Urade R, Hayashi Y, Kito M
Research Institute for Food Science, Kyoto University, Japan.
Biochim Biophys Acta. 1988 Dec 8;946(1):151-63. doi: 10.1016/0005-2736(88)90468-3.
125I-Labeled epidermal growth factor was incorporated into and highly concentrated in endosomes of Chinese hamster V79-UF cells during incubation at 37 degrees C for 8 min after binding to its receptors on the cell surface at 4 degrees C. From the labeled cells, endosomes were isolated by isopycnic centrifugation on a Percoll density gradient and then sucrose density gradients. The isolated endosomes were mostly free from contamination by Golgi, endoplasmic reticulum, lysosome, plasma membrane and mitochondria. Endosome membranes were found to differ from plasma membranes in the phospholipid composition. Sphingomyelin and phosphatidylserine were enriched in endosomes, compared with plasma membranes. Diacylphosphatidylcholine and diacylphosphatidylethanolamine were major phospholipids of the membranes in both organelles. The contents of molecular species of diacylphosphatidylcholine and diacylphosphatidylethanolamine with two monoenoic fatty acids were lower in endosomes than in plasma membranes. The differences in the polar head group and molecular species compositions of phospholipids between endosomes and plasma membranes did not change, regardless of whether or not the proportions of phospholipid molecular species in plasma membranes changed. The significance of the lipids in endosomes is discussed.
125I标记的表皮生长因子在4℃与中国仓鼠V79-UF细胞表面的受体结合后，于37℃孵育8分钟期间被内吞并高度浓缩在内体中。从标记的细胞中，通过在Percoll密度梯度上进行等密度离心，然后在蔗糖密度梯度上离心来分离内体。分离得到的内体大多不受高尔基体、内质网、溶酶体、质膜和线粒体的污染。发现内体膜在磷脂组成上与质膜不同。与质膜相比，鞘磷脂和磷脂酰丝氨酸在内体中富集。二酰基磷脂酰胆碱和二酰基磷脂酰乙醇胺是这两种细胞器膜中的主要磷脂。内体中二酰基磷脂酰胆碱和二酰基磷脂酰乙醇胺含两个单烯脂肪酸的分子种类含量低于质膜。无论质膜中磷脂分子种类的比例是否改变，内体与质膜之间磷脂极性头部基团和分子种类组成的差异都没有变化。文中讨论了内体中脂质的意义。
