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.
- Membrane glucocorticoid receptor
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology