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Mol. Cell. Biol., 10 1995, 5363-5368, Vol 15, No. 10
I Stein, M Neeman, D Shweiki, A Itin and E Keshet
Expression of vascular endothelial growth factor (VEGF), an endothelial
cell-specific mitogen and a potent angiogenic factor, is upregulated in
response to a hypoxic or hypoglycemic stress. Here we show that the
increase in steady-state levels of VEGF mRNA is partly due to
transcriptional activation but mostly due to increase in mRNA stability.
Both oxygen and glucose deficiencies result in extension of the VEGF mRNA
half-life in a protein synthesis-dependent manner. Viewing VEGF as a
stress-induced gene, we compared its mode of regulation with that of other
stress-induced genes. Results showed that under nonstressed conditions,
VEGF shares with the glucose transporter GLUT-1 a relatively short
half-life (0.64 and 0.52 h, respectively), which is extended fourfold and
more than eightfold, respectively, when cells are deprived of either oxygen
or glucose. In contrast, the mRNAs of another hypoxia-inducible and
hypoglycemia-inducible gene, grp78, as well as that of HSP70, were not
stabilized by these metabolic insults. To show that VEGF and GLUT-1 are
coinduced in differentially stressed microenvironments, multicell spheroids
representing a clonal population of glioma cells in which each cell layer
is differentially stressed were analyzed by in situ hybridization. Cellular
microenvironments conducive to induction of VEGF and GLUT-1 were completely
coincidental. These findings show that two different consequences of tissue
ischemia, namely, hypoxia and glucose deprivation, induce VEGF and GLUT-1
expression by similar mechanisms. These proteins function, in turn, to
satisfy the tissue needs through expanding its vasculature and improving
its glucose utilization, respectively.
Copyright © 1995, American Society for Microbiology
Stabilization of vascular endothelial growth factor mRNA by hypoxia and hypoglycemia and coregulation with other ischemia-induced genes
Department of Molecular Biology, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
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