Alterations in cellular proteome and secretome upon differentiation from monocyte to macrophage by treatment with phorbol myristate acetate: insights into biological processes.

Monocyte and macrophage are mainly involved in immune response and inflammatory processes. Monocytes circulate in the bloodstream and migrate to various tissues where they can differentiate to macrophages. However, the molecular basis of biological processes involved in this cellular differentiation remains ambiguous. This study was to investigate alterations in cellular and secreted proteins after this differentiation phase. Macrophage was differentiated from U937 human monocytic cell line by treatment with 100 ng/ml phorbol myristate acetate (PMA) for 48 h. Cellular and secreted proteins extracted from PMA-treated cells (macrophages) were compared with those of untreated cells (monocytes) using 2-DE (n=5 gels/condition; stained with Deep Purple fluorescence dye). Quantitative intensity analysis revealed 81 and 67 protein spots whose levels were significantly altered in cellular proteome and secretome. These proteins were subsequently identified by Q-TOF MS and/or MS/MS analyses. The altered levels of cellular elongation factor-2 (EF-2) and secreted alpha-tubulin were confirmed by Western blot analysis. Global protein network analysis demonstrated that these altered proteins were involved in cell death, lipid metabolism, cell morphology, cellular movement, and protein folding. Our data may provide some insights into molecular mechanisms of biological processes upon differentiation from monocytes to macrophages.