Abstract
Glucocorticoids (GC) induce apoptosis in malignant lymphoblasts, but the mechanism of this process as well as that of the clinically important GC resistance is unknown. We investigated GC resistance in Jurkat T-ALL cells in which ectopic GC receptor (GR) restores GC sensitivity, suggesting deficient GR expression. Jurkat cells expressed one wild-type and one mutated (R477H) GR allele. GR(R477H) ligand-binding-dependent nuclear import, as revealed by live-cell microscopy of YFP-tagged GR, was unaffected. Transactivation and transrepression were markedly impaired; however, GR(R477H) did not act in a dominant-negative manner, that is, did not prevent cell death, when introduced into a GC-sensitive cell line by retroviral gene transfer. Contrary to another GR heterozygous, but GC-sensitive, T-ALL model (CCRF-CEM), Jurkats expressed lower basal GR levels and did not auto-induce their GR, as revealed by 'real-time' RT-PCR and immunoblotting. Absent GR auto-induction could not be restored by transgenic GR and, hence, was not caused by reduced basal GR levels. Thus, inactivation of one GR gene results in haploinsufficiency if associated with lack of GR auto-induction.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
Animals
-
Apoptosis / genetics
-
Apoptosis / physiology
-
Bacterial Proteins / genetics
-
Bacterial Proteins / metabolism
-
Base Sequence
-
Blotting, Western
-
COS Cells
-
Cell Line, Tumor
-
Chlorocebus aethiops
-
Dexamethasone / pharmacology
-
Drug Resistance, Neoplasm / genetics*
-
Gene Expression Regulation, Leukemic / drug effects*
-
Genes, Dominant / genetics
-
Glucocorticoids / pharmacology*
-
Green Fluorescent Proteins / genetics
-
Green Fluorescent Proteins / metabolism
-
Heterozygote
-
Humans
-
Jurkat Cells
-
Kinetics
-
Luciferases, Renilla / genetics
-
Luminescent Proteins / genetics
-
Luminescent Proteins / metabolism
-
Mammary Tumor Virus, Mouse / genetics
-
Microscopy, Confocal
-
Point Mutation
-
Protein Transport / drug effects
-
Protein Transport / genetics
-
Radioligand Assay
-
Receptors, Glucocorticoid / genetics*
-
Receptors, Glucocorticoid / metabolism
-
Recombinant Fusion Proteins / genetics
-
Recombinant Fusion Proteins / metabolism
-
Reverse Transcriptase Polymerase Chain Reaction
-
Transcription Factors / genetics
-
Transcriptional Activation / drug effects
-
Transcriptional Activation / genetics
-
Transfection
-
Triamcinolone / metabolism
Substances
-
Bacterial Proteins
-
Glucocorticoids
-
Luminescent Proteins
-
Receptors, Glucocorticoid
-
Recombinant Fusion Proteins
-
TSC22D3 protein, human
-
Transcription Factors
-
green fluorescent protein, Aequorea victoria
-
yellow fluorescent protein, Bacteria
-
Green Fluorescent Proteins
-
Triamcinolone
-
Dexamethasone
-
Luciferases, Renilla