Agonist-free transformation of the glucocorticoid receptor in human B-lymphoma cells.
Nuclear translocation of activated glucocorticoid receptors (GRs) is a necessary step in the signal transduction by these GC hormones. Although in vitro activation of GRs can occur in the absence of a functional ligand, it is generally assumed that binding of a cognate hormone is required for activation of the intracellular GR. By indirect immunocytochemistry and Western-blot analysis, it was found that, in spontaneously aggregated human lymphoma DoHH2 cells, hormone-free GRs are located in the nucleus. Disruption of the aggregates redistributed GRs to a predominantly cytosolic location. Upon spontaneous re-aggregation the GR again became localized to the nucleus. Intracellular cross-linking of the heteromeric receptor complex was applied to investigate the protein composition of cytoplasmic and nuclear receptors. Untransformed, cytosolic GRs could be demonstrated by [3H]dexamethasone binding capacity and hsp90 co-immunoprecipitation, whereas absence of these characteristics suggested an activated conformation of the nuclear GRs. These observations suggest that cell-cell interactions are capable of transforming GRs in the absence of a ligand.
van den Berg
J D
JD
Division of Experimental Therapy, The Netherlands Cancer Institute, Amsterdam, The Netherlands.
Smets
L A
LA
van Rooij
H
H
D000244:Adenosine Diphosphate / Q000032:analysis; D000255:Adenosine Triphosphate / Q000032:analysis; D001665:Binding Sites; D002453:Cell Cycle; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism*; D003432:Cross-Linking Reagents; D003600:Cytosol / Q000737:chemistry / Q000378:metabolism; D003907:Dexamethasone / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D008024:Ligands; D016393:Lymphoma, B-Cell / Q000378:metabolism*; D011940:Receptor Aggregation / Q000502:physiology*; D011965:Receptors, Glucocorticoid / Q000032:analysis / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013388:Succinimides; D014407:Tumor Cells, Cultured
D003432:Cross-Linking Reagents; D005938:Glucocorticoids; D018841:HSP90 Heat-Shock Proteins; D008024:Ligands; D011965:Receptors, Glucocorticoid; D013388:Succinimides; D000244:Adenosine Diphosphate; D003907:Dexamethasone; D000255:Adenosine Triphosphate; C011240:dithiobis(succinimidylpropionate)