INFLUENCE OF TRIACYLGLYCEROL BIOSYNTHESIS RATE ON THE ASSEMBLY OF APO-B-100-CONTAINING LIPOPROTEINS IN HEP G2 CELLS

被引：83

作者：

BOREN, J

RUSTAEUS, S

WETTESTEN, M

ANDERSSON, M

WIKLUND, A

OLOFSSON, SO

机构：

[1] UNIV GOTEBORG,DEPT MED BIOCHEM,S-41390 GOTHENBURG,SWEDEN

[2] UNIV GOTEBORG,WALLENBERG LAB,GOTHENBURG,SWEDEN

来源：

ARTERIOSCLEROSIS AND THROMBOSIS | 1993年 / 13卷 / 12期

关键词：

APO-B-100; HEP G2 CELLS; TRIACYLGLYCEROL BIOSYNTHESIS;

D O I：

10.1161/01.ATV.13.12.1743

中图分类号：

R5 [内科学];

学科分类号：

1002 [临床医学]; 100201 [内科学];

摘要：

Apolipoprotein B-100 (apoB-100) appears in three forms in the endoplasmic reticulum of Hep G2 cells: (1) tightly bound to the membrane, ie, not extractable by sodium carbonate. This form is glycosylated but protease sensitive when present in intact microsomes, suggesting that it is only partially translocated to the microsomal lumen; (2) extractable by sodium carbonate and present on low-density lipoprotein-very-low-density lipoprotein (LDL-VLDL)-like particles. This form is glycosylated and secreted into the medium; and (3) extractable by sodium carbonate but having a higher density than the LDL-VLDL-like particles. This form, referred to as Fraction I, is glycosylated and protected against proteases when present in intact microsomal vesicles, indicating that it is completely translocated to the luminal side of the microsomal membrane. Fraction I is not secreted into the medium, but it disappears with time from the cell, suggesting that it is degraded. Oleic acid induced a 2.7-fold increase in the rate of the biosynthesis of triacylglycerol but not of phosphatidylcholine in Hep G2 cells. Incubation of the cells with oleic acid had no significant effect on the rate of initiation of the apoB-100-containing lipoproteins, nor did it influence the amount of apoB-100 that was associated with the membrane or the turnover of apoB-100 in the membrane. Instead, it increased the proportion of the nascent apoB polypeptides on initiated lipoproteins that was converted into full-length apoB-100 on LDL-VLDL-like particles, giving rise to an increased amount of these particles in the lumen of the secretory pathway. Pulse-chase experiments showed that incubation with oleic acid gave rise to an increased formation of LDL-VLDL-like particles ion behalf of the formation of Fraction I. This effect of oleic acid could partially explain the protective effect of the fatty acid on apoB-100, preventing it from undergoing posttranslational degradation.

引用

页码：1743 / 1754

页数：12

共 21 条

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