Hepatic proteomic analysis of selenoprotein F knockout mice by iTRAQ: An implication for the roles of selenoprotein F in metabolism and diseases

Expanding the Frontiers of Guardian Antioxidant Selenoproteins in Cardiovascular Pathophysiology

Significance: Physiological levels of reactive oxygen and nitrogen species (ROS/RNS) function as fundamental messengers for many cellular and developmental processes in the cardiovascular system. ROS/RNS involved in cardiac redox-signaling originate from diverse sources, and their levels are tightly controlled by key endogenous antioxidant systems that counteract their accumulation. However, dysregulated redox-stress resulting from inefficient removal of ROS/RNS leads to inflammation, mitochondrial dysfunction, and cell death, contributing to the development and progression of cardiovascular disease (CVD). Recent Advances: Basic and clinical studies demonstrate the critical role of selenium (Se) and selenoproteins (unique proteins that incorporate Se into their active site in the form of the 21st proteinogenic amino acid selenocysteine [Sec]), including glutathione peroxidase and thioredoxin reductase, in cardiovascular redox homeostasis, representing a first-line enzymatic antioxidant defense of the heart. Increasing attention has been paid to emerging selenoproteins in the endoplasmic reticulum (ER) (i.e., a multifunctional intracellular organelle whose disruption triggers cardiac inflammation and oxidative stress, leading to multiple CVD), which are crucially involved in redox balance, antioxidant activity, and calcium and ER homeostasis. Critical Issues: This review focuses on endogenous antioxidant strategies with therapeutic potential, particularly selenoproteins, which are very promising but deserve more detailed and clinical studies. Future Directions: The importance of selective selenoproteins in embryonic development and the consequences of their mutations and inborn errors highlight the need to improve knowledge of their biological function in myocardial redox signaling. This could facilitate the development of personalized approaches for the diagnosis, prevention, and treatment of CVD. Antioxid. Redox Signal. 40, 369-432.

LncRNA Tug1 relieves the steatosis of SelenoF-knockout hepatocytes via sponging miR-1934-3p

Metabolic dysfunction associated with fatty liver disease (MAFLD), always accompanied by disturbance of glucose and lipid metabolism, is becoming the most difficult obstacle in the next decades. In the current research, we uncover that the potent non-coding RNA Tug1, which is related to metabolic enzymes, regulates hepatocytes steatosis induced by sodium palmitate via miR-1934-3p absorbing. The knockdown of lncRNA-Tug1 distinctly rescues the increased expression level of glycolytic enzymes and fatty acid synthetase via releasing more mature miR-1934-3p in hepatocytes. Moreover, miR-1934-3p suppresses Selenoprotein F (SelenoF) through binding with the SelenoF 3'UTR effectors; importantly, we demonstrated that the deletion of SelenoF consistent with the lncRNA-Tug1's effecting on metabolism enzymes. In the current paper, the interaction of Tug1/miR-1934-3p/SelenoF was verified by the dual-luciferase reporter system, and IRS1/AKT pathway possesses the essential role in glucolipid metabolism when SelenoF is deleted. We concluded that lncRNA Tug1 functioned as ceRNA to alleviate steatosis and glycolysis in hepatocytes of C57BL/6 through adsorbing miR-1934-3p to release SelenoF and triggering IRS/AKT pathway. The Tug1/miR-1934-3p/SelenoF constructed the ceRNA interact network Selenoprotein F accelerates glucolipid metabolism via IRS1/AKT pathway SelenoF-/- alleviates steatosis in mice liver.

SELENOF Controls Proliferation and Cell Death in Breast-Derived Immortalized and Cancer Cells

SELENOF expression is significantly lower in aggressive breast tumors compared to normal tissue, indicating that its reduction or loss may drive breast tumorigenesis. Deletion of SELENOF in non-tumorigenic immortalized breast epithelial MCF-10A cells resulted in enhanced proliferation, both in adherent culture and matrix-assisted three-dimmensional (3D) growth. Modulation of SELENOF in vitro through deletion or overexpression corresponded to changes in the cell-cycle regulators p21 and p27, which is consistent with breast tumor expression data from the METABRIC patient database. Together, these findings indicate that SELENOF affects both proliferation and cell death in normal epithelial and breast cancer cells, largely through the regulation of p21 and p27. In glandular cancers like breast cancer, the filling of luminal space is one of the hallmarks of early tumorigenesis. Loss of SELENOF abrogated apoptosis and autophagy, which are required for the formation of hollow acini in MCF-10A cells in matrix-assisted 3D growth, resulting in luminal filling. Conversely, overexpression of SELENOF induced cell death via apoptosis and autophagy. In conclusion, these findings are consistent with the notion that SELENOF is a breast tumor suppressor, and its loss contributes to breast cancer etiology.

Distinct Roles of SELENOF in Different Human Cancers

SELENOF, previously known as SEP15, is a selenoprotein that contains selenium in the form of the amino acid selenocysteine. Like other selenoproteins, the role for SELENOF in carcinogenesis has been investigated due to its altered expression compared to the corresponding normal tissue, its molecular function, and the association of genetic variations in the SELENOF gene to cancer risk or outcome. This review summarizes SELENOF’s discovery, structure, cellular localization, and expression. SELENOF belongs to a new family of thioredoxin-like proteins. Published data summarized here indicate a likely role for SELENOF in redox protein quality control, and in the regulation of lipids, glucose, and energy metabolism. Current evidence indicates that loss of SELENOF contributes to the development of prostate and breast cancer, while its loss may be protective against colon cancer. Additional investigation into SELENOF’s molecular mechanisms and its impact on cancer is warranted.

Selenoprotein F (SELENOF)-mediated AKT1-FOXO3a-PYGL axis contributes to selenium supranutrition-induced glycogenolysis and lipogenesis

Mounting evidence showed that excess selenium (10.0-15.0-fold of adequate Se) intake caused severe hepatic lipid deposition in the vertebrate. However, the underlying mechanism remains unclear. The study was performed to elucidate the mechanism of Se supranutrition mediated-changes of lipid deposition and metabolism. We found that dietary excessive Se addition increased hepatic TGs and glucose contents, up-regulated lipogenic enzyme activities and reduced hepatic glycogen contents. Transcriptomic and immunoblotting analysis showed that Se supranutrition significantly influenced serine/threonine kinase 1 (AKT1)-forkhead box O3a (FOXO3a)-PYGL signaling and protein levels of SELENOF. Knockdown of SELENOF and PYGL by RNA interference revealed that the AKT1-FOXO3a-PYGL axis was critical for Se supranutrition-induced lipid accumulation. Moreover, Se supranutrition-induced lipid accumulation was via the increased DNA binding capacity of FOXO3a to PYGL promoter, which increased glycogenolysis, and accordingly promoted lipogenesis and lipid accumulation. Our finding provides new insight into the mechanism of Se supranutrition-induced lipid accumulation and suggests that SELENOF may be a therapeutic target for Se supranutrition induced-lipid disorders in the vertebrates.

iTRAQ-based quantitative proteomic analysis of Pelteobagrus vachelli liver in response to hypoxia

Dissolved oxygen is one of the determinants in the healthy farming of Pelteobagrus vachelli. This study, we conducted quantitative proteomics on the juvenile P. vachelli livers using iTRAQ. P. vachelli were treated by 3.75 ± 0.25 mg O₂/L (hypoxia group) and 7.25 ± 0.25 mg O₂/L (control group) for 90 days. The results revealed that under hypoxic conditions, P. vachelli grew slower than control group. Proteomic profiling enabled us to identify 2618 proteins, of which 176 were significantly differentially abundant proteins (DAPs). Verification of protein regulation based on qRT-PCR indicated that the proteomics data were reliable. The top 20 significantly DAPs (10 up-regulated, 10 down-regulated) were primarily involved in energy metabolism, apoptosis inhibition, and heavy metal detoxification. KEGG pathway enrichment analysis revealed significant enrichment of 'protein digestion and absorption', 'glycolysis/gluconeogenesis', and 'phagosome'. Combining the proteomics results of short-term hypoxia (treated with 0.70 ± 0.10 mg O₂ /L for 4 h), we screened 36 common DAPs. The analysis of the 36 common DAPs indicated that P. vachelli responded to the hypoxia by regulating energy supply, inhibiting apoptosis, and disturbing defensive system. Our results lay a theoretical foundation for the cultivation of hypoxia-tolerant species and eco-breeding of P. vachelli. SIGNIFICANCE OF THE STUDY: The hypoxia tolerance of Pelteobagrus vachelli is poor, which will seriously lead to its death in high-density culture. This study analysed the liver proteome of P. vachelli under long-term hypoxia stress (treated for 90 days at 3.75 ± 0.25 mg O₂/L), and then combined the proteome results of short-term hypoxia stress (treated for 4 h at 0.70 ± 0.10 mg O₂/L). The results showed P. vachelli responded to the hypoxia by regulating energy supply, inhibiting apoptosis and disturbing defensive system. The study contributes to the breeding of new hypoxia-tolerant species of P. vachelli and lays the theoretical foundation for eco-breeding.

Loss of SELENOF Induces the Transformed Phenotype in Human Immortalized Prostate Epithelial Cells

SELENOF is a member of the class of selenoproteins in which the amino acid selenocysteine is co-translationally inserted into the elongating peptide in response to an in-frame UGA codon located in the 3′-untranslated (3′-UTR) region of the SELENOF mRNA. Polymorphisms in the 3′-UTR are associated with an increased risk of dying from prostate cancer and these variations are functional and 10 times more frequent in the genomes of African American men. SELENOF is dramatically reduced in prostate cancer compared to benign adjacent regions. Using a prostate cancer tissue microarray, it was previously established that the reduction of SELENOF in the cancers from African American men was significantly greater than in cancers from Caucasian men. When SELENOF levels in human prostate immortalized epithelial cells were reduced with an shRNA construct, those cells acquired the ability to grow in soft agar, increased the ability to migrate in a scratch assay and acquired features of energy metabolism associated with prostate cancer. These results support a role of SELENOF loss in prostate cancer progression and further indicate that SELENOF loss and genotype may contribute to the disparity in prostate cancer mortality experienced by African American men.

Hepatic Proteomic Analysis of Selenoprotein T Knockout Mice by TMT: Implications for the Role of Selenoprotein T in Glucose and Lipid Metabolism

Selenoprotein T (SELENOT, SelT), a thioredoxin-like enzyme, exerts an essential oxidoreductase activity in the endoplasmic reticulum. However, its precise function remains unknown. To gain more understanding of SELENOT function, a conventional global Selenot knockout (KO) mouse model was constructed for the first time using the CRISPR/Cas9 technique. Deletion of SELENOT caused male sterility, reduced size/body weight, lower fed and/or fasting blood glucose levels and lower fasting serum insulin levels, and improved blood lipid profile. Tandem mass tag (TMT) proteomics analysis was conducted to explore the differentially expressed proteins (DEPs) in the liver of male mice, revealing 60 up-regulated and 94 down-regulated DEPs in KO mice. The proteomic results were validated by western blot of three selected DEPs. The elevated expression of Glycogen [starch] synthase, liver (Gys2) is consistent with the hypoglycemic phenotype in KO mice. Furthermore, the bioinformatics analysis showed that Selenot-KO-induced DEPs were mainly related to lipid metabolism, cancer, peroxisome proliferator-activated receptor (PPAR) signaling pathway, complement and coagulation cascades, and protein digestion and absorption. Overall, these findings provide a holistic perspective into SELENOT function and novel insights into the role of SELENOT in glucose and lipid metabolism, and thus, enhance our understanding of SELENOT function.

Se-Methylselenocysteine (SMC) Improves Cognitive Deficits by Attenuating Synaptic and Metabolic Abnormalities in Alzheimer's Mice Model: A Proteomic Study

Se-methylselenocysteine (SMC) is a major selenocompound in selenium (Se) enriched plants and has been found to ameliorate neuropathology and cognitive deficits in triple-transgenic mice model of Alzheimer's disease (3 × Tg-AD mice). To explore the underlying molecular mechanisms, the present study is designed to elucidate the protein changes in the cortex of SMC-treated 3 × Tg-AD mice. After SMC supplementation, proteomic analysis revealed that 181, 271, and 41 proteins were identified as differentially expressed proteins (DEPs) between 3 × Tg-AD mice vs wild type (AD/WT group), SMC-treated AD mice vs AD (AD + SMC/AD), and AD + SMC/WT group, respectively. Among these, 138 proteins in the diseased group were reversed by SMC treatment. The DEPs in AD/WT group and AD + SMC/AD group were mainly related to metabolism, synapses, and antioxidant proteins, while their levels were decreased in AD mice but up-regulated after treating with SMC. In addition, we found reduced ATP levels and destroyed synaptic structures in the AD mice brains, which were significantly ameliorated upon SMC treatment. Our study suggests that energy metabolism disorders, abnormal amino acid metabolism, synaptic dysfunction, and oxidative stress may be the key pathogenic phenomena of AD. SMC reversed the expression of proteins associated with them, which might be the main mechanism of its intervention in AD.

TMT-based quantitative proteomic analysis of hepatic tissue reveals the effects of dietary cyanidin-3-diglucoside-5-glucoside-rich extract on alleviating D-galactose-induced aging in mice

Cyanidin-3-diglucoside-5-glucoside (CY3D5G) derivatives as major pigments in red cabbage exhibit in vitro antioxidant effects. This study evaluated the effects of CY3D5G-rich extract on oxidative stress in D-galactose-induced accelerated aging. Thirty male C57BL/6 J mice were divided into three groups: a normal control group and two D-galactose-injected groups orally administered with or without CY3D5G-rich extract (700 μmol/kg body weight). Dietary supplementation of CY3D5G-rich extract for 6 weeks increased superoxide dismutase activity, glutathione peroxidase activity, and total antioxidant capacity while suppressed malondialdehyde content in serum (p < 0.05) and tissues. Hepatic proteome analysis revealed that 243 proteins were significantly modulated by experimental treatment (p < 0.05). CY3D5G-rich extract treatment suppressed proteins involved in electron transport chain and up-regulated proteins that play important roles in glycolysis, tricarboxylic acid cycle, and actin cytoskeleton. These changes in above metabolic pathways may contribute to reducing the production and release of ROS and attenuating oxidative damage in aged mice. SIGNIFICANCE: Anthocyanins are the most abundant dietary flavonoids with potential health benefits. The proteomic analysis of mice liver in this study revealed the effect of cyanidin-3-diglucoside-5-glucoside (CY3D5G) consumption in D-galactose-induced accelerated aging. In total, 2054 protein groups were quantified in all samples without any missing value, and 243 protein groups were identified with statistical significance (p < 0.05). Bioinformatics analysis suggested that electron transport chain, glycolysis, tricarboxylic acid cycle, and actin cytoskeleton were closely correlated with CY3D5G treatment. These findings provide useful information to understand the anti-aging effect of anthocyanin, and the results of which could promote the use of anthocyanins in food and pharmaceutical industries.

The acaricidal mechanism and active compounds against Psoroptes cuniculi of the methanol extract of Adonis coerulea Maxim II: Integrated proteomics and SPR analysis

Adonis coerulea Maxim. as a folk medicine, presented acaricidal acitvity. However, the mode of action and active compounds were unclear. In this study, using proteomics and surface plasmon resonance (SPR) technology the mode of action and active compounds of A. coerulea were investigated, as well as a sensitive and environmentally friendly analytical method developed. Proteomics analysis results showed that after treatment of mites with A. coerulea methanol extract (MEAC), 135 proteins were differentially expressed, most of them enriched in the myocardium pathway and participated in the function of the inflated cystic organ. Na+-K+-ATPase may be a potential target. Then, it was used as a target to capture the compounds from the extract using a SPR test. Twelve compounds were found, five compounds, namely ellagic acid, ouabain, convallatoxin, strophanthidin and cymarin presented the higher affinity with Na+-K+-ATPase in molecular docking test. Further study showed that the latter four compounds presented the stronger cytotoxicity and the inhibitory effect on Na+-K+-ATPase with IC50 values ranging with 2.38-0.56 μg/mL, and also showed toxicity against Psoroptes cuniculi. These results indicated that MEAC presented toxicity against mites by inhibiting Na+-K+-ATPase, and cardiac glycosides may be active compounds of this plant in terms of its acaricidal activity. Only 10 g of plant was used to investigate its active compounds. This study lays the foundation for developing sensitive methods for active compound detection.