Steroid receptor coactivators: servants and masters for control of systems metabolism

Deficiency of Nuclear Receptor Coactivator 3 Aggravates Diabetic Kidney Disease by Impairing Podocyte Autophagy

Nuclear receptors (NRs) are important transcriptional factors that mediate autophagy, preventing podocyte injury and the progression of diabetic kidney disease (DKD). However, the role of nuclear receptor coactivators that are powerful enhancers for the transcriptional activity of NRs in DKD remains unclear. In this study, a significant decrease in Nuclear Receptor Coactivator 3 (NCOA3) is observed in injured podocytes caused by high glucose treatment. Additionally, NCOA3 overexpression counteracts podocyte damage by improving autophagy. Further, Src family member, Fyn is identified to be the target of NCOA3 that mediates the podocyte autophagy process. Mechanistically, NCOA3 regulates the transcription of Fyn in a nuclear receptor, PPAR-γ dependent way. Podocyte-specific NCOA3 knockout aggravates albuminuria, glomerular sclerosis, podocyte injury, and autophagy in DKD mice. However, the Fyn inhibitor, AZD0530, rescues podocyte injury of NCOA3 knockout DKD mice. Renal NCOA3 overexpression with lentivirus can ameliorate podocyte damage and improve podocyte autophagy in DKD mice. Taken together, the findings highlight a novel target, NCOA3, that protects podocytes from high glucose injury by maintaining autophagy.

Steroid receptor coactivators in Treg and Th17 cell biology and function

Steroid receptor coactivators (SRCs) are master regulators of transcription that play key roles in human physiology and pathology. SRCs are particularly important for the regulation of the immune system with major roles in lymphocyte fate determination and function, macrophage activity, regulation of nuclear factor κB (NF-κB) transcriptional activity and other immune system biology. The three members of the p160 SRC family comprise a network of immune-regulatory proteins that can function independently or act in synergy with each other, and compensate for - or moderate - the activity of other SRCs. Recent evidence indicates that the SRCs are key participants in governing numerous aspects of CD4+ T cell biology. Here we review findings that establish the SRCs as essential regulators of regulatory T cells (Tregs) and T helper 17 (Th17) cells, with a focus on their crucial roles in Treg immunity in cancer and Treg-Th17 cell phenotypic plasticity.

Critical Roles of SRC-3 in the Development and Progression of Breast Cancer, Rendering It a Prospective Clinical Target

Breast cancer (BCa) is the most frequently diagnosed malignant tumor in women and is also one of the leading causes of cancer-related death. Most breast tumors are hormone-dependent and estrogen signaling plays a critical role in promoting the survival and malignant behaviors of these cells. Estrogen signaling involves ligand-activated cytoplasmic estrogen receptors that translocate to the nucleus with various co-regulators, such as steroid receptor co-activator (SRC) family members, and bind to the promoters of target genes and regulate their expression. SRC-3 is a member of this family that interacts with, and enhances, the transcriptional activity of the ligand activated estrogen receptor. Although SRC-3 has important roles in normal homeostasis and developmental processes, it has been shown to be amplified and overexpressed in breast cancer and to promote malignancy. The malignancy-promoting potential of SRC-3 is diverse and involves both promoting malignant behavior of tumor cells and creating a tumor microenvironment that has an immunosuppressive phenotype. SRC-3 also inhibits the recruitment of tumor-infiltrating lymphocytes with effector function and promotes stemness. Furthermore, SRC-3 is also involved in the development of resistance to hormone therapy and immunotherapy during breast cancer treatment. The versatility of SRC-3 in promoting breast cancer malignancy in this way makes it a good target, and methodical targeting of SRC-3 probably will be important for the success of breast cancer treatment.

AIB1/SRC-3/NCOA3 function in estrogen receptor alpha positive breast cancer

The estrogen receptor alpha (ERα) is a steroid receptor that is pivotal in the initiation and progression of most breast cancers. ERα regulates gene transcription through recruitment of essential coregulators, including the steroid receptor coactivator AIB1 (Amplified in Breast Cancer 1). AIB1 itself is an oncogene that is overexpressed in a subset of breast cancers and is known to play a role in tumor progression and resistance to endocrine therapy through multiple mechanisms. Here we review the normal and pathological functions of AIB1 in regard to its ERα-dependent and ERα-independent actions, as well as its genomic conservation and protein evolution. We also outline the efforts to target AIB1 in the treatment of breast cancer.

Arginase 1 and L-arginine coordinate fetal lung development and the initiation of labor in mice

Fetal development and parturition are precisely regulated processes that involve continuous crosstalk between the mother and the fetus. Our previous discovery that wild-type mice carrying steroid receptor coactivator (Src)-1 and Src-2 double-deficient fetuses exhibit impaired lung development and delayed labor, which indicates that the signals for parturition emanate from the fetus. In this study, we perform RNA sequencing and targeted metabolomics analyses of the lungs from fetal Src-1/-2 double-knockout mice and find that expression of arginase 1 (Arg1) is significantly decreased, accompanied by increased levels of the Arg1 substrate L-arginine. Knockdown of Arg1 in the lungs of fetal mice induces apoptosis of epithelial cells and dramatically delays initiation of labor. Moreover, treatment of human myometrial smooth muscle cells with L-arginine significantly inhibits spontaneous contractions by attenuating activation of NF-κB and downregulating expression of contraction-associated protein genes. Transcription factors GR and C/EBPβ increase transcription of Arg1 in an Src-1/Src-2-dependent manner. These findings provide new evidence that fetus-derived factors may play dual roles in coordinating fetal lung development and the initiation of labor.

Prolyl endopeptidase remodels macrophage function as a novel transcriptional coregulator and inhibits fibrosis

Macrophages are immune cells crucial for host defense and homeostasis maintenance, and their dysregulation is involved in multiple pathological conditions, such as liver fibrosis. The transcriptional regulation in macrophage is indispensable for fine-tuning of macrophage functions, but the details have not been fully elucidated. Prolyl endopeptidase (PREP) is a dipeptidyl peptidase with both proteolytic and non-proteolytic functions. In this study, we found that Prep knockout significantly contributed to transcriptomic alterations in quiescent and M1/M2-polarized bone marrow-derived macrophages (BMDMs), as well as aggravated fibrosis in an experimental nonalcoholic steatohepatitis (NASH) model. Mechanistically, PREP predominantly localized to the macrophage nuclei and functioned as a transcriptional coregulator. Using CUT&Tag and co-immunoprecipitation, we found that PREP was mainly distributed in active cis-regulatory genomic regions and physically interacted with the transcription factor PU.1. Among PREP-regulated downstream genes, genes encoding profibrotic cathepsin B and D were overexpressed in BMDMs and fibrotic liver tissue. Our results indicate that PREP in macrophages functions as a transcriptional coregulator that finely tunes macrophage functions, and plays a protective role against liver fibrosis pathogenesis.

ESR1 activating mutations: From structure to clinical application

Estrogen receptor-positive breast cancer is the most common type of both early and advanced breast cancer. Estrogen receptor alpha (ER) is a nuclear hormone receptor and a key driver of tumorigenesis and tumor progression in these breast cancers. As such, it is a key treatment target and a biomarker predictive of response to endocrine therapy. Activating ESR1 ligand binding domain mutations engender constitutive/ligand independent transcriptional activities and emerge following prolonged first-line hormone therapy regimens, mainly from aromatase inhibitors. The full scale of the biological and clinical significance of these mutations continue to evolve and additional studies are required to further discern the multimodal effects of these mutations on ER transcription, metastatic propensity, and the tumor microenvironment. Furthermore, recent and ongoing studies highlight the potential clinical utility of these mutations as therapeutic targets and dynamic biomarkers. Herein, we review the structure, functional consequences, and clinical implications of the activating ESR1 mutations in advanced estrogen receptor-positive breast cancer.

Steroid receptor coactivators - their role in immunity

Steroid Receptor Coactivators (SRCs) are essential regulators of transcription with a wide range of impact on human physiology and pathology. In immunology, SRCs play multiple roles; they are involved in the regulation of nuclear factor-κB (NF-κB), macrophage (MΦ) activity, lymphoid cells proliferation, development and function, to name just a few. The three SRC family members, SRC-1, SRC-2 and SRC-3, can exert their immunological function either in an independent manner or act in synergy with each other. In certain biological contexts, one SRC family member can compensate for lack of activity of another member, while in other cases one SRC can exert a biological function that competes against the function of another family counterpart. In this review we illustrate the diverse biological functionality of the SRCs with regard to their role in immunity. In the light of recent development of SRC small molecule inhibitors and stimulators, we discuss their potential relevance as modulators of the immunological activity of the SRCs for therapeutic purposes.

Nuclear Receptor Coregulators in Hormone-Dependent Cancers

Nuclear receptors (NRs) function collectively as a transcriptional signaling network that mediates gene regulatory actions to either maintain cellular homeostasis in response to hormonal, dietary and other environmental factors, or act as orphan receptors with no known ligand. NR complexes are large and interact with multiple protein partners, collectively termed coregulators. Coregulators are essential for regulating NR activity and can dictate whether a target gene is activated or repressed by a variety of mechanisms including the regulation of chromatin accessibility. Altered expression of coregulators contributes to a variety of hormone-dependent cancers including breast and prostate cancers. Therefore, understanding the mechanisms by which coregulators interact with and modulate the activity of NRs provides opportunities to develop better prognostic and diagnostic approaches, as well as novel therapeutic targets. This review aims to gather and summarize recent studies, techniques and bioinformatics methods used to identify distorted NR coregulator interactions that contribute as cancer drivers in hormone-dependent cancers.

Corticosteroid sensitization drives opioid addiction

The global crisis of opioid overdose fatalities has led to an urgent search to discover the neurobiological mechanisms of opioid use disorder (OUD). A driving force for OUD is the dysphoric and emotionally painful state (hyperkatifeia) that is produced during acute and protracted opioid withdrawal. Here, we explored a mechanistic role for extrahypothalamic stress systems in driving opioid addiction. We found that glucocorticoid receptor (GR) antagonism with mifepristone reduced opioid addiction-like behaviors in rats and zebrafish of both sexes and decreased the firing of corticotropin-releasing factor neurons in the rat amygdala (i.e., a marker of brain stress system activation). In support of the hypothesized role of glucocorticoid transcriptional regulation of extrahypothalamic GRs in addiction-like behavior, an intra-amygdala infusion of an antisense oligonucleotide that blocked GR transcriptional activity reduced addiction-like behaviors. Finally, we identified transcriptional adaptations of GR signaling in the amygdala of humans with OUD. Thus, GRs, their coregulators, and downstream systems may represent viable therapeutic targets to treat the "stress side" of OUD.

The NCOA1-CBP-NF-κB transcriptional complex induces inflammation response and triggers endotoxin-induced myocardial dysfunction

Inflammatory pathways represented by TLR4/NF-κB (Toll-like receptor 4/Nuclear factor-κB) axis signaling are activated in the pathogenesis of endotoxin-induced myocardial dysfunction (EIMD). However, the underlying mechanism by which NF-κB coordinates with other transcriptional coactivators/corepressors to regulate the expression of proinflammatory cytokine genes remains unclear. We established an EIMD-mouse model by intraperitoneal injection of lipopolysaccharides (LPS), and we discovered that NCOA1 (nuclear receptor coactivator 1) assembled with CBP (CREB binding protein) and NF-κB subunits to form a transcriptional complex that specifically bound to promoters of proinflammatory cytokine genes to activate their expression. LPS treatment also inhibited DNMT1 (DNA methyltransferase 1) expression, thereby decreasing DNA methylation of a CpG island located on the promoter of NCOA1 and causing NCOA1 overexpression. Screening small molecules that abolished NCOA1-CBP interaction in a yeast system identified a compound PSSM2126 that effectively blocked the NCOA1-CBP interaction in vitro and in vivo. Administration of PSSM2126 to EIMD mice significantly alleviated the inflammation response and improved cardiac function. Collectively, our results reveal that an NCOA1-dependent transactivation mechanism can regulate proinflammatory cytokine expression, thereby improving our understanding of the activation of NF-κB targets. The promising inhibition of the NCOA1-CBP interaction by PSSM2126 may provide a new therapeutic option for EIMD.

Expression and regulation of estrogen receptor 2 and its coregulators in mouse granulosa cells

The cooperative effects of estrogen and oocyte-derived paracrine factors (ODPFs) play critical roles in the normal development of ovarian follicles; however, the mechanism underlying this cooperation has not been well studied. The present study aimed to determine whether ODPFs affect estrogen signaling by regulating the expression of estrogen receptor (ESR) and its coregulators in mouse granulosa cells. Some transcripts encoding ESR coregulators were differentially expressed between cumulus and mural granulosa cells (MGCs). The transcript levels of ESR coregulators, including nuclear receptor corepressor 1 and activator 2, in cumulus cells were significantly suppressed by ODPFs; however, they increased when cumulus cell-oocyte complexes were treated with the transforming growth factor beta receptor I inhibitor, SB431542. Moreover, MGCs exhibited significantly higher ESR2 protein and transcript levels than those in cumulus cells. ODPFs promoted Esr2 expression in cumulus cells but had no effect on that in MGCs. Overall, regulation of the expression of ESR2 and its coregulators in cumulus cells by oocytes seems to be one of the mechanisms underlying estrogen-oocyte cooperation in well-developed antral follicles in mice.

Regulation of PXR Function by Coactivator and Corepressor Proteins: Ligand Binding Is Just the Beginning

The pregnane X receptor (PXR, NR1I2) is a nuclear receptor which exerts its regulatory function by heterodimerization with the retinoid-X-receptor α (RXRα, NR2B1) and binding to the promoter and enhancer regions of diverse target genes. PXR is involved in the regulation of drug metabolism and excretion, metabolic and immunological functions and cancer pathogenesis. PXR activity is strongly regulated by the association with coactivator and corepressor proteins. Coactivator proteins exhibit histone acetyltransferase or histone methyltransferase activity or associate with proteins having one of these activities, thus promoting chromatin decondensation and activation of the gene expression. On the contrary, corepressor proteins promote histone deacetylation and therefore favor chromatin condensation and repression of the gene expression. Several studies pointed to clear cell- and ligand-specific differences in the activation of PXR. In this article, we will review the critical role of coactivator and corepressor proteins as molecular determinants of the specificity of PXR-mediated effects. As already known for other nuclear receptors, understanding the complex mechanism of PXR activation in each cell type and under particular physiological and pathophysiological conditions may lead to the development of selective modulators with therapeutic potential.

An acetylation-enhanced interaction between transcription factor Sox2 and the steroid receptor coactivators facilitates Sox2 transcriptional activity and function

SRY-box 2 (Sox2) is a transcription factor with critical roles in maintaining embryonic stem (ES) cell and adult stem cell functions and in tumorigenesis. However, how Sox2 exerts its transcriptional function remains unclear. Here, we used an in vitro protein–protein interaction assay to discover transcriptional regulators for ES cell core transcription factors (Oct4, Sox2, Klf4, and c-Myc) and identified members of the steroid receptor coactivators (SRCs) as Sox2-specific interacting proteins. The SRC family coactivators have broad roles in transcriptional regulation, but it is unknown whether they also serve as Sox2 coactivators. We demonstrated that these proteins facilitate Sox2 transcriptional activity and act synergistically with p300. Furthermore, we uncovered an acetylation-enhanced interaction between Sox2 and SRC-2/3, but not SRC-1, demonstrating it is Sox2 acetylation that promotes the interaction. We identified putative Sox2 acetylation sites required for acetylation-enhanced interaction between Sox2 and SRC-3 and demonstrated that acetylation on these sites contributes to Sox2 transcriptional activity and recruitment of SRC-3. We showed that activation domains 1 and 2 of SRC-3 both display a preferential binding to acetylated Sox2. Finally, functional analyses in mouse ES cells demonstrated that knockdown of SRC-2/3 but not SRC-1 in mouse ES cells significantly downregulates the transcriptional activities of various Sox2 target genes and impairs ES cell stemness. Taken together, we identify specific SRC family proteins as novel Sox2 coactivators and uncover the role of Sox2 acetylation in promoting coactivator recruitment and Sox2 transcriptional function.

LMO3 reprograms visceral adipocyte metabolism during obesity

Abstract

Obesity and body fat distribution are important risk factors for the development of type 2 diabetes and metabolic syndrome. Evidence has accumulated that this risk is related to intrinsic differences in behavior of adipocytes in different fat depots. We recently identified LIM domain only 3 (LMO3) in human mature visceral adipocytes; however, its function in these cells is currently unknown. The aim of this study was to determine the potential involvement of LMO3-dependent pathways in the modulation of key functions of mature adipocytes during obesity. Based on a recently engineered hybrid rAAV serotype Rec2 shown to efficiently transduce both brown adipose tissue (BAT) and white adipose tissue (WAT), we delivered YFP or Lmo3 to epididymal WAT (eWAT) of C57Bl6/J mice on a high-fat diet (HFD). The effects of eWAT transduction on metabolic parameters were evaluated 10 weeks later. To further define the role of LMO3 in insulin-stimulated glucose uptake, insulin signaling, adipocyte bioenergetics, as well as endocrine function, experiments were conducted in 3T3-L1 adipocytes and newly differentiated human primary mature adipocytes, engineered for transient gain or loss of LMO3 expression, respectively. AAV transduction of eWAT results in strong and stable Lmo3 expression specifically in the adipocyte fraction over a course of 10 weeks with HFD feeding. LMO3 expression in eWAT significantly improved insulin sensitivity and healthy visceral adipose tissue expansion in diet-induced obesity, paralleled by increased serum adiponectin. In vitro, LMO3 expression in 3T3-L1 adipocytes increased PPARγ transcriptional activity, insulin-stimulated GLUT4 translocation and glucose uptake, as well as mitochondrial oxidative capacity in addition to fatty acid oxidation. Mechanistically, LMO3 induced the PPARγ coregulator Ncoa1, which was required for LMO3 to enhance glucose uptake and mitochondrial oxidative gene expression. In human mature adipocytes, LMO3 overexpression promoted, while silencing of LMO3 suppressed mitochondrial oxidative capacity. LMO3 expression in visceral adipose tissue regulates multiple genes that preserve adipose tissue functionality during obesity, such as glucose metabolism, insulin sensitivity, mitochondrial function, and adiponectin secretion. Together with increased PPARγ activity and Ncoa1 expression, these gene expression changes promote insulin-induced GLUT4 translocation, glucose uptake in addition to increased mitochondrial oxidative capacity, limiting HFD-induced adipose dysfunction. These data add LMO3 as a novel regulator improving visceral adipose tissue function during obesity.

Key messages

LMO3 increases beneficial visceral adipose tissue expansion and insulin sensitivity in vivo.

LMO3 increases glucose uptake and oxidative mitochondrial activity in adipocytes.

LMO3 increases nuclear coactivator 1 (Ncoa1).

LMO3-enhanced glucose uptake and mitochondrial gene expression requires Ncoa1.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-021-02089-9.

Illuminating the "Black Box" of Progesterone-Dependent Embryo Implantation Using Engineered Mice

Synchrony between progesterone-driven endometrial receptivity and the arrival of a euploid blastocyst is essential for embryo implantation, a prerequisite event in the establishment of a successful pregnancy. Advancement of embryo implantation within the uterus also requires stromal fibroblasts of the endometrium to transform into epithelioid decidual cells, a progesterone-dependent cellular transformation process termed decidualization. Although progesterone is indispensable for these cellular processes, the molecular underpinnings are not fully understood. Because human studies are restricted, much of our fundamental understanding of progesterone signaling in endometrial periimplantation biology comes from in vitro and in vivo experimental systems. In this review, we focus on the tremendous progress attained with the use of engineered mouse models together with high throughput genome-scale analysis in disclosing key signals, pathways and networks that are required for normal endometrial responses to progesterone during the periimplantation period. Many molecular mediators and modifiers of the progesterone response are implicated in cross talk signaling between epithelial and stromal cells of the endometrium, an intercellular communication system that is critical for the ordered spatiotemporal control of embryo invasion within the maternal compartment. Accordingly, derailment of these signaling systems is causally linked with infertility, early embryo miscarriage and gestational complications that symptomatically manifest later in pregnancy. Such aberrant progesterone molecular responses also contribute to endometrial pathologies such as endometriosis, endometrial hyperplasia and cancer. Therefore, our review makes the case that further identification and functional analysis of key molecular mediators and modifiers of the endometrial response to progesterone will not only provide much-needed molecular insight into the early endometrial cellular changes that promote pregnancy establishment but lend credible hope for the development of more effective mechanism-based molecular diagnostics and precision therapies in the clinical management of female infertility, subfertility and a subset of gynecological morbidities.

A genome-scale CRISPR Cas9 dropout screen identifies synthetically lethal targets in SRC-3 inhibited cancer cells

Steroid receptor coactivator 3 (SRC-3/NCoA3/AIB1), is a key regulator of gene transcription and it plays a central role in breast cancer (BC) tumorigenesis, making it a potential therapeutic target. Beyond its function as an important regulator of estrogen receptor transcriptional activity, SRC-3 also functions as a coactivator for a wide range of other transcription factors, suggesting SRC-3 inhibition can be beneficial in hormone-independent cancers as well. The recent discovery of a potent SRC-3 small molecule inhibitor, SI-2, enabled the further development of additional related compounds. SI-12 is an improved version of SI-2 that like SI-2 has anti-proliferative activity in various cancer types, including BC. Here, we sought to identify gene targets, that when inhibited in the presence of SI-12, would lead to enhanced BC cell cytotoxicity. We performed a genome-scale CRISPR-Cas9 screen in MCF-7 BC cells under conditions of pharmacological pressure with SI-12. A parallel screen was performed with an ER inhibitor, fulvestrant, to shed light on both common and distinct activities between SRC-3 and ERα inhibition. Bearing in mind the key role of SRC-3 in tumorigenesis of other types of cancer, we extended our study by validating potential hits identified from the MCF-7 screen in other cancer cell lines.

Chemical systems biology reveals mechanisms of glucocorticoid receptor signaling

Glucocorticoids display remarkable anti-inflammatory activity, but their use is limited by on-target adverse effects including insulin resistance and skeletal muscle atrophy. We used a chemical systems biology approach, ligand class analysis, to examine ligands designed to modulate glucocorticoid receptor activity through distinct structural mechanisms. These ligands displayed diverse activity profiles, providing the variance required to identify target genes and coregulator interactions that were highly predictive of their effects on myocyte glucose disposal and protein balance. Their anti-inflammatory effects were linked to glucose disposal but not muscle atrophy. This approach also predicted selective modulation in vivo, identifying compounds that were muscle-sparing or anabolic for protein balance and mitochondrial potential. Ligand class analysis defined the mechanistic links between the ligand-receptor interface and ligand-driven physiological outcomes, a general approach that can be applied to any ligand-regulated allosteric signaling system.

The Nuclear Orphan Receptor NR2F6 Promotes Hepatic Steatosis through Upregulation of Fatty Acid Transporter CD36

Nuclear receptors (NRs) are a superfamily of transcription factors which sense hormonal signals or nutrients to regulate various biological events, including development, reproduction, and metabolism. Here, this study identifies nuclear receptor subfamily 2, group F, member 6 (NR2F6), as an important regulator of hepatic triglyceride (TG) homeostasis and causal factor in the development of non-alcoholic fatty liver disease (NAFLD). Adeno-associated virus (AAV)-mediated overexpression of NR2F6 in the liver promotes TG accumulation in lean mice, while hepatic-specific suppression of NR2F6 improves obesity-associated hepatosteatosis, insulin resistance, and methionine and choline-deficient (MCD) diet-induced non-alcoholic steatohepatitis (NASH). Mechanistically, the fatty acid translocase CD36 is identified as a transcriptional target of NR2F6 to mediate its steatotic role. NR2F6 is able to bind directly onto the CD36 promoter region in hepatocytes and increases the enrichment of nuclear receptor coactivator 1 (SRC-1) and histone acetylation at its promoter. Of pathophysiological significance, NR2F6 is significantly upregulated in the livers of obese mice and NAFLD patients. Moreover, treatment with metformin decreases NR2F6 expression in obese mice, resulting in suppression of CD36 and reduced hepatic TG contents. Therefore, these results provide evidence for an unpredicted role of NR2F6 that contributes to liver steatosis and suggest that NR2F6 antagonists may present a therapeutic strategy for reversing or treating NAFLD/NASH pathogenesis.

Decreased 11β-hydroxysteroid dehydrogenase 1 in lungs of steroid receptor coactivator (Src)-1/-2 double-deficient fetal mice is caused by impaired glucocorticoid and cytokine signaling

Our previous research revealed that steroid receptor coactivators (Src)-1 and -2 serve a critical cooperative role in production of parturition signals, surfactant protein A and platelet-activating factor, by the developing mouse fetal lung (MFL). To identify the global landscape of genes in MFL affected by Src-1/-2 double-deficiency, we conducted RNA-seq analysis of lungs from 18.5 days post-coitum (dpc) Src-1^-/- /-2^-/- (dKO) vs. WT fetuses. One of the genes most highly downregulated (~4.8 fold) in Src-1/-2 dKO fetal lungs encodes 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1), which catalyzes conversion of inactive 11-dehydrocorticosterone to the glucocorticoid receptor (GR) ligand, corticosterone. Glucocorticoids were reported to upregulate 11β-HSD1 expression in various cell types via induction of C/EBP transcription factors. We observed that C/ebpα and C/ebpβ mRNA and protein were markedly reduced in Src-1/-2 double-deficient (Src-1/-2^d/d ) fetal lungs, compared to WT. Moreover, glucocorticoid induction of 11β-hsd1, C/ebpα and C/ebpβ in cultured MFL epithelial cells was prevented by the SRC family inhibitor, SI-2. Cytokines also contribute to the induction of 11β-HSD1. Expression of IL-1β and TNFα, which dramatically increased toward term in lungs of WT fetuses, was markedly reduced in Src-1/-2^d/d fetal lungs. Our collective findings suggest that impaired lung development and surfactant synthesis in Src-1/-2^d/d fetuses are likely caused, in part, by decreased GR and cytokine induction of C/EBP and NF-κB transcription factors. This results in reduced 11β-HSD1 expression and glucocorticoid signaling within the fetal lung, causing a break in the glucocorticoid-induced positive feedforward loop.

Phosphorylation of steroid receptor coactivator-3 (SRC-3) at serine 857 is regulated by the p38MAPK-MK2 axis and affects NF-κB-mediated transcription

Steroid receptor coactivator-3 (SRC-3) regulates the activity of both nuclear hormone receptors and a number of key transcription factors. It is implicated in the regulation of cell proliferation, inflammation and in the progression of several common cancers including breast, colorectal and lung tumors. Phosphorylation is an important regulatory event controlling the activities of SRC-3. Serine 857 is the most studied phospho-acceptor site, and its modification has been reported to be important for SRC-3-dependent tumor progression. In this study, we show that the stress-responsive p38MAPK-MK2 signaling pathway controls the phosphorylation of SRC-3 at S857 in a wide range of human cancer cells. Activation of the p38MAPK-MK2 pathway results in the nuclear translocation of SRC-3, where it contributes to the transactivation of NF-kB and thus regulation of IL-6 transcription. The identification of the p38MAPK-MK2 signaling axis as a key regulator of SRC-3 phosphorylation and activity opens up new possibilities for the development and testing of novel therapeutic strategies to control both proliferative and metastatic tumor growth.

SRC-2 Coactivator: a role in human metabolic evolution and disease

The large family of transcriptional coactivators originated with the cloning of the subfamily of Steroid Receptor Coactivators (SRC-1,2,3). These 3 coactivators serve as primary 'master genes' to direct the coordinate transcription of multiple genes required for physiological goals in cells, specifically, carbohydrate, lipid, or anabolic growth metabolisms. SRC-2 is of special interest in terms of lipid metabolism and energy accrual and is the topic of a collection of our research discoveries and publications described in this Perspective.

The Expression and Contribution of SRCs with Preeclampsia Placenta

The steroid hormones act by binding to their receptors and subsequently interacting with coactivators. Several classes of coactivators have been identified and shown to be essential in estradiol (E2) responsiveness. The major coregulators are the p160 steroid receptor coactivator (SRC) family. Although the function of SRCs in other organs has been well studied, it has not been thoroughly studied in the placenta. In addition, the correlation between preeclampsia (PE) and SRCs has not been examined previously. Therefore, we compared the expression patterns of SRCs in normal and PE placentas. In human PE placental tissues, SRC-1 mRNA, and protein levels were downregulated in the PE group. In addition, to assess the expression of SRCs in a PE environment, we used Reduced Uterine Perfusion Pressure (RUPP) model and placental cells were cultured in hypoxia condition. SRC-1 proteins were reduced in the placenta of PE-like rat RUPP model. Furthermore, SRCs proteins were significantly downregulated in hypoxia-grown placental cells. To examine the interaction between estrogen receptors (ERs) and SRC-1 protein, we performed co-immunoprecipitation. The interaction of SRC-1 with ERα was significantly stronger than that with ERβ. In PE placenta, the interaction of both ERα and ERβ with SRC-1 was stronger than that in normal placenta. In summary, our results demonstrate that expression levels of SRC-1, not SRC-2 and SRC-3, were decreased in hypoxia-induced PE placenta, which may further reduce the signaling of sex steroid hormones such as E2. The dysregulated signaling of E2 by SRC-1 expression could be associated with the PE placental symptoms of patients.

Steroid Receptor Coactivator-1 Expression in Pheochromocytoma: Clinicopathologic Correlation and Potential Diagnostic Pitfall

Pheochromocytoma is a relatively uncommon tumor, and the histomorphologic and biochemical features that may portend malignant behavior have poor overall consensus across various proposed classification systems. Steroid receptor coactivator-1 (SRC-1) is a nuclear protein that mediates transcriptional activity. Current diagnostic applications of SRC-1 are limited, and include distinguishing adrenocortical carcinoma (ACC) from renal cell carcinoma, and other mimickers. SRC-1 expression in pheochromocytoma has not been previously studied. Pheochromocytoma cases were retrieved from our Urological Pathology database and expert consultation files of the senior author, from 2015 to 2019. Clinicopathological data were obtained. SRC-1 expression was scored systematically. Thirty-eight cases were included, with a female predominance, and a mean age of 52 years (range, 16 to 75 y). Seven patients had heritable mutations including RET (n=3), VHL (2), SDHB (1), and ATM and PDGFRA (1). Two patients developed clinical metastasis, who individually had ATM and PDGFRA mutations, and SDHB p.V140F mutation. All heritable tumors were positive for SRC-1, including diffuse/strong staining and intensity in the VHL cases, and diffuse staining with variable intensity in RET cases. Diffuse positivity was seen in most of our heritable cases, providing evidence for a putative link between RET and downstream SRC-1 signaling. An inverse relationship was observed between SRC-1 expression and Pheochromocytoma of the Adrenal Gland Scaled Score/tumor size, suggesting that SRC-1 phenotype may become muted in pheochromocytomas that have malignant potential. SRC-1 expression in aggressive pheochromocytomas, may also be a potential diagnostic pitfall in view of the fact that these tumors may be misinterpreted as ACC in the primary or metastatic setting.

Circadian Clock Regulation of Hepatic Energy Metabolism Regulatory Circuits

The liver is a critical organ of energy metabolism. At least 10% of the liver transcriptome demonstrates rhythmic expression, implying that the circadian clock regulates large programmes of hepatic genes. Here, we review the mechanisms by which this rhythmic regulation is conferred, with a particular focus on the transcription factors whose actions combine to impart liver- and time-specificity to metabolic gene expression.

Engagement of Nuclear Coactivator 7 by 3-Hydroxyanthranilic Acid Enhances Activation of Aryl Hydrocarbon Receptor in Immunoregulatory Dendritic Cells

Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the first step in the kynurenine pathway of tryptophan (Trp) degradation that produces several biologically active Trp metabolites. L-kynurenine (Kyn), the first byproduct by IDO1, promotes immunoregulatory effects via activation of the Aryl hydrocarbon Receptor (AhR) in dendritic cells (DCs) and T lymphocytes. We here identified the nuclear coactivator 7 (NCOA7) as a molecular target of 3-hydroxyanthranilic acid (3-HAA), a Trp metabolite produced downstream of Kyn along the kynurenine pathway. In cells overexpressing NCOA7 and AhR, the presence of 3-HAA increased the association of the two molecules and enhanced Kyn-driven, AhR-dependent gene transcription. Physiologically, conventional (cDCs) but not plasmacytoid DCs or other immune cells expressed high levels of NCOA7. In cocultures of CD4⁺ T cells with cDCs, the co-addition of Kyn and 3-HAA significantly increased the induction of Foxp3⁺ regulatory T cells and the production of immunosuppressive transforming growth factor β in an NCOA7-dependent fashion. Thus, the co-presence of NCOA7 and the Trp metabolite 3-HAA can selectively enhance the activation of ubiquitary AhR in cDCs and consequent immunoregulatory effects. Because NCOA7 is often overexpressed and/or mutated in tumor microenvironments, our current data may provide evidence for a new immune check-point mechanism based on Trp metabolism and AhR.

Betulinic acid lowers lipid accumulation in adipocytes through enhanced NCoA1-PPARγ interaction

BACKGROUND

Investigation for a naturally occurring anti-obesity drug has become the need of society all over the world. Betulinic acid (BA) is a lupane-type pentacyclic triterpene and is sourced from various organisms. This high potential biologically active molecule is reported to have anti-obesity effect. In this study, we report the molecular mechanism of action of BA that underlies anti-obesity activity and also an improved method of its isolation common teak tree.

METHODS

Mouse pre-adipocyte cells were used to develop hyperlipidemic conditions in vitro. Change in expression of genes associated to adipogenesis was checked using quantitative real-time PCR (qPCR). Co-factor specificity of PPAR gamma was analyzed through immune precipitation and immunoblot.

RESULTS

Betulinic acid was found to be effective in reducing the lipid content in 3T3L1 cells. Level of PPAR gamma and LXR alpha was reduced in connection to reduced adipogenesis. Change in steroid responsive co-activators (SRCs) during BA treatment proved that the compound can impart profound change in co-factor selectivity, which is crucial in determining the activity profile of PPAR gamma. BA treatment enhanced the SRC-1 interaction with PPAR gamma while reducing the levels of SRC-3.

CONCLUSION

Present study has proved that betulinic acid, a promising candidate in anti-obesity drug development, has potential in regulating the activity of PPAR gamma through co-factor modulation.

Overexpression of steroid receptor coactivators alleviates hyperglycemia-induced endothelial cell injury in rats through activating the PI3K/Akt pathway

Hyperglycemia is a major factor in vascular endothelial injury that finally leads to a cardiovascular event. Steroid receptor coactivators (SRCs) are a group of non-DNA binding proteins that induce structural changes in steroid receptors (nuclear receptors) critical for transcriptional activation. SRCs, namely, SRC-1, SRC-2, and SRC-3, are implicated in the regulation of vascular homeostasis. In this study we investigate the role of SRCs in hyperglycemia-induced endothelial injury. Aortic endothelial cells were prepared from normal and diabetic rats, respectively. Diabetic rats were prepared by injection of streptozotocin (50 mg/kg, i.p.). The expression levels of SRC-1 and SRC-3 were significantly decreased in endothelial cells from the diabetic rats. Similar phenomenon was also observed in aortic endothelial cells from the normal rats treated with a high glucose (25 mM) for 4 h or 8 h. The expression levels of SRC-2 were little affected by hyperglycemia. Overexpression of SRC-1 and SRC-3 in high glucose-treated endothelial cells significantly increased the cell viability, suspended cell senescence, and inhibited cell apoptosis compared with the control cells. We further showed that overexpression of SRC-1 and SRC-3 markedly suppressed endothelial injury through restoring nitric oxide production, upregulating the expression of antioxidant enzymes (SOD, GPX, and CAT), and activating the PI3K/Akt pathway. The beneficial effects of SRC-1 and SRC-3 overexpression were blocked by treatment with the PI3K inhibitor LY294002 (10 mM) or with the Akt inhibitor MK-2206 (100 nM). In conclusion, hyperglycemia decreased SRC-1 and SRC-3 expression levels in rat aortic endothelial cells. SRC-1 and SRC-3 overexpression might protect against endothelial injury via inhibition of oxidative stress and activation of PI3K/Akt pathway.

Endocrine Resistance in Hormone Receptor Positive Breast Cancer-From Mechanism to Therapy

The importance and role of the estrogen receptor (ER) pathway has been well-documented in both breast cancer (BC) development and progression. The treatment of choice in women with metastatic breast cancer (MBC) is classically divided into a variety of endocrine therapies, 3 of the most common being: selective estrogen receptor modulators (SERM), aromatase inhibitors (AI) and selective estrogen receptor down-regulators (SERD). In a proportion of patients, resistance develops to endocrine therapy due to a sophisticated and at times redundant interference, at the molecular level between the ER and growth factor. The progression to endocrine resistance is considered to be a gradual, step-wise process. Several mechanisms have been proposed but thus far none of them can be defined as the complete explanation behind the phenomenon of endocrine resistance. Although multiple cellular, molecular and immune mechanisms have been and are being extensively studied, their individual roles are often poorly understood. In this review, we summarize current progress in our understanding of ER biology and the molecular mechanisms that predispose and determine endocrine resistance in breast cancer patients.

Retinoid signaling controlled by SRC-2 in decidualization revealed by transcriptomics

Establishment of a successful pregnancy requires not only implantation of a healthy embryo into a receptive uterus but also progesterone receptor (PGR)-dependent transformation of endometrial stromal cells (ESCs) into specialized decidual cells. Decidual cells support the developing embryo and are critical for placentation. We have previously shown that a known transcriptional coregulator of the PGR, steroid receptor coactivator-2 (SRC-2), is a critical driver of endometrial decidualization in both human and mouse endometrium. However, the full spectrum of genes transcriptionally controlled by SRC-2 in decidualizing ESCs has not been identified. Therefore, using an RNA- and chromatin immunoprecipitation-sequencing approach, we have identified the transcriptome of decidualizing human ESCs (hESCs) that requires SRC-2. We revealed that the majority of hESC genes regulated by SRC-2 are associated with decidualization. Over 50% of SRC-2-regulated genes are also controlled by the PGR. While ontology analysis showed that SRC-2-dependent genes are functionally linked to signaling processes known to underpin hESC decidualization, cell membrane processes were significantly enriched in this analysis. Follow-up studies showed that retinoid signaling is dependent on SRC-2 during hESC decidualization. Specifically, SRC-2 is required for full induction of the retinol transporter, stimulated by retinoic acid 6 (STRA6), which is essential for hESC decidualization. Together our findings show that a critical subset of genes transcriptionally reprogramed by PGR during hESC decidualization requires SRC-2. Among the multiple genes, pathways and networks that are dependent on SRC-2 during hESC decidualization, first-line analysis supports a critical role for this coregulator in maintaining retinoid signaling during progesterone-driven decidualization.

Predicting puberty in partial androgen insensitivity syndrome: Use of clinical and functional androgen receptor indices

Background

PAIS exhibits a complex spectrum of phenotypes and pubertal outcomes. The paucity of reliable prognostic indicators can confound management decisions including sex-of-rearing. We assessed whether external masculinisation score (EMS) at birth or functional assays correlates with pubertal outcome in PAIS patients and whether the EMS is helpful in sex assignment.

Methods

We collected pubertal outcome data for 27 male-assigned PAIS patients, all with confirmed androgen receptor (AR) mutations, including two previously uncharacterized variants (I899F; Y916C). Patients were grouped as follows; EMS at birth <5 and ≥ 5 (EMS in normal males is 12; median EMS in PAIS is 4·7) and pubertal outcomes compared.

Findings

Only 6/9 patients (67%) with EMS <5 underwent spontaneous onset of puberty, versus all 18 patients with EMS ≥5 (p = .03). Only 1/6 patients (17%) with EMS <5 developed adult genitalia reaching Tanner stage 4 or 5, versus 11/13 (85%) with EMS ≥5 (p = 0·01). There was no significant difference between the two groups of patients in being prescribed androgen replacement, who reached adult testicular volume ≥ 15 ml, pubic hair Tanner stage 4 or 5, above average adult height, had gynaecomastia, and mastectomy. No correlation was observed between EMS and in vitro AR function.

Interpretation

In PAIS with AR mutation, birth EMS is a simple predictor of spontaneous pubertal onset and satisfactory adult genitalia. This provides useful information when discussing the likely options for management at puberty.

Fund

European Commission Framework 7 Programme, NIHR Cambridge Biomedical Research Centre, BBSRC DTP.

SRC1 Deficiency in Hypothalamic Arcuate Nucleus Increases Appetite and Body Weight

Appetite is tightly controlled by neural and hormonal signals in animals. In general, steroid receptor co-activator 1 (SRC1) enhances steroid hormone signalling in energy balance and serves as a common co-activator of several steroid receptors, such as estrogen and glucocorticoid receptors. However, the key roles of SRC1 in energy balance remain largely unknown. We first confirmed that SRC1 is abundantly expressed in the hypothalamic arcuate nucleus (ARC), which is a critical centre for regulating feeding and energy balance; it is further co-localised with agouti-related protein and proopiomelanocortin neurons in the arcuate nucleus. Interestingly, local SRC1 expression changes with the transition between sufficiency and deficiency of food supply. To identify its direct role in appetite regulation, we repressed SRC1 expression in the hypothalamic ARC using lentivirus shRNA and found that SRC1 deficiency significantly promoted food intake and body weight gain, particularly in mice fed with a high-fat diet. We also found the activation of the AMP-activated protein kinase (AMPK) signalling pathway due to SRC1 deficiency. Thus, our results suggest that SRC1 in the ARC regulates appetite and body weight and that AMPK signalling is involved in this process. We believe that our study results have important implications for recognising the overlapping and integrating effects of several steroid hormones/receptors on accurate appetite regulation in future studies.

Steroid Receptor Coactivator-2 Controls the Pentose Phosphate Pathway through RPIA in Human Endometrial Cancer Cells

Steroid receptor coactivator-2 (SRC-2) is a transcriptional coregulator that modulates the activity of many transcription factors. Levels of SRC-2 are elevated in endometrial biopsies from polycystic ovary syndrome patients, a population predisposed to endometrial cancer (EC). Increased expression of SRC-2 is also detected in neoplastic endometrium suggesting a causal link between elevated SRC-2 expression and the emergence of endometrial disorders that can lead to cancer. Here, we reveal that SRC-2 knockdown reduces EC cell proliferation and anchorage-independence. Additionally, SRC-2 is required to maintain cellular glycolytic capacity and oxidative phosphorylation, processes essential for EC cell proliferation. Importantly, SRC-2 is critical for the normal performance of the pentose phosphate pathway (PPP). Perturbation of the PPP due to loss of SRC-2 expression may result from the depletion of ribose-5-P isomerase (RPIA), a key enzyme of the PPP. As with SRC-2, RPIA knockdown reduces EC cell proliferation, which is accompanied by a decrease in glycolytic capacity and oxidative phosphorylation. Glucose metabolite tracking experiments confirmed that knockdown of SRC-2 and RPIA downregulates the metabolic rate of both glycolysis and the PPP, highlighting a novel regulatory cross-talk between glycolysis and the PPP modulated by SRC-2.

Network analysis of SRC-1 reveals a novel transcription factor hub which regulates endocrine resistant breast cancer

Steroid receptor coactivator 1 (SRC-1) interacts with nuclear receptors and other transcription factors (TFs) to initiate transcriptional networks and regulate downstream genes which enable the cancer cell to evade therapy and metastasise. Here we took a top-down discovery approach to map out the SRC-1 transcriptional network in endocrine resistant breast cancer. First, rapid immunoprecipitation mass spectrometry of endogenous proteins (RIME) was employed to uncover new SRC-1 TF partners. Next, RNA sequencing (RNAseq) was undertaken to investigate SRC-1 TF target genes. Molecular and patient-derived xenograft studies confirmed STAT1 as a new SRC-1 TF partner, important in the regulation of a cadre of four SRC-1 transcription targets, NFIA, SMAD2, E2F7 and ASCL1. Extended network analysis identified a downstream 79 gene network, the clinical relevance of which was investigated in RNAseq studies from matched primary and local-recurrence tumours from endocrine resistant patients. We propose that SRC-1 can partner with STAT1 independently of the estrogen receptor to initiate a transcriptional cascade and control regulation of key endocrine resistant genes.

Hereditary palmoplantar keratodermas. Part I. Non-syndromic palmoplantar keratodermas: classification, clinical and genetic features

The term palmoplantar keratoderma (PPK) indicates any form of persistent thickening of the epidermis of palms and soles and includes genetic as well as acquired conditions. We review the nosology of hereditary PPKs that comprise an increasing number of entities with different prognoses, and a multitude of associated cutaneous and extracutaneous features. On the basis of the phenotypic consequences of the underlying genetic defect, hereditary PPKs may be divided into the following: (i) non-syndromic, isolated PPKs, which are characterized by a unique or predominant palmoplantar involvement; (ii) non-syndromic PPKs with additional distinctive cutaneous and adnexal manifestations, here named complex PPKs; (iii) syndromic PPKs, in which PPK is associated with specific extracutaneous manifestations. To date, the diagnosis of the different hereditary PPKs is based mainly on clinical history and features combined with histopathological findings. In recent years, the exponentially increasing use of next-generation sequencing technologies has led to the identification of several novel disease genes, and thus substantially contributed to elucidate the molecular basis of such a heterogeneous group of disorders. Here, we focus on hereditary non-syndromic isolated and complex PPKs. Syndromic PPKs are reviewed in the second part of this 2-part article, where other well-defined genetic diseases, which may present PPK among their phenotypic manifestations, are also listed and diagnostic and therapeutic approaches for PPKs are summarized.

Hyperactivation of nuclear receptor coactivators induces PERK-dependent cell death

Nuclear receptor coactivators (NCOAs) function as coactivators for nuclear receptors as well as several other transcription factors and potentiate their transcriptional activity. NCOAs play an important role in biology of hormone-dependent and -independent cancers. MCB-613 is a recently described, small molecule stimulator of NCOAs and anti-neoplastic compound that leads to the death of tumour cells due to increased cellular stress. In the present study we investigated the molecular mechanism of MCB-613-induced cell death. We report that absence of NCOA3 leads to compromised activation of PERK signalling pathway during unfolded protein response (UPR). We found that chemical and genetic inhibition of NCOA3 attenuated the expression of PERK at mRNA and protein level. We show that loss of NCOA3 renders cells hypersensitive to UPR induced cell death. Our results show that MCB-613 induced cell death is attenuated in NCOA3 knockout HeLa cells and MCB-613 leads to enhanced PERK signalling in wild-type HeLa cells. The knockdown of PERK provides resistance to MCB-613 mediated cell death while knockdown of XBP1 and ATF6 have no such effect. Our results suggest that hyperstimulation of NCOA3 by MCB-613 induces cell death by evoking constitutive PERK signalling. Taken together our results point to NCOA3 as an important determinant in regulating cell fate during ER stress, with too little and too much NCOA3 both producing deleterious effects.

Endocrine-disrupting chemicals and fatty liver disease

A growing epidemic of nonalcoholic fatty liver disease (NAFLD) is paralleling the increase in the incidence of obesity and diabetes mellitus in countries that consume a Western diet. As NAFLD can lead to life-threatening conditions such as cirrhosis and hepatocellular carcinoma, an understanding of the factors that trigger its development and pathological progression is needed. Although by definition this disease is not associated with alcohol consumption, exposure to environmental agents that have been linked to other diseases might have a role in the development of NAFLD. Here, we focus on one class of these agents, endocrine-disrupting chemicals (EDCs), and their potential to influence the initiation and progression of a cascade of pathological conditions associated with hepatic steatosis (fatty liver). Experimental studies have revealed several potential mechanisms by which EDC exposure might contribute to disease pathogenesis, including the modulation of nuclear hormone receptor function and the alteration of the epigenome. However, many questions remain to be addressed about the causal link between acute and chronic EDC exposure and the development of NAFLD in humans. Future studies that address these questions hold promise not only for understanding the linkage between EDC exposure and liver disease but also for elucidating the molecular mechanisms that underpin NAFLD, which in turn could facilitate the development of new prevention and treatment opportunities.

A resistance to thyroid hormone syndrome mutant operates through the target gene repertoire of the wild-type thyroid hormone receptor

Thyroid hormone receptors (TRs) play crucial roles in vertebrates. Wild-type (WT) TRs function primarily as hormone-regulated transcription factors. A human endocrine disease, Resistance to Thyroid Hormone (RTH)-Syndrome, is caused by inheritance of mutant TRs impaired in the proper regulation of target gene expression. To better understand the molecular basis of RTH we compared the target genes regulated by an RTH-TRβ1 mutant (R429Q) to those regulated by WT-TRβ1. With only a few potential exceptions, the vast majority of genes we were able to identify as regulated by the WT-TRβ1, positively or negatively, were also regulated by the RTH-TRβ1 mutant. We conclude that the actions of R429Q-TRβ1 in RTH-Syndrome most likely reflect the reduced hormone affinity observed for this mutant rather than an alteration in target gene repertoire. Our results highlight the importance of target gene specificity in defining the disease phenotype and improve our understanding of how clinical treatments impact RTH-Syndrome.

Transcriptional coregulator RIP140: an essential regulator of physiology

Transcriptional coregulators drive gene regulatory decisions in the transcriptional space. Although transcription factors including all nuclear receptors provide a docking platform for coregulators to bind, these proteins bring enzymatic capabilities to the gene regulatory sites. RIP140 is a transcriptional coregulator essential for several physiological processes, and aberrations in its function may lead to diseased states. Unlike several other coregulators that are known either for their coactivating or corepressing roles, in gene regulation, RIP140 is capable of acting both as a coactivator and a corepressor. The role of RIP140 in female reproductive axis and recent findings of its role in carcinogenesis and adipose biology have been summarised.

Nutrient-sensing nuclear receptors PPARα and FXR control liver energy balance

The nuclear receptors PPARα (encoded by NR1C1) and farnesoid X receptor (FXR, encoded by NR1H4) are activated in the liver in the fasted and fed state, respectively. PPARα activation induces fatty acid oxidation, while FXR controls bile acid homeostasis, but both nuclear receptors also regulate numerous other metabolic pathways relevant to liver energy balance. Here we review evidence that they function coordinately to control key nutrient pathways, including fatty acid oxidation and gluconeogenesis in the fasted state and lipogenesis and glycolysis in the fed state. We have also recently reported that these receptors have mutually antagonistic impacts on autophagy, which is induced by PPARα but suppressed by FXR. Secretion of multiple blood proteins is a major drain on liver energy and nutrient resources, and we present preliminary evidence that the liver secretome may be directly suppressed by PPARα, but induced by FXR. Finally, previous studies demonstrated a striking deficiency in bile acid levels in malnourished mice that is consistent with results in malnourished children. We present evidence that hepatic targets of PPARα and FXR are dysregulated in chronic undernutrition. We conclude that PPARα and FXR function coordinately to integrate liver energy balance.

SRC-2-mediated coactivation of anti-tumorigenic target genes suppresses MYC-induced liver cancer

Hepatocellular carcinoma (HCC) is the fifth most common solid tumor in the world and the third leading cause of cancer-associated deaths. A Sleeping Beauty-mediated transposon mutagenesis screen previously identified mutations that cooperate with MYC to accelerate liver tumorigenesis. This revealed a tumor suppressor role for Steroid Receptor Coactivator 2/Nuclear Receptor Coactivator 2 (Src-2/Ncoa2) in liver cancer. In contrast, SRC-2 promotes survival and metastasis in prostate cancer cells, suggesting a tissue-specific and context-dependent role for SRC-2 in tumorigenesis. To determine if genetic loss of SRC-2 is sufficient to accelerate MYC-mediated liver tumorigenesis, we bred Src-2-/- mice with a MYC-induced liver tumor model and observed a significant increase in liver tumor burden. RNA sequencing of liver tumors and in vivo chromatin immunoprecipitation assays revealed a set of direct target genes that are bound by SRC-2 and exhibit downregulated expression in Src-2-/- liver tumors. We demonstrate that activation of SHP (Small Heterodimer Partner), DKK4 (Dickkopf-4), and CADM4 (Cell Adhesion Molecule 4) by SRC-2 suppresses tumorigenesis in vitro and in vivo. These studies suggest that SRC-2 may exhibit oncogenic or tumor suppressor activity depending on the target genes and nuclear receptors that are expressed in distinct tissues and illuminate the mechanisms of tumor suppression by SRC-2 in liver.

Coregulator-mediated control of skeletal muscle plasticity - A mini-review

Skeletal muscle plasticity is a complex process entailing massive transcriptional programs. These changes are mediated by the action of nuclear receptors and other transcription factors. In addition, coregulator proteins have emerged as important players in this process by linking transcription factors to the RNA polymerase II complex and inducing changes in the chromatic structure. An accumulating body of work highlights the pleiotropic functions of coregulator proteins in the control of tissue-specific and whole body metabolism. In skeletal muscle, several coregulators have been identified as potent modulators of metabolic and myofibrillar plasticity. In this mini-review, we will discuss the control, function and physiological significance of these coregulators in skeletal muscle biology.

Glucocorticoid Signaling: An Update from a Genomic Perspective

Glucocorticoid hormones (GC) regulate essential physiological functions including energy homeostasis, embryonic and postembryonic development, and the stress response. From the biomedical perspective, GC have garnered a tremendous amount of attention as highly potent anti-inflammatory and immunosuppressive medications indispensable in the clinic. GC signal through the GC receptor (GR), a ligand-dependent transcription factor whose structure, DNA binding, and the molecular partners that it employs to regulate transcription have been under intense investigation for decades. In particular, next-generation sequencing-based approaches have revolutionized the field by introducing a unified platform for a simultaneous genome-wide analysis of cellular activities at the level of RNA production, binding of transcription factors to DNA and RNA, and chromatin landscape and topology. Here we describe fundamental concepts of GC/GR function as established through traditional molecular and in vivo approaches and focus on the novel insights of GC biology that have emerged over the last 10 years from the rapidly expanding arsenal of system-wide genomic methodologies.

Visualizing the Architectures and Interactions of Nuclear Receptors

Nuclear receptors (NRs) are master regulators of broad genetic programs in metazoans. These programs are regulated in part by the small-molecule ligands that bind NRs and modulate their interactions with transcriptional coregulatory factors. X-ray crystallography is now delivering more complete pictures of how the multidomain architectures of NR homo- and heterodimers are physically arranged on their DNA elements and how ligands and coactivator peptides act through these complexes. Complementary studies are also pointing to a variety of novel mechanisms by which NRs access their DNA-response elements within chromatin. Here, we review the new structural advances together with proteomic discoveries that shape our understanding of how NRs form a variety of functional interactions with collaborating factors in chromatin.

Dysregulation of Acetylation Enzymes Inanimal Models of Psychostimulant use Disorders: Evolving Stories

Substance use disorders are neuropsychiatric illnesses that have substantial negative biopsychosocial impact. These diseases are defined as compulsive abuse of licit or illicit substances despite adverse medicolegal consequences. Although much research has been conducted to elucidate the pathobiological bases of these disorders, much remains to be done to develop an overarching neurobiological understanding that might be translatable to beneficial pharmacological therapies. Recent advances in epigenetics promise to lead to such an elucidation. Here I provide a brief overview of observations obtained using some models of psychostimulant administration in rodents. The review identifies CREB binding protein (CBP), HDAC1, HDAC2, HADC3, HDAC4, and HDAC5 as important players in the acetylation and deacetylation processes that occur after contingent or non-contingent administration of psychostimulants. These observations are discussed within a framework that suggests a need for better animal models of addiction in order to bring these epigenetic advances to bear on the pharmacological treatment of human addicts.

NCOA1 promotes angiogenesis in breast tumors by simultaneously enhancing both HIF1α- and AP-1-mediated VEGFa transcription

Nuclear receptor coactivator 1 (NCOA1) is overexpressed in a subset of breast cancer and its increased expression positively correlates with disease recurrence and metastasis. Although NCOA1 is known to promote breast cancer metastasis through working with multiple transcription factors to upregulate the expression of Twist1, ITGA5, CSF-1, SDF1 and CXCR4, the role of NCOA1 in breast tumor angiogenesis has not been investigated. In this study, we found that the microvascular density (MVD) was significantly decreased and increased in Ncoa1-knockout and NCOA1-overexpressing mammary tumors, respectively, in several breast cancer mouse models. Knockout or knockdown of NCOA1 in breast cancer cell lines also markedly compromised their capability to induce angiogenesis in Matrigel plugs embedded subcutaneously in mice, while this compromised capability could be rescued by VEGFa treatment. At the molecular level, NCOA1 upregulates VEGFa expression in both mouse mammary tumors and cultured breast cancer cells, and it does so by associating with both c-Fos, which is recruited to the AP-1 site at bp −938 of the VEGFa promoter, and HIF1α, which is recruited to the HIF1α-binding element at bp −979 of the VEGFa promoter, to enhance VEGFa transcription. In 140 human breast tumors, high NCOA1 protein correlates with high MVD and patients with both high NCOA1 and high MVD showed significantly shorter survival time. In summary, this study revealed a novel mechanism that NCOA1 potentiates breast cancer angiogenesis through upregulating HIF1α and AP-1-mediated VEGFa expression, which reinforces the rational of targeting NCOA1 in controlling breast cancer progression and metastasis.