| Differentiation of naïve CD8+ T cells into effector cells is accompanied by changes in basal gene expression profiles that parallel the acquisition of effector functions. Among these, genes encoding glycolytic enzymes are upregulated following differentiation, which prompted investigation into the regulation of effector T cell function by glucose-dependent metabolism. Effector CD8+ T cells expressed higher levels of glycolytic enzymes and displayed greater glucose uptake, a higher glycolytic rate, and increased lactate production compared to naïve cells. Interestingly, glucose deprivation or 2-DOG selectively inhibited production of IFN-γ, an important cytokine for anti-tumor immunity, but IL-2 production was little affected. Cell viability of stimulated T cells was not augmented by glucose deprivation. Inhibition of IFN-γ occurred at the mRNA level, was not due to altered mRNA stability, and was not associated with inhibition of ERK, JNK, p38 MAPK, or MKK3/MKK6 phosphorylation nor alteration of DNA binding activity of ATF2, AP1, NFAT, NFκB, STAT4, or OCT1. RNA expression of the transcription factors T-bet and eomesodermin did not change in the presence of 2-DOG. Rather, induction of p70 S6K phosphorylation at residues 389 and 421/424 in response to CD3/CD28 ligation was markedly inhibited, suggesting an effect on regulated translation. Consistent with this observation, cycloheximide blocked induction of IFN-γ but not IL-2 mRNA. Also, gene array analysis showed that 2-DOG strongly inhibited mRNA expression of other genes specific to effector functions, such as GM-CSF, perforin, and cyclin D2. 2-DOG also blocked [3H]thymidine incorporation and cytolysis. Stimulation under conditions of hypoxia (1% O2) did not induce inhibition of IFN-γ production, cytolysis, nor p70 S6K phosphorylation. In fact, naïve and effector CD8+ T cells were found to consume little O 2. ATP levels did not decrease in cells stimulated for 3 hours in the presence of 1% O2, but were diminished in cells stimulated with 2-DOG. In conclusion, our results suggest that: (1) select effector functions such as IFN-γ production and cytolytic activity are glucose-dependent, (2) IFN-γ gene transcription in CD8+ T cells requires synthesis of an intermediate protein via a glucose-dependent mechanism, and (3) glucose may be a more important resource for T cells than oxygen.*; *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat; Microsoft Office. |
