TY - JOUR
T1 - Overexpression of GFAT activates PAI-1 promoter in mesangial cells
AU - James, Leighton R.
AU - Fantus, I. George
AU - Goldberg, Howard
AU - Ly, Hao
AU - Scholey, James W.
PY - 2000
Y1 - 2000
N2 - Effects of hyperglycemia on glomerular cells may be mediated by glucose entry into the hexosamine pathway, and mesangial cell (MC) expression of the hexosamine pathway rate-limiting enzyme glutamine:fructose-6-phosphate amido-transferase (GFAT) is increased in diabetic glomerulosclerosis. We hypothesized that GFAT activity would be an important determinant of gene expression in glomerular MC. When overexpressed in primary MC, GFAT produced a two- to threefold increase in the activity of plasminogen activator inhibitor-1 (PAI-1) promoter. There was a 1.4-fold increase in PAI-1 promoter activity in cells exposed to high glucose (20 mM), whereas in MC overexpressing GFAT, exposure to high glucose caused a 3.5- to 4-fold increase in promoter activity. PAI-1 promoter activation was dependent on GFAT enzyme activity because o-diazo-acetyly-L-serine and 6-diazo-5-oxonorleucine, inhibitors of GFAT enzyme activity, abrogated the activation of PAI-1 promoter in MC overexpressing GFAT. Glucosamine, which is downstream of GFAT in the hexosamine pathway, produced a 2.5-fold increase in the PAI-1 promoter activity. In addition to increasing the mRNA levels for transforming growth factor-β1 (TGF-β1), GFAT overexpression also increased mRNA levels for the TGF-β type I and type II receptors. TGF-β-neutralizing antibody did not normalize PAI-1 promoter activity in MC exposed to glucosamine or those overexpressing GFAT. We conclude that GFAT expression and activity are important determinants of gene expression in MC and that flux through the hexosamine pathway activates expression of genes implicated in vascular injury pathways.
AB - Effects of hyperglycemia on glomerular cells may be mediated by glucose entry into the hexosamine pathway, and mesangial cell (MC) expression of the hexosamine pathway rate-limiting enzyme glutamine:fructose-6-phosphate amido-transferase (GFAT) is increased in diabetic glomerulosclerosis. We hypothesized that GFAT activity would be an important determinant of gene expression in glomerular MC. When overexpressed in primary MC, GFAT produced a two- to threefold increase in the activity of plasminogen activator inhibitor-1 (PAI-1) promoter. There was a 1.4-fold increase in PAI-1 promoter activity in cells exposed to high glucose (20 mM), whereas in MC overexpressing GFAT, exposure to high glucose caused a 3.5- to 4-fold increase in promoter activity. PAI-1 promoter activation was dependent on GFAT enzyme activity because o-diazo-acetyly-L-serine and 6-diazo-5-oxonorleucine, inhibitors of GFAT enzyme activity, abrogated the activation of PAI-1 promoter in MC overexpressing GFAT. Glucosamine, which is downstream of GFAT in the hexosamine pathway, produced a 2.5-fold increase in the PAI-1 promoter activity. In addition to increasing the mRNA levels for transforming growth factor-β1 (TGF-β1), GFAT overexpression also increased mRNA levels for the TGF-β type I and type II receptors. TGF-β-neutralizing antibody did not normalize PAI-1 promoter activity in MC exposed to glucosamine or those overexpressing GFAT. We conclude that GFAT expression and activity are important determinants of gene expression in MC and that flux through the hexosamine pathway activates expression of genes implicated in vascular injury pathways.
KW - Diabetic nephropathy
KW - Gene expression
KW - Glutamine:fructose-6-phosphate amidotransferase
KW - Plasminogen activator inhibitor-1
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U2 - 10.1152/ajprenal.2000.279.4.f718
DO - 10.1152/ajprenal.2000.279.4.f718
M3 - Article
C2 - 10997922
AN - SCOPUS:0033680164
SN - 0363-6127
VL - 279
SP - F718-F727
JO - American Journal of Physiology - Renal Physiology
JF - American Journal of Physiology - Renal Physiology
IS - 4 48-4
ER -