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The role of N-linked glycosylation on the assembly and secretion of VLDL

N联糖基化对VLDL组装和分泌的作用

基本信息

批准号：
10671087
负责人：
MOGAMI Tomoko
金额：
$ 1.79万
依托单位：
National Institute of Health Sciences
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-10671087/
关键词：
apolipoprotein B VLDL secretion 糖鎖

项目摘要

Apolipoprotein B (apoB) is the huge glycoprotein that is essential for the assembly of very low density lipoproteins (VLDL). In this study, we investigated the role of N-linked glycosylation of apoB in the assembly and secretion of VLDL.Treatment of rat hepatocytes with tunicamycin (TM) decreased synthesis of apoB100 and secretion of apoB100 and apoB48. Secretion of recombinant human apoB variants (i.e. apoB17, B29, B34, B42, and B48 representing the amino-terminal 17%, 29% and so on of apoB) from transfected McA-RH7777 cells was also decreased by TM to different degrees. Since the amino-terminal 17% of apoB is essential for VLDL assembly, we tested the function of the singly glycosylation site (Asn^<158>) within B17. Asn^<158>-to-Gln substitution decreased secretion of apoB17 but had little effect on apoB37 and apoB48 secretion. In contrast, mutagenesis of all (five) glycosylation sites decreased the secretion of apoB50 at levels similar to that of their wild type counterparts treated with TM.Furthermore, the mutagenesis markedly diminished the secretion of mutated apoB50 as VLDL, although it had relatively little effect on apoB50 secretion as dense lipoproteins. Similarly, treatment of primary rat hepatocytes with TM decreased secretion of apoB48 as VLDL.In these cells, TM decreased the movement of apoB from the microsomal membranes to the lumen and thereby diminished the appearance of VLDL in the lumen. Thus, we conclude that N-linked glycosylation of apoB plays an important role in the assembly and secretion of VLDL.

载脂蛋白B（apoB）是极低密度脂蛋白（VLDL）组装所必需的巨大糖蛋白。在本研究中，我们研究了apoB的N-连接糖基化在极低密度脂蛋白（VLDL）组装和分泌中的作用。TM也不同程度地减少了转染的McA-RH 7777细胞中重组人apoB变体（即apoB氨基端17%、29%等的apoB 17、B29、B34、B42和B48等）的分泌。由于apoB的氨基末端17%对于VLDL组装是必需的，我们测试了B17内的单一糖基化位点（Asn^）的功能<158>。Asn^<158>-to-Gln取代可降低apoB 17的分泌，但对apoB 37和apoB 48的分泌影响不大。与此相反，所有（5个）糖基化位点的诱变降低了apoB 50的分泌水平与TM处理的野生型对应物相似。此外，诱变显着减少了突变的apoB 50作为VLDL的分泌，尽管它对apoB 50作为致密脂蛋白的分泌影响相对较小。同样地，用TM处理原代大鼠肝细胞减少了apoB 48作为VLDL的分泌，在这些细胞中，TM减少了apoB从微粒体膜向管腔的移动，从而减少了VLDL在管腔中的出现。因此，我们得出结论，N-连接的糖基化的载脂蛋白B中起着重要的作用，在组装和分泌的VLDL。