Phosphoproteomics quantitative characterization in Jurkat E6.1 and Jurkat Gamma1.

Phosphorylation is a reversible post-translational modification, playing a vital role in protein function. In T cells, protein phosphorylation is the key mechanism regulating T cell receptor – driven signaling pathways. In order to gain insights into the phosphoproteome evolution of T cell activation, we performed a large-scale quantitative phosphoproteomics study of Jurkat E6.1 (wild type) and Jurkat gamma1 (Phospholipase gamma1 null) cell clones upon costimulation with anti-CD3 and anti-CD28 antibodies at times ranging from 15 min to as long as 120 min. In total, we identified 5585 phosphopeptides belonging to 2008 phosphoproteins from both cell clones. We detected 130 and 114 novel phosphopeptides in Jurkat E6.1 and Jurkat gamma1 clones, respectively. A significantly lower number of proteins containing regulated phosphorylation sites were identified in Jurkat gamma1 in comparison to Jurkat E6.1, reflecting the vital role of Phospholipase gamma1 in T cell signaling. Several new phosphorylation sites from lymphocyte-specific protein tyrosine kinase (LCK) were identified. Of these, Serine-121 showed significant changes in JE6.1 while only small changes in the Jgamma1 clone.