SUMMARY Activated T cells engage aerobic glycolysis and anabolic metabolism for growth, proliferation, and effector functions. We propose that a glucose-poor tumor microenvironment limits aerobic glycolysis in tumor-infiltrating T cells, which suppresses tumoricidal effector functions. We discovered a new role for the glycolytic metabolite phosphoenolpyruvate (PEP) in sustaining T cell receptor-mediated Ca2+-NFAT signaling and effector functions by repressing sarco/ER Ca2+-ATPase (SERCA) activity. Tumor-specific CD4 and CD8 T cells could be metabolically reprogrammed by increasing PEP production through overexpression of phosphoenolpyruvate carboxykinase 1 (PCK1), which bolstered effector functions. Moreover, PCK1-overexpressing T cells restricted tumor growth and prolonged the survival of melanoma-bearing mice. This study uncovers new metabolic checkpoints for T cell activity and demonstrates that metabolic reprogramming of tumor-reactive T cells can enhance anti-tumor T cell responses, illuminating new forms of immunotherapy.

Depleting regulatory T cells (T reg cells) to counteract immunosuppressive features of the tumor microenvironment (TME) is an attractive strategy for cancer treatment; however, autoimmunity due to systemic impairment of their suppressive function limits its therapeutic potential. Elucidating approaches that specifically disrupt intratumoral T reg cells is direly needed for cancer immunotherapy. We found CD36 was selectively up-regulated in intrautumoral T reg cells as a central metabolic modulator. CD36 fine-tuned mitochondrial fitness via PPAR-β signaling, programming T reg cells to adapt to a lactic acid-enriched TME. Genetic ablation of Cd36 in T reg cells suppressed tumor growth accompanied by a decrease in intratumoral T reg cells and enhancement of anti-tumor activity in tumor-infiltrating lymphocytes without disrupting immune homeostasis. Furthermore, CD36 targeting elicited additive anti-tumor responses with anti-PD-1 therapy. Our findings uncover the unexplored metabolic adaptation that orchestrate survival and functions of intratumoral T reg cells, and the therapeutic potential of targeting this pathway for reprogramming the TME.

Human coxsackievirus (CV) belongs to the picornavirus family, which consists of over 200 medically relevant viruses. In picornavirus, a chymotrypsin-like protease (3C pro ) is required for viral replication by processing the polyproteins, and thus it is regarded as an antiviral drug target. A 3C-like protease (3CL pro ) also exists in human coronaviruses (CoV) such as 229E and the one causing severe acute respiratory syndrome (SARS). To combat SARS, we previously had developed peptidomimetic and zinc-coordinating inhibitors of 3CL pro . As shown in the present study, some of these compounds were also found to be active against 3C pro of CV strain B3 (CVB3). Several crystal structures of 3C pro from CVB3 and 3CL pro from CoV-229E and SARS-CoV in complex with the inhibitors were solved. The zinc-coordinating inhibitor is tetrahedrally coordinated to the His 40 -Cys 147 catalytic dyad of CVB3 3C pro . The presence of specific binding pockets for the residues of peptidomimetic inhibitors explains the binding specificity. Our results provide a structural basis for inhibitor optimization and development of potential drugs for antiviral therapies.