PRMT5-TRIM21 interaction regulates the senescence of osteosarcoma cells by targeting the TXNIP/p21 axis

Trim21 Regulates the Postnatal Development and Thermogenesis of Brown Adipose Tissue

Brown adipose tissue undergoes rapid postnatal development to mature and plays a crucial role in thermoregulation and energy expenditure, which protects against cold and obesity. Herein, it is shown that the expression of Trim21 mRNA level of interscapular brown adipose tissue elevates after birth, and peaks at P14 (postnatal day 14). Trim21 depletion severely impairs the maturation of interscapular brown adipose tissue, decreases the expression of a series of thermogenic genes, and reduces energy expenditure. Consistently, the loss of Trim21 also leads to a suppression of white adipose tissue "browning", in response to cold exposure and a β-adrenergic agonist, CL316,243. In addition, Trim21-/- mice are more prone to high-fat diet-induced obesity compared with the control littermates. Taken together, the study for the first time reveals a critical role of Trim21 in regulating iBAT postnatal development and thermogenesis.

The role of TXNIP in cancer: a fine balance between redox, metabolic, and immunological tumor control

Thioredoxin-interacting protein (TXNIP) is commonly considered a master regulator of cellular oxidation, regulating the expression and function of Thioredoxin (Trx). Recent work has identified that TXNIP has a far wider range of additional roles: from regulating glucose and lipid metabolism, to cell cycle arrest and inflammation. Its expression is increased by stressors commonly found in neoplastic cells and the wider tumor microenvironment (TME), and, as such, TXNIP has been extensively studied in cancers. In this review, we evaluate the current literature regarding the regulation and the function of TXNIP, highlighting its emerging role in modulating signaling between different cell types within the TME. We then assess current and future translational opportunities and the associated challenges in this area. An improved understanding of the functions and mechanisms of TXNIP in cancers may enhance its suitability as a therapeutic target.

Trim21 depletion alleviates bone loss in osteoporosis via activation of YAP1/β-catenin signaling

Despite the diverse roles of tripartite motif (Trim)-containing proteins in the regulation of autophagy, the innate immune response, and cell differentiation, their roles in skeletal diseases are largely unknown. We recently demonstrated that Trim21 plays a crucial role in regulating osteoblast (OB) differentiation in osteosarcoma. However, how Trim21 contributes to skeletal degenerative disorders, including osteoporosis, remains unknown. First, human and mouse bone specimens were evaluated, and the results showed that Trim21 expression was significantly elevated in bone tissues obtained from osteoporosis patients. Next, we found that global knockout of the Trim21 gene (KO, Trim21-/-) resulted in higher bone mass compared to that of the control littermates. We further demonstrated that loss of Trim21 promoted bone formation by enhancing the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) and elevating the activity of OBs; moreover, Trim21 depletion suppressed osteoclast (OC) formation of RAW264.7 cells. In addition, the differentiation of OCs from bone marrow-derived macrophages (BMMs) isolated from Trim21-/- and Ctsk-cre; Trim21f/f mice was largely compromised compared to that of the littermate control mice. Mechanistically, YAP1/β-catenin signaling was identified and demonstrated to be required for the Trim21-mediated osteogenic differentiation of BMSCs. More importantly, the loss of Trim21 prevented ovariectomy (OVX)- and lipopolysaccharide (LPS)-induced bone loss in vivo by orchestrating the coupling of OBs and OCs through YAP1 signaling. Our current study demonstrated that Trim21 is crucial for regulating OB-mediated bone formation and OC-mediated bone resorption, thereby providing a basis for exploring Trim21 as a novel dual-targeting approach for treating osteoporosis and pathological bone loss.

p53 in senescence - it's a marathon, not a sprint

The tumour suppressor p53, a stress-responsive transcription factor, plays a central role in cellular senescence. The role of p53 in senescence-associated stable proliferative arrest has been extensively studied. However, increasing evidence indicates that p53 also modulates the ability of senescent cells to produce and secrete diverse bioactive factors (collectively called the senescence-associated secretory phenotype, SASP). Senescence has been linked with both physiological and pathological conditions, the latter including ageing, cancer and other age-related disorders, in part through the SASP. Cellular functions are generally dictated by the expression profile of lineage-specific genes. Indeed, expression of SASP factors and their regulators are often biased by cell type. In addition, emerging evidence suggests that p53 contributes to deregulation of more stringent lineage-specific genes during senescence. P53 itself is also tightly regulated at the protein level. In contrast to the rapid and transient activity of p53 upon stress ('acute-p53'), during senescence and other prolonged pathological conditions, p53 activities are sustained and fine-tuned through a combination of different inputs and outputs ('chronic-p53').

ZSWIM1 Promotes the Proliferation and Metastasis of Lung Adenocarcinoma Cells through the STK38/MEKK2/ERK1/2 Axis

Investigating the functions of the proteins with no or less functional annotations is an important goal of the HPP (Human Proteome Project) Grand Project. In this study, we investigated the function of such a protein, ZSWIM1 (C20orf162), its gene located on chromosome 20. Its expression is upregulated in lung adenocarcinoma compared with the adjacent normal tissues and negatively correlated with the overall survival. Overexpressing ZSWIM1 markedly promotes the proliferation, migration, invasion as well as epithelial-to-mesenchymal transition in lung adenocarcinoma cells, while knocking down ZSWIM1 functions oppositely. The interactome of ZSWIM1 was identified by immunoprecipitation-mass spectrometry, and we verified the interaction of ZSWIM1 with the potential partner, STK38. ZSWIM1 antagonized the function of STK38. Mechanically, ZSWIM1 promoted the activation of MEKK2/ERK1/2 pathway through interacting with STK38, leading to the release of MEKK2. Taken together, ZSWIM1 can be annotated as an oncogene in lung adenocarcinoma, and the STK38/MEKK2/ERK1/2 axis mediates its promoting role in lung adenocarcinoma.

The emerging roles of TRIM21 in coordinating cancer metabolism, immunity and cancer treatment

Tripartite motif containing-21 (TRIM21), an E3 ubiquitin ligase, was initially found to be involved in antiviral responses and autoimmune diseases. Recently studies have reported that TRIM21 plays a dual role in cancer promoting and suppressing in the occurrence and development of various cancers. Despite the fact that TRIM21 has effects on multiple metabolic processes, inflammatory responses and the efficacy of tumor therapy, there has been no systematic review of these topics. Herein, we discuss the emerging role and function of TRIM21 in cancer metabolism, immunity, especially the immune response to inflammation associated with tumorigenesis, and also the cancer treatment, hoping to shine a light on the great potential of targeting TRIM21 as a therapeutic target.

Thioredoxin-Interacting Protein in Cancer and Diabetes

Significance: Thioredoxin-interacting protein (Txnip) is an α-arrestin protein that acts as a cancer suppressor. Txnip is simultaneously a critical regulator of energy metabolism. Other alpha-arrestin proteins also play key roles in cell biology and cancer. Recent Advances: Txnip expression is regulated by multilayered mechanisms, including transcriptional regulation, microRNA, messenger RNA (mRNA) stabilization, and protein degradation. The Txnip-based connection between cancer and metabolism has been widely recognized. Meanwhile, new aspects are proposed for the mechanism of action of Txnip, including the regulation of RNA expression and autophagy. Arrestin domain containing 3 (ARRDC3), another α-arrestin protein, regulates endocytosis and signaling, whereas ARRDC1 and ARRDC4 regulate extracellular vesicle formation. Critical Issues: The mechanism of action of Txnip is yet to be elucidated. The regulation of intracellular protein trafficking by arrestin family proteins has opened an emerging field of biology and medical research, which needs to be examined further. Future Directions: A fundamental understanding of the mechanism of action of Txnip and other arrestin family members needs to be explored in the future to combat diseases such as cancer and diabetes. Antioxid. Redox Signal. 36, 1001-1022.

PRMT5 regulates ATF4 transcript splicing and oxidative stress response

Protein methyltransferase 5 (PRMT5) symmetrically dimethylates arginine residues leading to regulation of transcription and splicing programs. Although PRMT5 has emerged as an attractive oncology target, the molecular determinants of PRMT5 dependency in cancer remain incompletely understood. Our transcriptomic analysis identified PRMT5 regulation of the activating transcription factor 4 (ATF4) pathway in acute myelogenous leukemia (AML). PRMT5 inhibition resulted in the expression of unstable, intron-retaining ATF4 mRNA that is detained in the nucleus. Concurrently, the decrease in the spliced cytoplasmic transcript of ATF4 led to lower levels of ATF4 protein and downregulation of ATF4 target genes. Upon loss of functional PRMT5, cells with low ATF4 displayed increased oxidative stress, growth arrest, and cellular senescence. Interestingly, leukemia cells with EVI1 oncogene overexpression demonstrated dependence on PRMT5 function. EVI1 and ATF4 regulated gene signatures were inversely correlated. We show that EVI1-high AML cells have reduced ATF4 levels, elevated baseline reactive oxygen species and increased sensitivity to PRMT5 inhibition. Thus, EVI1-high cells demonstrate dependence on PRMT5 function and regulation of oxidative stress response. Overall, our findings identify the PRMT5-ATF4 axis to be safeguarding the cellular redox balance that is especially important in high oxidative stress states, such as those that occur with EVI1 overexpression.

Locus-specific induction of gene expression from heterochromatin loci during cellular senescence

Senescence is a fate-determined state, accompanied by reorganization of heterochromatin. Although lineage-appropriate genes can be temporarily repressed through facultative heterochromatin, stable silencing of lineage-inappropriate genes often involves the constitutive heterochromatic mark, histone H3 lysine 9 trimethylation (H3K9me3). The fate of these heterochromatic genes during senescence is unclear. In the present study, we show that a small number of lineage-inappropriate genes, exemplified by the LCE2 skin genes, are derepressed during senescence from H3K9me3 regions in fibroblasts. DNA FISH experiments reveal that these gene loci, which are condensed at the nuclear periphery in proliferative cells, are decompacted during senescence. Decompaction of the locus is not sufficient for LCE2 expression, which requires p53 and C/EBPβ signaling. NLRP3, which is predominantly expressed in macrophages from an open topologically associated domain (TAD), is also derepressed in senescent fibroblasts due to the local disruption of the H3K9me3-rich TAD that contains it. NLRP3 has been implicated in the amplification of inflammatory cytokine signaling in senescence and aging, highlighting the functional relevance of gene induction from 'permissive' H3K9me3 regions in senescent cells.

YAP/miR-524-5p axis negatively regulates TXNIP expression to promote chondrosarcoma cell growth

Chondrosarcoma (CHS) is the second most common bone malignant tumor and currently has limited treatment options. We have recently demonstrated that thioredoxin interacting protein (TXNIP) plays a crucial role in the oncogenesis of bone sarcoma, yet its implication in CHS is underdetermined. In the present study, we first found that knockdown of TXNIP promotes the proliferation of CHS cell largely through increasing their glycolytic metabolism, which is well-known as Warburg effect for providing energy. Consistent with our previous report that YAP is fundamental for CHS cell growth, herein we revealed that YAP functioned as an upstream molecule of TXNIP, and that YAP negatively regulated TXNIP mRNA and protein expression both in vitro and in vivo. Mechanistically, although knockdown of YAP upregulated both the nuclear and cytoplasmic TXNIP expression, we did not observe any obvious interaction between YAP and TXNIP; instead, miRNA-524-5p was demonstrated to be required for YAP-regulated TXNIP expression and thus controlling CHS cell growth. Together, our study reveals that TXNIP is a tumor suppressor in terms of CHS, and that the YAP/miRNA-524-5p/TXNIP signaling axis may provide a novel clue for CHS targeted therapy.

Collateral Victim or Rescue Worker?-The Role of Histone Methyltransferases in DNA Damage Repair and Their Targeting for Therapeutic Opportunities in Cancer

Disrupted DNA damage signaling greatly threatens cell integrity and plays significant roles in cancer. With recent advances in understanding the human genome and gene regulation in the context of DNA damage, chromatin biology, specifically biology of histone post-translational modifications (PTMs), has emerged as a popular field of study with great promise for cancer therapeutics. Here, we discuss how key histone methylation pathways contribute to DNA damage repair and impact tumorigenesis within this context, as well as the potential for their targeting as part of therapeutic strategies in cancer.

Protein Arginine Methyltransferase 5 Functions via Interacting Proteins

The protein arginine methyltransferases (PRMTs) are involved in such biological processes as transcription regulation, DNA repair, RNA splicing, and signal transduction, etc. In this study, we mainly focused on PRMT5, a member of the type II PRMTs, which functions mainly alongside other interacting proteins. PRMT5 has been shown to be overexpressed in a wide variety of cancers and other diseases, and is involved in the regulation of Epstein-Barr virus infection, viral carcinogenesis, spliceosome, hepatitis B, cell cycles, and various signaling pathways. We analyzed the regulatory roles of PRMT5 and interacting proteins in various biological processes above-mentioned, to elucidate for the first time the interaction between PRMT5 and its interacting proteins. This systemic analysis will enrich the biological theory and contribute to the development of novel therapies.

Polarization of rheumatoid macrophages is regulated by the CDKN2B-AS1/ MIR497/TXNIP axis

The polarization of macrophages plays a critical role in the pathophysiology of rheumatoid arthritis. The macrophages can have pro-inflammatory M1 polarization and various types of alternative anti-inflammatory M2 polarization. Our preliminary results showed that the CDKN2B-AS1/MIR497/TXNIP axis might regulate macrophages of rheumatoid arthritis patients. Therefore, we hypothesized that this axis regulated the polarization of rheumatoid macrophages. Flow cytometry was used to determine the surface polarization markers in M1 or M2 macrophages from healthy donors and rheumatoid arthritis patients. The QPCR and Western Blotting were used to compare the expression of the CDKN2B-AS1/MIR497/TXNIP axis in these macrophages. We Knocked down and overexpressed the axis in the macrophage cell line MD to test its roles in macrophage polarization. Compared to cells from healthy donors, cells from rheumatoid arthritis patients expressed higher levels of CD40 and CD80 and lower levels of CD16, CD163, CD206, and CD200R after polarization, they also expressed higher CDKN2B-AS1, lower MIR497, and higher TXNIP. In macrophages from healthy donors, there was no correlation among CDKN2B-AS1, MIR497, and TXNIP. But in macrophages from patients, there were significant correlations. The CDKN2B-AS1 knockdown, MIR497 mimics suppressed the M1 polarization but promoted the M2 polarization in MD cells, while the MIR497 knockdown and the TXNIP overexpression did the opposite. This study demonstrated that elevated CDKN2B-AS1 in macrophages promotes the M1 polarization and inhibited the M2 polarization of macrophages by the CDKN2B-AS1/ MIR497/TXNIP axis.

Splicing alterations in healthy aging and disease

Alternative RNA splicing is a key step in gene expression that allows generation of numerous messenger RNA transcripts encoding proteins of varied functions from the same gene. It is thus a rich source of proteomic and functional diversity. Alterations in alternative RNA splicing are observed both during healthy aging and in a number of human diseases, several of which display premature aging phenotypes or increased incidence with age. Age-associated splicing alterations include differential splicing of genes associated with hallmarks of aging, as well as changes in the levels of core spliceosomal genes and regulatory splicing factors. Here, we review the current known links between alternative RNA splicing, its regulators, healthy biological aging, and diseases associated with aging or aging-like phenotypes. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Processing > Splicing Regulation/Alternative Splicing.

Splicing alterations in healthy aging and disease

Alternative RNA splicing is a key step in gene expression that allows generation of numerous messenger RNA transcripts encoding proteins of varied functions from the same gene. It is thus a rich source of proteomic and functional diversity. Alterations in alternative RNA splicing are observed both during healthy aging and in a number of human diseases, several of which display premature aging phenotypes or increased incidence with age. Age-associated splicing alterations include differential splicing of genes associated with hallmarks of aging, as well as changes in the levels of core spliceosomal genes and regulatory splicing factors. Here, we review the current known links between alternative RNA splicing, its regulators, healthy biological aging, and diseases associated with aging or aging-like phenotypes. This article is categorized under: RNA in Disease and Development > RNA in Disease RNA Processing > Splicing Regulation/Alternative Splicing.

Sequential targeting of YAP1 and p21 enhances the elimination of senescent cells induced by the BET inhibitor JQ1

Chondrosarcoma (CHS) is the second most common bone malignancy with limited therapeutic approaches. Our previous study has found that Yes associated protein 1 (YAP1) is downregulated in CHS cells treated with bromodomain and extraterminal domain (BET) inhibitor JQ1. However, the precise role of YAP1 in CHS is largely unknown. Herein, we found that YAP1 expression was upregulated in CHS tissues, and positively correlated with its grading score. Loss of YAP1 inhibited CHS proliferation and induced cellular senescence, while expression of YAP1 mutants revealed YAP1/TEA domain family member (TEAD)-dependent negative regulation of p21 and subsequent cellular senescence. These results were validated by in vivo experiments using stable shYAP1 cell lines. Mechanistically, negative regulation of p21 by YAP1 occurred post-transcriptionally via Dicer-regulated miRNA networks, specifically, the miR-17 family. Furthermore, we demonstrated that sequential targeting of YAP1 and p21 enhanced the elimination of JQ1-induced senescent cells in a Bcl-2-like 1 (Bcl-XL)/Caspase-3 dependent manner. Altogether, we unveil a novel role of YAP1 signaling in mediating CHS cell senescence and propose a one-two punch approach that sequentially targets the YAP1/p21 axis to eliminate senescent cells.

TRIM21-regulated Annexin A2 plasma membrane trafficking facilitates osteosarcoma cell differentiation through the TFEB-mediated autophagy

Osteosarcoma (OS) is the most common primary malignant bone tumor in children and adolescents, which is characterized by dysfunctional autophagy and poor differentiation. Our recent studies have suggested that the tripartite motif containing-21 (TRIM21) plays a crucial role in regulating OS cell senescence and proliferation via interactions with several proteins. Yet, its implication in autophagy and differentiation in OS is largely unknown. In the present study, we first showed that TRIM21 could promote OS cell autophagy, as determined by the accumulation of LC3-II, and the degradation of cargo receptor p62. Further, we were able to identify that Annexin A2 (ANXA2), as a novel interacting partner of TRIM21, was critical for TIRM21-induced OS cell autophagy. Although TRIM21 had a negligible effect on the mRNA and protein expressions of ANXA2, we did find that TRIM21 facilitated the translocation of ANXA2 toward plasma membrane (PM) in OS cells through a manner relying on TRIM21-mediated cell autophagy. This functional link has been confirmed by observing a nice co-expression of TRIM21 and ANXA2 (at the PM) in the OS tissues. Mechanistically, we demonstrated that TRIM21, via facilitating the ANXA2 trafficking at the PM, enabled to release the transcription factor EB (TFEB, a master regulator of autophagy) from the ANXA2-TFEB complex, which in turn entered into the nucleus for the regulation of OS cell autophagy. In accord with previous findings that autophagy plays a critical role in the control of differentiation, we also demonstrated that autophagy inhibited OS cell differentiation, and that the TRIM21/ANXA2/TFEB axis is implicated in OS cell differentiation through the coordination with autophagy. Taken together, our results suggest that the TRIM21/ANXA2/TFEB axis is involved in OS cell autophagy and subsequent differentiation, indicating that targeting this signaling axis might lead to a new clue for OS treatment.

Clinicopathological and Prognostic Significance of PRMT5 in Cancers: A System Review and Meta-Analysis

PURPOSE

Since protein arginine methyltransferase 5 (PRMT5) is abnormally expressed in various tumors, in this study we aim to assess the association between PRMT5 and clinicopathological and prognostic features.

METHODS

Electronic databases including PubMed, Web of Science, Scopus, ScienceDirect, and the Cochrane Library were searched until July 25, 2021. The critical appraisal of the eligible studies was performed using the Newcastle-Ottawa Quality Assessment Scale. Pooled hazard ratios (HR) and pooled odds ratios (OR) were calculated to assess the effect. Engauge Digitizer version 12.1, STATA version 15.1, and R version 4.0.5 were used to obtain and analysis the data.

RESULTS

A total of 32 original studies covering 15,583 patients were included. In our data, it indicated that high level of PRMT5 was significantly correlated with advanced tumor stage (OR = 2.12, 95% CI: 1.22-3.70, P =.008; I2 = 80.7%) and positively correlated with poor overall survival (HR = 1.59, 95% CI: 1.46-1.73, P < .001; I2 = 50%) and progression-free survival (HR = 1.53, 95% CI: 1.24-1.88, P < .001; I2 = 0%). In addition, sub-group analysis showed that high level of PRMT5 was associated with poor overall survival for such 5 kinds of cancers as hepatocellular carcinoma, pancreatic cancer, breast cancer, gastric cancer, and lung cancer.

CONCLUSION

For the first time we found PRMT5 was pan-cancerous as a prognostic biomarker and high level of PRMT5 was associated with poor prognosis for certain cancers.

Research Progress of TXNIP as a Tumor Suppressor Gene Participating in the Metabolic Reprogramming and Oxidative Stress of Cancer Cells in Various Cancers

Thioredoxin-interacting protein (TXNIP) is a thioredoxin-binding protein that can mediate oxidative stress, inhibit cell proliferation, and induce apoptosis by inhibiting the function of the thioredoxin system. TXNIP is important because of its wide range of functions in cardiovascular diseases, neurodegenerative diseases, cancer, diabetes, and other diseases. Increasing evidence has shown that TXNIP expression is low in tumors and that it may act as a tumor suppressor in various cancer types such as hepatocarcinoma, breast cancer, and lung cancer. TXNIP is known to inhibit the proliferation of breast cancer cells by affecting metabolic reprogramming and can affect the invasion and migration of breast cancer cells through the TXNIP-HIF1α-TWIST signaling axis. TXNIP can also prevent the occurrence of bladder cancer by inhibiting the activation of ERK, which inhibits apoptosis in bladder cancer cells. In this review, we find that TXNIP can be regulated by binding to transcription factors or other binding proteins and can also be downregulated by epigenetic changes or miRNA. In addition, we also summarize emerging insights on TXNIP expression and its functional role in different kinds of cancers, as well as clarify its participation in metabolic reprogramming and oxidative stress in cancer cells, wherein it acts as a putative tumor suppressor gene to inhibit the proliferation, invasion, and migration of different tumor cells as well as promote apoptosis in these cells. TXNIP may therefore be of basic and clinical significance for finding novel molecular targets that can facilitate the diagnosis and treatment of malignant tumors.

Leptin acts on mesenchymal stem cells to promote chemoresistance in osteosarcoma cells

Leptin signaling influences osteoblastogenesis and modulates the fate of mesenchymal stem cells (MSCs) during bone and cartilage regeneration. Although MSCs abound in the osteosarcoma (OS) microenvironment, and leptin exhibits pro-tumorigenic properties, leptin's influence on OS progression and chemoresistant signaling in MSCs remains unclear. Using cell viability and apoptosis assays, we showed that medium conditioned by leptin-treated human MSCs promotes cisplatin resistance in cultured human OS cells. Moreover, GFP-LC3 expression and chloroquine treatment experiments showed that this effect is mediated by stimulation of autophagy in OS cells. TGF-β expression in MSCs was upregulated by leptin and suppressed by leptin receptor knockdown. Silencing TGF-β in MSCs also abolished OS cell chemoresistance induced by leptin-conditioned medium. Cisplatin resistance was also induced when leptin-conditioned MSCs were co-injected with MG-63 OS cells to generate subcutaneous xenografts in nude mice. Finally, we observed a significant correlation between autophagy-associated gene expression in OS clinical samples and patient prognosis. We conclude that leptin upregulates TGF-β in MSCs, which promotes autophagy-mediated chemoresistance in OS cells.