RING-finger protein 5 promotes hepatocellular carcinoma progression and predicts poor prognosis

RING finger protein 5 protects against acute myocardial infarction by inhibiting ASK1

BACKGROUND

Myocardial infarction (MI) is a major disease with high morbidity and mortality worldwide. However, existing treatments are far from satisfactory, making the exploration of potent molecular targets more imperative. The E3 ubiquitin ligase RING finger protein 5 (RNF5) has been previously reported to be involved in several diseases by regulating ubiquitination-mediated protein degradation. Nevertheless, few reports have focused on its function in cardiovascular diseases, including MI.

METHODS

In this study, we established RNF5 knockout mice through precise CRISPR-mediated genome editing and utilized left anterior descending coronary artery ligation in 9-11-week-old male C57BL/6 mice. Subsequently, serum biochemical analysis and histopathological examination of heart tissues were performed. Furthermore, we engineered adenoviruses for modulating RNF5 expression and subjected neonatal rat cardiomyocytes to oxygen-glucose deprivation (OGD) to mimic ischemic conditions, demonstrating the impact of RNF5 manipulation on cellular viability. Gene and protein expression analysis provided insights into the molecular mechanisms. Statistical methods were rigorously employed to assess the significance of experimental findings.

RESULTS

We found RNF5 was downregulated in infarcted heart tissue of mice and NRCMs subjected to OGD treatment. RNF5 knockout in mice resulted in exacerbated heart dysfunction, more severe inflammatory responses, and increased apoptosis after MI surgery. In vitro, RNF5 knockdown exacerbated the OGD-induced decline in cell activity, increased apoptosis, while RNF5 overexpression had the opposite effect. Mechanistically, it was proven that the kinase cascade initiated by apoptosis signal-regulating kinase 1 (ASK1) activation was closely regulated by RNF5 and mediated RNF5's protective function during MI.

CONCLUSIONS

We demonstrated the protective effect of RNF5 on myocardial infarction and its function was dependent on inhibiting the activation of ASK1, which adds a new regulatory component to the myocardial infarction associated network and promises to enable new therapeutic strategy.

CEUS in prediction of early recurrence of hepatocellular carcinoma after curative resection and to stratify the risk of early recurrence: a retrospective observational study

PURPOSE

Early recurrence (ER) after surgery is related to early death in patients with hepatocellular carcinoma (HCC) after radical resection. To explore the role of preoperative contrast-enhanced ultrasound (CEUS) in predicting ER of HCC after curative resection and to stratify the risk of ER.

MATERIALS AND METHODS

This study evaluated consecutive 556 patients with HCC who were examined by CEUS during the 2 weeks before curative resection between January 2011 and December 2018. ER was defined as intrahepatic and/or extrahepatic recurrence within 2 year after resection of HCC. Univariate and logistic regression analyses were performed to identify independent risk factors for ER after surgical resection of HCC. Recurrence-free time (RFS) rates were analyzed and compared by log-rank test.

RESULTS

ER occurred in 307 (55.2%) of the 556 patients. Univariate and multivariate analyses revealed that a tumor size ≥ 30 mm and satellite nodules seen on CEUS, DL(deep learning) radiomics reoccurrence score based on the frame of image with the maximum intensity of CEUS and an elevated alpha-fetoprotein level were significantly associated with ER (P < .05). Based on the number of predictors present, patients with CEUS LR-5 HCC were stratified into three risk subgroups: risk group 3 (high-risk patients, 4 predictors), risk group 2 (medium-risk patients, 2-3 predictors), and risk group 1 (low-risk patients, 0-1 predictor). The 2-year RFS rate was 19.4% in risk group 3, 40.9% in risk group 2, and 48.1% in risk group 1; the corresponding mean RFS times were 14.0 ± 2.9 months, 43.7 ± 6.6 months, and 55.5 ± 2.8 months, respectively (P < .001).

CONCLUSIONS

Tumor size ≥ 30 mm and satellite nodules seen on CEUS, DL radiomics reoccurrence score based on the frame of image with the maximum intensity of CEUS and an elevated alpha-fetoprotein level can predict ER of HCC.

THE ROLE OF N6-METHYLADENOSINE METHYLTRANSFERASE RBM15 IN NONALCOHOLIC FATTY LIVER DISEASE

ABSTRACT

Nonalcoholic fatty liver disease (NAFLD) is a prevalent liver disorder with significant health implications. N6-methyladenosine (m6A) methyltransferase is known to exert regulatory functions in liver-related diseases. This study investigates the intricate role of RNA binding motif protein 15 (RBM15) in modulating inflammation and oxidative stress in NAFLD. An NAFLD model was induced in mice (male, C57BL/6J, 72 mice in the sham group) through a high-fat diet for 9 weeks, and hepatocytes were exposed to long chain-free fatty acids. The expression levels of RBM15, ring finger protein 5 (RNF5), and rho-kinase 1 (ROCK1) were assessed. RBM15 expression was intervened (injection of AAV9 virus at week 9 and detection at week 11). Liver damage was evaluated using staining assays, along with assessments of weight changes and lipid levels. Notably, RBM15 (decreased approximately 40%/60%) and RNF5 (decreased approximately 60%/75%) were poorly expressed while ROCK1 (increased approximately 2.5-fold) was highly expressed in liver tissues and cells. RBM15 overexpression mitigated liver damage, inflammation, and oxidative stress in NAFLD mice, resulting in reduced liver-to-body weight ratio (20%) and decreased levels of alanine aminotransferase (54%), aspartate aminotransferase (36%), total cholesterol (30%), and triglycerides (30%), and inhibited inflammation and oxidative stress levels. Mechanistically, RBM15 upregulated RNF5 expression through m6A methylation modification, and RNF5 suppressed ROCK1 protein levels through ubiquitination modification. RNF5 knockdown or ROCK1 overexpression accelerated inflammation and oxidative stress in NAFLD. Taken together, RBM15 upregulated RNF5 expression through m6A methylation modification. RNF5 inhibited ROCK1 expression through ubiquitination modification to mitigate NAFLD.

Downregulation of EphA2 stability by RNF5 limits its tumor-suppressive function in HER2-negative breast cancers

Ephrin receptor A2 (EphA2) plays dual functions in tumorigenesis through ligand-independent tumor promotion or ligand-dependent tumor suppression. However, the regulation of EphA2 tumor-suppressive function remains unclear. Here, we showed that RNF5 interacts with EphA2 and induces its ubiquitination and degradation, decreases the stability and cell surface distribution of EphA2 and alters the balance of its phosphorylation at S897 and Y772. In turn, RNF5 inhibition decreases ERK phosphorylation and increases p53 expression through an increase in the EphA2 level in HER2-negative breast cancer cells. Consequently, RNF5 inhibition increases the adhesion and decreases the migration of HER2-negative breast cancer cells, and RNF5 silencing suppresses the growth of xenograft tumors derived from ER-positive, HER2-negative breast cancer cells with increased EphA2 expression and altered phosphorylation. RNF5 expression is inversely correlated with EphA2 expression in breast cancers, and a high EphA2 level accompanied by a low RNF5 level is related to better survival in patients with ER-positive, HER2-negative breast cancers. These studies revealed that RNF5 negatively regulates EphA2 properties and suppresses its tumor-suppressive function in HER2-negative breast cancers.

Suppression of KSHV lytic replication and primary effusion lymphoma by selective RNF5 inhibition

Primary effusion lymphoma (PEL), a rare aggressive B-cell lymphoma in immunosuppressed patients, is etiologically associated with oncogenic γ-herpesvirus infection. Chemotherapy is commonly used to treat PEL but usually results in poor prognosis and survival; thus, novel therapies and drug development are urgently needed for PEL treatment. Here, we demonstrated that inhibition of Ring finger protein 5 (RNF5), an ER-localized E3 ligase, suppresses multiple cellular pathways and lytic replication of Kaposi sarcoma-associated herpesvirus (KSHV) in PEL cells. RNF5 interacts with and induces Ephrin receptors A3 (EphA3) and EphA4 ubiquitination and degradation. RNF5 inhibition increases the levels of EphA3 and EphA4, thereby reducing ERK and Akt activation and KSHV lytic replication. RNF5 inhibition decreased PEL xenograft tumor growth and downregulated viral gene expression, cell cycle gene expression, and hedgehog signaling in xenograft tumors. Our study suggests that RNF5 plays the critical roles in KSHV lytic infection and tumorigenesis of primary effusion lymphoma.

E3 ubiquitin ligase RNF5 attenuates pathological cardiac hypertrophy through STING

Ring-finger protein 5 (RNF5) is an E3 ubiquitin ligase which is expressed in a variety of human tissues. RNF5 is involved in the regulation of endoplasmic reticulum stress, inflammation, and innate immunity and plays an important role in the occurrence and development of various tumors. However, the role of RNF5 in cardiac hypertrophy has not been reported. In this study, we found the expression of RNF5 was increased in the hearts of mice with pathological cardiac hypertrophy. The loss-of-function research demonstrated that RNF5 deficiency exacerbated cardiac hypertrophy, whereas gain-of-function studies revealed that overexpression of RNF5 had opposite effects. The stimulator of interferon genes (STING) is a signaling molecule that can activate type I interferon immunity, which can meditate inflammation and immune response in many diseases. The protein-protein interaction experiments confirmed that STING interacted with RNF5. Further studies showed that RNF5 inhibited cardiac hypertrophy by promoting STING degradation through K48-linked polyubiquitination. Therefore, we defined RNF5 as importantly regulated signaling for cardiac hypertrophy.

Targeting of Ubiquitin E3 Ligase RNF5 as a Novel Therapeutic Strategy in Neuroectodermal Tumors

RNF5, an endoplasmic reticulum (ER) E3 ubiquitin ligase, participates to the ER-associated protein degradation guaranteeing the protein homeostasis. Depending on tumor model tested, RNF5 exerts pro- or anti-tumor activity. The aim of this study was to elucidate the controversial role of RNF5 in neuroblastoma and melanoma, two neuroectodermal tumors of infancy and adulthood, respectively. RNF5 gene levels are evaluated in publicly available datasets reporting the gene expression profile of melanoma and neuroblastoma primary tumors at diagnosis. The therapeutic effect of Analog-1, an RNF5 pharmacological activator, was investigated on in vitro and in vivo neuroblastoma and melanoma models. In both neuroblastoma and melanoma patients the high expression of RNF5 correlated with a better prognostic outcome. Treatment of neuroblastoma and melanoma cell lines with Analog-1 reduced cell viability by impairing the glutamine availability and energy metabolism through inhibition of F1Fo ATP-synthase activity. This latter event led to a marked increase in oxidative stress, which, in turn, caused cell death. Similarly, neuroblastoma- and melanoma-bearing mice treated with Analog-1 showed a significant delay of tumor growth in comparison to those treated with vehicle only. These findings validate RNF5 as an innovative drug target and support the development of Analog-1 in early phase clinical trials for neuroblastoma and melanoma patients.