Inhibition of glucocorticoid-induced apoptosis in 697 pre-B lymphocytes by the mineralocorticoid receptor N-terminal domain.
The glucocorticoid and mineralocorticoid receptors (GR and MR) share considerable structural and functional homology and bind as homodimers to hormone-response elements. We have shown previously that MR and GR can form heterodimers that inhibit transcription from a glucocorticoid (GC)-responsive gene and that this inhibition was mediated by the N-terminal domain (NTD) of MR. In this report, we examined the effect of NTD-MR on GC-induced apoptosis in the GC-sensitive pre-B lymphoma cell line, 697. In GC-treated 697 cells, we demonstrated that stable expression of NTD-MR blocks apoptosis and inhibits proteolytic processing of pro-caspases-3, -8, and -9 and poly(ADP-ribose) polymerase. Importantly, gel shift and immunoprecipitation analyses revealed a direct association between the GR and amino acids 203-603 of NTD-MR. We observed down-regulation of c-Myc and of the anti-apoptotic proteins Bcl-2 and Bfl-1 as well as high levels of the pro-apoptotic proteins Bax and Bid. Conversely, cells stably expressing NTD-MR exhibited increased expression of Bcl-2 and Bfl-1 and diminished levels of Bid and Bax. These data provide a potential mechanism for the observed inhibition of cytochrome c and Smac release from the mitochondria of NTD-MR cells and resultant resistance to GC-induced apoptosis. Thus, NTD-MR may mediate GC effects through heterodimerization with GR and ensuing inhibition of GC-regulated gene transcription.
Department of Biochemistry and Molecular Pharmacology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Sonia L
SL
Planey
Assia
A
Derfoul
Andrzej
A
Steplewski
Noreen M
NM
Robertson
Gerald
G
Litwack
D021581:Active Transport, Cell Nucleus; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D019281:Dimerization; D005938:Glucocorticoids / Q000037:antagonists & inhibitors*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D015778:Minor Histocompatibility Antigens; D024101:Mitochondrial Proteins / Q000378:metabolism; D010446:Peptide Fragments / Q000502:physiology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D015452:Precursor B-Cell Lymphoblastic Leukemia-Lymphoma / Q000473:pathology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D018161:Receptors, Mineralocorticoid / Q000502:physiology*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
D051017:Apoptosis Regulatory Proteins; C096816:BCL2-related protein A1; D002352:Carrier Proteins; D003574:Cytochrome c Group; C412403:DIABLO protein, human; D005938:Glucocorticoids; D047908:Intracellular Signaling Peptides and Proteins; D015778:Minor Histocompatibility Antigens; D024101:Mitochondrial Proteins; D010446:Peptide Fragments; D019253:Proto-Oncogene Proteins c-bcl-2; D018161:Receptors, Mineralocorticoid; D011065:Poly(ADP-ribose) Polymerases; D020169:Caspases