Figure S4.

L-Arginine Increases the Survival of Activated T Cells Independent of mTOR Signaling, Related to Figure 4

(A) Human naive CD4⁺ T cells were activated for 4 days, lysed and the phosphorylation levels of S6K1 (pThr389) and 4E-BP (pThr37/46) were analyzed by western blot. Rapamycin inhibited the phosphorylation of the mTOR targets, while DMSO or supplementation of the culture medium with 3 mM L-arginine had no effect. T cells hardly proliferated upon activation in culture medium containing no or 20 μM L-lysine and therefore phosphorylation of the target proteins could not be assessed.

(B) T cell survival experiment. Human naive CD4⁺ T cells were activated in Ctrl medium or in medium containing 100 nM rapamycin. On day 5, cells were washed to withdraw IL-2 and cell survival was measured at different time points.

(C) Same as in (B) but cell survival was only measured 5 days after IL-2 withdrawal. n = 7 from seven donors. Boxplot. Same as in Figures 2A and 2B.

(D) Metabolic profiling of CD4⁺ T cells activated in medium containing 100 nM rapamycin. The heat map shows the difference of metabolite abundances between rapamycin-treated cells and controls. n = 10 from two donors.