Neutral sphingomyelinase-2 (NSM2) is a member of a superfamily of enzymes responsible for conversion of sphingomyelin into phosphocholine and ceramide at the cytosolic leaflet of the plasma membrane. Upon specific ablation of NSM2, T cells proved to be hyper-responsive to CD3/CD28 co-stimulation, indicating that the enzyme acts to dampen early overshooting activation of these cells. It remained unclear whether hyper-reactivity of NSM2-deficient T cells is supported by a deregulated metabolic activity in these cells. Here, we demonstrate that ablation of NSM2 activity affects metabolism of the quiescent CD4⁺ T cells which accumulate ATP in mitochondria and increase basal glycolytic activity. This supports enhanced production of total ATP and metabolic switch early after TCR/CD28 stimulation. Most interestingly, increased metabolic activity in resting NSM2-deficient T cells does not support sustained response upon stimulation. While elevated under steady-state conditions in NSM2-deficient CD4⁺ T cells, the mTORC1 pathway regulating mitochondria size, oxidative phosphorylation, and ATP production is impaired after 24 h of stimulation. Taken together, the absence of NSM2 promotes a hyperactive metabolic state in unstimulated CD4⁺ T cells yet fails to support sustained T cell responses upon antigenic stimulation.

中性鞘磷脂酶-2（NSM2）是负责将鞘磷脂转化为质膜胞质小叶上的磷酸胆碱和神经酰胺的酶超家族的成员。NSM2的特定消融后，T细胞被证明对CD3 / CD28共同刺激反应过度，表明该酶可抑制这些细胞的早期超调活化。尚不清楚NSM2缺陷型T细胞的高反应性是否受到这些细胞中代谢活性失调的支持。在这里，我们证明了NSM2活性的消融会影响静态CD4 ^+的代谢T细胞在线粒体中积累ATP，并增加基础糖酵解活性。这支持在TCR / CD28刺激后早期提高总ATP的产生和代谢转换。最有趣的是，静止的NSM2缺陷T细胞中新陈代谢活动的增加不支持刺激后的持续反应。在稳态条件下，在缺乏NSM2的CD4 ⁺ T细胞中升高时，刺激24小时后，调节线粒体大小，氧化磷酸化和ATP产生的mTORC1途径受损。两者合计，NSM2的缺乏促进未经刺激的CD4 ⁺ T细胞过度活跃的代谢状态，但不能支持抗原刺激后持续的T细胞反应。