SCF FBXW17 E3 ubiquitin ligase regulates FBXL19 stability and cell migration

Molecular Regulation of Transforming Growth Factor-β1-induced Thioredoxin-interacting Protein Ubiquitination and Proteasomal Degradation in Lung Fibroblasts: Implication in Pulmonary Fibrosis

Thioredoxin-interacting protein (TXNIP) plays a critical role in regulation of cellular redox reactions and inflammatory responses by interacting with thioredoxin (TRX) or the inflammasome. The role of TXNIP in lung fibrosis and molecular regulation of its stability have not been well studied. Therefore, here we investigated the molecular regulation of TXNIP stability and its role in TGF-β1-mediated signaling in lung fibroblasts. TXNIP protein levels were significantly decreased in lung tissues from bleomycin-challenged mice. Overexpression of TXNIP attenuated transforming growth factor-β1 (TGF-β1)-induced phosphorylation of Smad2/3 and fibronectin expression in lung fibroblasts, suggesting that decrease in TXNIP may contribute to the pathogenesis of lung fibrosis. Further, we observed that TGF-β1 lowered TXNIP protein levels, while TXNIP mRNA levels were unaltered by TGF-β1 exposure. TGF-β1 induced TXNIP degradation via the ubiquitin-proteasome system. A serine residue mutant (TNXIP-S308A) was resistant to TGF-β1-induced degradation. Furthermore, downregulationof ubiquitin-specific protease-13 (USP13) promoted the TGF-β1-induced TXNIP ubiquitination and degradation. Mechanistic studies revealed that USP13 targeted and deubiquitinated TXNIP. The results of this study revealed that the decrease of TXNIP in lungs apparently contributes to the pathogenesis of pulmonary fibrosis and that USP13 can target TXNP for deubiquitination and regulate its stability.

FBXL19 promotes malignant behaviours by activating MAPK signalling and negatively correlates with prognosis in hepatocellular carcinoma

FBXL19 is a member of the Skp1-Cullin-F-box family of E3 ubiquitin ligases and is linked to a variety of vital biological processes, such as cell proliferation, migration, and differentiation. Previous studies have identified it as an oncogene in breast cancer and glioma. However, its role in hepatocellular carcinoma (HCC) remains unclear. To comprehensively elucidate its role in tumour biology and its underlying mechanisms, a variety of sophisticated methods, including bioinformatics analysis, RNA-sequencing technique, and in vitro cell biology experiments, were used. Here, we found that FBXL19 was upregulated in patients with HCC and correlated with poor prognosis. In in vitro experiments, the specific targeting of short hairpin RNAs via lentiviruses successfully induced the knockdown of FBXL19, resulting in notable inhibition of the proliferation, migration, and invasion of HCC cells. Furthermore, FBXL19 downregulation resulted in significant induction of G0/G1 phase cell cycle arrest. Importantly, FBXL19 knockdown inhibited tumour malignant behaviour primarily by inactivating extracellular signal-regulated protein kinase 1/2 and p38 mitogen-activated protein kinases. In conclusion, this study revealed that FBXL19 was upregulated in patients with HCC, and that its expression was negatively correlated with prognosis. Thus, FBXL19 displays oncogenic properties in HCC by activating mitogen-activated protein kinase signalling.

Osteocytes directly regulate osteolysis via MYD88 signaling in bacterial bone infection

The impact of bone cell activation on bacterially-induced osteolysis remains elusive. Here, we show that matrix-embedded osteocytes stimulated with bacterial pathogen-associated molecular patterns (PAMPs) directly drive bone resorption through an MYD88-regulated signaling pathway. Mice lacking MYD88, primarily in osteocytes, protect against osteolysis caused by calvarial injections of bacterial PAMPs and resist alveolar bone resorption induced by oral Porphyromonas gingivalis (Pg) infection. In contrast, mice with targeted MYD88 restoration in osteocytes exhibit osteolysis with inflammatory cell infiltration. In vitro, bacterial PAMPs induce significantly higher expression of the cytokine RANKL in osteocytes than osteoblasts. Mechanistically, activation of the osteocyte MYD88 pathway up-regulates RANKL by increasing binding of the transcription factors CREB and STAT3 to Rankl enhancers and by suppressing K48-ubiquitination of CREB/CREB binding protein and STAT3. Systemic administration of an MYD88 inhibitor prevents jawbone loss in Pg-driven periodontitis. These findings reveal that osteocytes directly regulate inflammatory osteolysis in bone infection, suggesting that MYD88 and downstream RANKL regulators in osteocytes are therapeutic targets for osteolysis in periodontitis and osteomyelitis.

Fbxw17 is dispensable for viability and fertility in mice

BACKGROUND

Skp1-Cullin-F-box (SCF) E3 ligase complex plays an important role in regulating spermatogenesis and fertility in mice. As a member of F-box proteins, the function of F-box and WD-40 domain protein 17 (Fbxw17) during spermatogenesis and fertility is unclear. In this study, we illustrate its function for spermatogenesis and fertility.

METHODS AND RESULTS

Here, we generated the Fbxw17 knockout (KO) mouse model by using the CRISPR/Cas9 system and analyzed the meiotic process and the fertility. Then, our results demonstrated that testis and sperm in the Fbxw17 KO mice had normal morphology. The testis weight, sperm count and fertility of Fbxw17 KO mice showed no significant difference compared with the wild-type mice. Subsequently, histological analysis of Fbxw17 KO mice revealed apparently normal germ cells of all stages and mature spermatozoa. Meanwhile, nuclear spread analysis showed that the synaptonemal complex formation and DSB repair proceeded normally in Fbxw17-deficient spermatocytes. Furthermore, we didn't find defects in the meiotic prophase I spermatocytes and germ cells showed no apparent apoptosis in Fbxw17 KO mice.

CONCLUSIONS

Our results show that Fbxw17 is dispensable for fertility in mice.

Circulating non-coding RNAs as new biomarkers and novel therapeutic targets in colorectal cancer

Colorectal cancer (CRC) is one of the most common malignant tumors, and a large number of patients are diagnosed and die every year. Due to the lack of appropriate diagnosis, prediction and treatment, early diagnosis rate of CRC is low and the prognosis is poor. Studies have found that abnormally expressed non-coding RNAs (ncRNAs) (including microRNAs (miRNAs), circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs),etc.) play an important regulatory role in the occurrence and development of CRC. Some studies have shown that they are stable in the blood and can be detected repeatedly. They are expected to be non-invasive biomarkers for early diagnosis, prognosis evaluation, and prediction of drug sensitivity of CRC, as well as potential applications in the treatment of CRC.

F-Box Protein FBXW17-Mediated Proteasomal Degradation of Protein Methyltransferase PRMT6 Exaggerates CSE-Induced Lung Epithelial Inflammation and Apoptosis

Chronic obstructive pulmonary disease (COPD) is a chronic debilitating lung disease, characterized by progressive airway inflammation and lung structural cell death. Cigarette smoke is considered the most common risk factor of COPD pathogenesis. Understanding the molecular mechanisms of persistent inflammation and epithelial apoptosis induced by cigarette smoke would be extremely beneficial for improving the treatment and prevention of COPD. A histone methyl modifier, protein arginine N-methyltransferase 6 (PRMT6), is reported to alleviate cigarette smoke extract (CSE)-induced emphysema through inhibiting inflammation and cell apoptosis. However, few studies have focused on the modulation of PRMT6 in regulating inflammation and cell apoptosis. In this study, we showed that protein expression of PRMT6 was aberrantly decreased in the lung tissue of COPD patients and CSE-treated epithelial cells. FBXW17, a member of the Skp1-Cullin-F-box (SCF) family of E3 ubiquitin ligases, selectively bound to PRMT6 in nuclei to modulate its elimination in the proteasome system. Proteasome inhibitor or silencing of FBXW17 abrogated CSE-induced PRMT6 protein degradation. Furthermore, negative alteration of FBXW17/PRMT6 signaling lessened the proapoptotic and proinflammatory effects of CSE in lung epithelial cells. Our study, therefore, provides a potential therapeutic target against the airway inflammation and cell death in CS-induced COPD.