Beyond Transcription: T cell-Intrinsic IRF5 Regulates Metabolism and Post-Transcriptional Responses in Autoimmunity 2309706
T cell activation is a meticulously orchestrated process that demands changes in cellular physiology, encompassing extensive transcriptional, translational, and metabolic reprogramming. While these layers of cellular regulation are crucial for T cell differentiation and function, the precise regulatory mechanisms that functionally link them remain incompletely defined. We investigated if T cell-intrinsic IRF5 exerts control beyond transcription and integrates with metabolic pathways. T cells from WT and Irf5-/- mice were activated in vitro (anti-CD3/CD28); activation (CD25, CD69, proliferation) was assessed by flow cytometry. CD40L mRNA and protein were measured. Metabolism was characterized via targeted metabolomics and nutrient transporter expression. Single-cell flow/scRNA-seq analyzed global T cell population shifts. In vivo, EAE models (Irf5-/-, T cell conditional Irf5-/-, adoptive transfer of MOG-specific Irf5-/- T cells) were used and EAE progression scored. Mechanistic analyses included mTORC1 activity, CD40L, glutamine transporters, and inflammatory cytokines in EAE mice. IRF5 is a novel T cell-intrinsic regulator of mTORC1 signaling and glutamine metabolism. Irf5 ablation impaired CD40L protein expression despite preserved mRNA induction. Loss of Irf5 shifted T cell metabolic programs and cellular bioenergetics. Single-cell analysis showed Irf5 deletion skewed T cell populations, altering differentiation. In vivo, conditional Irf5 deletion protected against EAE. Protection was due to suppressed mTORC1 activity, reduced CD40L, dysregulated glutamine transporter, and reduced inflammatory cytokines. IRF5 integrates TCR signaling, metabolic reprogramming, and effector function. It regulates transcription and critical post-transcriptional events, influencing mTORC1 signaling, CD40L expression, and glutamine metabolism. Modulating IRF5 may offer a strategy to manipulate aberrant T cell responses and mitigate T cell-mediated autoimmune conditions. Lupus Foundation of America Gina M. Finzi Fellowship (ZB), National Institutes of health grant 1R01AR076242 (BJB), National Institutes of health grant R03TR004623 (BJB), Department of Defense (DoD) CDMRP Lupus Research Program grant W81XWH-18-1-0674 (BJB), Th Therapeutic Approaches to Autoimmunity (THER)