Couttas Timothy Andrew, Rustam Yepy Hardi, Song Huitong, Qi Yanfei, Teo Jonathan David, Chen Jinbiao, Reid Gavin Edmund, Don Anthony Simon
Centenary Institute, The University of Sydney, Camperdown, NSW 2006, Australia.
Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, VIC 3010, Australia.
Metabolites. 2020 Jun 8;10(6):236. doi: 10.3390/metabo10060236.
The number, position, and configuration of double bonds in lipids affect membrane fluidity and the recruitment of signaling proteins. Studies on mammalian sphingolipids have focused on those with a saturated sphinganine or mono-unsaturated sphingosine long chain base. Using high-resolution liquid chromatography-tandem mass spectrometry (LC-MS/MS), we observed a marked accumulation of lipids containing a di-unsaturated sphingadiene base in the hippocampus of mice lacking the metabolic enzyme sphingosine kinase 2 (SphK2). The double bonds were localized to positions C4-C5 and C14-C15 of sphingadiene using ultraviolet photodissociation-tandem mass spectrometry (UVPD-MS/MS). Phosphorylation of sphingoid bases by sphingosine kinase 1 (SphK1) or SphK2 forms the penultimate step in the lysosomal catabolism of all sphingolipids. Both SphK1 and SphK2 phosphorylated sphinga-4,14-diene as efficiently as sphingosine, however deuterated tracer experiments in an oligodendrocyte cell line demonstrated that ceramides with a sphingosine base are more rapidly metabolized than those with a sphingadiene base. Since SphK2 is the dominant sphingosine kinase in brain, we propose that the accumulation of sphingadiene-based lipids in SphK2-deficient brains results from the slower catabolism of these lipids, combined with a bottleneck in the catabolic pathway created by the absence of SphK2. We have therefore uncovered a previously unappreciated role for SphK2 in lipid quality control.
脂质中双键的数量、位置和构型会影响膜流动性以及信号蛋白的募集。对哺乳动物鞘脂的研究主要集中在具有饱和鞘氨醇或单不饱和鞘氨醇长链碱基的那些脂质上。使用高分辨率液相色谱 - 串联质谱法（LC-MS/MS），我们观察到在缺乏代谢酶鞘氨醇激酶2（SphK2）的小鼠海马体中，含有二不饱和鞘二烯碱基的脂质显著积累。利用紫外光解离 - 串联质谱法（UVPD-MS/MS），双键定位于鞘二烯的C4 - C5和C14 - C15位置。鞘氨醇激酶1（SphK1）或鞘氨醇激酶2（SphK2）对鞘氨醇碱基的磷酸化是所有鞘脂溶酶体分解代谢的倒数第二步。SphK1和SphK2对鞘氨醇 - 4,14 - 二烯的磷酸化效率与对鞘氨醇的磷酸化效率相同，然而在少突胶质细胞系中的氘代示踪实验表明，具有鞘氨醇碱基的神经酰胺比具有鞘二烯碱基的神经酰胺代谢更快。由于SphK2是大脑中主要的鞘氨醇激酶，我们提出在SphK2缺陷型大脑中基于鞘二烯的脂质积累是由于这些脂质分解代谢较慢，以及由于缺乏SphK2而在分解代谢途径中形成的瓶颈所致。因此，我们发现了SphK2在脂质质量控制中一个以前未被认识到的作用。
