Clarke J T, Cook H W, Spence M W
Neurochem Res. 1985 Mar;10(3):427-38. doi: 10.1007/BF00964610.
To compare the subcellular distribution of endogenously synthesized and exogenous gangliosides, cultured murine neuroblastoma cells (N1E-115) were incubated in suspension for 22 h in the presence of D-[1-3H]galactose or [3H]GM1 ganglioside, transferred to culture medium containing no radioisotope for periods of up to 72 hr, and then subjected to subcellular fractionation and analysis of lipid-sialic acid and radiolabeled ganglioside levels. The results indicated that GM2 and GM3 were the principal gangliosides in the cells with only traces of GM1 and small amounts of disialogangliosides present. About 50% of the endogenously synthesized radiolabelled ganglioside in the four major subcellular membrane fractions studied was recovered from plasma membrane and only 10-15% from the crude mitochondrial membrane fraction. In contrast, 45% of the exogenous [3H]GM1 taken up into the same subcellular membrane fractions was recovered from the crude mitochondrial fraction; less than 15% was localized in the plasma membrane fraction. The results are similar to those obtained from previously reported studies on membrane phospholipid turnover. They suggest that exogenous GM1 ganglioside, like exogenous phosphatidylcholine, does not intermix freely with any quantitatively major pool of endogenous membrane lipid.
为了比较内源性合成和外源性神经节苷脂的亚细胞分布，将培养的小鼠神经母细胞瘤细胞（N1E-115）在含有D-[1-³H]半乳糖或[³H]GM1神经节苷脂的悬浮液中孵育22小时，转移至不含放射性同位素的培养基中长达72小时，然后进行亚细胞分级分离，并分析脂质唾液酸和放射性标记神经节苷脂的水平。结果表明，GM2和GM3是细胞中的主要神经节苷脂，仅存在微量的GM1和少量的二唾液酸神经节苷脂。在所研究的四个主要亚细胞膜组分中，约50%的内源性合成放射性标记神经节苷脂从质膜中回收，而从粗线粒体膜组分中仅回收10%-15%。相比之下，摄取到相同亚细胞膜组分中的外源性[³H]GM1有45%从粗线粒体组分中回收；定位在质膜组分中的不到15%。这些结果与先前报道的关于膜磷脂周转的研究结果相似。它们表明，外源性GM1神经节苷脂与外源性磷脂酰胆碱一样，不会与任何数量上占主要的内源性膜脂池自由混合。
