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Regulation of Peroxisome Proliferator-Activated Receptor γ Expression by Adipocyte Differentiation and Determination Factor 1/Sterol Regulatory Element Binding Protein 1: Implications for Adipocyte Differentiation and Metabolism 总被引:1,自引:0,他引:1
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Lluis Fajas Kristina Schoonjans Laurent Gelman Jae B. Kim Jamila Najib Genevieve Martin Jean-Charles Fruchart Michael Briggs Bruce M. Spiegelman Johan Auwerx 《Molecular and cellular biology》1999,19(8):5495-5503
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Overexpression of the adipocyte differentiation and determination factor-1 (ADD-1) or sterol regulatory element binding protein-1 (SREBP-1) induces the expression of numerous genes involved in lipid metabolism, including lipoprotein lipase (LPL). Therefore, we investigated whether LPL gene expression is controlled by changes in cellular cholesterol concentration and determined the molecular pathways involved. Cholesterol depletion of culture medium resulted in a significant induction of LPL mRNA in the 3T3-L1 preadipocyte cell line, whereas addition of cholesterol reduced LPL mRNA expression to basal levels. Similar to the expression of the endogenous LPL gene, the activity of the human LPL gene promoter was enhanced by cholesterol depletion in transient transfection assays, whereas addition of cholesterol caused a reversal of its induction. The effect of cholesterol depletion upon the human LPL gene promoter was mimicked by cotransfection of expression constructs encoding the nuclear form of SREBP-1a, -1c (also called ADD-1) and SREBP-2. Bioinformatic analysis demonstrated the presence of 3 potential sterol regulatory elements (SRE) and 3 ADD-1 binding sequences (ABS), also known as E-box motifs. Using a combination of in vitro protein-DNA binding assays and transient transfection assays of reporter constructs containing mutations in each individual site, a sequence element, termed LPL-SRE2 (SRE2), was shown to be the principal site conferring sterol responsiveness upon the LPL promoter. These data furthermore underscore the importance of SRE sites relative to E-boxes in the regulation of LPL gene expression by sterols and demonstrate that sterols contribute to the control of triglyceride metabolism via binding of SREBP to the LPL regulatory sequences. 相似文献
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Sterol regulatory element-binding proteins induce an entire pathway of cholesterol synthesis 总被引:2,自引:0,他引:2
Sakakura Y Shimano H Sone H Takahashi A Inoue N Toyoshima H Suzuki S Yamada N Inoue K 《Biochemical and biophysical research communications》2001,286(1):176-183
To evaluate the effects of sterol regulatory element-binding proteins (SREBPs) on the expression of the individual enzymes in the cholesterol synthetic pathway, we examined expression of these genes in the livers from wild-type and transgenic mice overexpressing nuclear SREBP-1a or -2. As estimated by a Northern blot analysis, overexpression of nuclear SREBP-1a or -2 caused marked increases in mRNA levels of the whole battery of cholesterogenic genes. This SREBP activation covers not only rate-limiting enzymes such as HMG CoA synthase and reductase that have been well established as SREBP targets, but also all the enzyme genes in the cholesterol synthetic pathway tested here. The activated genes include mevalonate kinase, mevalonate pyrophosphate decarboxylase, isopentenyl phosphate isomerase, geranylgeranyl pyrophosphate synthase, farnesyl pyrophosphate synthase, squalene synthase, squalene epoxidase, lanosterol synthase, lanosterol demethylase, and 7-dehydro-cholesterol reductase. These results demonstrate that SREBPs activate every step of cholesterol synthetic pathway, contributing to an efficient cholesterol synthesis. 相似文献
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Y Ikeda J Yamamoto M Okamura T Fujino S Takahashi K Takeuchi T F Osborne T T Yamamoto S Ito J Sakai 《The Journal of biological chemistry》2001,276(36):34259-34269
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Diminished hepatic response to fasting/refeeding and liver X receptor agonists in mice with selective deficiency of sterol regulatory element-binding protein-1c. 总被引:24,自引:0,他引:24
Guosheng Liang Jian Yang Jay D Horton Robert E Hammer Joseph L Goldstein Michael S Brown 《The Journal of biological chemistry》2002,277(11):9520-9528
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Soccio RE Adams RM Maxwell KN Breslow JL 《The Journal of biological chemistry》2005,280(19):19410-19418
The StarD4 and StarD5 proteins share approximately 30% identity, and each is a steroidogenic acute regulatory protein (StAR)-related lipid transfer (START) domain. We previously showed StarD4 expression is sterol-repressed, consistent with regulation by sterol regulatory element-binding proteins (SREBPs), whereas StarD5 is not sterol-regulated. Here we further address the regulation and function of StarD4 and StarD5. Unlike StAR, the START family prototype, StarD4 and StarD5 were not induced by steroidogenic stimuli in Leydig cells. However, StarD4 and StarD5 showed StAR-like activity in a cell culture steroidogenesis assay, indicating cholesterol transfer. In transgenic mice expressing active SREBPs, StarD4 was predominantly activated by SREBP-2 rather than SREBP-1a. The mouse and human StarD4 proximal promoters share approximately 70% identity, including several potential sterol regulatory elements (SREs). Reporters driven by the StarD4 promoter from either species were transfected into NIH-3T3 cells, and reporter activity was highly repressed by sterols. Site-directed mutagenesis of potential SREs identified a conserved functional SRE in the mouse (TCGGTCCAT) and human (TCATTCCAT) promoters. StarD5 was not sterol-repressed via SREBPs nor was it sterol-activated via liver X receptors (LXRs). Even though StarD4 and StarD5 were not LXR targets, their overexpression stimulated LXR reporter activity, suggesting roles in cholesterol metabolism. StarD5 expression increased 3-fold in free cholesterol-loaded macrophages, which activate the endoplasmic reticulum (ER) stress response. When NIH-3T3 cells were treated with agents to induce ER stress, StarD5 expression increased 6-8-fold. Because StarD4 is regulated by sterols via SREBP-2, whereas StarD5 is activated by ER stress, they likely serve distinct functions in cholesterol metabolism. 相似文献
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The E-box like sterol regulatory element mediates the suppression of human Delta-6 desaturase gene by highly unsaturated fatty acids 总被引:3,自引:0,他引:3
Nara TY He WS Tang C Clarke SD Nakamura MT 《Biochemical and biophysical research communications》2002,296(1):111-117
Delta-6 Desaturase (D6D) catalyzes the first step of the synthesis of highly unsaturated fatty acids (HUFA) that play pivotal roles in many biological functions. The D6D expression is under feedback regulation by dietary HUFA. We co-transfected D6D promoter-reporter constructs to HepG2 cells with an expression vector of nuclear form sterol regulatory element binding protein-1c (SREBP-1c). A 90-bp region of the D6D promoter was required for the activation by SREBP-1c as well as for the suppression of the promoter activity by HUFA. The region contained two candidates of sterol regulatory element (SRE). Mutation analysis identified E-box like SRE (SRE-2) as essential for both SREBP-1c activation and HUFA suppression. SRE-2 has a core sequence of CAGCAG, and is also conserved in stearoyl CoA desatruases. Because HUFA are primarily incorporated into phospholipids (PL), our results suggest that the primary role of SREBP-1c in liver is the regulation of fatty acid supply for PL rather than for triglycerides. 相似文献
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Dual regulation of mouse Delta(5)- and Delta(6)-desaturase gene expression by SREBP-1 and PPARalpha. 总被引:8,自引:0,他引:8
Takashi Matsuzaka Hitoshi Shimano Naoya Yahagi Michiyo Amemiya-Kudo Tomohiro Yoshikawa Alyssa H Hasty Yoshiaki Tamura Jun-ichi Osuga Hiroaki Okazaki Yoko Iizuka Akimitsu Takahashi Hirohito Sone Takanari Gotoda Shun Ishibashi Nobuhiro Yamada 《Journal of lipid research》2002,43(1):107-114
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