Proteomic analysis reveals core monocyte-derived cell differentiation proteome and highlights cellular identity-specific proteins

Monocytes can give rise to multiple highly specialized cell types to perform a wide array of functions, ranging from pathogen phagocytosis to bone resorption. This differentiation is induced by the binding of cytokines to dedicated receptors on the surface of monocytes, which results in the initiation of genetic programs that enable cells to perform their specialized functions. Given their common background, it is not surprising that monocyte-derived cells share abilities and cellular markers, yet their specialized functions require a dedicated set of proteins. In order to dissect the monocyte differentiation process and to define cell type-specific marker proteins, we differentiated circulating monocytes into dendritic cells, M1 and M2 macrophages, and osteoclasts, and assessed their proteomes by quantitative mass spectrometry throughout the differentiation process. Statistical analysis indicated that monocyte differentiation is a linear process characterized by a common core of proteins that is similarly affected among the distinct differentiation paths. Throughout the specialization process a cluster of RNA-binding and processing proteins was downregulated whereas proteins associated to metabolic processes were increased. Analysis of the specialized cells after 10 days of differentiation uncovered existing and putative novel dendritic cell markers. Combined, we here present a comprehensive proteomic analysis of monocyte differentiation uncovering shared and distinct proteomic features of differentiating monocytes and monocyte-derived cells.