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Bovine milk proteome: Quantitative changes in normal milk exosomes, milk fat globule membranes and whey proteomes resulting from Staphylococcus aureus mastitis

Timothy A. Reinhardt, Randy E. Sacco, Brian J. Nonnecke, John D. Lippolis
Journal of Proteomics 2013 v.82 pp. 141-154
Staphylococcus aureus, proteome, protein synthesis, milk proteins, exosomes, mammary gland function, neutrophils, milk, whey, milk fat, cows, bovine mastitis, protein composition
Milk protein expression in healthy cows and cows with mastitis will provide information important for the dairy food industry and immune function in the mammary gland. To facilitate protein discovery, milk was fractioned into whey, milk fat globule membranes (MFGM) and exosomes from healthy and Staphylococcus aureus infected cows. Amine-reactive isobaric tags (iTRAQ) were used to quantify protein changes between milk fractions isolated from healthy and S. aureus infected cows. 2971 milk proteins were identified with a false discovery rate of 0.1%. Greater than 300 milk proteins associated with host defense were identified and 94 were significantly differentially regulated in S. aureus infected milk compared to their uninfected controls. These differentially regulated host defense proteins were selectively segregated in the 3 milk compartments examined. An example of this segregation of host defense proteins was the partitioning and high concentration of proteins indicative of neutrophil extracellular traps (NETs) formation in the MFGM preparations from S. aureus infected milk as compared to exosomes or whey. Protein composition changes found in milk exosomes, MFGM and whey during an infection provides new and comprehensive information on milk protein composition in general as well as changes occurring during an infection.