Mycobacterial strain-specific temporal modulations of newly synthesized macrophage secretome

THP-1 macrophages were infected with four strains of Mycobacterium tuberculosis to study the temporal dynamics of newly synthesized proteins in the secretome. Temporal snapshots of secretome reflect the macrophage response to pathogenicity which in combination with intracellular events, completes the disease picture. However, such studies are compromised by limitations of quantitative proteomics. Metabolic labeling by SILAC allows a 3-plex experiment while isobaric chemical labeling by iTRAQ/TMT allows up to 8 to 10-plex respectively. This makes studying temporal proteome dynamics an intangible and elusive proposition. We have developed a new variant of hyperplexing method, combining triplex SILAC with 6-plex iTRAQ to achieve 18-plex quantitation in a single MS run. THP-1 macrophages were infected with H37Ra, H37Rv, BND433 and JAL2287 and the newly synthesized secreted host proteins were studied over six temporal frame still 30 hours post infection, at a difference of 4 hours each. For quantitation, the strains were encoded with two sets of triple SILAC- H37Ra & H37Rv in one and BND433 & JAL2287 in another with a control in each. These sets were then iTRAQ labeled to encode for temporal profiles across six time points in 6-plex iTRAQ. Effectively a 36-plex design with 4 replicates of each set, these experiments were completed within few days on the mass spectrometer. Using MaxQuant and in house developed tools and pipelines, we have analysed the data to map the temporal and strain specific dynamics of newly synthesized proteins in host. Hyperplexing enables large scale spatio-temporal systems biology studies where large number of samples can be processed simultaneously and in quantitative manner.