Cell cycle regulation of membrane glucocorticoid receptor in ccrf
-cem human acute lymphoblastic leukemic cells: correlation to
apoptosis..
Sackey, Faustina N. A., Cheryl S. Watson, and Bahiru Gametchu.
Departments of Pediatrics, Medical College of Wisconsin, Milwaukee,
WI, 53226 and Human Biological Chemistry and Genetics, University of
Texas, Medical Branch, Galveston, TX 77555
APStracts 4:0117E, 1997.
The human leukemic cell line (CCRF-CEM) and a subline enriched for the
plasma
membrane-resident glucocorticoid receptor (mGR) were studied for the
influence of
the cell cycle on the expression and function of mGR. Three
synchronization
procedures (double thymidine, colcemid, and combined thymidine
-colcemid blocks)
were used. Fluorescent microscopy and flow cytometry simultaneously
assessed
antibody-tagged mGR and DNA. In addition, mGR was quantitated and
characterized
by immunoprecipitation and immunoblotting. Apoptosis was assayed by
DNA
fragmentation (TUNEL assay), and by cell survival (trypan blue
exclusion). All
synchronization procedures demonstrated that progression from S to
G2/M stages
leads to cells having the highest levels of mGR expression and being
highly
glucocorticoid-sensitive in the apoptosis assays: 32 and 80%
sensitivity of wild type
and mGR-enriched cells, respectively, compared to 12 and 30%
sensitivity in
asynchronous cells. Therefore, mGR expression appears to be cell
cycle-regulated,
with its highest expression at late S-G2/M, where the cells are most
sensitive to the
lymphocytolytic effects of glucocorticoids.
Received 1996 December 31; accepted in final form 1997, May 30
APS Manuscript Number E636-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 11 June 1997