Upstream Stimulatory Factor (USF) Proteins Induce HumanTGF-β1Gene Activation via the Glucose-response Element–1013/–1002 in Mesangial Cells

Pyruvate carboxylase is an enzyme of the so-called pyruvate cycling pathways, which have been proposed to contribute to glucose-stimulated insulin secretion in pancreatic β-cells. In the rat insulinoma cell line 832/13, transcripts from both the distal and proximal gene promoter for pyruvate carboxylase are up-regulated by glucose, with pyruvate carboxylase being expressed mainly from the distal gene promoter. At position −408 to −392 relative to the transcription start site, the distal gene promoter was found to contain a ChoRE (carbohydrate response element). Its deletion abolishes glucose responsiveness of the promoter, and the sequence can mediate glucose responsiveness to a heterologous gene promoter. ChREBP (carbohydrate response element-binding protein) and its dimerization partner Mlx (Max-like protein X) bind to the ChoRE in vitro. ChREBP further binds to the distal promoter region at a high glucose concentration in situ. The E-box-binding transcription factors USF1/2 (upstream stimulatory factor 1/2) and E2A variant 2 [also known as E47 and TCF3 (transcription factor 3)] can also bind to the ChoRE. Overexpression of E2A diminishes the magnitude of the glucose response from the pyruvate carboxylase ChoRE. This illustrates that competition between ChREBP–Mlx and other factors binding to the ChoRE affects glucose responsiveness. We conclude that a ChoRE in the distal gene promoter contributes to the glucose-mediated expression of pyruvate carboxylase.

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Glycated albumin upregulates upstream stimulatory factor 2 gene transcription in mesangial cells

AJP Renal Physiology ◽

10.1152/ajprenal.00074.2010 ◽

2010 ◽

Vol 299 (1) ◽

pp. F121-F127 ◽

Cited By ~ 4

Author(s):

Yanzhang Li ◽

Shuxia Wang

Keyword(s):

Gene Expression ◽

Gene Transcription ◽

Mesangial Cells ◽

Glycated Albumin ◽

Diabetic Patients ◽

Dependent Manner ◽

Upstream Stimulatory Factor ◽

Protein Levels ◽

Glycated Proteins ◽

Stimulatory Factor

Diabetic nephropathy (DN) is the most common cause of end-stage renal failure. We previously demonstrated that a transcription factor called upstream stimulatory factor 2 (USF2) was upregulated in the kidneys from diabetic animals in vivo as well as in mesangial cells (MCs) exposed to high-glucose media in vitro. USF2 mediates glucose-induced thrombospondin 1 expression and transforming growth factor-β activity in MCs and plays a role in DN. Glycated proteins have been shown to accumulate in the kidneys of diabetic patients and contribute to DN. However, whether glycated proteins regulate USF2 expression in MCs and play a role in DN is unknown. In the present studies, we determined the effect of glycated albumin on UFS2 gene expression in primary rat MCs. We found that glycated albumin upregulated USF2 expression (mRNA and protein) in a dose- and time-dependent manner. We also demonstrated that glycated albumin stimulated USF2 gene expression at the transcriptional level. By using the luciferase-promoter deletion assay, site-directed mutagenesis, and transactivation assay, we identified a glycated albumin-responsive region in the USF2 gene promoter (−837 to −430, relative to the transcription start site) and demonstrated that glycated albumin-induced USF2 expression was mediated through NF-κB-dependent transactivation of the USF2 promoter. Furthermore, glycated albumin increased nuclear NF-κB subunit-p65 protein levels. siRNA-mediated p65 knockdown prevented glycated albumin-induced USF2 gene expression (promoter activity, mRNA, and protein levels). Taken together, these data suggest that glycated albumin upregulated USF2 gene transcription in MCs through NF-κB-dependent transactivation of the USF2 promoter.

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Upstream Stimulatory Factor Proteins Are Major Components of the Glucose Response Complex of the L-type Pyruvate Kinase Gene Promoter

Journal of Biological Chemistry ◽

10.1074/jbc.270.6.2640 ◽

1995 ◽

Vol 270 (6) ◽

pp. 2640-2643 ◽

Cited By ~ 81

Author(s):

Anne-Marie Lefran¸ois-Martinez ◽

Antoine Martinez ◽

Bénédicte Antoine ◽

Michel Raymondjean ◽

Axel Kahn

Keyword(s):

Pyruvate Kinase ◽

Gene Promoter ◽

Upstream Stimulatory Factor ◽

Kinase Gene ◽

Glucose Response ◽

Stimulatory Factor ◽

Response Complex

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Activation of renal renin-angiotensin system in upstream stimulatory factor 2 transgenic mice

AJP Renal Physiology ◽

10.1152/ajprenal.90493.2008 ◽

2009 ◽

Vol 296 (2) ◽

pp. F257-F265 ◽

Cited By ~ 13

Author(s):

Lihua Shi ◽

Dejan Nikolic ◽

Shu Liu ◽

Hong Lu ◽

Shuxia Wang

Keyword(s):

Transforming Growth Factor ◽

Mesangial Cells ◽

Kidney Injury ◽

Renin Angiotensin System ◽

Renal Diseases ◽

Ang Ii ◽

Upstream Stimulatory Factor ◽

Angiotensin System ◽

Renin Angiotensin ◽

Stimulatory Factor

Previously we demonstrated that upstream stimulatory factor 2 (USF2) transgenic (Tg) mice developed nephropathy including albuminuria and glomerular hypertrophy, accompanied by increased transforming growth factor (TGF)-β and fibronectin accumulation in the glomeruli. However, the mechanisms by which overexpression of USF2 induces kidney injury are unknown. USF has been shown to regulate renin expression. Moreover, the renin-angiotensin system (RAS) plays important roles in renal diseases. Therefore, in the present studies the effects of USF2 on the regulation of RAS in the kidney as well as in mesangial cells from USF2 (Tg) mice were examined. The role of USF2-mediated regulation of RAS in TGF-β production in mesangial cells was also determined. Our data demonstrate that USF2 (Tg) mice exhibit increased renin and angiotensin (ANG) II levels in the kidney. In contrast, renal expression of other components of RAS such as renin receptor, angiotensinogen, angiotensin-converting enzyme (ACE), ACE2, angiotensin type 1a (AT1a) receptor, and AT2 receptor was not altered in USF2 (Tg) mice. Similarly, mesangial cells isolated from USF2 (Tg) mice had increased renin and ANG II levels. Mesangial cells overexpressing USF2 also had increased TGF-β production, which was blocked by small interfering RNA-mediated renin gene knockdown or RAS blockade (enalapril or losartan). Collectively, these results suggest that USF2 promotes renal renin expression and stimulates ANG II generation, leading to activation of the intrarenal RAS. In addition, renin-dependent ANG II generation mediates the effect of USF2 on TGF-β production in mesangial cells, which may contribute to the development of nephropathy in USF2 (Tg) mice.

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