Nuclear phosphoproteomics analysis of resting and IL-2-stimulated T lymphocytes

The aim of the present project was to study in detail the site-specific phosphorylation events occurring both in resting as well as in T lymphocytes stimulated with IL-2 for five minutes. For that purpose we combined SILAC-based quantitative mass spectrometry analysis with phosphopeptide enrichment using TiO2 beads. We performed three biological replicas of the same experiment which resulted in the identification of above 8500 unique phosphosites corresponding to more than 3000 proteins. From the 6145 phosphosites that were consistently quantified in at least 2 out of the 3 replicas performed, we detected that 390 were regulated by IL-2 being the up-regulated phosphosites five times more abundant than the down-regulated ones. Those IL-2-dependent phosphosites corresponded to distinct proteins involved in distinct aspects of gene expression and cell cycle regulation.