Correlation of membrane glucocorticoid receptor levels with glucocorticoid-induced apoptotic competence using mutant leukemic and lymphoma cells lines

• Published in: Journal of cellular biochemistry Vol. 87; no. 2; pp. 133 - 146
• Main Authors: Gametchu, Bahiru, Watson, Cheryl S.
• Format: Journal Article
• Language: English
• Published: New York Wiley Subscription Services, Inc., A Wiley Company 2002
• Subjects: Animals; apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Binding Sites; Blotting, Western; Cell Membrane - metabolism; Centrifugation, Density Gradient - methods; Dexamethasone - pharmacology; Flow Cytometry; Fluorescent Antibody Technique, Direct; Glucocorticoids - pharmacology; Humans; Immunoblotting; leukemia; Leukemia - metabolism; Leukemia - pathology; lymphoma; Lymphoma - metabolism; Lymphoma - pathology; membrane glucocorticoid receptor; Mice; Protein Binding; Receptors, Glucocorticoid - genetics; Receptors, Glucocorticoid - metabolism; Receptors, Glucocorticoid - physiology; Statistics as Topic; steroid; Tumor Cells, Cultured
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.10288

We have studied the presence and functional implications of membrane glucocorticoid receptor (mGR) in several wild type (WT) and mutant mouse lymphoid cell lines (nuclear transfer decrease, NT−; nuclear transfer increase, NTi; and receptorless, R−). Direct fluorescent antibody staining revealed large aggregates of mGR‐specific fluorescing antigens in the plasma membrane of the WT and mGR‐enriched (mGR++) S‐49 cells. While R− cells totally lacked mGR, this receptor level was low in NT− and NTi groups. FACS analysis corroborated these results, showing a ∼4–10‐fold difference between the highest mGR levels (mGR++) and the R− and NTi cells. Membrane extracts were analyzed for mGR by immunoblotting. Multiple receptor forms, ranging in Mr from 94,000 to > 200,000, were observed in the WT cells, while only smaller peptides (85,000–94,000) were found in NT− cells. No detectable immunoreactive bands were identified in either membrane or cytosol immunoprecipitates of NTi and R− cell groups. Within 48 h post dexamethasone exposure > 98% of WT and mGR++ S‐49 cells underwent apoptosis, compared to 0–30% in the mutant cells, albeit the total receptor number is two to three times higher in NTi compared to WT. These results suggest a better correlation between the quantity and quality of mGRs (rather than total cellular GRs) and the ability of glucocorticoids (GCs) to lyse lymphoid cells. J. Cell. Biochem. 87: 133–146, 2002. © 2002 Wiley‐Liss, Inc.