Protein synthesis plays an important role in T cell activation. It is essential for immune function and proliferation of the activated T cell. We see that activation of quiescent Go T cells with ionomycin and PMA rapidly increases the rate of protein synthesis. Treatment with ionomycin alone did not induce protein synthesis, but treatment with PMA alone did induce protein synthesis, but at a reduced rate. In the presence of immunosuppressants FK506 and rapamycin, protein synthesis induced by ionomycin+PMA was reduced by no more than 40-50%. Proteins induced after activation with the above conditions were analyzed by SDS PAGE of metabolically labeled cells (35S-met). Ionomycin+PMA treatment and PMA treatment induce similar proteins. Inhibition by FK506 and rapamycin, however, may inhibit the biosynthesis of specific proteins. We are in the process of trying to identify these unique proteins. We have isolated polysomes from FK506 and rapamycin treated cells, and have used them as a source of translatable mRNAs for the purpose of synthesizing these induced proteins, in vitro. This will enable us to specifically identify these proteins and potentially clone these factors of interest, namely those potentially having a role in the induction of immune responsive genes such as IL-2, IL-2R and gamma-IFN. Concurrently, we are also interested in the regulation of protein synthesis by the activities of certain key translation initiation factors. We have evidence that the phosphorylation state of eIF-4alpha immediately increases upon mitogenic activation. The activity of the guanine- nucleotide exchange factor, eIF-2B also increases rapidly. We would like to identify what role these factors play in the control of protein synthesis during T cell activation.
