Limonoids, a novel type of inhibitors of sphingomyelin biosynthesis to study the membrane dynamics of sphingolipid domains

鞘磷脂是形成膜脂双层的重要细胞成分，也是细胞生长、凋亡和炎症的重要组成部分。利用选择性高通量显微镜筛选，我们最近分离到天然化合物，柠檬苦素类化合物，作为真核细胞膜中主要的鞘磷脂生物合成的新的抑制类型。为了更准确地了解它们的治疗特性，我们建立了实验条件来分析它们对各种鞘磷脂依赖事件的影响：1)柠檬苦素gedunin对鞘磷脂含量的调节提高了某些抗癌药物(阿霉素而不是紫杉醇)在HeLa细胞中的效率；2)柠檬苦素预处理细胞后，疟原虫和弓形虫在HeLa细胞中的鞘脂依赖生长减少，但本身具有毒性作用；3)由于柠檬苦素有利于膜上神经酰胺富含结构域的形成，我们试图分析新型硫酰类似物在体外单层囊泡中神经酰胺跨神经膜的运动；4)鞘磷脂的膜分布对控制二酰甘油跨双层运动的各种事件具有重要意义。

Sphingolipids are important cell components for the formation of membrane lipid bilayers as well as for cell growth, apoptosis and inflammation. Using a selective high-throughput microscopy-based screening, we recently isolated natural compounds, Limonoids as new inhibitor type of the biosynthesis of sphingomyelin, the major sphingolipid in eukaryotic membranes. In order to precise their therapeutic properties, we set up the experimental conditions to analyze their effects on various sphingolipid-dependent events: 1) modulation of sphingolipid content by limonoid Gedunin pretreatment improved the efficiency of some anticancer drugs (doxorubicin but not Paclitaxel) in HeLa cells; 2) sphingolipid-dependent growth of Plasmodium malaria parasite in erythrocytes and Toxoplasma parasite in HeLa cells was decreased by limonoid Gedunin pretreatment of the cells but had a toxic effect by itself; 3) since Limonoids favored the formation of ceramide-rich domains in the membrane, we tried to analyse the ceramide transbilayer movement in vitro in unilamellar vesicles with new type of sulhydryl analogs of ceramides; 4) the membrane distribution of sphingomyelin is important to control various events as diacylglycerol transbilayer movement .