Lafont Elodie, Dupont Romain, Andrieu-Abadie Nathalie, Okazaki Toshiro, Schulze-Osthoff Klaus, Levade Thierry, Benoist Hervé, Ségui Bruno
INSERM UMR1037, Centre de Recherches en Cancérologie de Toulouse, Equipe 4, BP84225, 31432 Toulouse Cedex 4, France.
Biochim Biophys Acta. 2012 Apr;1821(4):684-93. doi: 10.1016/j.bbalip.2012.01.012. Epub 2012 Jan 28.
Ceramide, a biologically active sphingolipid in cell death signaling, accumulates upon CD95L treatment, concomitantly to apoptosis induction in Jurkat leukemia T cells. Herein, we show that ceramide did not increase in caspase-8 and -10-doubly deficient Jurkat cells in response to CD95L, indicating that apical caspases are essential for CD95L-triggered ceramide formation. Jurkat cells are typically defined as type 2 cells, which require the activation of the mitochondrial pathway for efficient apoptosis induction in response to CD95L. Caspase-9-deficient Jurkat cells significantly resisted CD95L-induced apoptosis, despite ceramide accumulation. Knock-down of sphingomyelin synthase 1, which metabolizes ceramide to sphingomyelin, enhanced (i) CD95L-triggered ceramide production, (ii) cytochrome c release from the mitochondria and (iii) caspase-9 activation. Exogenous ceramide-induced caspase-3 activation and apoptosis were impaired in caspase-9-deficient Jurkat cells. Conversely, caspase-9 re-expression in caspase-9-deficient Jurkat cells restored caspase-3 activation and apoptosis upon exogenous ceramide treatment. Collectively, our data provide genetic evidence that CD95L-triggered endogenous ceramide increase in Jurkat leukemia T cells (i) is not a mere consequence of cell death and occurs mainly in a caspase-9-independent manner, (ii) is likely involved in the pro-apoptotic mitochondrial pathway leading to caspase-9 activation.
神经酰胺是细胞死亡信号传导中的一种生物活性鞘脂，在CD95L处理后会积累，同时伴随Jurkat白血病T细胞中的凋亡诱导。在此，我们表明，在响应CD95L时，caspase-8和-10双缺陷的Jurkat细胞中神经酰胺不会增加，这表明顶端半胱天冬酶对于CD95L触发的神经酰胺形成至关重要。Jurkat细胞通常被定义为2型细胞，其需要激活线粒体途径以有效诱导响应CD95L的凋亡。尽管神经酰胺积累，但caspase-9缺陷的Jurkat细胞显著抵抗CD95L诱导的凋亡。敲低将神经酰胺代谢为鞘磷脂的鞘磷脂合酶1，增强了（i）CD95L触发的神经酰胺产生，（ii）细胞色素c从线粒体的释放以及（iii）caspase-9的激活。在caspase-9缺陷的Jurkat细胞中，外源性神经酰胺诱导的caspase-3激活和凋亡受损。相反，在caspase-9缺陷 的Jurkat细胞中重新表达caspase-9可恢复外源性神经酰胺处理后的caspase-3激活和凋亡。总体而言，我们的数据提供了遗传学证据，表明Jurkat白血病T细胞中CD95L触发的内源性神经酰胺增加（i）不仅仅是细胞死亡的结果，并且主要以caspase-9非依赖性方式发生，（ii）可能参与导致caspase-9激活的促凋亡线粒体途径。
