Tafazzin-Mediated Cardiolipin Remodeling Controls Metabolic Stress Response and Effector Function of Inflammatory T Cells

Clonal expansion and effector differentiation of T cells require extensive metabolic reprogramming. This includes the restructuring of the inner mitochondrial membrane (IMM) to enhance respiration by increasing chemiosmotic coupling efficiency. Cardiolipin, a unique phospholipid that is exclusively synthesized and localized in the IMM, modulates the biophysical properties of the electron transport chain (ETC) in tissues with high energy demands, such as cardiomyocytes and skeletal muscle. However, it remains unclear whether cardiolipin is also important for metabolic remodeling during T helper (Th) cell differentiation. In this study, we show that cardiolipin transacylation, catalyzed by the enzyme Tafazzin, supports the clonal expansion and effector function of inflammatory Th1 and Th17 cells in vitro and in models of autoimmune colitis and encephalomyelitis. At the molecular level, we demonstrate that loss of Tafazzin-mediated cardiolipin maturation induces a metabolic and transcriptional stress response in Th cells to compensate for impaired coupling efficiency of the ETC complexes and disrupted cellular redox homeostasis. However, the genetic program that restores cellular homeostasis and mitigates oxidative stress concurrently impairs the effector functions of inflammatory T cells, such as cytokine production. Our findings also provide insights into the complex clinical manifestation of patients with Barth syndrome (BTHS) caused by mutations in the human TAFAZZIN gene. BTHS is characterized by cardiac and skeletal myopathy as well as neutropenia and an increased susceptibility to infections. Although the molecular basis of the immunodeficiency remains poorly understood, our findings suggest that impaired Th cell function contributes to the immunopathology observed in BTHS patients.