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Arteriosclerosis Thrombosis and Vascular Biology
Article . 2012 . Peer-reviewed
Data sources: Crossref
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HNF4α Increases Liver-Specific Human ATP-Binding Cassette Transporter A1 Expression and Cholesterol Efflux to Apolipoprotein A-I in Response to Cholesterol Depletion

Authors: Nobumichi, Ohoka; Keiichiro, Okuhira; Hongyan, Cui; Weijia, Wu; Ryuichiro, Sato; Mikihiko, Naito; Tomoko, Nishimaki-Mogami;

HNF4α Increases Liver-Specific Human ATP-Binding Cassette Transporter A1 Expression and Cholesterol Efflux to Apolipoprotein A-I in Response to Cholesterol Depletion

Abstract

Objective— Hepatic ATP-binding cassette transporter A1 (ABCA1) plays the major role in maintaining plasma high-density lipoprotein levels by producing cholesterol-accepting nascent high-density lipoprotein, whereas peripheral ABCA1 is responsible for releasing cellular cholesterol. We previously reported that in rodents, cholesterol depletion reduces ABCA1 expression in peripheral but not hepatic cells by increasing a liver-specific ABCA1 transcript via the sterol regulatory element-binding protein-2 system. However, the regulatory element is not conserved in humans. Here we investigated the mechanism of sterol-regulated human hepatic ABCA1 gene expression. Methods and Results— ABCA1 mRNA variant type L3 is a novel and human-liver-specific transcript accounting for ≈25% of total ABCA1 mRNA in the liver and is induced by cellular cholesterol depletion. Specific knockdown or forced expression revealed that type L3 produces functional ABCA1 protein in cholesterol efflux. We identified a regulatory enhancer element for L3 expression lying within intron 3 of the human ABCA1 gene, to which hepatocyte nuclear factor (HNF) 4α binds in response to cholesterol depletion. HNF4α knockdown abolished induction of liver-specific L3 and L2b transcripts (and consequently the liver-type response of ABCA1 expression to cellular cholesterol status) and diminished cholesterol efflux activity. Conclusion— These findings indicate that HNF4α regulates human hepatic ABCA1 expression in response to cholesterol depletion.

Keywords

Binding Sites, Apolipoprotein A-I, Hep G2 Cells, Transfection, Introns, Up-Regulation, Cholesterol, Enhancer Elements, Genetic, HEK293 Cells, Hepatocyte Nuclear Factor 4, Liver, Genes, Reporter, Hepatocytes, Humans, ATP-Binding Cassette Transporters, RNA Interference, RNA, Messenger, Regulatory Elements, Transcriptional, ATP Binding Cassette Transporter 1

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    popularity
    This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
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    influence
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Powered by OpenAIRE graph
citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
23
Top 10%
Average
Average
bronze