Preferential synthesis of the 78-Kd glucose-regulated protein in
glucocorticoid-treated S49 mouse lymphoma cells
M Lam, LJ Vimmerstedt, LK Schlatter, JO Hensold and CW Distelhorst
Department of Medicine, Case Western Reserve University School of Medicine,
Cleveland, OH.
To investigate the mechanism of glucocorticoid-induced lymphocytolysis, we
used two-dimensional gel electrophoresis to analyze the effect of
dexamethasone on the synthesis of individual proteins in S49 mouse lymphoma
cells. We found that synthesis of a 78-Kd protein is preferentially
maintained following dexamethasone treatment, at a time when the synthesis
of most other cellular proteins is decreased. Synthesis of this protein
could also be induced by tunicamycin, suggesting that it might be the 78-Kd
glucose-regulated protein (GRP78). The identity of the 78-Kd protein with
GRP78 was confirmed by limited chymotryptic mapping and immunoprecipitation
analysis. Preferential synthesis of GRP78 in dexamethasone-treated cells
was not secondary to alterations in the glycosylation of cellular proteins.
Significantly, steady-state levels of GRP78 mRNA were unchanged following
dexamethasone treatment. Preferential synthesis of GRP78 in
glucocorticoid-treated S49 cells may reflect the unique property of GRP78
mRNA to be translated under conditions that interfere with the translation
of most other cellular mRNAs. GRP78 is a highly conserved protein that is
essential for cell viability. Preferential synthesis of GRP78 may be a
protective response to metabolic events that interfere with normal mRNA
translation in glucocorticoid-treated mouse lymphoma cells.
Volume 79,
Issue 12,
pp. 3285-3292,
06/15/1992
Copyright © 1992 by The American Society of Hematology
