Proteomic Profiling of Secreted Proteins, Exosomes, and Microvesicles in Cell Culture Conditioned Media.

Secreted proteins are of tremendous biological interest since they can act as ligands for receptors to activate downstream signalling cascades or be used as biomarkers if altered abundance is correlated with a specific pathological state. Proteins can be secreted either as soluble molecules or as part of extracellular vesicles (i.e., exosomes or microvesicles). The complete proteomic profiling of secretomes requires analysis of secreted proteins and extracellular vesicles. Hence, the method described here enriches for microvesicles, exosomes, and secreted proteins from conditioned media using differential centrifugation. The three fractions are then analyzed by mass spectrometry-based proteomics for in-depth characterization and comparison of the protein secretome of cell lines.