Biochemical Analysis of Activated T Lymphocytes: Protein Phosphorylation and Ras, ERK, and JNK Activation

One of the earliest detectable responses following TCR ligation is the phosphorylation of cellular proteins on either serine, threonine, or tyrosine residues. These covalent modifications are mediated by kinases, and are thought to facilitate various cellular functions, including enzyme activation and protein-protein interactions necessary for the initiation and propagation of catalytic cascades. The coordinated activation of several of these enzymatic cascades following TCR ligation is thought to be necessary for the synthesis and/or activation of the transcription factors that initiate cytokine gene expression, as well as for mediating cell-cycle progression and other T-cell effector functions.