Müller P, Pomorski T, Porwoli S, Tauber R, Herrmann A
Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, Institut für Biologie/Biophysik, Germany.
Hepatology. 1996 Dec;24(6):1497-503. doi: 10.1053/jhep.1996.v24.pm0008938187.
The redistribution of spin-labeled phospholipid analogs across the plasma membrane of HepG2 cells, either in suspension or grown as monolayers, was investigated. After incorporation into the outer membrane leaflet spin-labeled aminophospholipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) moved rapidly to the inner monolayer, whereas the analog of phosphatidylcholine (PC) disappeared more slowly from the outer leaflet. The fast, inward movement of the aminophospholipids was abolished after adenosine triphosphate (ATP)-depletion of cells, suggesting the presence of an aminophospholipid translocase in the plasma membrane of these cells. Compared with human red blood cells, the activity of the aminophospholipid translocase is two orders of magnitude higher in HepG2 cells. From these data, a transverse phospholipid asymmetry can be inferred with the aminophospholipids mainly concentrated on the inner monolayer and the choline-containing phospholipids on the outer leaflet. The relevance of the enrichment of PC in the outer membrane leaflet for the formation and composition of the bile is discussed.
研究了自旋标记的磷脂类似物在悬浮培养或单层生长的HepG2细胞的质膜上的重新分布情况。掺入外膜小叶的自旋标记氨基磷脂磷脂酰丝氨酸（PS）和磷脂酰乙醇胺（PE）迅速移动到内单层，而磷脂酰胆碱（PC）类似物从外小叶消失得较慢。细胞的三磷酸腺苷（ATP）耗尽后，氨基磷脂的快速内向移动被消除，这表明这些细胞质膜中存在氨基磷脂转位酶。与人类红细胞相比，HepG2细胞中氨基磷脂转位酶的活性高两个数量级。从这些数据可以推断出横向磷脂不对称性，其中氨基磷脂主要集中在内单层，而含胆碱的磷脂在外小叶。讨论了外膜小叶中PC富集与胆汁形成和组成的相关性。
