Gannamedi, D. P. | bioRxiv Science

bioRxiv2026

Matrix nucleotide homeostasis couples energetic state to mitochondrial translation

Mitochondrial protein synthesis is essential for oxidative phosphorylation, yet how organellar energetic state regulates the mitochondrial translation machinery remains poorly understood. Here, we show that mitochondrial translation is acutely sensitive to ATP synthase-dependent bioenergetic state. Pharmacological inhibition of the F1Fo-ATP synthase with oligomycin or citreoviridin rapidly and selectively suppresses mitochondrial protein synthesis, while mitoribosome profiling reveals a genome-wide loss of productive ribosome engagement. ATP synthase inhibition induces inner-membrane hyperpolarization, depletes bioavailable matrix ATP, and reduces matrix GTP availability. Relieving hyperpolarization restores nucleotide pools and mitochondrial translation despite persistent ATP synthase inhibition, whereas selective restoration of matrix GTP markedly rescues protein synthesis when adenine nucleotide exchange is restricted. These findings identify matrix GTP availability as a proximal energetic constraint on mitochondrial translation and reveal an organelle-intrinsic mechanism coupling ATP synthase-dependent bioenergetic state to mitoribosome activity.

cell biology↗

bioRxiv2026

Pharmacologic DPP-4 inhibition promotes CD8⁺ T cell metabolic fitness to enhance anti-tumor activity

Metabolic dysfunction is a hallmark of CD8+ T cell exhaustion in the tumor microenvironment. Thus, there is growing interest in developing strategies that enhance anti-tumor functions of CD8+ T cells via metabolic reprogramming. Here, we identify dipeptidyl peptidase 4 (DPP-4) as a previously unknown regulator of CD8+ T cell function and metabolism. We discovered that DPP-4 is upregulated in exhausted CD8+ T cells. Pharmacological inhibition of DPP-4 with the FDA-approved anti-diabetic drug sitagliptin transcriptionally and metabolically reprogrammed CD8+ T cells, increasing spare mitochondrial respiratory capacity, proliferation, cytotoxic mediator production, and antigen-specific cancer cell killing capability. The functional effects of sitagliptin were dependent on upregulation of glutamate decarboxylase 1 (GAD1), an enzyme that feeds glutamate into the tricarboxylic acid (TCA) cycle, highlighting a new role for GAD1 in CD8+ T cell respiration and proliferation. We found that systemic inhibition of DPP-4 in preclinical mouse glioblastoma (GBM) models prolongs survival in a CD8+ T cell-dependent manner, and retrospective clinical cohort analysis revealed better outcomes in GBM patients using DPP-4 inhibitors. Importantly, preconditioning of Chimeric Antigen Receptor (CAR) T-cells with DPP-4 inhibition enhanced their cytotoxicity, persistence, and therapeutic efficacy in pediatric GBM. Together, our findings provide mechanistic and biological rationale for repurposing readily accessible DPP-4 inhibitors to enhance anti-tumor CD8+ T cell responses.

immunology↗