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 marow 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.