Sterol-Mediated Regulation of SREBP-1a,1b,1c and SREBP-2 in Cultured Human Cells

Kawabe, Yojiro; Honda, Makoto; Wada, Yoichiro; Yazaki, Yoshio; Suzuki, Takahiro; Ohba, Y; Nabata, Hiroyuki; Endo, Akira; Matsumoto, Akiyo; Itakura, Hiroshige; Kodama, Tatsuhiko

doi:10.1006/bbrc.1994.2095

Cited by 19 publications

(13 citation statements)

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“…We also demonstrated that NPC1L1 promoter activity was regulated by cholesterol concentration, suggesting that NPC1L1 promoter regulation was similar to other cholesterol metabolism genes, such as HMG-CoA reductase, LDL receptor and high-density lipoprotein receptor. [22][23][24] Besides, our results were consistent with data reported by other group, NPC1L1 transcription activity was inhibited while cells were treated with ezetimibe. 25 In addition, it has been reported that NPC1L1 promoter is regulated mainly by SREBP-2, a transcription factor-regulated cholesterol metabolism-related genes expression.…”

Section: Identification Of Npc1l1 Polymorphismssupporting

confidence: 93%

The g.−762T>C polymorphism of the NPC1L1 gene is common in Chinese and contributes to a higher promoter activity and higher serum cholesterol levels

et al. 2009

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Niemann-Pick type C1-like 1 (NPC1L1) protein is responsible for intestinal cholesterol absorption. The aim of the study was to identify genetic polymorphisms of the NPC1L1 gene as well as their functional significance. The method involved screening of promoter and coding regions of the NPC1L1 gene for genetic polymorphisms by direct DNA sequencing of genomic DNA from 50 individuals. Functional studies on promoter polymorphisms were performed using luciferase assay. Association between the polymorphisms and serum cholesterol levels were investigated in 224 individuals. The results showed that in total, 11 single nucleotide polymorphisms were identified. Among them, a promoter polymorphism, g.À762T4C, and a synonymous polymorphism, g.1679C4G, were common (34 and 36%, respectively). These two polymorphisms were highly linked (D¢ value¼0.7459, P-value o0.00001). For the g.À762T4C promoter polymorphism, luciferase assay in HepG2 cell line demonstrated that the À762C allele had a significantly higher promoter activity than the À762T allele (1.30 ± 0.22 vs 0.37 ± 0.06, 3.5-fold, Po0.05). We also showed that the NPC1L1 promoter activity was downregulated by cholesterol content in both genotypes. When association studies were performed, we found that À762C allele was associated with significantly higher serum total cholesterol and LDL-cholesterol content levels in a recessive model (LDL-cholesterol value¼131.2 ± 8.1 vs 116.4 ± 2.2 mg dl -1 ; total cholesterol value¼214.7 ± 9.0 mg dl -1 vs 196.9 ± 2.6, P-value o0.05, n¼224). In conclusion, the C allele at À762 position of the NPC1L1 gene was common in people of Chinese ethnicity. The À762C allele had a higher promoter activity and was associated with a higher serum total cholesterol and LDL-cholesterol level.

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Section: Identification Of Npc1l1 Polymorphismssupporting

confidence: 93%

The g.−762T>C polymorphism of the NPC1L1 gene is common in Chinese and contributes to a higher promoter activity and higher serum cholesterol levels

et al. 2009

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“…Again, we failed to observe an increase in luminescence in response to ALLN in HepG2 cells treated with either 10% serum or LPDS. This observation is in agreement with the recent report that the inhibition of SREBP-1 degradation by ALLN treatment of HepG2 cells increased the mRNA levels for the LDL receptor but not for squalene synthase (8).…”

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confidence: 93%

“…This cDNA, designated ADD1, activated transcription of a reporter gene containing an "E-box" sequence present in the promoter of fatty acid synthase in transfected NIH 3T3 cells. Cloned SREBP cDNA contain two major classes of proteins, SREBP-1 (5) and SREBP-2 (8). Three different cDNAs for SREBP-1 were isolated, suggesting multiple forms of the mRNA and perhaps different proteins as well.…”

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confidence: 99%

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Molecular Cloning and Functional Analysis of the Promoter of the Human Squalene Synthase Gene

Guan

Jiang

Koch

et al. 1995

Journal of Biological Chemistry

102

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Squalene synthase (farnesyl-diphosphate:farnesyl-diphosphate farnesyltransferase, EC 2.5.1.21) is the first enzyme specific to the cholesterol biosynthetic pathway. The activity of rat hepatic squalene synthase is regulated by dietary cholesterol and by the dietary 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) 1 reductase inhibitors, lovastatin, or fluvastatin (1, 2). The activity of human squalene synthase (HSS) and the level of its mRNA are regulated by sterols in the human hepatoma cell line HepG2. Sterol-mediated regulation has been localized to a 10-base pair (bp) element in the 5Ј-flanking region of other sterolregulated genes. This 10-bp sterol regulatory element 1 (SRE-1) mediates increased transcription of the genes encoding HMG-CoA synthase and the low density lipoprotein (LDL) receptor in sterol-depleted cells, and its activity is inhibited by sterols (3, 4). Proteins that bind to the SRE-1 of the LDL receptor (SREBPs) were purified by DNA affinity chromatography from nuclear extracts of HeLa cells. A cDNA for SREBP-1 was isolated from adipocyte cDNA library (5). This cDNA, designated ADD1, activated transcription of a reporter gene containing an "E-box" sequence present in the promoter of fatty acid synthase in transfected NIH 3T3 cells. Cloned SREBP cDNA contain two major classes of proteins, SREBP-1 (5) and SREBP-2 (8). Three different cDNAs for SREBP-1 were isolated, suggesting multiple forms of the mRNA and perhaps different proteins as well. The physiological significance of these subclasses is unclear (6). Different SREBP-1 proteins may have specific physiological roles because mRNAs for the various isoforms are differentially regulated by sterol depletion in HepG2 cells (8).Proteolytic cleavage of the C-terminal membrane-associated domain of the nascent SREBP-1 (125 kDa) forms its nuclear form (68 kDa). This proteolytic maturation was proposed to be accomplished by a sterol-inhibited protease. The calpain inhibitor N-acetyl-leucyl-leucyl-norleucinal (ALLN) induced the mRNA for HMG-CoA synthase and was proposed to inhibit the degradation of the mature SREBP-1 (9).In other sterol-regulated genes, the SRE-1 is not involved in sterol-mediated transcriptional regulation. Although the promoter region of farnesyl diphosphate synthase contains multiple forms of the SRE-1 element, these elements are not involved in the sterol-mediated transcriptional regulation (10). Similarly, the promoter of the hamster HMG-CoA reductase contains unique sites for sterol regulation. Red 25, a nuclear hamster liver protein, binds to this regulatory region but did not bind to the sterol regulatory regions of the LDL receptor and HMG-CoA synthase promoters (11).In this report we characterize the 5Ј region of the HSS gene. The promoter activity and the sterol-mediated regulation of this DNA were assessed by fusing 5Ј-flanking DNA to a luciferase reporter gene and transfecting it into HepG2 cells and Chinese hamster ovary (CHO-K1) cells. A 69 bp DNA sequence confers transcriptional competence and sterol regulation. ADD1...

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“…Once cholesteryl esters are cleaved by LAL, free cholesterol exits the lysosome and participates in the modulation of cholesterol and fatty acid metabolism via the sterol regulatory element-binding protein (SREBP) system. [31][32][33][34] Free cholesterol, a product of LAL hydrolysis of CE, leaves the lysosome and leads to downregulation of endogenous cellular cholesterol synthesis and LDL receptormediated uptake through the cholesterol sensing mechanisms of the cell. The free fatty acids generated by LAL and their metabolites released from the lysosome could be ligands for the peroxisome proliferated-activator receptor-␥ (PPAR␥), a master regulator of lipogenesis, macrophage maturation, antiinflammation, and glucose homeostasis in the body.…”

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confidence: 99%

Reduction of Atherosclerotic Plaques by Lysosomal Acid Lipase Supplementation

Du¹,

Schiavi²,

Wan³

et al. 2004

ATVB

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Objective-Proof of principle is presented for targeted enzyme supplementation by using lysosomal acid lipase to decrease aortic and coronary wall lipid accumulation in a mouse model of atherosclerosis. Methods and Results-Mice with LDL receptor deficiency were placed on an atherogenic diet and developed predictable aortic and coronary atheroma. ␣-Mannosyl-terminated human lysosomal acid lipase (phLAL) was produced in Pichia pastoris, purified, and administered intravenously to such mice with either early or late lesions. phLAL injections reduced plasma, hepatic, and splenic cholesteryl esters and triglycerides in affected mice. phLAL was detected in hepatic Kupffer cells and in atheromatous foam cells. Repeated enzyme injections were well tolerated, with no obvious adverse effects. In addition, the coronary and aortic atheromatous lesions were (1) eliminated in their early stages and (2) quantitatively and qualitatively reduced in their advanced stages. A therosclerosis is the number 1 cause of mortality and morbidity in the developed countries. A number of interventions or preventions delay the consequences of atherosclerosis, eg, low cholesterol diet and exercise, HMG-CoA reductase inhibitors, and coronary artery bypass. However, they are not suitable for all patients, and few have been shown to promote regression of lesions. Therefore, new approaches are needed for the treatment and prevention of atherosclerosis. Several stages characterize the progression of atherosclerotic lesions. 1,2 The earliest lesion is the "fatty streak," an aggregation of lipid-rich macrophages and T-lymphocytes within the intimae layer of an artery. The fatty streaks evolve into intermediate lesions that have a layer of foamy macrophages and smooth muscle cells. This develops into complex and occlusive lesions, as well as fibrous plaques. These plaques have a dense cap of connective tissue, with embedded smooth muscle cells overlaying a core of lipid and necrotic debris. Macrophages are present at all lesional stages with excessive cholesterol and cholesteryl esters in lysosomes. Continuing development of atherosclerotic plaques requires progressive macrophage processing of cholesteryl esters in and through the lysosomes. Perpetuation and maturation of the plaques depends on additional complex inflammatory and scarring processes. Lysosomal acid lipase (LAL) is the only hydrolase for cleavage of cholesteryl esters delivered to the lysosomes. 3 The receptors that mediate cholesteryl ester uptake into macrophage include those for LDL and oxidized LDL (oxLDL), ie, LDL receptor (LDL-R), the scavenger receptors type AI and AII (SR-AI and SR-AII), 4 -6 the scavenger receptor type B1 (SR-BI), 7-9 CD36, 10 and the LDL receptor related protein (LRP). 11 All of these, except SR-BI, direct associated lipids to the lysosome. 12-15 Furthermore, modification of LDL by oxidation, aggregation, and glycation occurs in the atherosclerotic lesions by histochemical and biochemical studies. 16 -20 The delivery of oxidized LDL to lysosomes of macropha...

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Sterol-Mediated Regulation of SREBP-1a,1b,1c and SREBP-2 in Cultured Human Cells

Cited by 19 publications

References 0 publications

The g.−762T>C polymorphism of the NPC1L1 gene is common in Chinese and contributes to a higher promoter activity and higher serum cholesterol levels

The g.−762T>C polymorphism of the NPC1L1 gene is common in Chinese and contributes to a higher promoter activity and higher serum cholesterol levels

Molecular Cloning and Functional Analysis of the Promoter of the Human Squalene Synthase Gene

Reduction of Atherosclerotic Plaques by Lysosomal Acid Lipase Supplementation

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