Calcium Signaling Group, Department of Biochemistry and Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
Institute for Neuroimmunology and Multiple Sclerosis Research, University Medical Center Göttingen, 37075 Göttingen, Germany.
Sci Signal. 2021 Nov 16;14(709):eabe3800. doi: 10.1126/scisignal.abe3800.
The formation of Ca microdomains during T cell activation is initiated by the production of nicotinic acid adenine dinucleotide phosphate (NAADP) from its reduced form NAADPH. The reverse reaction—NAADP to NAADPH—is catalyzed by glucose 6-phosphate dehydrogenase (G6PD). Here, we identified NADPH oxidases NOX and DUOX as NAADP-forming enzymes that convert NAADPH to NAADP under physiological conditions in vitro. T cells express NOX1, NOX2, and, to a minor extent, DUOX1 and DUOX2. Local and global Ca signaling were decreased in mouse T cells with double knockout of and but not with knockout of or Ca microdomains in the first 15 s upon T cell activation were significantly decreased in but not in T cells, whereas both DUOX1 and DUOX2 were required for global Ca signaling between 4 and 12 min after stimulation. Our findings suggest that a DUOX2- and G6PD-catalyzed redox cycle rapidly produces and degrades NAADP through NAADPH as an inactive intermediate.
T 细胞激活过程中 Ca 微区的形成是由其还原形式 NADPH 生成烟酰胺腺嘌呤二核苷酸磷酸（NAADP）引发的。相反的反应——NAADP 到 NADPH——是由葡萄糖 6-磷酸脱氢酶（G6PD）催化的。在这里，我们鉴定出 NADPH 氧化酶 NOX 和 DUOX 是 NAADP 形成酶，它们在体外生理条件下将 NAADPH 转化为 NAADP。T 细胞表达 NOX1、NOX2，以及在较小程度上表达 DUOX1 和 DUOX2。在 和 双敲除的小鼠 T 细胞中，局部和全局 Ca 信号均降低，但在 或 敲除的 T 细胞中没有降低。在 T 细胞激活后的最初 15 秒内，Ca 微区的 Ca 信号明显降低，但在 T 细胞中没有降低，而 DUOX1 和 DUOX2 都需要在刺激后 4 到 12 分钟之间进行全局 Ca 信号转导。我们的发现表明，DUOX2 和 G6PD 催化的氧化还原循环通过 NADPH 作为无活性中间物快速产生和降解 NAADP。
