T cell exhaustion is characterized by reduced effector function, impaired proliferation, altered cytokine production, and compromised immune responses, particularly in chronic infections and cancer. Immune checkpoint molecules binding to exhaustion markers on T cells, including PD-1 and TIM-3, resulting in metabolic energy depletion, ultimately reducing immune-mediated clearance of tumor cells. Cellular protein expression is often resultant of chromatin accessibility to transcription factors (TFs), where accessible chromatin binding regions allow for TFs to bind and modulate protein expression, dictating cellular behaviors. Through prior flow cytometry analyses, the Chang Lab has found an association between elevated pyruvate or hypoxia levels and enhanced expression of the exhaustion marker TIM-3 in CD8+ T cells. We hypothesized that pyruvate accumulation in CD8+ T cells results in a signaling cascade that ultimately results in elevated TIM-3 expression and is correlated with cellular exhaustion. In this project, we found that pyruvate-induced TIM-3 expression is sensitive to metabolic inhibitors, further compounding the influence of metabolism in dictating T cell exhaustion phenotypes. Furthermore, we sought to better understand the signaling network that associates pyruvate accumulation, TIM-3 expression, and T cell exhaustion. Utilizing in vitro and molecular biology approaches, we have unraveled the complexity of this signaling pathway; identifying the importance of histone modification and JunB, JunD, and Bach2 TFs as critical regulators of pyruvate-induced TIM-3 expression. Collectively, these results provide significant insight into the role of pyruvate in modulating CD8+ T cell exhaustion
