M-CSF Induces Monocyte Survival by Activating NF-κB p65 Phosphorylation at Ser276 via Protein Kinase C

Macrophage colony-stimulating factor (M-CSF) promotes mononuclear phagocyte survival and proliferation. The transcription factor Nuclear Factor-kappaB (NF-kappa B) is a key regulator of genes involved in M-CSF-induced mononuclear phagocyte survival and this study focused at identifying the mechanism of NF-kappa B transcriptional activation. Here, we demonstrate that M-CSF stimulated NF-kappa B transcriptional activity in human monocyte-derived macrophages (MDMs) and the murine macrophage cell line RAW 264.7. The general protein kinase C (PKC) inhibitor Ro-31-8220, the conventional PKC alpha/beta inhibitor Go-6976, overexpression of dominant negative PKC alpha constructs and PKC alpha siRNA reduced NF-kappa B activity in response to M-CSF. Interestingly, Ro-31-8220 reduced Ser276 phosphorylation of NF-kappa Bp65 leading to decreased M-CSF-induced monocyte survival. In this report, we identify conventional PKCs, including PKC alpha as important upstream kinases for M-CSF-induced NF-kappa B transcriptional activation, NF-kappa B-regulated gene expression, NF-kappa B p65 Ser276 phosphorylation, and macrophage survival. Lastly, we find that NF-kappa B p65 Ser276 plays an important role in basal and M-CSF-stimulated NF-kappa B activation in human mononuclear phagocytes.