Nfil3 Is a Glucocorticoid-Regulated Gene Required for Glucocorticoid-Induced Apoptosis in Male Murine T Cells

Abstract

Glucocorticoids (GCs) have essential roles in the regulation of development, integrated metabolism, and immune and neurological responses, and act primarily via the glucocorticoid receptor (GR). In most cells, GC treatment results in down-regulation of GR mRNA and protein levels via negative feedback mechanisms. However, in GC-treated thymocytes, GR protein levels are maintained at a high level, increasing sensitivity of thymocytes to GCs, resulting in apoptosis termed glucocorticoid-induced cell death (GICD). CD4(+)CD8(+) double-positive thymocytes and thymic natural killer T cells in particular are highly sensitive to GICD. Although GICD is exploited via the use of synthetic GC analogues in the treatment of hematopoietic malignancies, the intracellular molecular pathway of GICD is not well understood. To explore GICD in thymocytes, the authors performed whole genome expression microarray analysis in mouse GR exon 2 null vs wild-type thymus RNA 3 hours after dexamethasone treatment. Identified and validated direct GR targets included P21 and Bim, in addition to an important transcriptional regulator Nfil3, which previously has been associated with GICD and is essential for natural killer cell development in vivo. Immunostaining of NFIL3 in whole thymus localized NFIL3 primarily to the medullary region, and double labeling colocalized NFIL3 to apoptotic cells. In silico analysis revealed a putative GC response element 5 kb upstream of the Nfil3 promoter that is strongly conserved in the rat genome and was confirmed to bind GR by chromatin immunoprecipitation. The knockdown of Nfil3 mRNA levels to 20% of normal using specific small interfering RNAs abrogated GICD, indicating that NFIL3 is required for normal GICD in CTLL-2 T cells.

E4BP4 is an insulin-induced stabilizer of nuclear SREBP-1c and promotes SREBP-1c-mediated lipogenesis

“…The mRNA oscillations of E4bp4 were detected in the suprachiasmatic nuclei, liver, adipose tissues, aorta, skeletal muscles, and adrenal glands (36,37). In addition to its regulation by the circadian clock, E4bp4 mRNA can be induced by glucocorticoids (38), insulin (39), and cAMP (40) in various cell types and tissues, indicative of tissuespecific regulation and functions of E4BP4. Previously, we reported that levels of E4bp4 mRNA and protein are elevated in hepatocytes from refed mice and induction of E4BP4 is required for the suppression of the fasting hormone, Fgf21, during the refed state (39).…”

New Frontiers for the NFIL3 bZIP Transcription Factor in Cancer, Metabolism and Beyond

“…In glucocorticoid (GC) signal transduction, Nfil3 may induce cell death 3,72, . The glucocorticoid receptor (GR) is normally regulated by a negative feedback mechanism upon activation; the GR mRNA and protein are down-regulated after GC addition 3 .…”

“…In glucocorticoid (GC) signal transduction, Nfil3 may induce cell death 3,72, . The glucocorticoid receptor (GR) is normally regulated by a negative feedback mechanism upon activation; the GR mRNA and protein are down-regulated after GC addition 3 . However, in certain GC treated murine leukemic T cell lines, GR activation is not attenuated leading to glucocorticoid induced cell death 3,72,73 .…”

Glucocorticoid-mediated co-regulation of RCAN1-1, E4BP4 and BIM in human leukemia cells susceptible to apoptosis

“…GR-mediated upregulation of E4BP4 , and subsequent induction of BIM , has been reported in correlation with apoptosis in lymphoid and osteoblastic cells [9, 27]. GR has been shown to regulate E4BP4 transcription via a GR binding sequence (GBS) located ~5kb upstream of the transcription start site [28, 29]. We have demonstrated that E4BP4 regulates BIM expression [9], however, the mechanism of this regulation is currently being investigated.…”