Extracellular proteomes of M-CSF (CSF-1) and GM-CSF-dependent macrophages

Macrophage colony-stimulating factor (M-CSF) (also known as CSF-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) have distinct effects on macrophage lineage populations, which are likely to be contributing to their functional heterogeneity. A comparative proteomic analysis of proteins released into culture media from such populations after M-CSF and GM-CSF exposure was carried out. Adherent macrophage populations, termed bone marrow-derived macrophage (BMM) and GM-BMM, were generated after treatment of murine bone marrow precursors with M-CSF and GM-CSF, respectively. Proteins in 16-h serum-free conditioned media (CM) were identified by two-dimensional gel electrophoresis and mass spectrometry. Respective protein profiles from BMM and GM-BMM CM were distinct and there was the suggestion of a switch from primarily signal peptide-driven secretion to non-classical secretion pathways from BMM to GM-BMM. Extracellular expression of cathepsins (lysosomal proteases) and their inhibitors seems to be a characteristic difference between these macrophage cell types with higher levels usually observed in BMM-CM. Furthermore, we have identified a number of proteins in BMM-CM and GM-BMM-CM that could be involved in various tissue regeneration and inflammatory (immune) processes, respectively. The uncharacterized protein C19orf10, a protein found at high levels in the synovial fluid of arthritis patients, was also differentially regulated; its extracellular levels were upregulated in the presence of GM-CSF.