LncBADR promotes T cell-mediated autoimmunity by binding Mccc1 and Pcca to regulate BCAAs degradation.

T cell dysfunction is a pivotal driving factor in autoimmune diseases, yet its underlying regulatory mechanisms remain incompletely understood. The role of long non-coding RNAs (lncRNAs) in immune regulation has gradually been recognized, although their functional mechanisms in T cells remain elusive. This study focuses on lncBADR (LncRNA Branched-chain Amino acids Degradation Regulator), elucidating its mechanism by which it regulates branched-chain amino acids (BCAAs) metabolism to influence T cell effector functions. Mice with specific knockout of lncBADR (T cell^lncBADR-/-) exhibited markedly ameliorated experimental autoimmune encephalomyelitis (EAE) symptoms. Mechanistic investigations revealed that lncBADR inhibits BCAAs degradation by binding to the enzymes Mccc1 and Pcca, leading to the accumulation of BCAAs within T-cells. This, in turn, activates the mTOR-Stat1 signaling pathway, promoting IFN-γ secretion and exacerbating EAE pathology. In contrast, knockout of lncBADR restored BCAAs degradation, significantly reducing IFN-γ secretion in T cells and suppressing their pathogenic functions. Further studies demonstrated that high-BCAAs feeding partially reversed the protective effects of lncBADR knockout, indicating that lncBADR plays a crucial role in autoimmune inflammation by regulating BCAAs metabolism. This study offers new insights into targeting lncBADR or modulating BCAAs metabolism as potential therapeutic strategies for autoimmune diseases.