Hepatocellular carcinoma (HCC) is the sixth most prevalent malignancy worldwide, and represents a major global health challenge. While surgical resection at early stages offers favorable prognosis with 5-year survival rates exceeding 70%, the clinical reality in China reveals a contrasting scenario, where over 60% of patients present with advanced disease, resulting in a dramatic decline in 5-year survival to below 12.5%. The immunological landscape plays a pivotal role in HCC pathogenesis and progression, comprising two complementary arms: the innate immune system's rapid-response mechanism for immediate tumor surveillance and the adaptive immune system's antigen-specific targeting with immunological memory capabilities. Emerging evidence has highlighted ubiquitination, a sophisticated post-translational modification system, as a critical regulator of immune homeostasis in HCC pathogenesis. This molecular process exerts precise control through three primary mechanisms: (1) Modulation of immune cell activation thresholds via proteasomal degradation of signaling proteins, (2) Orchestrating immune cell differentiation through stability regulation of transcriptional factors, and (3) Maintenance of immune tolerance by dynamic modification of checkpoint regulators. Such multifaceted regulation affects both innate immune recognition pathways (e.g., NF-κB and STING signaling) and adaptive immune effectors (particularly T cell receptor signaling cascades). This comprehensive review establishes a threefold Objective: First, to elucidate the mechanistic interplay between ubiquitination networks and HCC-related immune dysregulation; Second, to systematically analyze how innate immune-associated ubiquitination events drive hepatocarcinogenesis through chronic inflammation modulation; and third, to critically evaluate recent clinical advances combining ubiquitination-targeted therapies (e.g., proteasome inhibitors and E3 ligase modulators) with immunotherapeutic regimens. Our synthesis revealed that strategic manipulation of ubiquitination pathways can potentiate PD-1/PD-L1 blockade efficacy while mitigating therapeutic resistance, particularly through modulation of tumor-associated macrophages and exhausted T cell populations. By integrating fundamental mechanistic insights with translational clinical data, this review provides a conceptual framework for the development of next-generation diagnostic biomarkers and rational therapeutic combinations. The proposed strategy of ubiquitination-immune axis modulation holds significant potential to transform current HCC management paradigms, offering new avenues for precision immunotherapy for this challenging malignancy.

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a significant global health threat. The molecular mechanisms underlying regulation of MASLD remain largely unknown. This study aimed to investigate the role of the WW domain-containing ubiquitin E3 ligase 1 (WWP1)-enhancer-of-split and hairy-related protein 1 (SHARP1)-C/EBPβ signal loop in MASLD.

In vivo and in vitro models of MASLD were established applying high-fat diet-fed (HFD) mice and free fatty acid (FFA)-treated hepatocytes. The relationships among SHARP1, WWP1, and C/EBPβ were examined using bioinformatics, immunoprecipitation, immunofluorescence, luciferase assays, chromatin immunoprecipitation. MASLD progression was evaluated based on food intake, energy expenditure, insulin resistance, hepatic steatosis, inflammation and white fat growth.

SHARP1 were significantly reduced in the MASLD livers of mouse and human and in FA-treated hepatocytes. Hepatocyte-specific SHARP1 overexpression significantly inhibited MASLD development in HFD-fed mice. Wild-type SHARP1, but not deficient SHARP1 (SHARP1-K/R and SHARP1-P/A), was ubiquitinated and degraded by the E3 ligase WWP1. Wild-type SHARP1 was not ubiquitinated when WWP1 was deficient (WWP1-C886A, WWP1-C890A, WWP1-ΔWW3). Deficient SHARP1 exhibited better inhibitory activity against MASLD than the wild-type SHARP1. WWP1 overexpression reversed the suppression of MASLD induced by wild-type SHARP1 but did not affect that induced by deficient SHARP1. Deficient WWP1 did not inhibit the wild-type SHARP1-induced MASLD amelioration. Furthermore, in FA-treated hepatocytes, the interaction between SHARP1 and C/EBPβ weakened, resulting in more C/EBPβ binding to the Wwp1 promoter and subsequent WWP1 upregulation. SHARP1 overexpression or WWP1 interference partially blocked the effects of C/EBPβ on MASLD. Hesperidin was identified as a novel WWP1 inhibitor, and it significantly blocked WWP1 overexpression-induced MASLD progression.

The WWP1-SHARP1-C/EBPβ signal loop accelerates MASLD progression. This study provides novel insights into novel biomarkers and treatment approaches for MASLD.

Extracellular vesicles (EVs) of different sizes are secreted by cells and may contain microRNAs (miRNAs) among its cargo. These miRNAs in EVs can induce changes in gene expression and function of recipient cells. In different cells EVs content can change with age and physiological state affecting tissue function. Based on this, the aim of this study was to characterize the miRNA content and role of small EVs (sEVs) from cyclic female mice in the modulation of liver transcriptome in estropausal mice. Two-month-old female mice were induced to estropause using 4-vinylcyclohexene diepoxide (VCD). At six months of age, VCD-treated mice were divided into placebo group (VCD) and sEVs treated group (VCD + sEVs), which received 10 injections at 3-day intervals of sEVs isolated from serum of donor cyclic female mice. A group of cyclic mice also received placebo injection and served as controls (CTL). sEVs injection in mice undergoing estropause had no effect on body mass, insulin sensitivity or organ weight. We observed ten miRNAs differentially regulated in serum sEVs of VCD compared to CTL mice. In the liver we observed 931 genes differentially expressed in VCD + sEVs compared to VCD mice. Interestingly, eight pathways were up-regulated in liver by VCD treatment and down-regulated by sEVs treatment, indicating that sEVs from cyclic mice can reverse changes promoted by estropause in liver. The expression of Cyp4a12a, which is male-specific, was elevated in VCD females but not normalized by sEVs treatment. Our findings indicate that miRNA content in sEVs is regulated by estropause in mice independent of age. Additionally, treatment of estropausal mice with sEVs from cyclic mice can partially reverse changes in the liver transcriptome.

Ischemia-reperfusion (I/R) injury describes the pathological process wherein tissue damage, initially caused by insufficient blood supply (ischemia), is exacerbated upon the restoration of blood flow (reperfusion). This phenomenon can lead to irreversible tissue damage and is commonly observed in contexts such as cardiac surgery and stroke, where blood supply is temporarily obstructed. During ischemic conditions, the anaerobic metabolism of tissues and organs results in compromised enzyme activity. Subsequent reperfusion exacerbates mitochondrial dysfunction, leading to increased oxidative stress and the accumulation of reactive oxygen species (ROS). This cascade ultimately triggers cell death through mechanisms such as autophagy and mitophagy. Autophagy constitutes a crucial catabolic mechanism within eukaryotic cells, facilitating the degradation and recycling of damaged, aged, or superfluous organelles and proteins via the lysosomal pathway. This process is essential for maintaining cellular homeostasis and adapting to diverse stress conditions. As a cellular self-degradation and clearance mechanism, autophagy exhibits a dualistic function: it can confer protection during the initial phases of cellular injury, yet potentially exacerbate damage in the later stages. This paper aims to elucidate the fundamental mechanisms of autophagy in I/R injury, highlighting its dual role in regulation and its effects on both organ-specific and systemic responses. By comprehending the dual mechanisms of autophagy and their implications for organ function, this study seeks to explore the potential for therapeutic interventions through the modulation of autophagy within clinical settings.

Ubiquitination modifications can affect hepatocellular carcinoma (HCC) progression through various signaling pathways. However, no significant results have been observed regarding protein ubiquitination in HCC's therapeutic transformation. This study aimed to explore the research areas related to ubiquitination and HCC from a bibliometric perspective.

Articles and reviews on HCC and ubiquitination published between 2000 and 2023 were obtained from the Web of Science Core Collection (WOSCC). CiteSpace, VOSviewer, and R-bibliometrix were used for the bibliometric and visualization analyses.

Altogether, 358 papers on ubiquitination and HCC were extracted from the WOSCC. Over 24 years, the number of publications has increased. Since the beginning of 2019, studies related to this topic have increased significantly, indicating that the role of ubiquitination modification in HCC is currently popular. China is the leading country in this field with the largest number of publications. The Chinese Academy of Sciences is one of the most influential institutions. Qiao, Yongxia, and Zhang Jie are highly productive authors with major achievements. The journal Cell Death & Disease had the highest number of publications, and the most highly cited journal was Oncogene. The highest citation burst intensity was Sung (2021). In the keyword strategy map, "cancer antigens" are popular keywords in HCC and ubiquitination research.

A comprehensive visual analysis of ubiquitination and HCC research was conducted using bibliometric methods, showing the publications and popular topics in this field over the past two decades, thus providing references for the future direction of ubiquitination and HCC research.

Metabolic dysfunction-associated steatotic liver disease (MASLD), the most prevalent chronic liver condition globally, lacks adequate and effective therapeutic remedies in clinical practice. Recent studies have increasingly highlighted the close connection between the ubiquitin-proteasome system (UPS) and the progression of MASLD. This relationship is crucial for understanding the disease's underlying mechanism. As a sophisticated process, the UPS govern protein stability and function, maintaining protein homeostasis, thus influencing a multitude of elements and biological events of eukaryotic cells. It comprises four enzyme families, namely, ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), ubiquitin-protein ligases (E3), and deubiquitinating enzymes (DUBs). This review aims to delve into the array of pathways and therapeutic targets implicated in the ubiquitination within the pathogenesis of MASLD. Therefore, this review unveils the role of ubiquitination in MASLD while spotlighting potential therapeutic targets within the context of this disease.

Recent studies have implicated altered ubiquitination/de-ubiquitination pathway in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD). Here, we investigated the potential role of a deubiquitinase, ubiquitin-specific peptidase 25 (USP25), in MASLD. Analysis of mRNA profiling data showed that both human and mouse MASLD are associated with reduced expression of USP25 in hepatocytes. Usp25 deficiency exacerbated HFD-induced liver lipid accumulation and MASLD in mice. Rescue experiments with USP25 induction in hepatocytes protected mice against HFD-induced MASLD. Through comprehensive transcriptome sequence and pulldown-LC-MS/MS analysis, we identified that peroxisome proliferator-activated receptor α (PPARα) is involved in USP25's protective actions and may be the substrate protein of USP25. Cell-based experiments show that USP25 interacts with PPARα directly via its USP domain and the histidine at position 608 of USP25 exerts deubiquitination to increase protein stability by removing the K48 ubiquitin chain at PPARα's lysine at position 429. USP25 reduces palmitate (PA)-induced lipid accumulation in hepatocytes via increasing PPARα. Finally, we show that the protective effects of Usp25 induction are nullified in Ppara-deficient mice with HFD. In summary, this study presents a new USP25-PPARα axis in hepatocytes and highlights a novel function of USP25 in MASLD, suggesting that it may be targeted to combat the disease.

Non-alcoholic fatty liver disease (NAFLD) is the prevalent liver disease. Ovarian tumor domain-containing 7B (OTUD7B) is a deubiquitinating enzyme and its role in NAFLD remains unclear. In high-fat diet (HFD)-induced NAFLD mouse model and palmitic acid (PA)-treated HepG2 cells, OTUD7B expression was decreased. Adenoviral overexpression of OTUD7B in mice resulted in reduced body weight and liver injury, with decreased serum aminotransferase (ALT) and aspartate aminotransferase (AST) levels. OTUD7B overexpression attenuated hepatic lipid deposition (serum TG, TC, LDL-C, HDLC, and FFA levels), which might be through the suppression of lipogenesis and β-oxidation-related genes. The contents of hepatic inflammatory factors (TNF-α, IL-6, and IL-1β) were decreased following OTUD7B overexpression in NAFLD mice. A mechanism study indicated that the protective effect of OTUD7B overexpression might be associated with β-catenin signal activation. OTUD7B overexpression promoted PA-induced β-catenin activity in TopFlash assay, and increased total β-catenin and c-myc levels in cells. The increase in β-catenin levels was contributed to the stabilization via inhibiting K48-linked ubiquitination and proteasomal degradation by OTUD7B. NR4A2 role in NASH has been proved. NR4A2 ChIP-seq and RNA-seq data excluded transcriptional regulation of NR4A2 to OTUD7B, and it was experimentally evidenced that NR4A2 bound to OTUD7B promoter region and positively transcriptionally regulate OTUD7B expression. In summary, OTUD7B overexpression ameliorated hepatic inflammation and steatosis in NAFLD. The possible mechanism of OTUD7B might be through the inhibition of β-catenin degradation by removing K48-linked ubiquitination, which might be regulated by NR4A2.

Exosomes are extracellular vesicles secreted by cells that contain microRNAs (miRNAs). These miRNAs can induce changes in gene expression and function of recipient cells. In different cells exosome content can change with age and physiological state affecting tissues function and health.

Therefore, the aim of this study was to characterize the miRNA content and role of exosomes from cyclic female mice in the modulation of liver transcriptome in estropausal mice.

Two-month-old female mice were induced to estropause using 4-vinylcyclohexene diepoxide (VCD). At six months of age VCD-treated mice were divided in control group (VCD) and exosome treated group (VCD+EXO), which received 10 injections at 3-day intervals of exosomes extracted from serum of cyclic female mice (CTL).

Exosome injection in estropausal mice had no effect on body mass, insulin sensitivity or organ weight. We observed ten miRNAs differentially regulated in serum exosomes of VCD compared to CTL mice. In the liver we observed 931 genes differentially expressed in VCD+EXO compared to VCD mice. Interestingly, eight pathways were up-regulated in liver by VCD treatment and down-regulated by exosome treatment, indicating that exosomes from cyclic mice can reverse changes promoted by estropause in liver. Cyp4a12a expression which is male-specific was increased in VCD females and not reversed by exosome treatment.

Our findings indicate that miRNAs content in exosomes is regulated by estropause in mice independent of age. Additionally, treatment of estropausal mice with exosomes from cyclic mice can partially reverse changes in liver transcriptome.

Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. Ubiquitin-specific peptidase 25 (USP25) in adipocytes has been proven to be involved in insulin resistance, a noteworthy characteristic of NAFLD. However, the roles of USP25 in NAFLD remain unclear. In this study, we aimed to elucidate the role of USP25 in NAFLD. Hepatic USP25 protein levels were measured in NAFLD patients and models. USP25 expression was manipulated in both mice and cells to evaluate its role in NAFLD. A downstream target of USP25 in NAFLD progression was identified through proteomic profiling analyses and confirmed. Additionally, a USP25 inhibitor was used to determine whether USP25 could be a viable treatment target for NAFLD. We found that USP25 protein levels were significantly decreased in the livers of NAFLD patients and NAFLD model mice. USP25 protein levels were also decreased in both mouse primary hepatocytes and Huh7 cells treated with free fatty acids (FFAs). We also found that Usp25 knockout mice presented much more severe hepatic steatosis when they were fed a high-fat diet. Similarly, knocking down USP25 in Huh7 cell lines aggravated FFA-induced steatosis, whereas USP25 overexpression ameliorated FFA-induced steatosis in Huh7 cell lines. Further proteomic profiling revealed that the peroxisome proliferator-activated receptor alpha (PPARα) signaling pathway was a downstream target of USP25, which was confirmed in both mice and cell lines. Moreover, USP25 could stabilize PPARα by promoting its deubiquitination. Finally, a USP25 inhibitor exacerbated diet-induced steatosis in mice. In conclusion, USP25 may play a role in NAFLD through the PPARα signaling pathway and could be a potential therapeutic target for NAFLD.

Sulfenylation is a reversible oxidative posttranslational modification (PTM) of proteins on cysteine residues. Despite the dissection of various biological functions of cysteine sulfenylation, its roles in hepatic fibrosis remain elusive. Here, we report that EphB2, a receptor tyrosine kinase previously implicated in liver fibrosis, is regulated by cysteine sulfenylation during the fibrotic progression of liver. Specifically, EphB2 is sulfenylated at the residues of Cys636 and Cys862 in activated hepatic stellate cells (HSCs), leading to the elevation of tyrosine kinase activity and protein stability of EphB2 and stronger interactions with focal adhesion kinase for the activation of downstream mitogen-activated protein kinase signaling. The inhibitions of both EphB2 kinase activity and cysteine sulfenylation by idebenone (IDE), a marketed drug with potent antioxidant activity, can markedly suppress the activation of HSCs and ameliorate hepatic injury in two well-recognized mouse models of liver fibrosis. Collectively, this study reveals cysteine sulfenylation as a new type of PTM for EphB2 and sheds a light on the therapeutic potential of IDE for the treatment of liver fibrosis.

Metabolic disorders include obesity, nonalcoholic fatty liver disease, insulin resistance and type 2 diabetes. It has become a major health issue around the world. Ubiquitin-proteasome system (UPS) is essential for nearly all cellular processes, functions as a primary pathway for intracellular protein degradation. Recent researches indicated that dysfunctions in the UPS may result in the accumulation of toxic proteins, lipotoxicity, oxidative stress, inflammation, and insulin resistance, all of which contribute to the development and progression of metabolic disorders. An increasing body of evidence indicates that specific dietary polyphenols ameliorate metabolic disorders by preventing lipid synthesis and transport, excessive inflammation, hyperglycemia and insulin resistance, and oxidative stress, through regulation of the UPS. This review summarized the latest research progress of natural polyphenols improving metabolic disorders by regulating lipid accumulation, inflammation, oxidative stress, and insulin resistance through the UPS. In addition, the possible mechanisms of UPS-mediated prevention of metabolic disorders are comprehensively proposed. We aim to provide new angle to the development and utilization of polyphenols in improving metabolic disorders.

Hepatocellular adenoma (HCA) and hepatocellular carcinoma (HCC) can be difficult to differentiate but must be diagnosed correctly as treatment and prognosis for these tumors differ markedly. Relevant diagnostic biomarkers are thus needed, and those identified in dogs may have utility in human medicine because of the similarities between human and canine HCA and HCC. A tRNA-derived fragment (tRF), tRNA-Val, is a promising potential biomarker for canine mammary gland tumors but has not previously been investigated in hepatic tumors. Accordingly, we aimed to elucidate the potential utility of tRNA-Val as a biomarker for canine HCA and HCC using clinical samples (tumor tissue and plasma extracellular vesicles [EVs]) and tumor cell lines with qRT-PCR assays. We also investigated relevant functions and signaling pathways with bioinformatic analyses (Gene Ontology and Kyoto Encyclopedia of Genes and Genomes). tRNA-Val was markedly downregulated in HCC tumor tissue versus HCA tumor tissue and normal liver tissue, and a similar trend was shown in plasma EVs and HCC cell lines versus healthy controls. Based on areas under the receiver operating characteristic curves (AUCs), tRNA-Val significantly distinguished HCC (AUC = 1.00, p = 0.001) from healthy controls in plasma EVs and HCC from HCA (AUC = 0.950, p = 0.01). Bioinformatics analysis revealed that tRNA-Val may be primarily involved in DNA repair, mRNA processing, and splicing and may be linked to the N-glycan and ubiquitin-mediated proteasome pathways. This is the first report on the expression of tRNA-Val in canine HCC and HCA and its possible functions and signaling pathways. We suggest that tRNA-Val could be a promising novel biomarker to distinguish canine HCC from HCA. This study provides evidence for a greater understanding of the role played by tRNA-Val in the development of canine HCC.

Non-alcoholic steatohepatitis (NASH) is rapidly surpassing viral hepatitis as the primary cause of hepatocellular carcinoma (HCC). However, understanding of NASH-progressed HCC remains poor, which might impede HCC diagnosis and therapy. In this study, we aim to identify shared transcriptional changes between NASH and HCC, of which we focused on E3 ligase TRIM45. We found TRIM45 exacerbates HCC cells proliferation and metastasis in vitro and in vivo. Further transcriptome analysis revealed TRIM45 predominantly affects fatty acid metabolism and oleic acid restored impaired proliferation and metastasis of TRIM45-deficient HCC cells. IP-tandem mass spectrum and FABP5 depriving experiment indicated that TRIM45 enhance fatty acid synthesis depending on FABP5 presence. Interestingly, we found TRIM45 directly added K33-type and K63-type poly-ubiquitin chains to FABP5 NLS domain, which ultimately promoted FABP5 nuclear translocation. Nuclear FABP5 interacted with PPARγ to facilitate downstream lipid synthesis gene expression. We observed TRIM45 accelerated NASH-to-HCC transition and exacerbated both NASH and NASH-HCC with the enhanced fatty acid production in vivo. Moreover, high concentration of fatty acid increased TRIM45 expression. The established mechanism was substantiated by gene expression correlation in TCGA-LIHC. Collectively, our research revealed a common lipid reprograming process in NASH and HCC and identified the cyclical amplification of the TRIM45-FABP5-PPARγ-fatty acid axis. This signaling pathway offers potential therapeutic targets for therapeutic intervention in NASH and NASH-progressed HCC.

The ubiquitin-proteasome system (UPS) is a multi-step process that serves as the primary pathway for protein degradation within cells. UPS activity also plays a crucial role in regulating various life processes, including the cell cycle, signal transduction, DNA repair, and others. The F-box protein Skp2, a crucial member of the UPS, plays a central role in the development of various diseases. Skp2 controls cancer cell growth and drug resistance by ubiquitinating modifications to a variety of proteins. This review emphasizes the multifaceted role of Skp2 in a wide range of cancers and the mechanisms involved, highlighting the potential of Skp2 as a therapeutic target in cancer. Additionally, we describe the impactful influence exerted by Skp2 in various other diseases beyond cancer.

Alcoholic fatty liver disease (AFLD) is characterized by abnormal lipid droplet accumulation in liver. Epigenetic regulation plays an important role in the pathogenesis of AFLD. Comprehensive bioinformatics analysis revealed that an E3 ubiquitin ligase, F-box and leucine-rich repeats protein 5 (FBXL5), was significantly upregulated in AFLD mice.

The mouse model of AFLD was established by feeding Lieber-DeCarli liquid diet containing ethanol. An in vitro model of AFLD was established by treating HepG2 cells with ethanol (EtOH). The FBXL5 expression was assessed by quantitative real-time PCR (qRT-PCR) and western blotting assays. The levels of triglyceride (TG), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lipid accumulation were analyzed by enzyme-linked immunosorbent assay (ELISA) and Nile red staining.

The FBXL5 expression was markedly up-regulated in in vivo and in vitro models of AFLD compared with controls. Functionally, FBXL5 knockdown alleviated lipid accumulation in EtOH-treated HepG2 cells. Mechanistically, FBXL5 directly interacted with transcription factor EB (TFEB) and accelerated its ubiquitination-mediated degradation. TFEB knockdown reversed the effect of FBXL5 inhibition on decreasing EtOH-induced lipid accumulation.

Our data suggest that FBXL5 promotes lipid accumulation in AFLD by promoting the ubiquitination and degradation of TFEB.

Nonalcoholic fatty liver disease (NAFLD) is one of the most common liver disorders and accompanied by multiple metabolic dysfunctions. Although excessive lipid accumulation in hepatocytes has been identified as a crucial mediator of NAFLD development, the underlying mechanisms are very complicated and remain largely unknown. In this study, we reported that upregulated expression of the seven in absentia homolog 1 (Siah1) in the liver exacerbated NAFLD progression. Conversely, Siah1 downregulation markedly alleviated the high fat diet-induced accumulation of hepatic fat and expression of genes related to lipid metabolism in vitro and in vivo. The mechanistic study revealed that Siah1 interacted with sterol carrier protein 2 (Scp2) and promotes its ubiquitination and degradation, suggesting that Siah1 is an important activator of Scp2 ubiquitination in the context of NAFLD. Our results demonstrated that Siah1 regulated the lipid accumulation in NAFLD by interacting with Scp2. Thus, this study presents Siah1 as a promising therapeutic target in the development of NAFLD.

The functions of liver fatty acid binding protein 1 (FABP1) in the regulation of nonalcoholic fatty liver disease (NAFLD) have been previously established. However, how FABP1 expression is dynamically regulated in metabolic disorders is unclear. Previous studies have reported that ubiquitin proteasome-mediated degradation of FABP1 is involved, but the mechanism remains unknown.

Dysregulated expression of hepatic FABP1 and Derlin-1 was observed in NAFLD patients. We performed mice hepatic tissue coimmunoprecipitation based mass spectrum assays. Interaction between Derlin-1 and FABP1, and its impact on FABP1 ubiquitination status was evaluated by coimmunoprecipitation. The role of Derlin-1 in lipid deposition was tested using adenovirus-mediated overexpression in C57BL/6 mice, as well as by Derlin-1 overexpression or knockdown in HepG2 cells.

As a subunit of the endoplasmic reticulum-associated degradation complex, Derlin-1 was negatively associated with NAFLD patients, interacted with and ubiquitinated FABP1. Derlin-1 suppressed FABP1 levels and inhibited lipid deposition through a FABP1-dependent pathway. Additionally, Trim25, an E3 ubiquitin ligase present in the endoplasmic reticulum, was recruited to promote Derlin-1-related polyubiquitylation of FABP1, thereby creating a ubiquitin-associated network for FABP1 regulation. Derlin-1 overexpression ameliorated hepatic steatosis in both C57BL/6 mice and HepG2 cells, and contributed to attenuated weight gain, lower liver weight, and visceral fat mass.

FABP1 was degraded by Derlin-1 through ubiquitin modification. Negative regulation of FABP1 by Derlin-1 overexpression, suppressed lipid metabolism and alleviated lipid deposition in vivo and in vitro. Hence, Derlin-1 activation in hepatocytes may represent a potential therapeutic strategy for NAFLD.

Nonalcoholic fatty liver disease (NAFLD) begins with excessive triglyceride accumulation in the liver, and overly severe hepatic steatosis progresses to nonalcoholic steatohepatitis (NASH), which is characterized by lipid peroxidation, inflammation, and fibrosis. Ubiquitin-specific proteinase 14 (USP14) regulates inflammation, hepatocellular carcinoma and viral infection, but the effect of USP14 on NAFLD is unknown. The aim of this study was to reveal the role of USP14 in the progression of NAFLD and its underlying mechanism. We demonstrated that hepatic USP14 expression was significantly increased in NAFLD in both humans and mice. Hepatic USP14 overexpression exacerbated diet-induced hepatic steatosis, inflammation and fibrosis in mice, in contrast to the results of hepatic USP14 knockdown. Furthermore, palmitic/oleic acid-induced lipid peroxidation and inflammation in hepatocytes were markedly increased by USP14 overexpression but decreased by USP14 knockdown. Notably, in vivo or in vitro data show that USP14 promotes NAFLD progression in a cytochrome p4502E1 (CYP2E1)-dependent manner, which exacerbates hepatocyte oxidative stress, impairs the mitochondrial respiratory chain and inflammation by promoting CYP2E1 protein levels. Mechanistically, we demonstrated by immunoprecipitation and ubiquitination analysis that USP14 inhibits the degradation of heat shock protein 90 alpha family class A member 1 (HSP90AA1) by decreasing its lysine 48-linkage ubiquitination. Meanwhile, upregulation of HAP90AA1 protein promotes CYP2E1 protein accumulation. Collectively, our data indicate that an unknown USP14-HSP90AA1-CYP2E1 axis contributes to NAFLD progression, and we propose that inhibition of USP14 may be an effective strategy for NASH treatment.

The liver ensures organismal homeostasis through modulation of physiological functions over the course of the day. How liver diseases such as nonalcoholic steatohepatitis (NASH) affect daily transcriptome rhythms in the liver remains elusive.

To start closing this gap, we evaluated the impact of NASH on the diurnal regulation of the liver transcriptome in mice. In addition, we investigated how stringent consideration of circadian rhythmicity affects the outcomes of NASH transcriptome analyses.

Comparative rhythm analysis of the liver transcriptome from diet-induced NASH and control mice showed an almost 3-hour phase advance in global gene expression rhythms. Rhythmically expressed genes associated with DNA repair and cell-cycle regulation showed increased overall expression and circadian amplitude. In contrast, lipid and glucose metabolism-associated genes showed loss of circadian amplitude, reduced overall expression, and phase advances in NASH livers. Comparison of NASH-induced liver transcriptome responses between published studies showed little overlap (12%) in differentially expressed genes (DEGs). However, by controlling for sampling time and using circadian analytical tools, a 7-fold increase in DEG detection was achieved compared with methods without time control.

NASH had a strong effect on circadian liver transcriptome rhythms with phase- and amplitude-specific effects for key metabolic and cell repair pathways, respectively. Accounting for circadian rhythms in NASH transcriptome studies markedly improves DEG detection and enhances reproducibility.

The conjugation of neural precursor cell expressed, developmentally downregulated 8 (NEDD8) to target proteins, termed neddylation, participates in many cellular processes and is aberrant in various pathological diseases. Its relevance to liver function and failure remains poorly understood. Herein, we show dysregulated expression of NAE1, a regulatory subunit of the only NEDD8 E1 enzyme, in human acute liver failure. Embryonic- and adult-onset deletion of NAE1 in hepatocytes causes hepatocyte death, inflammation, and fibrosis, culminating in fatal liver injury in mice. Hepatic neddylation deficiency triggers oxidative stress, mitochondrial dysfunction, and hepatocyte reprogramming, potentiating liver injury. Importantly, NF-κB-inducing kinase (NIK), a serine/Thr kinase, is a neddylation substrate. Neddylation of NIK promotes its ubiquitination and degradation. Inhibition of neddylation conversely causes aberrant NIK activation, accentuating hepatocyte damage and inflammation. Administration of N-acetylcysteine, a glutathione surrogate and antioxidant, mitigates liver failure caused by hepatic NAE1 deletion in adult male mice. Therefore, hepatic neddylation is important in maintaining postnatal and adult liver homeostasis, and the identified neddylation targets/pathways provide insights into therapeutically intervening acute liver failure.

Hepatocellular carcinoma (HCC) is the most common primary liver cancer in the world. In malignant liver cancer, the increase of aerobic glycolysis indicates that the possibility of tumorigenesis is greatly enhanced. TRIM37 is a member of the TRIM family of proteins that possesses E3 ubiquitin ligase activity and has been implicated in the occurrence and prognosis of many different tumors. However, the stability of P53 plays an important role in preventing tumorigenesis. The mechanism by which TRIM37 regulates the stability of P53 through ubiquitin in the progression of hepatocellular carcinoma is still unclear.

Real-time quantitative polymerase chain reaction (qRT-PCR) and Western blotting were used to detect the expression of mRNA and protein in HCC cells. Lactic acid production, glucose uptake, and ATP levels were measured by BioVision kit. The following were used to assess the in vitro function of TRIM37 in HCC cells: cell counting kit-8 (CCK-8), colony formation assay, cell migration and invasion assay, and flow cytometry. We observed the effect of TRIM37 on the growth of transplanted tumors in nude mice. Co-Immunoprecipitation (Co-IP) revealed a binding relationship between TRIM37 and P53.

The expression of TRIM37 in hepatocellular carcinoma (HCC) tissues was higher than that of normal tissues according to an analysis of The Cancer Genome Atlas (TCGA) database.Loss-of-function assays indicated that TRIM37 inhibited the proliferation, colony formation, migration, and invasion of liver cancer cells. The mechanism is as follows: TRIM37 interacts with the P53 protein to induce E3 ligase activity, ubiquitination, and degradation, further promoting the malignant characteristics of hepatocellular carcinoma, thus promoting the process of glycolysis. Genetic knockdown of P53 reversed the promoting function of TRIM37 on the growth and metastasis of hepatocellular carcinoma cells.

Our study showed that the TRIM37-P53 axis plays a role in the progression of liver cancer, and thus is a potential target for the treatment of liver cancer.

Alcoholic hepatitis (AH) is the most severe form of alcoholic liver disease for which there is no efficacious treatment aiding most patients. AH manifests differently in individuals, with some patients showing debilitating symptoms more so than others. Previous studies showed significant metabolic dysregulation associated with AH. Therefore, we sought to analyze how the activity of metabolic pathways differed in the liver of patients with varying degrees of AH severity. We utilized a genome-scale metabolic modeling approach that allowed for integration of a generic human cellular metabolic model with specific RNA-seq data corresponding to healthy and multiple liver disease states to predict the metabolic fluxes within each disease state. Additionally, we performed a systems-level analysis of the transcriptomic data and predicted metabolic flux data to identify the regulatory and functional differences in liver metabolism with increasing severity of AH. Our results provide unique insights into the sequential dysregulation of the solute transport mechanisms underlying the glutathione metabolic pathway with increasing AH disease severity. We propose targeting of the solute transporters in the glutathione pathway to mimic the flux activity of the healthy liver state as a potential therapeutic intervention for AH.