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Overexpression of nuclear coactivator steroid receptor coactivator 1 (SRC-1) and aberrant activation of the Hedgehog (Hh) signaling pathway are associated with various tumorigenesis; however, the significance of SRC-1 in colorectal cancer (CRC) and its contribution to the activation of Hh signaling are unclear. Here, we identified a conserved Hh signaling signature positively correlated with SRC-1 expression in CRC based on TCGA database; SRC-1 deficiency significantly inhibited the proliferation, survival, migration, invasion, and tumorigenesis of both human and mouse CRC cells, and SRC-1 knockout significantly suppressed azoxymethane/dextran sodium sulfate (AOM/DSS)-induced CRC in mice. Mechanistically, SRC-1 promoted the expression of GLI family zinc finger 2 (GLI2), a major downstream transcription factor of Hh pathway, and cooperated with GLI2 to enhance multiple Hh-regulated oncogene expression, including Cyclin D1, Bcl-2, and Slug. Pharmacological blockages of SRC-1 and Hh signaling retarded CRC progression in human CRC cell xenograft mouse model. Together, our studies uncover an SRC-1/GLI2-regulated Hh signaling looping axis that promotes CRC tumorigenesis, offering an attractive strategy for CRC treatment.

Octocrylene (OC) is an extensively prescribed organic ultraviolet B filter used in sunscreen products. Due to its extensive use, a significant level of OC is detected in marine and freshwater environments. Notably, the bioaccumulation of OC in aquatic biota may affect human health. In this study, the effect of OC on metabolism was investigated using the adipogenesis model of human bone marrow mesenchymal stem cells (hBM-MSCs). OC promoted adiponectin production during adipogenesis in hBM-MSCs compared to the vehicle-treated control (EC

Germline mutations to the breast cancer 2 (BRCA2) gene have been associated with hereditary breast cancer. In addition to estrogen uptake, BRCA2 expression increases in the S phase of the cell cycle and largely contributes to DNA damage repair associated with DNA replication. However, the role of BRCA2 in estrogen induction remains unclear. An expression plasmid was created to induce BRCA2 activation upon the addition of estradiol by introducing mutations to the binding sequences for the transcription factors USF1, E2F1, and NF-κB within the promoter region of BRCA2. Then, the estrogen receptor (ER) sites of the proteins that interact with BRCA2 upon the addition of estradiol were identified. Both proteins were bound by the helical domain of BRCA2 and activation function-2 of the ER, suggesting that this binding may regulate the transcriptional activity of pS2, a target gene of the estradiol-ER, by suppressing the binding of SRC-1, a coactivator required for activation of the transcription factor.

The regulatory mechanism and function of steroid receptor coactivator-1 (SRC-1) was determined in vitro and the role played in gastric cancer was investigated. The study collected 64 patients with gastric cancer tissue and paracancerous tissue to investigate the clinical patterns of SRC-1 expression in gastric cancer. Quantitative polymerase chain reaction, Western blot, enzyme-linked immunosorbent assay, and immunofluorescence staining were used in this study. In patients with gastric cancer, SRC-1 serum expression levels were up-regulated. Over-expression of SRC-1 promoted cell growth and cell metastasis in vitro model of gastric cancer. However, down-regulation of SRC-1 reduced cell growth and cell metastasis in vitro model of gastric cancer. SRC-1 over-expression induced vascular endothelial growth factor C (VEGFC) protein expressions in vitro model by activation of nuclear factor-kappa B (NF-kB) expression. The inhibition of NF-κB reduced the pro-cancer effects of SRC-1 on cell growth and cell metastasis in vitro model of gastric cancer through inhibition of VEGFC expression. These results suggest that SRC-1 promoted cell metastasis of gastric cancer via VEGFC activator by NF-κB. These novel findings may shed further light on the pathogenesis of gastric cancer and on potential precursor markers.

Steroid receptor coactivator 1 (SRC-1) is one of the coactivators recruited by the nuclear receptors (NRs) when NRs are activated by steroid hormones, such as glucocorticoid. SRC-1 is abundant in hippocampus and hypothalamus and is also related to some major risk factors for depression, implicated by its reduced expression after stress and its effect on hypothalamus-pituitary-adrenal gland axis function. However, whether SRC-1 is involved in the formation of depression remains unclear. In this study, we firstly established chronic unpredictable stress (CUS) to induce depressive-like behaviors in mice and found that SRC-1 expression was reduced by CUS. A large number of studies have shown that neuroinflammation is associated with stress-induced depression and lipopolysaccharide (LPS) injection can lead to neuroinflammation and depressive-like behaviors in mice. Our result indicated that LPS treatment also decreased SRC-1 expression in mouse brain, implying the involvement of SRC-1 in the process of inflammation and depression. Next, we showed that the chronic unpredictable mild stress (CUMS) failed to elicit the depressive-like behaviors and dramatically promoted the expression of SRC-1 in brain of wild type mice. What's more, the SRC-1 knockout mice were more susceptible to CUMS to develop depressive-like behaviors and presented the changed expression of glucocorticoid receptor. However, SRC-1 deficiency did not affect the microglia activation induced by CUMS. Altogether, these results indicate a correlation between SRC-1 level and depressive-like behaviors, suggesting that SRC-1 might be involved in the development of depression induced by stress.

Background: Thyroid hormone (triiodothyronine [T3]) plays an important role in regulating vertebrate developmental, cellular, and metabolic processes via T3 receptor (TR). Liganded TR recruit coactivator complexes that include steroid receptor coactivators (SRC1, SRC2 or SRC3), which are histone acetyltransferases, to T3-responsive promoters. The functions of endogenous coactivators during T3-dependent mammalian adult organ development remain largely unclear, in part, due to the difficulty to access and manipulate late-stage embryos and neonates. We use Xenopus metamorphosis as a model for postembryonic development in vertebrates. This process is controlled by T3, involves drastic changes in every organ/tissue, and can be easily manipulated. We have previously found that SRC3 was upregulated in the intestine during amphibian metamorphosis. Methods: To determine the function of endogenous SRC3 during intestinal remodeling, we have generated Xenopus tropicalis animals lacking a functional SRC3 gene and analyzed the resulting phenotype. Results: Although removing SRC3 had no apparent effect on external development and animal gross morphology, the SRC3 (-/-) tadpoles displayed a reduction in the acetylation of histone H4 in the intestine compared with that in wild-type animals. Further, the expression of TR target genes was also reduced in SRC3 (-/-) tadpoles during intestinal remodeling. Importantly, SRC3 (-/-) tadpoles had inhibited/delayed intestinal remodeling during natural and T3-induced metamorphosis, including reduced adult intestinal stem cell proliferation and apoptosis of larval epithelial cells. Conclusion: Our results, thus, demonstrate that SRC3 is a critical component of the TR-signaling pathway in vivo during intestinal remodeling.

Protein arginine methyltransferase 5 (PRMT5) has previously been reported to be upregulated in many malignant tumors. This study investigated the significance of PRMT5 in endometrial carcinoma (EC) and explored its function in tumorigenesis. Immunohistochemistry was performed to evaluate PRMT5 expression in 62 EC and 66 endometrial hyperplasia samples. The functions of PRMT5 were investigated by cell counting kit‐8, plate colony formation, wound healing, and transwell and flow cytometry assays. Quantitative reverse transcription‐polymerase chain reaction and western blotting were used to measure the expression of PRMT5, changes in estrogen receptor α (ERα), and related functional proteins. Coimmunoprecipitation was performed to examine the interaction of PRMT5 with ERα and its coactivator steroid receptor coactivator‐1 (SRC1). Compared to endometrial hyperplasia tissue, PRMT5 was overexpressed in endometrioid adenocarcinoma (EAC) but not overexpressed in mucinous EC. The main expression pattern of PRMT5 in EAC was cytoplasmic. However, the positive cases of endometrial hyperplasia showed both cytoplasmic and nuclear positivity in the endometrial glands or were mainly positive in stromal cells. Knockdown of PRMT5 significantly inhibited the growth and migration ability of EAC cells and promoted their apoptosis by regulating cyclin D1, c‐myc, p53, and Bcl2 proteins. Furthermore, PRMT5 could form a complex with ERα and SRC1 to promote the expression of ERα. In conclusion, PRMT5 plays a significant role in the progression of EAC by interacting with ERα and impacting the cell cycle signaling pathways.

The constitutive active/androstane receptor (CAR) is a nuclear receptor that functions as a xenobiotic sensor, which regulates the expression of enzymes involved in drug metabolism and of efflux transporters. Evaluation of the binding properties between CAR and a drug was assumed to facilitate the prediction of drug-drug interaction, thereby contributing to drug discovery. The purpose of this study is to construct a system for the rapid evaluation of interactions between CAR and drugs. We prepared recombinant CAR protein using the Escherichia coli expression system. Since isolated CAR protein is known to be unstable, we designed a fusion protein with the CAR binding sequence of the nuclear receptor coactivator 1 (NCOA1), which was expressed as a fusion protein with maltose binding protein (MBP), and purified it by several chromatography steps. The thus-obtained CAR/NCOA1 tethered protein (CAR-NCOA1) was used to evaluate the interactions of CAR with agonists and inverse agonists by a thermal denaturation experiment using differential scanning fluorometry (DSF) in the presence and absence of drugs. An increase in the melting temperature was observed with the addition of the drugs, confirming the direct interaction between them and CAR. DSF is easy to set up and compatible with multiwell plate devices (such as 96-well plates). The use of DSF and the CAR-NCOA1 fusion protein together allows for the rapid evaluation of the interaction between a drug and CAR, and is thereby considered to be useful in drug discovery.

The present study was designed to investigate comparative expressions of follicle-stimulating hormone beta subunit (FSHβ) and nuclear receptor coactivator 1 (NCOA1) genes by real-time polymerase chain reaction, using polymerase chain reaction single-strand conformation polymorphism methods to investigate the effects of gene polymorphisms on reproductive traits, including total number of kits born (TNB) and number of born alive (NBA) in pink-eyed white mink. Four single-nucleotide polymorphisms were identified in the FSHβ and NCOA1 genes. The g.1228G>A polymorphism of FSHβ was associated with NBA and TNB (P < 0.01). The g.151536T>C polymorphism of NCOA1 was associated with NBA and TNB (P < 0.01). The NCOA1 mRNA levels in hypothalamus, ovary, and uterus during the first half of gestation were higher than during the middle term and last half of gestation (P < 0.01). The FSHβ mRNA levels in the hypothalamus and uterus were higher during the first half of gestation than during the middle term and last half of gestation (P < 0.05). In conclusion, the g.1866T>C polymorphism of FSHβ and the g.151536T>C polymorphism of NCOA1 could be molecular markers for reproductive traits, and expressions of FSHβ and NCOA1 might be involved in the regulation of embryo attachment mechanisms in pink-eyed white mink breeding.

Targeted therapy is receiving considerable attention from the researchers around the globe owing to the increased drug-resistance and incidences of cancer recurrences. MicroRNAs (miRNAs) exhibits tremendous potential as a candidate for molecular targeted therapy in cancer. Unfortunately, majority of research related to microRNAs are focussed on either a particular miRNA or a set of unrelated miRNAs. There is lack of holistic knowledge on differential co-expression of miRNA clusters in regulating the gene expression under physiological conditions. Previously, we reported the cooperative effect of hsa-miR-23a~27a~24-2 cluster in inducing ER (Endoplasmic Reticulum) stress-mediated apoptotic cell death of HEK cells. In the present study, we have investigated the common anti-cancer effects of individual members of this cluster. Our in silico analysis identified twelve common target genes distributed across three independent clusters. Furthermore, we found NCOA1, NLK, and RAP1B to fall in a single cluster with NCOA1 as a central hub molecule. Prognostic analysis showed profound involvement of these three genes in the breast cancer progression and metastasis. We further demonstrated that alteration in the levels of individual members of miR-23a~27a~24-2 cluster commonly regulates the invasive migration of breast cancer cells by modulating EMT and cytoskeletal pathway proteins. Our results reveal a new insight into the therapeutic potential of individual members of the pro-apoptotic hsa-miR-23a~27a~24-2 cluster family against metastatic breast cancer.

Context Genetic variants affecting the nuclear hormone receptor coactivator steroid receptor coactivator, SRC-1, have been identified in people with severe obesity and impair melanocortin signaling in cells and mice. As a result, obese patients with SRC-1 deficiency are being treated with a melanocortin 4 receptor agonist in clinical trials. Objective Here, our aim was to comprehensively describe and characterize the clinical phenotype of SRC-1 variant carriers to facilitate diagnosis and clinical management. Methods In genetic studies of 2462 people with severe obesity, we identified 23 rare heterozygous variants in SRC-1. We studied 29 adults and 18 children who were SRC-1 variant carriers and performed measurements of metabolic and endocrine function, liver imaging, and adipose tissue biopsies. Findings in adult SRC-1 variant carriers were compared to 30 age- and body mass index (BMI)-matched controls. Results The clinical spectrum of SRC-1 variant carriers included increased food intake in children, normal basal metabolic rate, multiple fractures with minimal trauma (40%), persistent diarrhea, partial thyroid hormone resistance, and menorrhagia. Compared to age-, sex-, and BMI-matched controls, adult SRC-1 variant carriers had more severe adipose tissue fibrosis (46.2% vs 7.1% respectively, P = .03) and a suggestion of increased liver fibrosis (5/13 cases vs 2/13 in controls, odds ratio = 3.4), although this was not statistically significant. Conclusion SRC-1 variant carriers exhibit hyperphagia in childhood, severe obesity, and clinical features of partial hormone resistance. The presence of adipose tissue fibrosis and hepatic fibrosis in young patients suggests that close monitoring for the early development of obesity-associated metabolic complications is warranted.

Aberrantly elevated steroid receptor coactivator-1 (SRC-1) expression and activity are strongly correlated with cancer progression and metastasis. Here we report, for the first time, the development of a proteolysis targeting chimera (PROTAC) that is composed of a selective SRC-1 binder linked to a specific ligand for UBR box, a unique class of E3 ligases recognizing N-degrons. We showed that the bifunctional molecule efficiently and selectively induced the degradation of SRC-1 in cells through the N-degron pathway. Importantly, given the ubiquitous expression of the UBR protein in most cells, PROTACs targeting the UBR box could degrade a protein of interest regardless of cell types. We also showed that the SRC-1 degrader significantly suppressed cancer cell invasion and migration in vitro and in vivo. Together, these results demonstrate that the SRC-1 degrader can be an invaluable chemical tool in the studies of SRC-1 functions. Moreover, our findings suggest PROTACs based on the N-degron pathway as a widely useful strategy to degrade disease-relevant proteins.

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.

Cellular aging occurs as a cell loses its ability to maintain homeostasis. Aging cells eliminate damaged cellular compartments and other senescence factors via self-renewal. The mechanism that regulates cellular rejuvenation remains to be further elucidated. Using budding yeast gametogenesis as a model, we show here that the endosomal sorting complex required for transport (ESCRT) III regulates nuclear envelope organization. During gametogenesis, the nuclear pore complex (NPC) and other senescence factors are sequestered away from the prospore nuclei. We show that the LEM-domain protein Heh1 (Src1) facilitates the nuclear recruitment of ESCRT-III, which is required for meiotic NPC sequestration and nuclear envelope remodeling. Furthermore, ESCRT-III-mediated nuclear reorganization appears to be critical for gamete rejuvenation, as hindering this process curtails either directly or indirectly the replicative lifespan in gametes. Our findings demonstrate the importance of ESCRT-III in nuclear envelope remodeling and its potential role in eliminating senescence factors during gametogenesis.

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.

Sox2 (SRY-box 2) is a transcription factor with critical roles in maintaining embryonic 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 embryonic stem 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 acts 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 (AD1) and 2 (AD2) of SRC-3 both display a preferential binding to acetylated Sox2. Finally, functional analyses in mouse embryonic stem (ES) cells demonstrated that knockdown of SRC-2/3 but not SRC-1 in mouse ES cells significantly down-regulates 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.

Steroid receptors (SRs) are ligand-dependent transcription factors (TFs) relevant to key cellular processes in both physiology and pathology, including some types of cancer. SOX2 is a master TF of pluripotency and self-renewal of embryonic stem cells, and its dysregulation is also associated with various types of human cancers. A potential crosstalk between these TFs could be relevant in malignant cells yet, to the best of our knowledge, no formal study has been performed thus far. Here we show, by quantitative live-cell imaging microscopy, that ectopic expression of SOX2 disrupts the formation of hormone-dependent intranuclear condensates of many steroid receptors (SRs), including those formed by the glucocorticoid receptor (GR). SOX2 also reduces GR's binding to specific DNA targets and modulates its transcriptional activity. SOX2-driven effects on GR condensates do not require the intrinsically disordered N-terminal domain of the receptor and, surprisingly, neither relies on GR/SOX2 interactions. SOX2 also alters the intranuclear dynamics and compartmentalization of the SR coactivator NCoA-2 and impairs GR/NCoA-2 interactions. These results suggest an indirect mechanism underlying SOX2-driven effects on SRs involving this coactivator. Together, these results highlight that the transcriptional program elicited by GR relies on its nuclear organization and is intimately linked to the distribution of other GR partners, such as the NCoA-2 coactivator. Abnormal expression of SOX2, commonly observed in many tumors, may alter the biological action of GR and, probably, other SRs as well. Understanding this crosstalk may help to improve steroid hormone-based therapies in cancers with elevated SOX2 expression.

Nuclear receptors constitute one of the largest families of transcription factors that regulate genes in metazoans in response to small molecule ligands. Many receptors harbor two transactivation domains, one at each end of the protein sequence. Whereas the molecular mechanisms of transactivation mediated by the ligand-binding domain at the C-terminus of the protein are generally well established, the mechanism involving the N-terminal domain called activation function 1 (AF1) has remained elusive. Previous studies implicated the AF1 domain as a significant contributor towards the overall transcriptional activity of the NR4A family of nuclear receptors and suggested that the steroid receptor coactivators (SRCs) play an important role in this process. Here we show that a short segment within the AF1 domain of the NR4A receptor Nurr1 can directly engage with the SRC1 PAS-B domain. We also show that this segment forms a helix upon binding to a largely hydrophobic groove on PAS-B, overlapping with the surface engaged by the STAT6 transcription factor, suggesting that this mode of recruitment could be shared by diverse transcription factors including other nuclear receptors.

AIMS PRRX1-NCOA1-rearranged fibroblastic tumour is a recently described, rare mesenchymal tumour. Only four cases have been previously reported. The aim of this article is to report six additional cases of this unusual mesenchymal neoplasm, with an emphasis on its differential diagnosis. METHODS AND RESULTS The six cases were from three females and three males (age, 20-49 years; median, 42 years). Three tumours were located on the abdominal wall; two from the shoulder/axillary areas, and one on the lateral hip. All presented as slow-growing subcutaneous nodules, ranging from 26 to 55 mm (median, 40 mm). The tumours consisted of circumscribed, variably cellular nodules composed of relatively bland plump spindled to epithelioid cells arranged singly, in cords, and occasionally in nests, embedded in hyalinised and collagenous stroma. Small hypocellular myxoid zones with ropey collagen fibres were present, as were irregularly dilated, gaping, crescent-shaped or staghorn-like thin-walled vessels, best appreciated at the periphery. Immunohistochemistry for CD34, S100, MUC4 and STAT6 was consistently negative. RNA-sequencing revealed PRRX1-NCOA1 fusions in all cases. Of the four cases with limited follow-up (1.5-4 months), none recurred following local surgical excision. CONCLUSIONS The morphological features of PRRX1-NCOA1-rearranged fibroblastic tumour overlap with those of RB1-deficient soft-tissue tumours, solitary fibrous tumour, and low-grade fibromyxoid sarcoma/sclerosing epithelioid fibrosarcoma. This differential diagnosis can be resolved with a combination of careful morphological study and the application of a panel of immunostains, although molecular genetic study is most definitive. The natural history of PRRX1-NCOA1-rearranged fibroblastic tumour appears to be quite favourable, although longer-term study of a larger number of cases is warranted.

Alveolar rhabdomyosarcoma (ARMS) is associated with PAX3/PAX7-FOXO1 fusion, which confers specific clinic and biologic characteristics with inferior outcomes. A minority of tumors still histologically classified as "true" ARMS lack the canonical PAX-FOXO1 fusion but have new molecular alterations. We present the first case of PAX3-NCOA1 ARMS with clinical data and follow-up in a two-year-old girl with ARMS of the tongue and nodal extension, treated with chemotherapy, hemi glossectomy, lymph node dissection, and brachytherapy to conserve oral function and limit long-term sequelae. Given the rarity of such variant fusion in ARMS, international collaboration is required to evaluate its prognostic value.

The cIMPACT-NOW Update 7 has replaced the WHO nosology of “ependymoma, RELA fusion positive” by “Supratentorial-ependymoma, C11orf95-fusion positive”. This modification reinforces the idea that supratentorial-ependymomas exhibiting fusion that implicates the C11orf95 (now called ZFTA) gene with or without the RELA gene, represent the same histomolecular entity. A hot off the press molecular study has identified distinct clusters of the DNA methylation class of ZFTA fusion-positive tumors. Interestingly, clusters 2 and 4 comprised tumors of different morphologies, with various ZFTA fusions without involvement of RELA. In this paper, we present a detailed series of thirteen cases of non-RELA ZFTA-fused supratentorial tumors with extensive clinical, radiological, histopathological, immunohistochemical, genetic and epigenetic (DNA methylation profiling) characterization. Contrary to the age of onset and MRI aspects similar to RELA fusion-positive EPN, we noted significant histopathological heterogeneity (pleomorphic xanthoastrocytoma-like, astroblastoma-like, ependymoma-like, and even sarcoma-like patterns) in this cohort. Immunophenotypically, these NFκB immunonegative tumors expressed GFAP variably, but EMA constantly and L1CAM frequently. Different gene partners were fused with ZFTA: NCOA1/2, MAML2 and for the first time MN1. These tumors had epigenetic homologies within the DNA methylation class of ependymomas-RELA and were classified as satellite clusters 2 and 4. Cluster 2 (n = 9) corresponded to tumors with classic ependymal histological features (n = 4) but also had astroblastic features (n = 5). Various types of ZFTA fusions were associated with cluster 2, but as in the original report, ZFTA:MAML2 fusion was frequent. Cluster 4 was enriched with sarcoma-like tumors. Moreover, we reported a novel anatomy of three ZFTA:NCOA1/2 fusions with only 1 ZFTA zinc finger domain in the putative fusion protein, whereas all previously reported non-RELA ZFTA fusions have 4 ZFTA zinc fingers. All three cases presented a sarcoma-like morphology. This genotype/phenotype association requires further studies for confirmation. Our series is the first to extensively characterize this new subset of supratentorial ZFTA-fused ependymomas and highlights the usefulness of ZFTA FISH analysis to confirm the existence of a rearrangement without RELA abnormality.

Steroid receptor coactivator-1 (SRC-1) is a transcription coactivator playing a pivotal role in mediating a wide range of signaling pathways by interacting with related transcription factors and nuclear receptors. Aberrantly elevated SRC-1 activity is associated with cancer metastasis and progression, and therefore, suppression of SRC-1 is emerging as a promising therapeutic strategy. In this study, we developed a novel SRC-1 degrader for targeted degradation of cellular SRC-1. This molecule consists of a selective ligand for SRC-1 and a bulky hydrophobic group. Since the hydrophobic moiety on the protein surface could mimic a partially denatured hydrophobic region of a protein, SRC-1 could be recognized as an unfolded protein and experience the chaperone-mediated degradation in the cells through the ubiquitin–proteasome system (UPS). Our results demonstrate that a hydrophobic-tagged chimeric molecule is shown to significantly reduce cellular levels of SRC-1 and suppress cancer cell migration and invasion. Together, these results highlight that our SRC-1 degrader represents a novel class of therapeutic candidates for targeting cancer metastasis. Moreover, we believe that the hydrophobic tagging strategy would be widely applicable to develop peptide-based protein degraders with enhanced cellular activity.

Necroptosis is an alternative form of programmed cell death that generally occurs under apoptosis‐deficient conditions. Our previous work showed that connexin32 (Cx32) promotes the malignant progress of hepatocellular carcinoma (HCC) by enhancing the ability of resisting apoptosis in vivo and in vitro. Whether triggering necroptosis is a promising strategy to eliminate the apoptosis‐resistant HCC cells with high Cx32 expression remains unknown. In this study, we found that Cx32 expression was positively correlated with the expression of necroptosis protein biomarkers in human HCC specimens, cell lines, and a xenograft model. Treatment with shikonin, a well‐used necroptosis inducer, markedly caused necroptosis in HCC cells. Interestingly, overexpressed Cx32 exacerbated shikonin‐induced necroptosis, but downregulation of Cx32 alleviated necroptosis in vitro and in vivo. Mechanistically, Cx32 was found to bind to Src and promote Src‐mediated caspase 8 phosphorylation and inactivation, which ultimately reduced the activated caspase 8‐mediated proteolysis of receptor‐interacting serine‐threonine protein kinase 1/3, the key molecule for necroptosis activation. In conclusion, we showed that Cx32 contributed to the activation of necroptosis in HCC cells through binding to Src and then mediating the inactivation of caspase 8. The present study suggested that necroptosis inducers could be more favorable than apoptosis inducers to eliminate HCC cells with high expression of Cx32., Connexin32 promotes shikonin‐induced necroptosis in hepatocellular carcinoma by interacting with Src and enhancing Src‐mediated caspase 8 phosphorylation on Tyr380. We identified the novel role of connexin32 in necroptosis and elucidated connexin32 as a potential target for pronecroptosis therapy in hepatocellular carcinoma.

The steroid receptor coactivator-1 (SRC-1) is a nuclear receptor co-activator, known to play key roles in both estrogen response in bone and in breast cancer metastases. We previously demonstrated that the P1272S single nucleotide polymorphism (SNP; P1272S; rs1804645) in SRC-1 decreases the activity of estrogen receptor in the presence of selective estrogen receptor modulators (SERMs) and that it is associated with a decrease in bone mineral density (BMD) after tamoxifen therapy, suggesting it may disrupt the agonist action of tamoxifen. Given such dual roles of SRC-1 in the bone microenvironment and in tumor cell-intrinsic phenotypes, we hypothesized that SRC-1 and a naturally occurring genetic variant, P1272S, may promote breast cancer bone metastases. We developed a syngeneic, knock-in mouse model to study if the SRC-1 SNP is critical for normal bone homeostasis and bone metastasis. Our data surprisingly reveal that the homozygous SRC-1 SNP knock-in increases tamoxifen-induced bone protection after ovariectomy. The presence of the SRC-1 SNP in mammary glands resulted in decreased expression levels of SRC-1 and reduced tumor burden after orthotopic injection of breast cancer cells not bearing the SRC-1 SNP, but increased metastases to the lungs in our syngeneic mouse model. Interestingly, the P1272S SNP identified in a small, exploratory cohort of bone metastases from breast cancer patients was significantly associated with earlier development of bone metastasis. This study demonstrates the importance of the P1272S SNP in both the effect of SERMs on BMD and the development of tumor in the bone.

Background: Spindle cell rhabdomyosarcoma (S-RMS) is a rare tumor that was previously considered as an uncommon variant of embryonal RMS (ERMS) and recently reclassified as a distinct RMS subtype with NCOA2, NCOA1, and VGLL2 fusion genes. In this study, we established a cell line (S-RMS1) derived from a four-month-old boy with infantile spindle cell RMS harboring SRF-NCOA2 gene fusion. Methods: Morphological and molecular characteristics of S-RMS1 were analyzed and compared with two RMS cell lines, RH30 and RD18. Whole genome sequencing of S-RMS1 and clinical exome sequencing of genomic DNA were performed. Results: S-RMS1 showed cells small in size, with a fibroblast-like morphology and positivity for MyoD-1, myogenin, desmin, and smooth muscle actin. The population doubling time was 3.7 days. Whole genome sequencing demonstrated that S-RMS1 retained the same genetic profile of the tumor at diagnosis. A Western blot analysis showed downregulation of AKT-p and YAP-p while RT-qPCR showed upregulation of endoglin and GATA6 as well as downregulation of TGFßR1 and Mef2C transcripts. Conclusion: This is the first report of the establishment of a cell line from an infantile spindle cell RMS with SRF-NCOA2 gene fusion. S-RMS1 should represent a useful tool for the molecular characterization of this rare and almost unknown tumor.

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. Keywords: Adipogenesis, Betulinic acid, NMR, PPAR gamma, Tectona grandis

Objective Fatty acids are important for biological function; however, in excess, they can cause metabolic dysregulation. Methods to image and detect fatty acids in real time are lacking. Therefore, the current study examined the dynamics of fatty acid trafficking and signaling utilizing novel fluorescent and luminescent approaches. Methods We generated fluorescent and luminescent-based genetically-encoded sensors based upon the ligand-dependent interaction between PPARα and SRC-1 to image and detect cellular dynamics of fatty acid trafficking. Results The use of a fluorescent sensor demonstrates that fatty acids traffic rapidly from lipid droplets to the nucleus. Both major lipases ATGL and HSL contribute to fatty acid signaling from lipid droplet to nucleus, however, their dynamics differ. Furthermore, direct activation of lipolysis, independent of receptor-mediated signaling is sufficient to promote lipid droplet to nuclear trafficking of fatty acids. A luminescent-based sensor that reports intracellular fatty acid levels is amenable to high-throughput analysis. Conclusions Fatty acids traffic from lipid droplets to the nucleus within minutes of stimulated lipolysis. Genetically-encoded fluorescent and luminescent based sensors can be used to probe the dynamics of fatty acid trafficking and signaling., Graphical abstract Image 1, Highlights • Genetically-encoded fatty acid sensors report on the temporal and spatial regulation of lipolysis. • A fluorescence-based fatty acid sensor can detect fatty acids within minutes of lipolysis. • Fatty acids dynamically traffic from lipid droplets to the nucleus to modulate gene expression. • A luminescence-based fatty acid sensor is amenable to high-throughput analysis.

Steroid receptor coactivator 1 (SRC-1) is a transcriptional coactivator for steroid receptors and other transcription factors. SRC-1 has been shown to play an important role in the progression of breast cancer and prostate cancer. However, its role in glioma progression remains unknown. Here, in this study, we report that SRC-1 is upregulated in the vessels of human glioma and exerts important regulatory functions. Specifically, SRC-1 expression significantly enhanced basic fibroblast growth factor (bFGF)-mediated angiogenesis in vivo. Downregulating of SRC-1 expression suppressed endothelial cell migration and tube formation in vitro and upregulated the expression of pro-angiogenic factors, including vascular endothelial growth factor (VEGF) and matrix metallopeptidase (MMP)-9 in glioma cells. These SRC-1-mediated effects were dependent on the activation of polyomavirus enhancer activator 3 (PEA3) transcriptional activity. VEGF and VEGF inducer GS4012 induced the direct binding of SRC-1 and PEA3 in glioma cells, and PEA3 could directly bind with VEGF and MMP-9 promoter under GS4012 treatment in glioma cell. The expression of pro-angiogenic factors induced by SRC-1 was abrogated by sh-PEA3 knockdown. Taken together, these novel outcomes indicated that SRC-1 modulated endothelial cell (EC) function and facilitated a pro-angiogenic microenvironment through PEA3 signaling. Moreover, a combination of targeting SRC-1 and PEA3 signaling in glioma could be a promising strategy for suppressing tumor angiogenesis.

Uterine mesenchymal tumors are genetically heterogenous; those with uniform cytomorphology, best exemplified by endometrial stromal tumors, often contain various fusion genes. Novel fusions involving ESR1 and GREB1, key factors in sex hormone pathways, have been implicated in rare uterine mesenchymal tumors. Particularly, the fusions between 5'-ESR1/GREB1 and 3'-NCOA2/NCOA3 were recently identified in 4 uterine tumors resembling ovarian sex-cord tumor (UTROSCT). By RNA sequencing, pathology review, and FISH screening, we identified 4 uterine sarcomas harboring rearranged GREB1, including GREB1-NCOA2 and the novel GREB1-NR4A3, GREB1-SS18, and GREB1-NCOA1, validated by RT-PCR and/or FISH. They occurred in the myometrium of postmenopausal women and were pathologically similar despite minor differences. Tumor cells were generally uniform and epithelioid, with vesicular nuclei and distinct to prominent nucleoli. Growth patterns included solid sheets, trabeculae/cords, nests, and fascicles. Only 1 tumor showed small foci of definitive sex-cord components featuring well-formed tubules, retiform structures, Leydig-like cells, and lipid-laden cells and exhibiting convincing immunoreactivity to sex-cord markers (calretinin, α-inhibin, and Melan-A). In contrast, all the 4 classic UTROSCT we collected occurred in premenopausal patients, consisted predominantly of unequivocal sex-cord elements, prominently expressed multiple sex-cord markers, and harbored ESR1-NCOA3 fusion. Combined with previously reported cases, GREB1-rearranged tumors involved significantly older women (P=0.001), tended to be larger and more mitotically active, showed more variable and often inconspicuous sex-cord differentiation, and appeared to behave more aggressively than ESR1-rearranged UTROSCT. Therefore, these 2 groups of tumors might deserve separate consideration, despite some overlapping features and the possibility of belonging to the same disease spectrum.

SRC3, a highly conserved member of the steroid receptor coactivator (SRC) family, is recruited by transcription factors to regulate cellular function. Previously, we demonstrated that SRC1, another highly conserved member of the SRC family, interacts with RORγt to regulate Th17 differentiation. However, the relationship between SRC1 and SRC3 in the regulation of Th17 cell function remains unknown. In this study, we demonstrate that mouse SRC3 interacts with RORγt in Th17 cells but not in thymocytes. In addition, Src3−/− mice exhibited defective Th17 differentiation and induction of experimental autoimmune encephalomyelitis but normal thymocyte development. Furthermore, a K313 to arginine mutation of RORγt (RORγt-K313R), which disrupts the interaction of RORγt with SRC3 but not with SRC1, impairs Th17 differentiation but not thymocyte development. These data suggest that SRC3 works with SRC1 to regulate RORγt-dependent Th17 differentiation but is not essential for RORγt-dependent thymocyte development.

Summary Aims The G‐protein‐coupled estrogen receptor GPR30 (also referred to as GPER) has been implicated in the estrogenic regulation of hippocampal plasticity and spatial memory; however, the molecular mechanisms are largely unclear. Methods In this study, we initially examined the levels of GPR30 in the hippocampus of postnatal, ovariectomy (OVX)‐ and letrozole (LET)‐treated female mice. Under G1, G15, and/or OVX treatment, the spatial memory, spine density, levels of ERα, ERβ, and SRC‐1, selected synaptic proteins, mTORC2 signals (Rictor and p‐AKT Ser473), and actin polymerization dynamics were subsequently evaluated. Furthermore, G1, G15, and/or E2 combined with SRC‐1 and/or PI3K inhibitors, actin cytoskeleton polymerization modulator JPK, and CytoD treatments were used to address the mechanisms that underlie GPR30 regulation in vitro. Finally, mTORC2 activator A‐443654 (A4) was used to explore the role of mTORC2 in GPR30 regulation of spatial memory. Results The results showed that high levels of GPR30 were detected in the adult hippocampus and the levels were downregulated by OVX and LET. OVX induced an impairment of spatial memory, and changes in other parameters previously described were reversed by G1 and mimicked by G15. Furthermore, the E2 effects on SRC‐1 and mTORC2 signals, synaptic proteins, and actin polymerization were inhibited by G15, whereas G1 effects on these parameters were inhibited by the blockade of SRC‐1 or PI3K; the levels of synaptic proteins were regulated by JPK and CytoD. Importantly, G15‐induced actin depolymerization and spatial memory impairment were rescued by mTORC2 activation with A4. Conclusions Taking together, these results demonstrated that decreased GPR30 induces actin depolymerization through SRC‐1 and PI3K/mTORC2 pathways and ultimately impairs learning and memory, indicating its potential role as a therapeutic target against hippocampus‐based, E2‐related memory impairments.

Background: Thyroid hormone (TH) acts on TH receptors (TRs) and regulates gene transcription by binding of TRs to TH response elements (TREs) in target gene promoters. The transcriptional activity of TRs is modulated by interactions with TR-coregulatory proteins. Mutations in TRα cause resistance to thyroid hormone alpha (RTHα). In this study, we analyzed if, beyond reduced triiodothyronine (T3) affinity, altered interactions with cofactors or different TREs could account for the differential impaired transcriptional activity of different mutants. Methods: We evaluated four mutants derived from patients (D211G, M256T, A263S, and R384H) and three artificial mutants at equivalent positions in patients with RTHβ (T223A, L287V, and P398H). The in vitro transcriptional activity was evaluated on TRE-luciferase reporters (DR4, IR0, and ER6). The affinity for T3 and interaction with coregulatory proteins (nuclear receptor corepressor 1 [NCoR1] and steroid receptor coactivator 1 [SRC1]) were also determined. Results: We found that the affinity for T3 was significantly reduced for all mutants, except for TRα1-T223A. The reduction in the T3 sensitivity of the transcriptional activity on three TREs, the dissociation of the corepressor NCoR1, and the association of the coactivator SRC1 recruitment for each mutant correlated with the reduced affinity for T3. We did not observe mutation-specific alterations in interactions with cofactors or TREs. Conclusions: In summary, the degree of impaired transcriptional activity of mutants is mainly determined by their reduced affinity for T3.

Nuclear receptor farnesoid X receptor (FXR) functions as the major bile acid sensor coordinating cholesterol metabolism, lipid homeostasis, and absorption of dietary fats and vitamins. Because of its central role in metabolism, FXR represents an important drug target to manage metabolic and other diseases, such as primary biliary cirrhosis and nonalcoholic steatohepatitis. FXR and nuclear receptor retinoid X receptor α (RXRα) form a heterodimer that controls the expression of numerous downstream genes. To date, the structural basis and functional consequences of the FXR/RXR heterodimer interaction have remained unclear. Herein, we present the crystal structures of the heterodimeric complex formed between the ligand-binding domains of human FXR and RXRα. We show that both FXR and RXR bind to the transcriptional coregulator steroid receptor coactivator 1 with higher affinity when they are part of the heterodimer complex than when they are in their respective monomeric states. Furthermore, structural comparisons of the FXR/RXRα heterodimers and the FXR monomers bound with different ligands indicated that both heterodimerization and ligand binding induce conformational changes in the C terminus of helix 11 in FXR that affect the stability of the coactivator binding surface and the coactivator binding in FXR. In summary, our findings shed light on the allosteric signal transduction in the FXR/RXR heterodimer, which may be utilized for future drug development targeting FXR.

Glucocorticoid receptor (GR) is an essential transcription factor (TF), controlling metabolism, development and immune responses. SUMOylation regulates chromatin occupancy and target gene expression of GR in a locus-selective manner, but the mechanism of regulation has remained elusive. Here, we identify the protein network around chromatin-bound GR by using selective isolation of chromatin-associated proteins and show that the network is affected by receptor SUMOylation, with several nuclear receptor coregulators and chromatin modifiers preferring interaction with SUMOylation-deficient GR and proteins implicated in transcriptional repression preferring interaction with SUMOylation-competent GR. This difference is reflected in our chromatin binding, chromatin accessibility and gene expression data, showing that the SUMOylation-deficient GR is more potent in binding and opening chromatin at glucocorticoid-regulated enhancers and inducing expression of target loci. Blockage of SUMOylation by a SUMO-activating enzyme inhibitor (ML-792) phenocopied to a large extent the consequences of GR SUMOylation deficiency on chromatin binding and target gene expression. Our results thus show that SUMOylation modulates the specificity of GR by regulating its chromatin protein network and accessibility at GR-bound enhancers. We speculate that many other SUMOylated TFs utilize a similar regulatory mechanism.

MicroRNAs (miRNAs) are known as important regulators of gene expression and play important roles in diverse biological activities. However, the involvement of miRNAs in cerebral ischemia remains elusive. In the present study, using the middle cerebral artery occlusion (MCAO) model and oxygen-glucose deprivation/reperfusion (OGD/RP)-induced cell injury model, we found that the expression levels of miR-34c-5p were significantly reduced in MCAO rats and OGD/RP cells. Overexpression of miR-34c-5p could improve the increased brain infarction, brain water content and neurological scores in MCAO rats, as well as the abnormal expression of inflammatory cytokines (TNF-α, IL-6, COX-2, iNOS, IL-10) in OGD/RP cells. Moreover, overexpression of miR-34c-5p was found to inhibit the activity of nuclear factor-kappa B (NF-κB) by regulating the expression of nuclear receptor coactivator 1 (NCOA1), and increase the apoptotic rate of cortical neurons by inhibiting the expression of Caspase-3 and Bax and upregulating the expression of Bcl-2. Taken together, our findings demonstrated that miR-34c-5p plays an important role in cerebral ischemia/reperfusion injury, which may be mediated through inflammatory and apoptotic signaling pathways.

Recurrent fusion genes involving C11orf95, C11orf95‐RELA, have been identified only in supratentorial ependymomas among primary CNS tumors. Here, we report hitherto histopathologically unclassifiable high‐grade tumors, under the tentative label of “ependymoma‐like tumors with mesenchymal differentiation (ELTMDs),” harboring C11orf95‐NCOA1/2 or ‐RELA fusion. We examined the clinicopathological and molecular features in five cases of ELTMDs. Except for one adult case (50 years old), all cases were in children ranging from 1 to 2.5 years old. All patients presented with a mass lesion in the cerebral hemisphere. Histologically, all cases demonstrated a similar histology with a mixture of components. The major components were embryonal‐appearing components forming well‐delineated tumor cell nests composed of small uniform cells with high proliferative activity, and spindle‐cell mesenchymal components with a low‐ to high‐grade sarcoma‐like appearance. The embryonal‐appearing components exhibited minimal ependymal differentiation including a characteristic EMA positivity and tubular structures, but histologically did not fit with ependymoma because they lacked perivascular pseudorosettes, a histological hallmark of ependymoma, formed well‐delineated nests, and had diffuse and strong staining for CAM5.2. Molecular analysis identified C11orf95‐NCOA1, ‐NCOA2, and ‐RELA in two, one, and two cases, respectively. t‐distributed stochastic neighbor embedding analysis of DNA methylation data from two cases with C11orf95‐NCOA1 or ‐NCOA2 and a reference set of 380 CNS tumors revealed that these two cases were clustered together and were distinct from all subgroups of ependymomas. In conclusion, although ELTMDs exhibited morphological and genetic associations with supratentorial ependymoma with C11orf95‐RELA, they cannot be regarded as ependymoma. Further analyses of more cases are needed to clarify their differences and similarities., We report hitherto histopathologically unclassifiable high‐grade tumors, ELTMDs.ELTMDs exhibited minimal ependymal differentiation and C11orf95‐NCOA1/2 or ‐RELA.

Multicellular organisms have evolved sophisticated mechanisms to recover and maintain original tissue functions following injury. Injury responses require a robust transcriptomic response associated with cellular reprogramming involving complex gene expression programs critical for effective tissue repair following injury. Steroid receptor coactivators (SRCs) are master transcriptional regulators of cell–cell signaling that is integral for embryogenesis, reproduction, normal physiological function, and tissue repair following injury. Effective therapeutic approaches for facilitating improved tissue regeneration and repair will likely involve temporal and combinatorial manipulation of cell-intrinsic and cell-extrinsic factors. Pleiotropic actions of SRCs that are critical for wound healing range from immune regulation and angiogenesis to maintenance of metabolic regulation in diverse organ systems. Recent evidence derived from studies of model organisms during different developmental stages indicates the importance of the interplay of immune cells and stromal cells to wound healing. With SRCs being the master regulators of cell–cell signaling integral to physiologic changes necessary for wound repair, it is becoming clear that therapeutic targeting of SRCs provides a unique opportunity for drug development in wound healing. This review will provide an overview of wound healing–related functions of SRCs with a special focus on cellular and molecular interactions important for limiting tissue damage after injury. Finally, we review recent findings showing stimulation of SRCs following cardiac injury with the SRC small molecule stimulator MCB-613 can promote cardiac protection and inhibit pathologic remodeling after myocardial infarction.

International journal of molecular sciences 21(22), 8457 (1-13) (2020). doi:10.3390/ijms21228457, The retinoid X receptor (RXR) is a ligand-sensing transcription factor acting mainly as a universal heterodimer partner for other nuclear receptors. Despite presenting as a potential therapeutic target for cancer and neurodegeneration, adverse effects typically observed for RXR agonists, likely due to the lack of isoform selectivity, limit chemotherapeutic application of currently available RXR ligands. The three human RXR isoforms exhibit different expression patterns; however, they share high sequence similarity, presenting a major obstacle toward the development of subtype-selective ligands. Here, we report the discovery of the saturated fatty acid, palmitic acid, as an RXR ligand and disclose a uniform set of crystal structures of all three RXR isoforms in an active conformation induced by palmitic acid. A structural comparison revealed subtle differences among the RXR subtypes. We also observed an ability of palmitic acid as well as myristic acid and stearic acid to induce recruitment of steroid receptor co-activator 1 to the RXR ligand-binding domain with low micromolar potencies. With the high, millimolar endogenous concentrations of these highly abundant lipids, our results suggest their potential involvement in RXR signaling., Published by Molecular Diversity Preservation International, Basel

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., NR2F6 (nuclear receptor subfamily 2, group F, member 6) is increased in the livers of obese mice and patients with non‐alcoholic fatty liver disease. It transcriptionally upregulates the fatty acid transporter CD36 to enhance fatty acid uptake in hepatocytes, thereby promoting liver steatosis. These findings identify an important role for NR2F6 in the regulation of hepatic lipid homeostasis.

In this study, we investigated how Roux-en-Y gastric bypass (RYGB) enhances glucagon-like peptide 1 (GLP-1) response in GK rats and explored the potential link between RYGB-stimulated BAs/FXR signalling and GLP-1R-linked signalling in β-cells, a key pathway that regulates glucose-stimulated insulin secretion (GSIS). Here we show that RYGB restores GLP-1R expression in GK rat islets. This involves increased total BAs as well as chenodeoxycholic acid (CDCA), leading to FXR activation, increasing FXR binding to the promoter of Glp-1r and enhancing occupancy of histone acetyltransferase steroid receptor coactivator-1 (SRC1), thus increasing histone H3 acetylation at the promoter. These coordinated events bring about increased GLP-1R expression, resulting in greater GLP-1 response in β-cells. Moreover, ablation of FXR suppressed the stimulatory effects of GLP-1. Thus, this study unravels the crucial role of the BAs/FXR/SRC1 axis-controlled GLP-1R expression in β-cells, which results in enhanced incretin effect and normalized blood glucose of GK rats after RYGB.