Differential Modulation of ACAT1 and ACAT2 Transcription and Activity by Long Chain Free Fatty Acids in Cultured Cells

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• 作者：Toru Seo ; Peter M. Oelkers ; Mara R. Giattina ; Tilla S. Worgall ; Stephen L. Sturley ; and Richard J. Deckelbaum
• 刊名：Biochemistry
• 出版年：2001
• 出版时间：April 17, 2001
• 年：2001
• 卷：40
• 期：15
• 页码：4756 - 4762
• 全文大小：69K
• 年卷期：v.40,no.15(April 17, 2001)
• ISSN：1520-4995

文摘

Fatty acyl CoA and cholesterol are the substrates for cholesteryl ester synthesis by acyl coenzymeA:cholesterol acyltransferase (ACAT). Two ACAT genes have been identified; ACAT1 is expressedubiquitously while ACAT2 is primarily expressed in intestine and liver. We tested effects of differentfree fatty acids (FFAs) on ACAT1 and ACAT2 expression and activity in HepG2 human hepatocytes andTHP1 human macrophages. Incubation of oleic acid, arachidonic acid, or eicosapentaenoic acid, but not25-hydroxycholesterol, induced ACAT1 mRNA levels 1.5-2-fold in HepG2, with no affect on ACAT2mRNA. FFA had no affect on ACAT1 mRNA in THP1 cells. To determine if FFAs affect ACAT1 orACAT2 posttranscriptionally, cells were labeled with [³H]cholesterol in the presence of the different FFAsfor 1-5 h. Both HepG2 and THP1 cells showed the greatest cholesteryl ester production with oleic acid.This was also confirmed by the observation that more [³H]oleic acid incorporated into CE compared to[³H]eicosapentaenoic acid, even though there was no difference in the total uptake of these FFAs. InACAT-deficient SRD4, CHO cells stably transfected with human ACAT1 or ACAT2, ACAT1 expressingcells showed a strong preference for oleic acid while ACAT2 expressing cells utilized unsaturated FFAs.Acyl CoA substrate specificity was further tested in microsomes isolated from these cells as well asHepG2 and THP1. THP1 and ACAT1 cells utilized oleoyl CoA preferentially. In contrast, HepG2 andACAT2 microsomes utilized linolenoyl CoA as well. We conclude that FFAs increase ACAT1 mRNAlevels in a cell specific manner, and furthermore that the ACAT reactions exhibit differential FFA utilization.