigated. As determined by enzymatic and immunochemical methods, translocation of PKC could not be observed in lipopeptide stimulated bone marrow derived macrophages. Our studies showed that the membrane-associated form of PKC displayed different characteristics than the cytosolic form. The second messengers, inositoltrisphosphate, cAMP and cGMP, did not seem to be involved in signal transduction. Unlike LPS, Pam3Cys-Ala-Gly induced a rapid rise in cytosolic Ca2+, which was due to an influx of extracellular calcium as well as to a redistribution of intracellular calcium. The data suggest that one major intracellular signal transduction mechanism initiated by lipopeptide consists of altering internal Ca2+ concns.