Modulation of intracellular leucine through deletion of the branched chain amino transferase (BCAT) influences CD4+ T cell differentiation and effector function 2921

Abstract Description CD4+ T cell subsets, each with diverse metabolic needs, orchestrate a fine-tuned immune response. Leucine, a branched chain amino acid, is catabolized by the cytosolic and mitochondrial branched chain aminotransferase (BCATc and BCATm). While leucine supports T cell activation and function, it is unknown if modulation of BCAT influence CD4+ T cell differentiation. Therefore, we sought to interrogate the role of leucine and the two BCAT isoenzymes in CD4+ T cell differentiation and function. CD4+ T cells, isolated from mice with T cells deficient in BCATc (BCATcKO) or BCATm (BCATmKO), underwent in vitro differentiation to CD4+ T cell subsets. A multifaceted approach of flow cytometry, RT-PCR, and ELISA confirmed differentiation and monitored changes in lineage specific transcription factors and cytokine secretion. BCATc and BCATm-deficient T cells, differentiated to Tregs, demonstrated enhanced Foxp3 levels (92% and 70.5%), with increased IL-10 secretion (23% and 67%), compared to Tregs with normal levels of BCATc or BCATm. Simultaneously, BCATc-deficient Tregs exhibited a Th1-like phenotype with increased Tbet expression (133%). BCATc-deficient T cells, differentiated to Th1 cells, increased Tbet expression (32%) and IFNγ secretion (53%). Treatment of Tregs and Th1 cells with n-acetyl leucine amide (NALA), a leucine antagonist, reversed observed phenotypes. The data indicate leucine availability impacts CD4+ T cell differentiation and function in a subset-dependent manner. Funding Sources NIH NCI 1R15CA249796-01A1 Topic Categories Immune Response Regulation: Molecular Mechanisms (IRM)