Assistant Professor Oklahoma Medical Research Foundation, United States
Disclosure(s):
Meng Zhao, PhD: No financial relationships to disclose
Introduction/Rationale: Invariant natural killer T (iNKT) cells are innate-like T cells with rapid effector functions. Distinct metabolic programs support their differentiation and function. We found that iNKT cells exhibit higher mitochondrial content, activity, and a punctate morphology compared to conventional CD4⁺ T cells. Notably, the mitochondrial fusion regulator Opa1, but not the fission factor Drp1, is specifically required for iNKT cell differentiation: NKT1 and NKT17 subsets are markedly reduced in Opa1-deficient mice, whereas NKT2 cells remain unaffected.
Methods: We used complementary approaches, including conditional genetic models, flow cytometry, thymic organ culture, confocal imaging, and transcriptomic analyses, to dissect how mitochondrial dynamics influence iNKT cell development and signaling.
Results: The differentiation defect is cell-intrinsic and not rescued by Bcl-XL overexpression. Opa1 loss leads to increased mitochondrial volume and decreased membrane potential, indicating dysfunction supported by transcriptional changes. Metabolic reprogramming accompanies this defect, with increased Glut1 expression and 2-NBDG uptake, while LDHA appears to compensate for Opa1 loss. TCR signaling is impaired: NF-κB, AP-1, and mTOR activities are reduced, whereas PLZF and Egr2, downstream of Ca²⁺/NFAT, are elevated. Consistently, TCR-induced Ca²⁺ flux is altered. Remarkably, simultaneous loss of Opa1 and Drp1, which induces mitochondrial stasis, partially restores iNKT cell homeostasis, proliferation, and TCR signaling in Opa1-deficient cells.
Conclusion: These findings uncover a critical role for Opa1-mediated mitochondrial dynamics in coordinating TCR signaling and metabolic programs that shape iNKT cell differentiation.
