Acquired Glucocorticoid Resistance Due to Homologous Glucocorticoid Receptor Downregulation: A Modern Look at an Age-Old Problem

For over 70 years, the unique anti-inflammatory properties of glucocorticoids (GCs), which mediate their effects via the ligand-activated transcription factor, the glucocorticoid receptor alpha (GRα), have allowed for the use of these steroid hormones in the treatment of various autoimmune and inflammatory-linked diseases. However, aside from the onset of severe side-effects, chronic GC therapy often leads to the ligand-mediated downregulation of the GRα which, in turn, leads to a decrease in GC sensitivity, and effectively, the development of acquired GC resistance. Although the ligand-mediated downregulation of GRα is well documented, the precise factors which influence this process are not well understood and, thus, the development of an acquired GC resistance presents an ever-increasing challenge to the pharmaceutical industry. Recently, however, studies have correlated the dimerization status of the GRα with its ligand-mediated downregulation. Therefore, the current review will be discussing the major role-players in the homologous downregulation of the GRα pool, with a specific focus on previously reported GC-mediated reductions in GRα mRNA and protein levels, the molecular mechanisms through which the GRα functional pool is maintained and the possible impact of receptor conformation on GC-mediated GRα downregulation.

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The Inhibitor of NF-KB Kinase, IKKβ Regulates the Transcriptional Activity of GLI1 By Blocking Its Proteasomal Degradation

Blood ◽

10.1182/blood.v124.21.2199.2199 ◽

2014 ◽

Vol 124 (21) ◽

pp. 2199-2199

Author(s):

Nitin Kumar Agarwal ◽

Chae Hwa Kim ◽

Kranthi Kunkalla ◽

Izidore S. Lossos ◽

Francisco Vega

Keyword(s):

Mass Spectrometry ◽

Transcription Factor ◽

Transcriptional Activity ◽

Molecular Mechanisms ◽

Ion Trap ◽

Conflicts Of Interest ◽

Tumor Development ◽

B Cell Lymphoma ◽

Protein Levels ◽

Data Links

Abstract GLI1 is a Hedgehog (Hh) related transcription factor originally discovered as an amplified product in gliomas. Inappropriate activation of the GLI1 has been shown in many cancers including diffuse large B cell lymphoma (DLBCL). We previously showed that GLI1 mediated canonical Hh signaling is constitutive active in DLBCL and contributes to cell survival, proliferation and enhances chemotolerance. Although the importance of GLI1 in tumor development is well recognized, the molecular mechanisms controlling the transcriptional activity of GLI1 are poorly characterized. To identify regulatory components that participate in the transcriptional activity of GLI1, we explored GLI1 putative interacting proteins by liquid chromatography tandem mass spectrometry following immunoprecipitation of endogenous GLI1. We detected that the inhibitor of NF-KB kinase, IKKβ, is one of the proteins associated with GLI1 transcription factor. Here we investigate the regulatory role of IKKβ in the transcriptional activity of GLI1. We show that IKKβ regulates the transcriptional activity of GLI1 by phosphorylating GLI1 in C-terminal region and modulating its protein stability. Short stimulation of SUDHL4 and DOHH2 cells with TNF-α (20ng/mL) resulted in increased GLI1 protein levels. Similar results were observed in 293T cells transiently transfected with GLI1 and IKKβ kinase constructs. Moreover, silencing of IKKβ using siRNA and shRNAs led to decreased GLI1 protein levels and its transcriptional activity in DLBCL cell lines with constitutive activation of the NF-KB. Next, we characterized nine probable IKKβ dependent GLI1 phosphorylation sites (S543-S548, S1070, S1071 and S1074 identified by nanospray ion trap mass spectrometry) using mutational and deletions studies. We show that IKKβ phosphorylates GLI1 at Thr1074 and decreases binding between GLI1 and HECT-type E3 ubiquitin ligase (ITCH) resulting in reduced GLI1 polyubiquitination and degradation. Point mutation of Threonine 1074 to Alanine prevents IKKβ-mediated GLI1 phosphorylation and facilitates GLI1-ITCH interaction, polyubiquitination and degradation of GLI1 in the proteasome. Collectively, our data links IKKβ-mediated NF-kB signaling to the transcriptional activity of GLI1 and illustrates a novel cross talk between these two pathways. This is of clinical interest because activation of the NF-kB pathway is frequent in DLBCL and the connection between Hh and NF-kB pathways may open novel therapeutic avenues for DLBCL. Disclosures No relevant conflicts of interest to declare.

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Uteroplacental insufficiency alters hepatic expression, phosphorylation, and activity of the glucocorticoid receptor in fetal IUGR rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00211.2005 ◽

2005 ◽

Vol 289 (5) ◽

pp. R1348-R1353 ◽

Cited By ~ 34

Author(s):

Mariana Baserga ◽

Merica A. Hale ◽

Robert A. McKnight ◽

Xing Yu ◽

Christopher W. Callaway ◽

...

Keyword(s):

Gene Expression ◽

Transcription Factor ◽

Glucocorticoid Receptor ◽

Chromatin Structure ◽

P53 Protein ◽

Mrna Levels ◽

Artery Ligation ◽

Pregnant Rat ◽

Hepatic Expression ◽

Protein Levels

Uteroplacental insufficiency (UPI) induces persistent changes in hepatic gene expression secondary to altered chromatin dynamics in the intrauterine growth- restricted (IUGR) rat liver. The glucocorticoid receptor (GR) is a transcription factor that when activated can induce changes in chromatin structure. To begin the process of identifying pathways by which IUGR affects chromatin structure, we hypothesized that UPI in the rat induces a significant increase in endogenous glucocorticoids (corticosterone) and increases GR expression and activation. To prove our hypothesis, we induced IUGR through bilateral uterine artery ligation of the pregnant rat. At day 1, UPI significantly increased corticosterone levels and was associated with increased total GR mRNA and protein levels in the liver, as well as increased hepatic phosphorylation of GR serine 211. Moreover, cyclin-dependent kinase 2 (CDK2) cyclinA/CDK2 protein levels, which selectively phosphorylate GR serine 211, were also significantly increased. To assess activity of the GR, we measured protein levels of the transcription factor p53 whose levels are downregulated, at least in part, by active GR. In this study, UPI decreased p53 protein and its downstream target Bax mRNA levels. We conclude that UPI in rats affects GR expression and activity in the liver. We speculate that these alterations early in life may contribute to the changes in chromatin structure and gene expression previously described in the IUGR liver.

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Hlx homeobox transcription factor negatively regulates interferon-γ production in monokine-activated natural killer cells

Blood ◽

10.1182/blood-2006-10-050096 ◽

2006 ◽

Vol 109 (6) ◽

pp. 2481-2487 ◽

Cited By ~ 16

Author(s):

Brian Becknell ◽

Tiffany L. Hughes ◽

Aharon G. Freud ◽

Bradley W. Blaser ◽

Jianhua Yu ◽

...

Keyword(s):

Transcription Factor ◽

Nk Cells ◽

Natural Killer ◽

Molecular Mechanisms ◽

Interferon Γ ◽

Tumor Surveillance ◽

Protein Levels ◽

Homeobox Transcription Factor ◽

Ifn Γ

Abstract Natural killer (NK) cells contribute to host immunity, including tumor surveillance, through the production of interferon gamma (IFN-γ). Although there is some knowledge about molecular mechanisms that induce IFN-γ in NK cells, considerably less is known about the mechanisms that reduce its expression. Here, we investigate the role of the Hlx transcription factor in IFN-γ production by NK cells. Hlx expression is induced in monokine-activated NK cells, but with delayed kinetics compared to IFN-γ. Ectopic Hlx expression decreases IFN-γ synthesis in primary human NK cells and IFN-γ promoter activity in an NK-like cell line. Hlx protein levels inversely correlate with those of STAT4, a requisite factor for optimal IFN-γ transcription. Mechanistically, we provide evidence indicating that Hlx overexpression accelerates dephosphorylation and proteasome-dependent degradation of the active Y693-phosphorylated form of STAT4. Thus, Hlx expression in activated NK cells temporally controls and limits the monokine-induced production of IFN-γ, in part through the targeted depletion of STAT4.

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Mechanisms and triggers of adaptation to hypoxia

Reviews on Clinical Pharmacology and Drug Therapy ◽

10.17816/rcf193269-280 ◽

2021 ◽

Vol 19 (3) ◽

pp. 269-280

Author(s):

Andrey V. Lyubimov ◽

Dmitriy V. Cherkashin ◽

Semen V. Efimov ◽

Andrey E. Alanichev ◽

Valeriy S. Ivanov ◽

...

Keyword(s):

Transcription Factor ◽

Side Effects ◽

Partial Pressure ◽

Molecular Mechanisms ◽

Oxygen Metabolism ◽

External Factors ◽

Iron Chelators ◽

Adaptation To Hypoxia ◽

Partial Pressure Of Oxygen ◽

Prophylactic Use

It is believed that hypoxia-induced factor (HIF1) is the key mediator of oxygen metabolism. It was first identified as a transcription factor activated in cells and tissues by lowering the partial pressure of oxygen (O2). The HIF1 activator spectrum includes both external factors hypoxia, psycho-emotional stress and in ternal factors and varies from hormones to iron chelators. This review is dedicated to the molecular mechanisms of HIF1 activation, some of its natural activators HIF1, the potential for which is due to the low level of toxicity and the reduced likelihood of undesirable side effects. In turn, this opens up new options to treat diseases associated with local and general ischemia and hypoxia, the possibilities of their prophylactic use for researchers and clinicians in order to reduce the degree of damage in the event of an unforeseen condition of acute injurious to organs and tissues by hypoxia and reperfusion after it.

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Ethanol-Induced Mitochondrial Damage in Sertoli Cells is Associated with Parkin Overexpression and Activation of Mitophagy

Cells ◽

10.3390/cells8030283 ◽

2019 ◽

Vol 8 (3) ◽

pp. 283 ◽

Cited By ~ 5

Author(s):

Nabil Eid ◽

Yuko Ito ◽

Akio Horibe ◽

Yoshinori Otsuki ◽

Yoichi Kondo

Keyword(s):

Transcription Factor ◽

Sertoli Cells ◽

Molecular Mechanisms ◽

Mitochondrial Damage ◽

Control Group ◽

Protective Mechanism ◽

Adult Rats ◽

Therapeutic Implications ◽

Protein Levels ◽

Enhanced Expression

This study was conducted to elucidate the involvement of the PINK1-Parkin pathway in ethanol-induced mitophagy among Sertoli cells (SCs). In the research, adult rats were given intraperitoneal injections of ethanol (5 gm/kg) and sacrificed at various time periods within 24 h. Transmission electron microscopy was applied to reveal enhanced mitochondrial damage in SCs of the ethanol-treated rats (ETRs) in association with a significant increase in numbers of mitophagic vacuoles (mitophagosomes and autolysosomes) in contrast to very low levels in a control group treated with phosphate-buffered saline (PBS). This enhancement was ultra-structurally verified via observation of trapped mitochondria within LC3-labeled membranes, upregulation of LC3 protein levels, colocalization of LC3 and cytochrome c, and reduced expression of mitochondrial proteins. Importantly, Parkin expression was found to be upregulated in ETR SCs, specifically in mitochondria and mitophagosomes in addition to colocalization with PINK1 and pan-cathepsin, indicating augmented mitophagy. Transcription factor EB (TFEB, a transcription factor for autophagy and mitophagy proteins) was also found to be upregulated in nuclei of ETR SCs and associated with enhanced expression of iNOS. Enhanced Parkin-related mitophagy in ETR SCs may be a protective mechanism with therapeutic implications. To the authors’ knowledge, this is the first report demonstrating the ultrastructural characteristics and molecular mechanisms of Parkin-related mitophagy in ETR SCs.

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Activation of BDNF by transcription factor Nrf2 contributes to antidepressant-like actions in rodents

Translational Psychiatry ◽

10.1038/s41398-021-01261-6 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Wei Yao ◽

Song Lin ◽

Jin Su ◽

Qianqian Cao ◽

Yueyue Chen ◽

...

Keyword(s):

Transcription Factor ◽

Synaptic Transmission ◽

Molecular Mechanisms ◽

Brain Regions ◽

Related Factor ◽

Transcriptional Repressors ◽

Protein Levels ◽

Repressor Proteins ◽

Chronic Social Defeat Stress ◽

Fast Acting

AbstractThe transcription factor erythroid 2-related factor 2 (Nrf2) and brain-derived neurotrophic factor (BDNF) play a key role in depression. However, the molecular mechanisms underlying the crosstalk between Nrf2 and BDNF in depression remain unclear. We examined whether Nrf2 regulates the transcription of Bdnf by binding to its exon I promoter. Furthermore, the role of Nrf2 and BDNF in the brain regions from mice with depression-like phenotypes was examined. Nrf2 regulated the transcription of Bdnf by binding to its exon I promoter. Activation of Nrf2 by sulforaphane (SFN) showed fast-acting antidepressant-like effects in mice by activating BDNF as well as by inhibiting the expression of its transcriptional repressors (HDAC2, mSin3A, and MeCP2) and revising abnormal synaptic transmission. In contrast, SFN did not affect the protein expression of BDNF and its transcriptional repressor proteins in the medial prefrontal cortex (mPFC) and hippocampus, nor did it reduce depression-like behaviors and abnormal synaptic transmission in Nrf2 knockout mice. In the mouse model of chronic social defeat stress (CSDS), protein levels of Nrf2 and BDNF in the mPFC and hippocampus were lower than those of control and CSDS-resilient mice. In contrast, the protein levels of BDNF transcriptional repressors in the CSDS-susceptible mice were higher than those of control and CSDS-resilient mice. These data suggest that Nrf2 activation increases the expression of Bdnf and decreases the expression of its transcriptional repressors, which result in fast-acting antidepressant-like actions. Furthermore, abnormalities in crosstalk between Nrf2 and BDNF may contribute to the resilience versus susceptibility of mice against CSDS.

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The Transcriptional Complex Sp1/KMT2A by Up-Regulating Restrictive Element 1 Silencing Transcription Factor Accelerates Methylmercury-Induced Cell Death in Motor Neuron-Like NSC34 Cells Overexpressing SOD1-G93A

Frontiers in Neuroscience ◽

10.3389/fnins.2021.771580 ◽

2021 ◽

Vol 15 ◽

Author(s):

Natascia Guida ◽

Luca Sanguigno ◽

Luigi Mascolo ◽

Lucrezia Calabrese ◽

Angelo Serani ◽

...

Keyword(s):

Cell Death ◽

Transcription Factor ◽

Motor Neuron ◽

Molecular Mechanisms ◽

Gene Promoter ◽

Promoter Sequence ◽

Protein Levels ◽

Lysine Methyltransferase ◽

Transcriptional Complex ◽

Lateral Sclerosis

Methylmercury (MeHg) exposure has been related to amyotrophic lateral sclerosis (ALS) pathogenesis and molecular mechanisms of its neurotoxicity has been associated to an overexpression of the Restrictive Element 1 Silencing Transcription factor (REST). Herein, we evaluated the possibility that MeHg could accelerate neuronal death of the motor neuron-like NSC34 cells transiently overexpressing the human Cu2+/Zn2+superoxide dismutase 1 (SOD1) gene mutated at glycine 93 (SOD1-G93A). Indeed, SOD1-G93A cells exposed to 100 nM MeHg for 24 h showed a reduction in cell viability, as compared to cells transfected with empty vector or with unmutated SOD1 construct. Interestingly, cell survival reduction in SOD1-G93A cells was associated with an increase of REST mRNA and protein levels. Furthermore, MeHg increased the expression of the transcriptional factor Sp1 and promoted its binding to REST gene promoter sequence. Notably, Sp1 knockdown reverted MeHg-induced REST increase. Co-immunoprecipitation experiments demonstrated that Sp1 physically interacted with the epigenetic writer Lysine-Methyltransferase-2A (KMT2A). Moreover, knocking-down of KMT2A reduced MeHg-induced REST mRNA and protein increase in SOD1-G93A cells. Finally, we found that MeHg-induced REST up-regulation triggered necropoptotic cell death, monitored by RIPK1 increased protein expression. Interestingly, REST knockdown or treatment with the necroptosis inhibitor Necrostatin-1 (Nec) decelerated MeH-induced cell death in SOD1-G93A cells. Collectively, this study demonstrated that MeHg hastens necroptotic cell death in SOD1-G93A cells via Sp1/KMT2A complex, that by epigenetic mechanisms increases REST gene expression.

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Acidovorax citrulli Type III Effector AopP Suppresses Plant Immunity by Targeting the Watermelon Transcription Factor WRKY6

Frontiers in Plant Science ◽

10.3389/fpls.2020.579218 ◽

2020 ◽

Vol 11 ◽

Author(s):

Xiaoxiao Zhang ◽

Yuwen Yang ◽

Mei Zhao ◽

Linlin Yang ◽

Jie Jiang ◽

...

Keyword(s):

Transcription Factor ◽

Molecular Mechanisms ◽

Plant Immunity ◽

Type Iii ◽

Protein Levels ◽

Bacterial Fruit Blotch ◽

Acidovorax Citrulli ◽

Molecular Pattern

Acidovorax citrulli (Ac) is the causal agent of bacterial fruit blotch (BFB), and BFB poses a threat to global watermelon production. Despite its economic importance, the molecular mechanisms underlying Ac pathogenicity and virulence are not well understood, particularly with regard to its type III secreted effectors. We identify a new effector, AopP, in Ac and confirm its secretion and translocation. AopP suppresses reactive oxygen species burst and salicylic acid (SA) content and significantly contributes to virulence. Interestingly, AopP interacts with a watermelon transcription factor, ClWRKY6, in vivo and in vitro. ClWRKY6 shows typical nuclear localization, and AopP and ClWRKY6 co-localize in the nucleus. Ac infection, SA, and the pathogen-associated molecular pattern flg22Ac promote ClWRKY6 production, suggesting that ClWRKY6 is involved in plant immunity and SA signaling. Furthermore, ClWRKY6 positively regulates PTI and SA production when expressed in Nicotiana benthamiana. Importantly, AopP reduces ClWRKY6 mRNA and ClWRKY6 protein levels, suggesting that AopP suppresses plant immunity by targeting ClWRKY6. In summary, we identify a novel effector associated with the virulence mechanism of Ac, which interacts with the transcription factor of the natural host, watermelon. The findings of this study provide insights into the mechanisms of watermelon immune responses and may facilitate molecular breeding for bacterial fruit blotch resistance.

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Disease- and treatment-associated acquired glucocorticoid resistance

Endocrine Connections ◽

10.1530/ec-18-0421 ◽

2018 ◽

Vol 7 (12) ◽

pp. R328-R349 ◽

Cited By ~ 6

Author(s):

Legh Wilkinson ◽

Nicolette J D Verhoog ◽

Ann Louw

Keyword(s):

Glucocorticoid Receptor ◽

Disease Progression ◽

Side Effect ◽

Molecular Mechanisms ◽

Current Understanding ◽

Side Effect Profile ◽

Major Threat ◽

Development Of Resistance ◽

Current Review ◽

Over Time

The development of resistance to glucocorticoids (GCs) in therapeutic regimens poses a major threat. Generally, GC resistance is congenital or acquired over time as a result of disease progression, prolonged GC treatment or, in some cases, both. Essentially, disruptions in the function and/or pool of the glucocorticoid receptor α (GRα) underlie this resistance. Many studies have detailed how alterations in GRα function lead to diminished GC sensitivity; however, the current review highlights the wealth of data concerning reductions in the GRα pool, mediated by disease-associated and treatment-associated effects, which contribute to a significant decrease in GC sensitivity. Additionally, the current understanding of the molecular mechanisms involved in driving reductions in the GRα pool is discussed. After highlighting the importance of maintaining the level of the GRα pool to combat GC resistance, we present current strategies and argue that future strategies to prevent GC resistance should involve biased ligands with a predisposition for reduced GR dimerization, a strategy originally proposed as the SEMOGRAM–SEDIGRAM concept to reduce the side-effect profile of GCs.

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Transcription factor/DNA interactions visualized by electron spectroscopic imaging

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122654 ◽

1992 ◽

Vol 50 (1) ◽

pp. 450-451

Author(s):

David P. Bazett-Jones ◽

Mark L. Brown

Keyword(s):

Transcription Factor ◽

Dna Sequences ◽

Transcription Initiation ◽

Molecular Mechanisms ◽

Phosphorus Content ◽

Spectroscopic Imaging ◽

Electron Spectroscopic Imaging ◽

Dna Backbone ◽

Two Parameters ◽

High Level

A multisubunit RNA polymerase enzyme is ultimately responsible for transcription initiation and elongation of RNA, but recognition of the proper start site by the enzyme is regulated by general, temporal and gene-specific trans-factors interacting at promoter and enhancer DNA sequences. To understand the molecular mechanisms which precisely regulate the transcription initiation event, it is crucial to elucidate the structure of the transcription factor/DNA complexes involved. Electron spectroscopic imaging (ESI) provides the opportunity to visualize individual DNA molecules. Enhancement of DNA contrast with ESI is accomplished by imaging with electrons that have interacted with inner shell electrons of phosphorus in the DNA backbone. Phosphorus detection at this intermediately high level of resolution (≈lnm) permits selective imaging of the DNA, to determine whether the protein factors compact, bend or wrap the DNA. Simultaneously, mass analysis and phosphorus content can be measured quantitatively, using adjacent DNA or tobacco mosaic virus (TMV) as mass and phosphorus standards. These two parameters provide stoichiometric information relating the ratios of protein:DNA content.

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