Differences in nuclear retention characteristics of agonist-activated glucocorticoid receptor may determine specific responses.
We studied the glucocorticoid response to the synthetic steroid pregna-1,4-diene-11beta-ol-3,20-dione (DeltaHOP) in several cell types and correlated its biological effect with the ability of the glucocorticoid receptor (GR) to be retained in the nuclear compartment. We observed that the DeltaHOP-transformed GR was diffusely distributed in the nucleus compared to the discrete structures observed for the dexamethasone (DEX)-transformed GR. Despite the fact that the receptor was entirely nuclear upon binding of each steroid and exhibited identical nuclear export rates, a greater amount of DeltaHOP-transformed GR was recovered in the cytoplasmic fraction after hypotonic cell lysis. Furthermore, accelerated nuclear export of GR was evidenced in digitonin-permeabilized cells treated with ATP and molybdate. Inasmuch as limited trypsinization of DEX-GR and DeltaHOP-GR complexes yielded different proteolytic products, we conclude that GR undergoes a differential conformational change upon binding of each ligand. We propose that these conformational differences may consequently lead to changes of stability in the interaction of the GR with chromatin. Therefore, the dynamic exchange of liganded GR with chromatin is likely to have significant consequences for the observed pleiotropic physiological responses triggered by glucocorticoid ligands, not only in different tissues but also in the same cell type.
Vicent
Guillermo P
GP
Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
Pecci
Adalí
A
Ghini
Alberto
A
Piwien-Pilipuk
Graciela
G
Galigniana
Mario D
MD
D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000235:genetics; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002451:Cell Compartmentation / Q000187:drug effects* / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002467:Cell Nucleus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D003907:Dexamethasone / Q000378:metabolism / Q000494:pharmacology; D004717:Endometrium / Q000187:drug effects / Q000378:metabolism; D005057:Eukaryotic Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D005938:Glucocorticoids / Q000378:metabolism / Q000494:pharmacology*; D006908:Hydroxyprogesterones / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D051379:Mice; D008968:Molecular Conformation; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011965:Receptors, Glucocorticoid / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism; D051020:bcl-X Protein
C494812:Bcl2l1 protein, mouse; C494813:Bcl2l1 protein, rat; D005938:Glucocorticoids; D006908:Hydroxyprogesterones; D019253:Proto-Oncogene Proteins c-bcl-2; D011965:Receptors, Glucocorticoid; D051020:bcl-X Protein; C038404:pregna-1,4-diene-11-ol-3,20-dione; D003907:Dexamethasone