Identification of a form of acyl-CoA:cholesterol acyltransferase specific to liver and intestine in nonhuman primates
Identification of a form of acyl-CoA:cholesterol acyltransferase specific to liver and intestine in nonhuman primates
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DOI：
10.1074/jbc.273.41.26747
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发表时间：
1998-10-09
影响因子：
4.8
通讯作者：
Rudel, LL
中科院分区：
文献类型：
--
作者：
Anderson, RA;Joyce, C;Rudel, LL
本研究表明，在非人灵长类动物肝细胞中存在两种不同形式的胆固醇酯化酶：胆固醇酰基转移酶(ACAT)；一种与最初从人类基因组DNA中克隆的相似，这里称为ACAT1，而另一种基因产物，这里称为ACAT2。灵长类ACAT2基因产物是从非洲绿猴肝脏cDNA文库中克隆的。对分离的ACAT2全长克隆的序列分析表明，ACAT2有一个开放阅读框，编码一个526个氨基酸的蛋白质，与ACAT1的N端101个氨基酸的序列基本没有相似性，但其余425个氨基酸的序列预测有57%的同源性。将克隆的ACAT2基因导入两种不同类型的哺乳动物细胞，获得了对ACAT抑制剂敏感的ACAT活性。Northern印迹分析表明，ACAT2基因主要在猕猴的肝脏和肠道表达。相反，ACAT1基因在几乎所有被检测的组织中都有表达。根据ACAT2的氨基酸序列进行的拓扑预测表明，它有七个跨膜结构域，其构型将推测的酶活性部位放置在内质网的管腔中。ACAT2在内质网膜上的这种定位，除了仅在肝脏和肠道表达外，还表明该酶可能具有主要功能，即将胆固醇酯分泌到含有载脂蛋白B的脂蛋白中。
The present study demonstrates that two different forms of the intracellular cholesterol esterification enzyme acyl-CoA:cholesterol acyltransferase (ACAT) are present in the nonhuman primate hepatocyte; one is similar to that originally cloned from human genomic DNA, here termed ACAT1, while a second gene product, termed ACAT2, is reported here. The primate ACAT2 gene product was cloned from an African green monkey liver cDNA library. Sequence analysis of an isolated, full-length clone of ACAT2 cDNA identified an open reading frame encoding a 526-amino acid protein with essentially no sequence similarity to the ACAT1 cDNA over the N-terminal 101 amino acids but with 57% identity predicted over the remaining 425 amino acids. Transfection of the cloned ACAT2 cDNA into two different mammalian cell types resulted in the production of abundant ACAT activity which was sensitive to ACAT inhibitors. Northern blot analysis showed that the ACAT2 mRNA was expressed primarily in liver and intestine in monkeys. In contrast, ACAT1 mRNA was expressed in almost all tissues examined. Topologic predictions from the amino acid sequence of ACAT2 indicates that it has seven trans-membrane domains in a configuration that places the putative active site of the enzyme in the lumen of the endoplasmic reticulum. This orientation of ACAT2 in the endoplasmic reticulum membrane, in addition to its expression only in liver and intestine, suggests that this enzyme may have as a primary function, the secretion of cholesteryl esters into apoB-containing lipoproteins.