Coordinate modulation of glucocorticoid receptor and glutaminase
gene expression with glutamine metabolism in llc-pk1-f+ cells.
Gowda, B., M. Sar, X. Mu, J. Cidlowski, and T. Welbourne.
Department of Physiology, LSUMC, Shreveport, LA, and National
Institutes of Environmental Health Sciences and Department of Cell
Biology and Anatomy, UNC Chapel Hill, NC
APStracts 2:0358C, 1995.
The effect of glucocorticoid receptor on glutaminase gene expression
and related glutamine metabolism was studied in proximal tubule-like
LLC-PK1-F+ cells. These cells express functional glucocorticoid
receptors as demonstrated by immunoreactivity with anti
-glucocorticoid receptor antibody, specific ligand binding and a 14
-fold increase in CAT reporter gene activity following exposure to
dexamethasone, 10-6M. Dexamethasone exposure for 18h increased
glutaminase mRNA and activity 32 and 42%, respectively, (both,
p<0.05 paired t test) associated with a small, 9%, but
significant increase in glutamine utilization (p<0.05). In an
effect to elicit a greater response, endogenous glucocorticoid
receptors were supplemented by transfecting cells with a plasmid,
pMAMGR, expressing the rat glucocorticoid receptor gene. Transfected
cells expressed a 39-fold increase in CAT activity with dexamethasone
treatment confirming a higher level of functional receptors but
glutaminase mRNA and activity were now decreased 34 and 32%,
respectively, associated with a 15% fall in glutamine utilization
following 18h exposure to dexamethasone. This biphasic response in
glutaminase gene expression was mirrored by glucocorticoid receptor
mRNA which increased 41% after dexamethasone in LLC-PK1-F+ cells, but
decreased 63% after transfection (both p<0.05). These findings
are consonant with glucocorticoid receptor gene modulation of
glutaminase gene expression and glutamine utilization.
Received 14 February 1995; accepted in final form 7 September
1995.
APS Manuscript Number C81-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95