Transcriptional coregulator RIP140: an essential regulator of physiology

Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries

The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.

The Transcription Coregulator RIP140 Inhibits Cancer Cell Proliferation by Targeting the Pentose Phosphate Pathway

Cancer cells switch their metabolism toward glucose metabolism to sustain their uncontrolled proliferation. Consequently, glycolytic intermediates are diverted into the pentose phosphate pathway (PPP) to produce macromolecules necessary for cell growth. The transcription regulator RIP140 controls glucose metabolism in tumor cells, but its role in cancer-associated reprogramming of cell metabolism remains poorly understood. Here, we show that, in human breast cancer cells and mouse embryonic fibroblasts, RIP140 inhibits the expression of the gene-encoding G6PD, the first enzyme of the PPP. RIP140 deficiency increases G6PD activity as well as the level of NADPH, a reducing cofactor essential for macromolecule synthesis. Moreover, G6PD knock-down inhibits the gain of proliferation observed when RIP140 expression is reduced. Importantly, RIP140-deficient cells are more sensitive to G6PD inhibition in cell proliferation assays and tumor growth experiments. Altogether, this study describes a novel role for RIP140 in regulating G6PD levels, which links its effect on breast cancer cell proliferation to metabolic rewiring.

RIP140 inhibits glycolysis-dependent proliferation of breast cancer cells by regulating GLUT3 expression through transcriptional crosstalk between hypoxia induced factor and p53

Glycolysis is essential to support cancer cell proliferation, even in the presence of oxygen. The transcriptional co-regulator RIP140 represses the activity of transcription factors that drive cell proliferation and metabolism and plays a role in mammary tumorigenesis. Here we use cell proliferation and metabolic assays to demonstrate that RIP140-deficiency causes a glycolysis-dependent increase in breast tumor growth. We further demonstrate that RIP140 reduces the transcription of the glucose transporter GLUT3 gene, by inhibiting the transcriptional activity of hypoxia inducible factor HIF-2α in cooperation with p53. Interestingly, RIP140 expression was significantly associated with good prognosis only for breast cancer patients with tumors expressing low GLUT3, low HIF-2α and high p53, thus confirming the mechanism of RIP140 anti-tumor activity provided by our experimental data. Overall, our work establishes RIP140 as a critical modulator of the p53/HIF cross-talk to inhibit breast cancer cell glycolysis and proliferation.

A truncating NRIP1 variant in an Arabic family with congenital anomalies of the kidneys and urinary tract

Congenital anomalies of the kidneys and urinary tract (CAKUT) constitute the most common cause of early-onset chronic kidney disease. In a previous study, we identified a heterozygous truncating variant in nuclear receptor-interacting protein 1 (NRIP1) as CAKUT causing via dysregulation of retinoic acid signaling. This large family remains the only family with NRIP1 variant reported so far. Here, we describe one additional CAKUT family with a truncating variant in NRIP1. By whole-exome sequencing, we identified one heterozygous frameshift variant (p.Asn676Lysfs*27) in an isolated CAKUT patient with bilateral hydroureteronephrosis and right grade V vesicoureteral reflux (VUR) and in the affected father with left renal hypoplasia. The variant is present twice in a heterozygous state in the gnomAD database of 125,000 control individuals. We report the second CAKUT family with a truncating variant in NRIP1, confirming that loss-of-function mutations in NRIP1 are a novel monogenic cause of human autosomal dominant CAKUT.

NRIP1 is activated by C-JUN/C-FOS and activates the expression of PGR, ESR1 and CCND1 in luminal A breast cancer

Using chip array assays, we identified differentially expressed genes via a comparison between luminal A breast cancer subtype and normal mammary ductal cells from healthy donors. In silico analysis confirmed by western blot and immunohistochemistry revealed that C-JUN and C-FOS transcription factors are activated in luminal A patients as potential upstream regulators of these differentially expressed genes. Using a chip-on-chip assay, we identified potential C-JUN and C-FOS targets. Among these genes, the NRIP1 gene was revealed to be targeted by C-JUN and C-FOS. This was confirmed after identification and validation with transfection assays specific binding of C-JUN and C-FOS at consensus binding sites. NRIP1 is not only upregulated in luminal A patients and cell lines but also regulates breast cancer-related genes, including PR, ESR1 and CCND1. These results were confirmed by NRIP1 siRNA knockdown and chip array assays, thus highlighting the putative role of NRIP1 in PGR, ESR1 and CCND1 transcriptional regulation and suggesting that NRIP1 could play an important role in breast cancer ductal cell initiation.

A Truncated NRIP1 Mutant Amplifies Microsatellite Instability of Colorectal Cancer by Regulating MSH2/MSH6 Expression, and Is a Prognostic Marker of Stage III Tumors

Simple Summary

The alteration of mismatch repair (MMR) genes leads to microsatellite instability and plays a key role in colorectal cancer (CRC) pathogenesis and prognosis. The transcription factor NRIP1 is involved in intestinal tumorigenesis and is a good prognostic marker in CRC. In this study, we demonstrate that NRIP1 induces MSH2 and MSH6 MMR gene transcription and reduces microsatellite instability. A dominant-negative truncated NRIP1 mutant amplifies the MMR-deficient phenotype and appears as a key player in MSI-driven tumorigenesis since it significantly correlates with a short overall survival of patients with advanced CRC, especially MLH1-deficient ones.

Abstract

Microsatellite instability (MSI) is related to the alteration of mismatch repair (MMR) genes and plays a key role in colorectal cancer (CRC) pathogenesis. We previously reported that the transcription factor Nuclear Receptor Interacting Protein 1 (NRIP1) is involved in sporadic intestinal tumorigenesis. The aim of this study was to decipher its role in MSI CRC. By using different mouse models and engineered cell lines, we demonstrated that NRIP1 increased MSH2 and MSH6 MMR gene transcription and mRNA/protein levels. In human CRC cells, NRIP1 expression was associated with decreased MSI and the hypermutator phenotype, and with resistance to chemotherapy drugs. Using a cohort of 194 CRC patients, we detected in 22% of the cases a MSI-induced frameshift mutation in the NRIP1 coding sequence. This genetic alteration generates a truncated protein with a dominant negative activity that increased human CRC cell proliferation and impaired the regulation of MSH2 and MSH6 gene expression. Moreover, the NRIP1 mutant correlated with a decreased overall survival of patients with advanced CRC, especially when MLH1-deficient. By decreasing the expression of MSH2 and MSH6 gene expression, the NRIP1 variant may amplify MLH1-dependent CRC progression and behave as a new prognostic marker of advanced MSI CRC.

Modulation of mitochondrial and inflammatory homeostasis through RIP140 is neuroprotective in an adrenoleukodystrophy mouse model

AIMS

Mitochondrial dysfunction and inflammation are at the core of axonal degeneration in several multifactorial neurodegenerative diseases, including multiple sclerosis, Alzheimer's disease, and Parkinson's disease. The transcriptional coregulator RIP140/NRIP1 (receptor-interacting protein 140) modulates these functions in liver and adipose tissue, but its role in the nervous system remains unexplored. Here, we investigated the impact of RIP140 in the Abcd1^- mouse model of X-linked adrenoleukodystrophy (X-ALD), a genetic model of chronic axonopathy involving the convergence of redox imbalance, bioenergetic failure, and chronic inflammation.

METHODS AND RESULTS

We provide evidence that RIP140 is modulated through a redox-dependent mechanism driven by very long-chain fatty acids (VLCFAs), the levels of which are increased in X-ALD. Genetic inactivation of RIP140 prevented mitochondrial depletion and dysfunction, bioenergetic failure, inflammatory dysregulation, axonal degeneration and associated locomotor disabilities in vivo in X-ALD mouse models.

CONCLUSIONS

Together, these findings show that aberrant overactivation of RIP140 promotes neurodegeneration in X-ALD, underscoring its potential as a therapeutic target for X-ALD and other neurodegenerative disorders that present with metabolic and inflammatory dyshomeostasis.

RIP140 Represses Intestinal Paneth Cell Differentiation and Interplays with SOX9 Signaling in Colorectal Cancer

RIP140 is a major transcriptional coregulator of gut homeostasis and tumorigenesis through the regulation of Wnt/APC signaling. Here, we investigated the effect of RIP140 on Paneth cell differentiation and its interplay with the transcription factor SOX9. Using loss of function mouse models, human colon cancer cells, and tumor microarray data sets we evaluated the role of RIP140 in SOX9 expression and activity using RT-qPCR, immunohistochemistry, luciferase reporter assays, and GST-pull down. We first evidence that RIP140 strongly represses the Paneth cell lineage in the intestinal epithelium cells by inhibiting Sox9 expression. We then demonstrate that RIP140 interacts with SOX9 and inhibits its transcriptional activity. Our results reveal that the Wnt signaling pathway exerts an opposite regulation on SOX9 and RIP140. Finally, the levels of expression of RIP140 and SOX9 exhibit a reverse response and prognosis value in human colorectal cancer biopsies. This work highlights an intimate transcriptional cross-talk between RIP140 and SOX9 in intestinal physiopathology.

Contribution of PGC-1α to Obesity- and Caloric Restriction-Related Physiological Changes in White Adipose Tissue

Peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α) regulates mitochondrial DNA replication and mitochondrial gene expression by interacting with several transcription factors. White adipose tissue (WAT) mainly comprises adipocytes that store triglycerides as an energy resource and secrete adipokines. The characteristics of WAT vary in response to systemic and chronic metabolic alterations, including obesity or caloric restriction. Despite a small amount of mitochondria in white adipocytes, accumulated evidence suggests that mitochondria are strongly related to adipocyte-specific functions, such as adipogenesis and lipogenesis, as well as oxidative metabolism for energy supply. Therefore, PGC-1α is expected to play an important role in WAT. In this review, we provide an overview of the involvement of mitochondria and PGC-1α with obesity- and caloric restriction-related physiological changes in adipocytes and WAT.

New insights into the genetic basis of premature ovarian insufficiency: Novel causative variants and candidate genes revealed by genomic sequencing

Ovarian deficiency, including premature ovarian insufficiency (POI) and diminished ovarian reserve (DOR), represents one of the main causes of female infertility. POI is a genetically heterogeneous condition but current understanding of its genetic basis is far from complete, with the cause remaining unknown in the majority of patients. The genes that regulate DOR have been reported but the genetic basis of DOR has not been explored in depth. Both conditions are likely to lie along a continuum of degrees of decrease in ovarian reserve. We performed genomic analysis via whole exome sequencing (WES) followed by in silico analyses and functional experiments to investigate the genetic cause of ovarian deficiency in ten affected women. We achieved diagnoses for three of them, including the identification of novel variants in STAG3, GDF9, and FANCM. We identified potentially causative FSHR variants in another patient. This is the second report of biallelic GDF9 and FANCM variants, and, combined with functional support, validates these genes as bone fide autosomal recessive "POI genes". We also identified new candidate genes, NRIP1, XPO1, and MACF1. These genes have been linked to ovarian function in mouse, pig, and zebrafish respectively, but never in humans. In the case of NRIP1, we provide functional support for the deleterious nature of the variant via SUMOylation and luciferase/β-galactosidase reporter assays. Our study provides multiple insights into the genetic basis of POI/DOR. We have further elucidated the involvement of GDF9, FANCM, STAG3 and FSHR in POI pathogenesis, and propose new candidate genes, NRIP1, XPO1, and MACF1, which should be the focus of future studies.

Nuclear receptor co-repressor RIP140 regulates diurnal expression of cytochrome P450 2b10 in mouse liver

Elucidating the mechanisms for circadian expression of drug-metabolizing enzymes is essential for a better understanding of dosing time-dependent drug metabolism and pharmacokinetics. CYP2B6 (Cyp2b10 in mice) is an important enzyme responsible for metabolism and detoxification of approximately 10% of drugs. Here, we aimed to investigate a potential role of nuclear receptor co-repressor RIP140 in circadian regulation of Cyp2b10 in mice.We first uncovered diurnal rhythmicity in hepatic RIP140 mRNA and protein with peak values at ZT10 (ZT, zeitgeber time). RIP140 ablation up-regulated Cyp2b10 expression and blunted its rhythm in mice and in AML-12 cells. Consistent with a negative regulatory effect, overexpression of RIP140 inhibited Cyp2b10 promoter activity and reduced cellular Cyp2b10 expression.Furthermore, RIP140 suppressed Car- and Pxr-mediated transactivation of Cyp2b10, and the suppressive effects were attenuated when the RIP140 gene was silenced. Chromatin immunoprecipitation assays revealed that recruitment of RIP140 protein to the Cyp2b10 promoter was circadian time-dependent in wild-type mice. More extensive recruitment was observed at ZT10 than at ZT2 consistent with the rhythmic pattern of RIP140 protein. However, the time-dependency of RIP140 recruitment was lost in RIP140^-/- mice.Additionally, we identified a D-box and a RORE cis-element in RIP140 promoter. D-box- and RORE-acting clock components such as Dbp, E4bp4, Rev-erbα/β and Rorα transcriptionally regulated RIP140, potentially accounting for its rhythmic expression.In conclusion, RIP140 regulates diurnal expression of Cyp2b10 in mouse liver through periodical repression of Car- and Pxr-mediated transactivation. This co-regulator-driven mechanism represents a novel source of diurnal rhythmicity in drug-metabolizing enzymes.

Differential in Vitro Biological Action, Coregulator Interactions, and Molecular Dynamic Analysis of Bisphenol A (BPA), BPAF, and BPS Ligand-ERα Complexes

BACKGROUND

Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) that might be harmful to human health. Recently, there has been widespread usage of bisphenol chemicals (BPs), such as bisphenol AF (BPAF) and bisphenol S (BPS), as replacements for BPA. However, the potential biological actions, toxicity, and the molecular mechanism of these compounds are still poorly understood.

OBJECTIVES

Our objective was to examine the estrogenic effects of BPA, BPAF, and BPS and the molecular mechanisms of action in the estrogen receptor alpha (ERα) complex.

METHODS

In vitro cell models were used to compare the estrogenic effects of BPA, BPAF, and BPS to estrogen. Microarray Assay for Real-Time Coregulator-Nuclear receptor Interaction (MARCoNI) analysis was used to identify coregulators of BPA, BPAF, and BPS, and molecular dynamic (MD) simulations were used to determine the compounds binding in the ERα complex.

RESULTS

We demonstrated that BPA and BPAF have agonistic activity for both ERα and ERβ, but BPS has ERα-selective specificity. We concluded that coregulators were differentially recruited in the presence of BPA, BPAF, or BPS. Interestingly, BPS recruited more corepressors when compared to BPA and BPAF. From a series of MD analysis, we concluded that BPA, BPAF, and BPS can bind to the ER-ligand-binding domain with differing energetics and conformations. In addition, the binding surface of coregulator interactions on ERα was characterized for the BPA, BPAF, and BPS complexes.

CONCLUSION

These findings further our understanding of the molecular mechanisms of EDCs, such as BPs, in ER-mediated transcriptional activation, biological activity, and their effects on physiological functions in human health. https://doi.org/10.1289/EHP2505.

FLT1 and transcriptome-wide polyadenylation site (PAS) analysis in preeclampsia

Maternal symptoms of preeclampsia (PE) are primarily driven by excess anti-angiogenic factors originating from the placenta. Chief among these are soluble Flt1 proteins (sFlt1s) produced from alternatively polyadenylated mRNA isoforms. Here we used polyadenylation site sequencing (PAS-Seq) of RNA from normal and PE human placentae to interrogate transcriptome-wide gene expression and alternative polyadenylation signatures associated with early-onset PE (EO-PE; symptom onset < 34 weeks) and late-onset PE (LO-PE; symptom onset > 34 weeks) cohorts. While we observed no general shift in alternative polyadenylation associated with PE, the EO-PE and LO-PE cohorts do exhibit gene expression profiles distinct from both each other and from normal placentae. The only two genes upregulated across all transcriptome-wide PE analyses to date (microarray, RNA-Seq and PAS-Seq) are NRIP1 (RIP140), a transcriptional co-regulator linked to metabolic syndromes associated with obesity, and Flt1. Consistent with sFlt1 overproduction being a significant driver of clinical symptoms, placental Flt1 mRNA levels strongly correlate with maternal blood pressure. For Flt1, just three mRNA isoforms account for > 94% of all transcripts, with increased transcription of the entire locus driving Flt1 upregulation in both EO-PE and LO-PE. These three isoforms thus represent potential targets for therapeutic RNA interference (RNAi) in both early and late presentations.