Comparison of the role of glucosamine synthesis in the stimulation
of tgf[alpha] gene transcription by glucose and egf.
Roos, Mark D., Inn Oc Han, Andrew J. Paterson, and Jeffrey E. Kudlow.
Departments of Medicine and Cell Biology, Division of Endocrinology
and Metabolism, University of Alabama at Birmingham, Birmingham, AL
35294
APStracts 2:0351C, 1995.
Transforming growth factor-[alpha] (TGF[alpha]) gene transcription is
regulated by both epidermal growth factor (EGF) and glucose. Previous
studies have suggested that the metabolism of glucose to glucosamine
through the enzyme glutamine:fructose-6-phosphate amidotransferase
(GFAT) plays a critical role in the glucose signaling. In this paper,
we compared the role of GFAT in the glucose and EGF signals. We found
that although EGF stimulates GFAT mRNA accumulation in MDA468 cells,
this affect of EGF occurred several hours after TGF[alpha]
transcription increased. MDA468 cells also exhibited a TGF[alpha]
transcriptional response to low concentrations of glucose. The
TGF[alpha] response to glucose but not EGF could be inhibited by a
blocker of GFAT activity. Blockade of GFAT was confirmed using
Western blotting with the RL2 antibody which recognizes an epitope on
proteins containing N-acetylglucosamine. Exposure of cells to glucose
increased the RL2 signal on several polypeptides but this change
could be blocked by inhibition of GFAT. These results support the
notion that glucose stimulation of TGF[alpha] expression requires
GFAT but EGF stimulation does not.
Received 17 April 1995; accepted in final form 14 September 1995.
APS Manuscript Number C213-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95