Ubiquitination of nuclear receptors

Regulation of PXR in drug metabolism: chemical and structural perspectives

INTRODUCTION

Pregnane X receptor (PXR) is a master xenobiotic sensor that transcriptionally controls drug metabolism and disposition pathways. PXR activation by pharmaceutical drugs, natural products, environmental toxins, etc. may decrease drug efficacy and increase drug-drug interactions and drug toxicity, indicating a therapeutic value for PXR antagonists. However, PXR's functions in physiological events, such as intestinal inflammation, indicate that PXR activators may be useful in certain disease contexts.

AREAS COVERED

We review the reported roles of PXR in various physiological and pathological processes including drug metabolism, cancer, inflammation, energy metabolism, and endobiotic homeostasis. We then highlight specific cellular and chemical routes that modulate PXR activity and discuss the functional consequences. Databases searched and inclusive dates: PubMed, 1 January 1980 to 10 January 2024.

EXPERT OPINION

Knowledge of PXR's drug metabolism function has helped drug developers produce small molecules without PXR-mediated metabolic liabilities, and further understanding of PXR's cellular functions may offer drug development opportunities in multiple disease settings.

A preliminary study on the pathology and molecular mechanism of fumonisin B1 nephrotoxicity in young quails

Fumonisin B1 (FB1) is a widely present mycotoxin that accumulates in biological systems and poses a health risk to animals. However, few studies have reported the molecular mechanism by which FB1 induces nephrotoxicity. The aim of this study was to assess the extent of nephrotoxicity during FB1 exposure and the possible molecular mechanisms behind it. Therefore, 180 young quails were equally divided into two groups. The control group was fed typical quail food, while the experimental group was fed quail food containing 30 mg·kg-1 FB1. Various parameters were assessed, which included histopathological, ultrastructural changes, levels of biochemical parameters, oxidative indicators, inflammatory factors, possible target organelles mitochondrial and endoplasmic reticulum (ER)-related factors, nuclear xenobiotic receptors (NXR) response, and cytochrome P450 system (CYP450s)-related factors in the kidneys on days 14, 28, and 42. The results showed that FB1 can induce oxidative stress through NXR response and disorder of the CYP450s system, leading to mitochondrial dysfunction and ER stress, promoting the expression of inflammatory factors (including IL-1β, IL-6, and IL-8) and causing kidney damage. This study elucidated the possible molecular mechanism by which FB1 induces nephrotoxicity in young quails.

Stable expression of a truncated TLX variant drives differentiation of induced pluripotent stem cells into self-renewing neural stem cells for production of extracellular vesicles

Background

Neural stem cells (NSCs)-derived extracellular vesicles (EVs) possess great potential in treating severe neurological and cerebrovascular diseases, as they carry the modulatory and regenerative ingredients of NSCs. Induced pluripotent stem cells (iPSCs)-derived NSCs culture represents a sustainable source of therapeutic EVs. However, there exist two major challenges in obtaining a scalable culture of NSCs for high-efficiency EVs production: (1) the heterogeneity of iPSC-derived NSCs culture impairs the production of high-quality EVs and (2) the intrinsic propensity of neuronal or astroglial differentiation of NSCs during prolonged culturing reduces the number of NSCs for preparing EVs. A NSCs strain that is amenable to stable self-renewal and proliferation is thus greatly needed for scalable and long-term culture.

Methods

Various constructs of the genes encoding the orphan nuclear receptor NR2E1 (TLX) were stably transfected in iPSCs, which were subsequently cultured in a variety of differentiation media for generation of iNSCs^TLX. Transcriptomic and biomarker profile of iNSCs^TLX were investigated. In particular, the positivity ratios of Sox2/Nestin and Musashi/Vimentin were used to gauge the homogeneity of the iNSCs^TLX culture. The iNSCs expressing a truncated version of TLX (TLX-TP) was expanded for up to 45 passages, after which its neuronal differentiation potential and EV activity were evaluated.

Results

Stable expression of TLX-TP could confer the iPSCs with rapid and self-driven differentiation into NSCs through stable passaging up to 225 days. The long-term culture of NSCs maintained the highly homogenous expression of NSC-specific biomarkers and potential of neuronal differentiation. EVs harvested from the TLX-expressing NSCs cultures exhibited anti-inflammatory and neuroprotective activities.

Conclusions

iPSC-derived NSCs stably expressing TLX-TP is a promising cell line for scalable production of EVs, which should be further exploited for therapeutic development in neurological treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03131-4.

Exercise improves high-fat diet-induced metabolic disorder by promoting HDAC5 degradation through the ubiquitin-proteasome system in skeletal muscle

Histone deacetylase 4/5 are essential for regulating metabolic gene expression, AMPKα2 regulates HDAC4/5 activity and the expression of MuRF1 during exercise. In this study, we used wild type and AMPKα2-/- mice to explore the potential regulatory relationship between AMPKα2 and HDAC4/5 expression during exercise. Firstly, we fed C57BL/6J mice with high-fat diet for eight-week to assess the effects of high-fat diet on skeletal muscle metabolism and HDAC4/5 expression. We then performed a six-week treadmill exercise on both wild type and AMPKα2-/- mice. After exercise, the expressions of HDAC4/5 were examined in both gastrocnemius and soleus. The citrate synthase activity and proteins involved in skeletal muscle oxidative process were assessed. To determine the relationship of HDAC4/5 and skeletal muscle oxidative capacity, citrate synthase activity was assessed after silencing HDAC4/5. Moreover, HDAC5 ubiquitination and the association of MuRF1 to HDAC5 were also investigated. Our results showed that six-week exercise increased the skeletal muscle oxidative capacity and decreased HDAC4/5 expression only in soleus. HDAC5 silencing increased C2C12 cells oxidative capacity. Proteasome inhibition by MG132 abolished exercise-induced HDAC5 degradation mediated by MuRF1-ubiquitin-proteasome system. However, the UPS did not dominantly account for exercise-induced HDAC4 degradation. Exercise up-regulated MuRF1-HDAC5 association in wild type mice but not in AMPKα2-/- mice. Our results revealed that six-week exercise increased the skeletal muscle oxidative capacity and promoted HDAC5 degradation in soleus through the UPS, MuRF1 mediated HDAC5 ubiquitination. Although AMPKα2 played partial role in regulating MuRF1 expression and HDAC5 ubiquitination, exercise-induced HDAC5 degradation did not fully depend on AMPKα2.

UBE2G1 Is a Critical Component of Immune Response to the Infection of Pseudomonas Plecoglossicida in Large Yellow Croaker (Larimichthys crocea)

The large yellow croaker (Larimichthys crocea) is one of the most economically valuable mariculture fish in China. Infection of Pseudomonas plecoglossicida can cause an outbreak of “internal organ white-spot disease”, which seriously affects the aquaculture of the large yellow croaker. Ubiquitylation is closely related to the post-translation modification of proteins and plays a vital role in many hosts’ immune defense pathways, while the E2-binding enzyme is a key factor in ubiquitination. Our previous genome-wide association study found that the ubiquitin-binding enzyme E2G1 (designed LcUbe2g1) was one of the candidate genes related to disease resistance in large yellow croaker. In this study, we analyzed the molecular characteristics, function, and immune mechanism of the LcUbe2g1. The full-length cDNA is 812 bp, with an open reading frame of 513 bp, encoding 170 amino acid residues. The results of the RT-qPCR and immunohistochemistry analysis revealed that its transcription and translation were significantly activated by the infection of P. plecoglossicida in large yellow croaker. Immunocytochemistry experiments verified the co-localization of LcUBE2G1 and the ubiquitin proteins in the head kidney cells of large yellow croaker. Through GST pull-down, we found that LcUBE2G1 interacted with NEDD8 to co-regulate the ubiquitination process. The above results indicate that LcUBE2G1 is essential in the regulation of ubiquitination against P. plecoglossicida infection in large yellow croaker, which lays a foundation for further study on the resistance mechanism of internal organ white-spot disease.

Estrogen Receptor β as a Candidate Regulator of Sex Differences in the Maternal Immune Activation Model of ASD

Interestingly, more males are diagnosed with autism spectrum disorder (ASD) than females, yet the mechanism behind this difference is unclear. Genes on the sex chromosomes and differential regulation by sex steroid hormones and their receptors are both candidate mechanisms to explain this sex-dependent phenotype. Nuclear receptors (NRs) are a large family of transcription factors, including sex hormone receptors, that mediate ligand-dependent transcription and may play key roles in sex-specific regulation of immunity and brain development. Infection during pregnancy is known to increase the probability of developing ASD in humans, and a mouse model of maternal immune activation (MIA), which is induced by injecting innate immune stimulants into pregnant wild-type mice, is commonly used to study ASD. Since this model successfully recaptures the behavioral phenotypes and male bias observed in ASD, we will discuss the potential role of sex steroid hormones and their receptors, especially focusing on estrogen receptor (ER)β, in MIA and how this signaling may modulate transcription and subsequent inflammation in myeloid-lineage cells to contribute to the etiology of this neurodevelopmental disorder.

Functions of nuclear receptors SUMOylation

The nuclear receptor superfamily is a family of ligand-activated transcription factors that play a key role in cell metabolism and human diseases. They can be modified after translation, such as acetylation, ubiquitination, phosphorylation and SUMOylation. Crosstalk between SUMO and ubiquitin, phosphorylation and acetylation regulates a variety of metabolic and physiological activities. Nuclear receptors play an important role in lipid metabolism, inflammation, bile acid homeostasis and autophagy. SUMOylation nuclear receptors can regulate their function and affect cell metabolism. It also provides a potential therapeutic target for atherosclerosis, tumor and other metabolic and inflammation-related diseases. This review focuses on the function of SUMOylation nuclear receptors.

Chemical Screening of Nuclear Receptor Modulators

Nuclear receptors are ligand-inducible transcriptional factors that control multiple biological phenomena, including proliferation, differentiation, reproduction, metabolism, and the maintenance of homeostasis. Members of the nuclear receptor superfamily have marked structural and functional similarities, and their domain functionalities and regulatory mechanisms have been well studied. Various modulators of nuclear receptors, including agonists and antagonists, have been developed as tools for elucidating nuclear receptor functions and also as drug candidates or lead compounds. Many assay systems are currently available to evaluate the modulation of nuclear receptor functions, and are useful as screening tools in the discovery and development of new modulators. In this review, we cover the chemical screening methods for nuclear receptor modulators, focusing on assay methods and chemical libraries for screening. We include some recent examples of the discovery of nuclear receptor modulators.

c-Cbl: An Important Regulator and a Target in Angiogenesis and Tumorigenesis

Casitas B lineage lymphoma (c-Cbl) is a multifunctional protein with a ubiquitin E3 ligase activity capable of degrading diverse sets of proteins. Although previous work had focused mainly on c-Cbl mutations in humans with hematological malignancies, recent emerging evidence suggests a critical role of c-Cbl in angiogenesis and human solid organ tumors. The combination of its unique structure, modular function, and ability to channelize cues from a rich network of signaling cascades, empowers c-Cbl to assume a central role in these disease models. This review consolidates the structural and functional insights based on recent studies that highlight c-Cbl as a target with tantalizing therapeutic potential in various models of angiogenesis and tumorigenesis.