The dialogue between the ubiquitin-proteasome system and autophagy: Implications in ageing

AAV mediated carboxyl terminus of Hsp70 interacting protein overexpression mitigates the cognitive and pathological phenotypes of APP/PS1 mice

JOURNAL/nrgr/04.03/01300535-202501000-00033/figure1/v/2024-05-14T021156Z/r/image-tiff The E3 ubiquitin ligase, carboxyl terminus of heat shock protein 70 (Hsp70) interacting protein (CHIP), also functions as a co-chaperone and plays a crucial role in the protein quality control system. In this study, we aimed to investigate the neuroprotective effect of overexpressed CHIP on Alzheimer's disease. We used an adeno-associated virus vector that can cross the blood-brain barrier to mediate CHIP overexpression in APP/PS1 mouse brain. CHIP overexpression significantly ameliorated the performance of APP/PS1 mice in the Morris water maze and nest building tests, reduced amyloid-β plaques, and decreased the expression of both amyloid-β and phosphorylated tau. CHIP also alleviated the concentration of microglia and astrocytes around plaques. In APP/PS1 mice of a younger age, CHIP overexpression promoted an increase in ADAM10 expression and inhibited β-site APP cleaving enzyme 1, insulin degrading enzyme, and neprilysin expression. Levels of HSP70 and HSP40, which have functional relevance to CHIP, were also increased. Single nuclei transcriptome sequencing in the hippocampus of CHIP overexpressed mice showed that the lysosomal pathway and oligodendrocyte-related biological processes were up-regulated, which may also reflect a potential mechanism for the neuroprotective effect of CHIP. Our research shows that CHIP effectively reduces the behavior and pathological manifestations of APP/PS1 mice. Indeed, overexpression of CHIP could be a beneficial approach for the treatment of Alzheimer's disease.

Novel prospects in targeting neurodegenerative disorders via autophagy

Protein aggregation occurs as a consequence of dysfunction in the normal cellular proteostasis, which leads to the accumulation of toxic fibrillar aggregates of certain proteins in the cell. Enhancing the activity of proteolytic pathways may serve as a way of clearing these aggregates in a cell, and consequently, autophagy has surfaced as a promising target for the treatment of neurodegenerative disorders. Several strategies involving small molecule compounds that stimulate autophagic pathway of cell have been discovered. However, despite many compounds having demonstrated favorable outcomes in experimental disease models, the translation of these findings into clinical benefits for patient's remains limited. Consequently, alternative strategies are actively being explored to effectively target neurodegeneration via autophagy modulation. Recently, newer approaches such as modulation of expression of autophagic genes have emerged as novel and interesting areas of research in this field, which hold promising potential in neuroprotection. Similarly, as discussed for the first time in this review, the use of autophagy-inducing nanoparticles by utilizing their physicochemical properties to stimulate the autophagic process, rather than relying on their role as drug carriers, offers a completely fresh avenue for targeting neurodegeneration without the risk of drug-associated adverse effects. This review provides fresh perspectives on developing autophagy-targeted therapies for neurodegenerative disorders. Additionally, it discusses the challenges and impediments of implementing these strategies to alleviate the pathogenesis of neurodegenerative disorders in clinical settings and highlights the prospects and directions of future research in this context.

Bidirectional modulation of extracellular vesicle-autophagy axis in acute lung injury: Molecular mechanisms and therapeutic implications

Acute lung injury (ALI), a multifactorial pathological condition, manifests through heightened inflammatory responses, compromised lung epithelial-endothelial barrier function, and oxidative stress, potentially culminating in respiratory failure and mortality. This study explores the intricate interplay between two crucial cellular mechanisms-extracellular vesicles (EVs) and autophagy-in the context of ALI pathogenesis and potential therapeutic interventions.EVs, bioactive membrane-bound structures secreted by cells, serve as versatile carriers of molecular cargo, facilitating intercellular communication and significantly influencing disease progression. Concurrently, autophagy, an essential intracellular degradation process, maintains cellular homeostasis and has emerged as a promising therapeutic target in ALI and acute respiratory distress syndrome.Our research unveils a fascinating "EV-Autophagy dual-drive pathway," characterized by reciprocal regulation between these two processes. EVs modulate autophagy activation and inhibition, while autophagy influences EV production, creating a dynamic feedback loop. This study posits that precise manipulation of this pathway could revolutionize ALI treatment strategies.By elucidating the mechanisms underlying this cellular crosstalk, we open new avenues for targeted therapies. The potential for engineered EVs to fine-tune autophagy in ALI treatment is explored, alongside innovative concepts such as EV-based vaccines for ALI prevention and management. This research not only deepens our understanding of ALI pathophysiology but also paves the way for novel, more effective therapeutic approaches in critical care medicine.

An Introductory Guide to Using Bloomington Drosophila Stock Center and FlyBase for Aging Research

Studies on numerous species have demonstrated strikingly conserved mechanisms that determine the aging process, from yeasts to worms, flies, zebrafish, mice, and humans. The fruit fly Drosophila melanogaster is an excellent model organism for studying the biological basis of normal aging and etiology of age-related diseases. Since its inception in 1967, the Bloomington Drosophila Stock Center (BDSC) has grown into the largest collection of documented D. melanogaster strains (currently > 91,000). This paper aims to briefly review conserved mechanisms of aging and provides a guide to help users understand the organization of stock listings on the BDSC website and familiarize themselves with the search functions on BDSC and FlyBase, with an emphasis on using genes in conserved pathways as examples to find stocks for aging studies.

Potential of the nanoplatform and PROTAC interface to achieve targeted protein degradation through the Ubiquitin-Proteasome system

In eukaryotic cells, the ubiquitin-proteasome system (UPS) plays a crucial role in selectively breaking down specific proteins. The ability of the UPS to target proteins effectively and expedite their removal has significantly contributed to the evolution of UPS-based targeted protein degradation (TPD) strategies. In particular, proteolysis targeting chimeras (PROTACs) are an immensely promising tool due to their high efficiency, extensive target range, and negligible drug resistance. This breakthrough has overcome the limitations posed by traditionally "non-druggable" proteins. However, their high molecular weight and constrained solubility impede the delivery of PROTACs. Fortunately, the field of nanomedicine has experienced significant growth, enabling the delivery of PROTACs through nanoscale drug-delivery systems, which effectively improves the stability, solubility, drug distribution, tissue-specific accumulation, and stimulus-responsive release of PROTACs. This article reviews the mechanism of action attributed to PROTACs and their potential implications for clinical applications. Moreover, we present strategies involving nanoplatforms for the effective delivery of PROTACs and evaluate recent advances in targeting nanoplatforms to the UPS. Ultimately, an assessment is conducted to determine the feasibility of utilizing PROTACs and nanoplatforms for UPS-based TPD. The primary aim of this review is to provide innovative, reliable solutions to overcome the current challenges obstructing the effective use of PROTACs in the management of cancer, neurodegenerative diseases, and metabolic syndrome. Therefore, this is a promising technology for improving the treatment status of major diseases.

Handelin alleviates cachexia- and aging-induced skeletal muscle atrophy by improving protein homeostasis and inhibiting inflammation

BACKGROUND

Handelin is a bioactive compound from Chrysanthemum indicum L. that improves motor function and muscle integrity during aging in Caenorhabditis elegans. This study aimed to further evaluate the protective effects and molecular mechanisms of handelin in a mouse muscle atrophy model induced by cachexia and aging.

METHODS

A tumour necrosis factor (TNF)-α-induced atrophy model was used to examine handelin activity in cultured C2C12 myotubes in vitro. Lipopolysaccharide (LPS)-treated 8-week-old model mice and 23-month-old (aged) mice were used to examine the therapeutic effects of handelin on cachexia- and aging-induced muscle atrophy, respectively, in vivo. Protein and mRNA expressions were analysed by Western blotting, ELISA and quantitative PCR, respectively. Skeletal muscle mass was measured by histological analysis.

RESULTS

Handelin treatment resulted in an upregulation of protein levels of early (MyoD and myogenin) and late (myosin heavy chain, MyHC) differentiation markers in C2C12 myotubes (P < 0.05), and enhanced mitochondrial respiratory (P < 0.05). In TNF-α-induced myotube atrophy model, handelin maintained MyHC protein levels, increased insulin-like growth factor (Igf1) mRNA expression and phosphorylated protein kinase B protein levels (P < 0.05). Handelin also reduced atrogin-1 expression, inhibited nuclear factor-κB activation and reduced mRNA levels of interleukin (Il)6, Il1b and chemokine ligand 1 (Cxcl1) (P < 0.05). In LPS-treated mice, handelin increased body weight (P < 0.05), the weight (P < 0.01) and cross-sectional area (CSA) of the soleus muscle (P < 0.0001) and improved motor function (P < 0.05). In aged mice, handelin slightly increased the weight of the tibialis anterior muscle (P = 0.06) and CSA of the tibialis anterior and gastrocnemius muscles (P < 0.0001). In the tibialis anterior muscle of aged mice, handelin upregulated mRNA levels of Igf1 (P < 0.01), anti-inflammatory cytokine Il10 (P < 0.01), mitochondrial biogenesis genes (P < 0.05) and antioxidant-related enzymes (P < 0.05) and strengthened Sod and Cat enzyme activity (P < 0.05). Handelin also reduced lipid peroxidation and protein carbonylation, downregulated mRNA levels of Fbxo32, Mstn, Cxcl1, Il1b and Tnf (P < 0.05), and decreased IL-1β levels in serum (P < 0.05). Knockdown of Hsp70 or using an Hsp70 inhibitor abolished the ameliorating effects of handelin on myotube atrophy.

CONCLUSIONS

Handelin ameliorated cachexia- and aging-induced skeletal muscle atrophy in vitro and in vivo, by maintaining homeostasis of protein synthesis and degradation, possibly by inhibiting inflammation. Handelin is a potentially promising drug candidate for the treatment of muscle wasting.

Essential oil from Fructus Alpinia zerumbet ameliorates atherosclerosis by activating PPARγ-LXRα-ABCA1/G1 signaling pathway

BACKGROUND

Atherosclerosis (AS) is a progressive chronic disease. Currently, cardiovascular diseases (CVDs) caused by AS is responsible for the global increased mortality. Yanshanjiang as miao herb in Guizhou of China is the dried and ripe fruit of Fructus Alpinia zerumbet. Accumulated evidences have confirmed that Yanshanjiang could ameliorate CVDs, including AS. Nevertheless, its effect and mechanism on AS are still largely unknown.

PURPOSE

To investigate the role of essential oil from Fructus Alpinia zerumbet (EOFAZ) on AS, and the potential mechanism.

METHODS

A high-fat diet (HFD) ApoE-/- mice model of AS and a oxLDL-induced model of macrophage-derived foam cells (MFCs) were reproduced to investigate the pharmacological properties of EOFAZ on AS in vivo and foam cell formation in vitro, respectively. The underlying mechanisms of EOFAZ were investigated using Network pharmacology and molecular docking. EOFAZ effect on PPARγ protein stability was measured using a cellular thermal shift assay (CETSA). Pharmacological agonists and inhibitors and gene interventions were employed for clarifying EOFAZ's potential mechanism.

RESULTS

EOFAZ attenuated AS progression in HFD ApoE-/- mice. This attenuation was manifested by the reduced aortic intima plaque development, increased collagen content in aortic plaques, notable improvement in lipid profiles, and decreased levels of inflammatory factors. Moreover, EOFAZ inhibited the formation of MFCs by enhancing cholesterol efflux through activiting the PPARγ-LXRα-ABCA1/G1 pathway. Interestingly, the pharmacological knockdown of PPARγ impaired the beneficial effects of EOFAZ on MFCs. Additionally, our results indicated that EOFAZ reduced the ubiquitination degradation of PPARγ, and the chemical composition of EOFAZ directly bound to the PPARγ protein, thereby increasing its stability. Finally, PPARγ knockdown mitigated the protective effects of EOFAZ on AS in HFD ApoE-/- mice.

CONCLUSION

These findings represent the first confirmation of EOFAZ's in vivo anti-atherosclerotic effects in ApoE-/- mice. Mechanistically, its chemical constituents can directly bind to PPARγ protein, enhancing its stability, while reducing PPARγ ubiquitination degradation, thereby inhibiting foam cell formation via activation of the PPARγ-LXRα-ABCA1/G1 pathway. Simultaneously, EOFAZ could ameliorates blood lipid metabolism and inflammatory microenvironment, thus synergistically exerting its anti-atherosclerotic effects.

Fangchinoline alleviates cognitive impairments through enhancing autophagy and mitigating oxidative stress in Alzheimer's disease models

Introduction: Alzheimer's disease (AD) is a debilitating, progressive, neurodegenerative disorder characterized by the deposition of amyloid-β (Aβ) peptides and subsequent oxidative stress, resulting in a cascade of cytotoxic effects. Fangchinoline (Fan), a bisbenzylisoquinoline alkaloid isolated from traditional Chinese herb Stephania tetrandra S. Moorec, has been reported to possess multiple potent biological activities, including anti-inflammatory and antioxidant properties. However, the potential neuroprotective efficacy of Fan against AD remains unknown. Methods: N2AAPP cells, the mouse neuroblastoma N2A cells stably transfected with human Swedish mutant APP695, were served as an in vitro AD model. A mouse model of AD was constructed by microinjection of Aβ1-42 peptides into lateral ventricle of WT mice. The neuroprotective effects of Fan on AD were investigated through a combination of Western blot analysis, immunoprecipitation and behavioral assessments. Results and discussion: It was found that Fan effectively attenuated the amyloidogenic processing of APP by augmenting autophagy and subsequently fostering lysosomal degradation of BACE1 in N2AAPP cells, as reflected by the decrease in P62 levels, concomitant with the increase in Beclin-1 and LC3-II levels. More importantly, Fan significantly ameliorated cognitive impairment in an Aβ1-42-induced mouse model of AD via the induction of autophagy and the inhibition of oxidative stress, as evidenced by an increase in antioxidants including glutathione reductase (GR), total antioxidant capacity (T-AOC), nuclear factor erythroid-2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and superoxide dismutase-1 (SOD-1) and a decrease in pro-oxidants including hydrogen peroxide (H2O2) and inducible nitric oxide synthase (i-NOS), coupled with a reduction in apoptosis marker, cleaved caspase-3. Taken together, our study demonstrate that Fan ameliorates cognitive dysfunction through promoting autophagy and mitigating oxidative stress, making it a potential therapeutic agent for AD.

Identification of plasma proteomic signatures associated with the progression of cardia gastric cancer and precancerous lesions

Objective

Considering that there are no effective biomarkers for the screening of cardia gastric cancer (CGC), we developed a noninvasive diagnostic approach, employing data-independent acquisition (DIA) proteomics to identify candidate protein markers.

Methods

Plasma samples were obtained from 40 subjects, 10 each for CGC, cardia high-grade dysplasia (CHGD), cardia low-grade dysplasia (CLGD), and healthy controls. Proteomic profiles were obtained through liquid chromatography-mass spectrometry (LC-MS/MS-based DIA proteomics. Candidate plasma proteins were identified by weighted gene co-expression network analysis (WGCNA) combined with machine learning and further validated by the Human Protein Atlas (HPA) database. The area under the receiver operating characteristic curve (AUC) was used to evaluate the performance of the biomarker panel.

Results

There was a clear distinction in proteomic features among CGC, CHGD, CLGD, and the healthy controls. According to the WGCNA, we found 42 positively associated and 164 inversely associated proteins related to CGC progression and demonstrated several canonical cancer-associated pathways. Combined with the results from random forests, LASSO regression, and immunohistochemical results from the HPA database, we identified three candidate proteins (GSTP1, CSRP1, and LY6G6F) that could together distinguish CLGD (AUC = 0.91), CHGD (AUC = 0.99) and CGC (AUC = 0.98) from healthy controls with excellent accuracy.

Conclusions

The panel of protein biomarkers showed promising diagnostic potential for CGC and precancerous lesions. Further validation and a larger-scale study are warranted to assess its potential clinical applications, suggesting a potential avenue for CGC prevention in the future.

Mechanisms and pathology of protein misfolding and aggregation

Despite advances in machine learning-based protein structure prediction, we are still far from fully understanding how proteins fold into their native conformation. The conventional notion that polypeptides fold spontaneously to their biologically active states has gradually been replaced by our understanding that cellular protein folding often requires context-dependent guidance from molecular chaperones in order to avoid misfolding. Misfolded proteins can aggregate into larger structures, such as amyloid fibrils, which perpetuate the misfolding process, creating a self-reinforcing cascade. A surge in amyloid fibril structures has deepened our comprehension of how a single polypeptide sequence can exhibit multiple amyloid conformations, known as polymorphism. The assembly of these polymorphs is not a random process but is influenced by the specific conditions and tissues in which they originate. This observation suggests that, similar to the folding of native proteins, the kinetics of pathological amyloid assembly are modulated by interactions specific to cells and tissues. Here, we review the current understanding of how intrinsic protein conformational propensities are modulated by physiological and pathological interactions in the cell to shape protein misfolding and aggregation pathology.

Relationship between the Ubiquitin-Proteasome System and Autophagy in Colorectal Cancer Tissue

BACKGROUND

Dysregulation of the autophagy process via ubiquitin is associated with the occurrence of a number of diseases, including cancer. The present study analyzed the changes in the transcriptional activity of autophagy-related genes and the ubiquitination process (UPS) in colorectal cancer tissue. (2) Methods: The process of measuring the transcriptional activity of autophagy-related genes was analyzed by comparing colorectal cancer samples from four clinical stages I-IV (CS I-IV) of adenocarcinoma to the control (C). The transcriptional activity of genes associated with the UPS pathway was determined via the microarray technique (HG-U133A, Affymetrix). (3) Results: Of the selected genes, only PTEN-induced kinase 1 (PINK1) indicated statistical significance for all groups of colon cancer tissue transcriptome compared to the control. The transcriptional activity of the protein tyrosine phosphatase non-receptor type 22 (PTPN22) gene increased in all stages of the cancer, but the p-value was only less than 0.05 in CSIV vs. C. Forkhead box O1 (FOXO 1) and ubiquitin B (UBB) are statistically overexpressed in CSI. (4) Conclusions: The pathological expression changes in the studied proteins observed especially in the early stages of colorectal cancer suggest that the dysregulation of ubiquitination and autophagy processes occur during early neoplastic transformation. Stopping or slowing down the processes of removal of damaged proteins and their accumulation may contribute to tumor progression and poor prognosis.

Tubulin degradation: Principles, agents, and applications

The microtubule system plays an important role in the mitosis and growth of eukaryotic cells, and it is considered as an appealing and highly successful molecular target for cancer treatment. In fact, microtubule targeting agents, such as paclitaxel and vinblastine, have been approved by FDA for tumor therapy, which have achieved significant therapeutic effects and sales performance. At present, microtubule targeting agents mainly include microtubule-destabilizing agents, microtubule-stabilizing agents, and a few tubulin degradation agents. Although there are few reports about tubulin degradation agents at present, tubulin degradation agents show great potential in overcoming multidrug resistance and reducing neurotoxicity. In addition, some natural drugs could specifically degrade tubulin in tumor cells, but have no effect in normal cells, thus showing a good biosafety profile. Therefore, tubulin degradation agents might exhibit a better application. Currently, some small molecules have been designed to promote tubulin degradation with potent antiproliferative activities, showing the potential for cancer treatment. In this work, we reviewed the reports on tubulin degradation, and focused on the degradation mechanism and important functional groups of chemically synthesized compounds, hoping to provide help for the degradation design of tubulin.

Corylifol A ameliorates muscle atrophy by inhibiting TAOK1/p38-MAPK/FoxO3 pathway in cancer cachexia

BACKGROUND

Corylifol A (CYA) is one of the main active components of Psoralea corylifolia L. CYA had been reported to have ameliorating effects on dexamethasone-induced atrophy of C2C12 mouse skeletal myotubes, but its effects on cancer cachexia were unclear. Here, we checked the influence of CYA on muscle atrophy in cancer cachexia mice and tried to clarify its mechanisms.

METHODS

C26 tumour-bearing mice were applied as the animal model to examine the effects of CYA in attenuating cachexia symptoms. The in vitro cell models of TNF-α-induced C2C12 myotubes or ad-mRFP-GFP-LC3B-transfected C2C12 myotubes were used to check the influence of CYA on myotube atrophy based on both ubiquitin proteasome system (UPS) and autophagy-lysosome system. The possible direct targets of CYA were searched using the biotin-streptavidin pull-down assay and then confirmed using the Microscale thermophoresis binding assay. The levels of related signal proteins in both in vitro and in vivo experiments were examined using western blotting and immunocytochemical assay.

RESULTS

The administration of CYA prevented body weight loss and muscle wasting in C26 tumour-bearing mice without affecting tumour growth. At the end of the experiment, the body weight of mice treated with 30 mg/kg of CYA (23.59 ± 0.94 g) was significantly higher than that of the C26 model group (21.66 ± 0.56 g) with P < 0.05. The values of gastrocnemius muscle weight/body weight of mice treated with 15 or 30 mg/kg CYA (0.53 ± 0.02% and 0.54 ± 0.01%, respectively) were both significantly higher than that of the C26 model group (0.45 ± 0.01%) with P < 0.01. CYA decreased both UPS-mediated protein degradation and autophagy in muscle tissues of C26 tumour-bearing mice as well as in C2C12 myotubes treated with TNF-α. The thousand-and-one amino acid kinase 1 (TAOK1) was found to be the direct binding target of CYA. CYA inhibited the activation of TAOK1 and its downstream p38-MAPK pathway thus decreased the level and nuclear location of FoxO3. siRNA knockdown of TAOK1 or regulation of the p38-MAPK pathway using activator or inhibitor could affect the ameliorating effects of CYA on myotube atrophy.

CONCLUSIONS

CYA ameliorates cancer cachexia muscle atrophy by decreasing both UPS degradation and autophagy. The ameliorating effects of CYA on muscle atrophy might be based on its binding with TAOK1 and inhibiting the TAOK1/p38-MAPK/FoxO3 pathway.

Neuron-specific proteasome activation exerts cell non-autonomous protection against amyloid-beta (Aβ) proteotoxicity in Caenorhabditis elegans

Proteostasis reinforcement is a promising approach in the design of therapeutic interventions against proteinopathies, including Alzheimer's disease. Understanding how and which parts of the proteostasis network should be enhanced is crucial in developing efficient therapeutic strategies. The ability of specific tissues to induce proteostatic responses in distal ones (cell non-autonomous regulation of proteostasis) is attracting interest. Although the proteasome is a major protein degradation node, nothing is known on its cell non-autonomous regulation. We show that proteasome activation in the nervous system can enhance the proteasome activity in the muscle of Caenorhabditis elegans. Mechanistically, this communication depends on Small Clear Vesicles, with glutamate as one of the neurotransmitters required for the distal regulation. More importantly, we demonstrate that this cell non-autonomous proteasome activation is translated into efficient prevention of amyloid-beta (Αβ)-mediated proteotoxic effects in the muscle of C. elegans but notably not to resistance against oxidative stress. Our in vivo data establish a mechanistic link between neuronal proteasome reinforcement and decreased Aβ proteotoxicity in the muscle. The identified distal communication may have serious implications in the design of therapeutic strategies based on tissue-specific proteasome manipulation.

Targeting proteostasis network in osteoporosis: Pathological mechanisms and therapeutic implications

As the most common bone disease, osteoporosis (OP) increases bone fragility and makes patients more vulnerable to the threat of osteoporotic fractures. With the ageing population in today's society, OP has become a huge and growing public health problem. Unfortunately, the clear pathogenesis of OP is still under exploration, and effective interventions are still scarce. Therefore, exploring new targets for pharmacological interventions to develop promising therapeutic drugs for OP is of great clinical value. Previous studies have shown that normal bone remodeling depends on proteostasis, whereas loss of proteostasis during ageing leads to the dysfunctional proteostasis network (PN) that fails to maintain bone homeostasis. Nevertheless, only a few studies have revealed the pathophysiological relationship between bone metabolism and a single component of PN, yet the role of PN as a whole in the pathogenesis of OP is still under investigation. This review comprehensively summarized the role of PN in the pathogenesis of OP and further discussed the potential of PN as innovative drug targets for the therapy of OP.

E3 Ubiquitin Ligases in Endothelial Dysfunction and Vascular Diseases: Roles and Potential Therapies

ABSTRACT

Ubiquitin E3 ligases are a structurally conserved family of enzymes that exert a variety of regulatory functions in immunity, cell death, and tumorigenesis through the ubiquitination of target proteins. Emerging evidence has shown that E3 ubiquitin ligases play crucial roles in the pathogenesis of endothelial dysfunction and related vascular diseases. Here, we reviewed the new findings of E3 ubiquitin ligases in regulating endothelial dysfunction, including endothelial junctions and vascular integrity, endothelial activation, and endothelial apoptosis. The critical role and potential mechanism of E3 ubiquitin ligases in vascular diseases, such as atherosclerosis, diabetes, hypertension, pulmonary hypertension, and acute lung injury, were summarized. Finally, the clinical significance and potential therapeutic strategies associated with the regulation of E3 ubiquitin ligases were also proposed.

A bioinformatic investigation of proteasome and autophagy expression in the central nervous system

The ubiquitin proteasome system (UPS) and autophagy lysosome pathway (ALP) are crucial in the control of protein quality. However, data regarding the relative significance of UPS and ALP in the central nervous system (CNS) are limited. In the present study, using publicly available data, we computed the quantitative expression status of UPS- and ALP-related genes and their products in the CNS as compared with that in other tissues and cells. We obtained human and mouse gene expression datasets from the reference expression dataset (RefEx) and Genevestigator (a tool for handling curated transcriptomic data from public repositories) as well as human proteomics data from the proteomics database (ProteomicsDB). The expression levels of genes and proteins in four categories-ubiquitin, proteasome, autophagy, and lysosome--in the cells and tissues were assessed. Perturbation of the gene expression by drugs was also analyzed for the four categories. Compared with that for ubiquitin, autophagy, and lysosome, gene expression for proteasome was consistently lower in the CNS of mice but was more pronounced in humans. Neural stem cells and neurons showed low proteasome gene expression as compared with embryonic stem cells. Proteomic analyses, however, did not show trends similar to those observed in the gene expression analyses. Perturbation analyses revealed that azithromycin and vitamin D3 upregulated the expression of both UPS and ALP. Gene and proteomic expression data could offer a fresh perspective on CNS pathophysiology. Our results indicate that disproportional expression of UPS and ALP might affect CNS disorders and that this imbalance might be redressed by several therapeutic candidates.

Antagonizing the irreversible thrombomodulin-initiated proteolytic signaling alleviates age-related liver fibrosis via senescent cell killing

Cellular senescence is a stress-induced, stable cell cycle arrest phenotype which generates a pro-inflammatory microenvironment, leading to chronic inflammation and age-associated diseases. Determining the fundamental molecular pathways driving senescence instead of apoptosis could enable the identification of senolytic agents to restore tissue homeostasis. Here, we identify thrombomodulin (THBD) signaling as a key molecular determinant of the senescent cell fate. Although normally restricted to endothelial cells, THBD is rapidly upregulated and maintained throughout all phases of the senescence program in aged mammalian tissues and in senescent cell models. Mechanistically, THBD activates a proteolytic feed-forward signaling pathway by stabilizing a multi-protein complex in early endosomes, thus forming a molecular basis for the irreversibility of the senescence program and ensuring senescent cell viability. Therapeutically, THBD signaling depletion or inhibition using vorapaxar, an FDA-approved drug, effectively ablates senescent cells and restores tissue homeostasis in liver fibrosis models. Collectively, these results uncover proteolytic THBD signaling as a conserved pro-survival pathway essential for senescent cell viability, thus providing a pharmacologically exploitable senolytic target for senescence-associated diseases.

The influence of NQO2 on the dysfunctional autophagy and oxidative stress induced in the hippocampus of rats and in SH-SY5Y cells by fluoride

INTRODUCTION

For investigating the mechanism of brain injury caused by chronic fluorosis, this study was designed to determine whether NRH:quinone oxidoreductase 2 (NQO2) can influence autophagic disruption and oxidative stress induced in the central nervous system exposed to a high level of fluoride.

METHODS

Sprague-Dawley rats drank tap water containing different concentrations of fluoride for 3 or 6 months. SH-SY5Y cells were either transfected with NQO2 RNA interference or treated with NQO2 inhibitor or activator and at the same time exposed to fluoride. The enrichment of gene signaling pathways related to autophagy was evaluated by Gene Set Enrichment Analysis; expressions of NQO2 and autophagy-related protein 5 (ATG5), LC3-II and p62, and mammalian target of rapamycin (mTOR) were quantified by Western-blotting or fluorescent staining; and the levels of malondialdehyde (MDA) and superoxide dismutase (SOD) assayed biochemically and reactive oxygen species (ROS) detected by flow cytometry.

RESULTS

In the hippocampal CA3 region of rats exposed to high fluoride, the morphological characteristics of neurons were altered; the numbers of autophagosomes in the cytoplasm and the levels of NQO2 increased; the level of p-mTOR was decreased, and the levels of ATG5, LC3-II and p62 were elevated; and genes related to autophagy enriched. In vitro, in addition to similar changes in NQO2, p-mTOR, ATG5, LC3 II, and p62, exposure of SH-SY5Y cells to fluoride enhanced MDA and ROS contents and reduced SOD activity. Inhibition of NQO2 with RNAi or an inhibitor attenuated the disturbance of the autophagic flux and enhanced oxidative stress in these cells exposed to high fluoride.

CONCLUSION

Our findings indicate that NQO2 may be involved in regulating autophagy and oxidative stress and thereby exerts an impact on brain injury caused by chronic fluorosis.

Reversible protein assemblies in the proteostasis network in health and disease

While proteins populating their native conformations constitute the functional entities of cells, protein aggregates are traditionally associated with cellular dysfunction, stress and disease. During recent years, it has become clear that large aggregate-like protein condensates formed via liquid-liquid phase separation age into more solid aggregate-like particles that harbor misfolded proteins and are decorated by protein quality control factors. The constituent proteins of the condensates/aggregates are disentangled by protein disaggregation systems mainly based on Hsp70 and AAA ATPase Hsp100 chaperones prior to their handover to refolding and degradation systems. Here, we discuss the functional roles that condensate formation/aggregation and disaggregation play in protein quality control to maintain proteostasis and why it matters for understanding health and disease.

Mitofusin-2 mediates cannabidiol-induced neuroprotection against cerebral ischemia in rats

Cannabidiol (CBD) reportedly exerts protective effects against many psychiatric disorders and neurodegenerative diseases, but the mechanisms are poorly understood. In this study, we explored the molecular mechanism of CBD against cerebral ischemia. HT-22 cells or primary cortical neurons were subjected to oxygen-glucose deprivation insult followed by reoxygenation (OGD/R). In both HT-22 cells and primary cortical neurons, CBD pretreatment (0.1, 0.3, 1 μM) dose-dependently attenuated OGD/R-induced cell death and mitochondrial dysfunction, ameliorated OGD/R-induced endoplasmic reticulum (ER) stress, and increased the mitofusin-2 (MFN2) protein level in HT-22 cells and primary cortical neurons. Knockdown of MFN2 abolished the protective effects of CBD. CBD pretreatment also suppressed OGD/R-induced binding of Parkin to MFN2 and subsequent ubiquitination of MFN2. Overexpression of Parkin blocked the effects of CBD in reducing MFN2 ubiquitination and reduced cell viability, whereas overexpressing MFN2 abolished Parkin's detrimental effects. In vivo experiments were conducted on male rats subjected to middle cerebral artery occlusion (MCAO) insult, and administration of CBD (2.5, 5 mg · kg-1, i.p.) dose-dependently reduced the infarct volume and ER stress in the brains. Moreover, the level of MFN2 within the ischemic penumbra of rats was increased by CBD treatment, while the binding of Parkin to MFN2 and the ubiquitination of MFN2 was decreased. Finally, short hairpin RNA against MFN2 reversed CBD's protective effects. Together, these results demonstrate that CBD protects brain neurons against cerebral ischemia by reducing MFN2 degradation via disrupting Parkin's binding to MFN2, indicating that MFN2 is a potential target for the treatment of cerebral ischemia.

UXT attenuates the CGAS-STING1 signaling by targeting STING1 for autophagic degradation

STING1 (stimulator of interferon response cGAMP interactor 1), the pivotal adaptor protein of CGAS (cyclic GMP-AMP synthase)-STING1 signaling, is critical for type I IFN production of innate immunity. However, excessive or prolonged activation of STING1 is associated with autoinflammatory and autoimmune diseases. Thus, preventing STING1 from over-activation is important to maintain immune homeostasis. Here, we reported that UXT (ubiquitously expressed prefoldin like chaperone), a small chaperone-like protein, was essential to prevent the excessive activation of STING1-mediated type I IFN signaling through autophagic degradation of STING1 via SQSTM1 (sequestosome 1). Upon DNA mimics or cyclic GMP-AMP (cGAMP) stimulation, UXT specifically interacted with STING1 and promoted STING1 degradation through selective macroautophagy/autophagy. Moreover, UXT was required for more efficient autophagic degradation of STING1 by facilitating the interaction of SQSTM1 and STING1. The in vivo role of UXT in attenuating the CGAS-STING1 signaling was further confirmed in the mouse model of DNA-virus infection and the TMPD (2,6,10,14-tetramethylpentadecane)-induced murine lupus model. Intriguingly, the expression of UXT was consistently impaired and exhibited a remarkable inverse correlation with type I IFN signature in the leukocytes and PBMCs (peripheral blood mononuclear cells) of several large SLE (systemic lupus erythematosus) cohorts. Importantly, the replenishment of UXT effectively suppressed the production of IFNs and ISGs in the PBMCs of SLE patients. Taken together, our study reveals a novel regulatory role of UXT in autophagic degradation of STING1 to maintain immune homeostasis. UXT might be a potential therapeutic target for alleviating aberrant type I IFNs in autoimmune diseasesAbbreviations: 3-MA: 3-methyladenine; BMDMs: bone marrow-derived macrophages; cGAMP: cyclic GMP-AMP; CGAS: cyclic gmp-amp synthase; cKO: conditional knockout; CXCL10: C-X-C motif chemokine ligand 10; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HSV-1: herpes simplex virus type 1; HTDNA: herring testes DNA; IFIT1: interferon induced protein with tetratricopeptide repeats 1; IFNA4: interferon alpha 4; IFNB: interferon beta; IRF3: interferon regulatory factor 3; ISD: interferon stimulatory DNA; ISGs: IFN-stimulated genes; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MEFs: mouse embryonic fibroblasts; RNA-seq: RNA sequencing; PBMCs: peripheral blood mononuclear cells; RSAD2: radical S-adenosyl methionine domain containing 2; SLE: systemic lupus erythematosus; SQSTM1: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1; TMPD: 2,6,10,14-tetramethylpentadecane; UXT: ubiquitously expressed prefoldin like chaperone.

Aging-accelerated differential production and aggregation of STAT3 protein in neuronal cells and neural stem cells in the male mouse spinal cord

Aging-affected cellular compositions of the spinal cord are diverse and region specific. Age leads to the accumulation of abnormal protein aggregates and dysregulation of proteostasis. Dysregulated proteostasis and protein aggregates result from dysfunction of the ubiquitin-proteasome system (UPS) and autophagy. Understanding the molecular mechanisms of spinal cord aging is essential and important for scientists to discover new therapies for rejuvenation. We found age-related increases in STAT3 and decreases in Tuj1 in aging mouse spinal cords, which was characterized by increased expression of P16. Coaggregation of lysine-48 and lysine-63 ubiquitin with STAT3 was revealed in aging mouse spinal cords. STAT3-ubiquitin aggregates formed via lysine-48 and lysine-63 linkages were increased significantly in the aging spinal cords but not in central canal ependymal cells or neural stem cells in the spinal cord. These results highlight the increase in STAT3 and its region-specific aggregation and ubiquitin-conjugation during spinal cord aging.

Ubiquitin C-terminal hydrolase L1 (UCHL1), a double-edged sword in mammalian oocyte maturation and spermatogenesis

BACKGROUND

Recent studies have shown that ubiquitin-mediated cell apoptosis can modulate protein interaction and involve in the progress of oocyte maturation and spermatogenesis. As one of the key regulators involved in ubiquitin signal, ubiquitin C-terminal hydrolase L1 (UCHL1) is considered a molecular marker associated with spermatogonia stem cells. However, the function of UCHL1 was wildly reported to regulate various bioecological processes, such as Parkinson's disease, lung cancer, breast cancer and colon cancer, how UCHL1 affects the mammalian reproductive system remains an open question.

METHODS

We identified papers through electronic searches of PubMed database from inception to July 2022.

RESULTS

Here, we summarize the important function of UCHL1 in controlling mammalian oocyte development, regulating spermatogenesis and inhibiting polyspermy, and we posit the balance of UCHL1 was essential to maintaining reproductive cellular and tissue homeostasis.

CONCLUSION

This study considers the 'double-edged sword' role of UCHL1 during gametogenesis and presents new insights into UCHL1 in germ cells.

Protein degradation: expanding the toolbox to restrain cancer drug resistance

Despite significant progress in clinical management, drug resistance remains a major obstacle. Recent research based on protein degradation to restrain drug resistance has attracted wide attention, and several therapeutic strategies such as inhibition of proteasome with bortezomib and proteolysis-targeting chimeric have been developed. Compared with intervention at the transcriptional level, targeting the degradation process seems to be a more rapid and direct strategy. Proteasomal proteolysis and lysosomal proteolysis are the most critical quality control systems responsible for the degradation of proteins or organelles. Although proteasomal and lysosomal inhibitors (e.g., bortezomib and chloroquine) have achieved certain improvements in some clinical application scenarios, their routine application in practice is still a long way off, which is due to the lack of precise targeting capabilities and inevitable side effects. In-depth studies on the regulatory mechanism of critical protein degradation regulators, including E3 ubiquitin ligases, deubiquitylating enzymes (DUBs), and chaperones, are expected to provide precise clues for developing targeting strategies and reducing side effects. Here, we discuss the underlying mechanisms of protein degradation in regulating drug efflux, drug metabolism, DNA repair, drug target alteration, downstream bypass signaling, sustaining of stemness, and tumor microenvironment remodeling to delineate the functional roles of protein degradation in drug resistance. We also highlight specific E3 ligases, DUBs, and chaperones, discussing possible strategies modulating protein degradation to target cancer drug resistance. A systematic summary of the molecular basis by which protein degradation regulates tumor drug resistance will help facilitate the development of appropriate clinical strategies.

The E3 ubiquitin ligase TRIM31 attenuates NLRP3 inflammasome activation in Helicobacter pylori-associated gastritis by regulating ROS and autophagy

BACKGROUND

The NLRP3 inflammasome activation is the molecular basis of Helicobacter pylori (Hp)-associated gastritis. Tripartite motif (TRIM) 31 is involved in diverse pathological events. However, whether TRIM31 plays a role in the activation of NLRP3 inflammasome in Hp infection is not clarified.

METHODS

A mouse model of chronic Hp infection was established, and the gastric tissues were subjected to the polymerase chain reaction, western blotting, histopathological analysis, and RNA sequencing. The mitochondrial membrane potential and ROS in the human gastric epithelium GES-1 cells with or without Hp infection were measured by flow cytometry. GES-1 cells with or without TRIM31 knockdown were transfected with mCherry-EGFP-LC3 adenovirus. After rapamycin and bafilomycin A1 stimulation, autophagy flux in the above primed GES-1 cells was assessed by laser confocal microscope. Lysosomal acidification and expression levels of cathepsin B and cathepsin D in GES-1 cells with Hp infection were measured.

RESULTS

NLRP3 inflammasome was activated in the gastric tissues of mice with chronic Hp infection in vivo and the GES-1 cells with Hp infection in vitro. TRIM31 was downregulated in Hp infection. TRIM31 negatively regulated the NLRP3 inflammasome activation. Enhanced ROS, impaired autophagy flux, and decreased expression of lysosomal cathepsin B and cathepsin D were observed in TRIM31-deficient GES-1 cells with Hp infection. In turn, inhibition of ROS led to the decreased expression of NLRP3 inflammasome.

CONCLUSIONS

Together, our data identified that TRIM31 negatively regulated the activation of NLRP3 inflammasome in Hp-associated gastritis by affecting ROS and autophagy of gastric epithelial cells. Video abstract.

Aging: Epigenetic modifications

Aging is one of the most complex and irreversible health conditions characterized by continuous decline in physical/mental activities that eventually poses an increased risk of several diseases and ultimately death. These conditions cannot be ignored by anyone but there are evidences that suggest that exercise, healthy diet and good routines may delay the Aging process significantly. Several studies have demonstrated that Epigenetics plays a key role in Aging and Aging-associated diseases through methylation of DNA, histone modification and non-coding RNA (ncRNA). Comprehension and relevant alterations in these epigenetic modifications can lead to new therapeutic avenues of age-delaying contrivances. These processes affect gene transcription, DNA replication and DNA repair, comprehending epigenetics as a key factor in understanding Aging and developing new avenues for delaying Aging, clinical advancements in ameliorating aging-related diseases and rejuvenating health. In the present article, we have described and advocated the epigenetic role in Aging and associated diseases.

MFAP2, upregulated by m1A methylation, promotes colorectal cancer invasiveness via CLK3

BACKGROUND

Distant metastasis is the main cause of mortality in colorectal cancer (CRC) patients. N1-methyladenosine (m1A) is a type of epitranscriptome modification. While its regulatory effect on mRNA and its role in CRC metastasis remain unclear.

METHODS

The m1A methylation profile of mRNAs in CRC was revealed by m1A methylated RNA immunoprecipitation sequencing. The expression of MFAP2 in tumor tissues was measured by immunohistochemistry and then correlated with the clinical characteristics and prognosis of CRC patients. The role of MFAP2 in the invasiveness of CRC cells was evaluated by transwell assays and peritoneal metastatic model in nude mice. The downstream targets of MFAP2 was screened by mass spectrometry analysis. Then the role of MFAP2-CLK3 signaling axis was verified by cotransfecting MFAP2 siRNA and CLK3 plasmid in CRC cells.

RESULTS

Microfibril associated protein 2 (MFAP2) mRNA was overexpressed and m1A-hypermethylated in CRC. High expression of MFAP2 was closely related to lymph node metastasis and distant metastasis, leading to poor prognosis in patients with CRC. In vivo and in vitro studies showed that silencing of MFAP2 inhibited the migration, invasion and metastasis of CRC cells. CDC Like Kinase 3 (CLK3) was a potential downstream target of MFAP2. Further studies showed that MFAP2 depletion might induce autophagic degradation of CLK3, and the role of MFAP2 in the invasiveness of CRC cells was dependent on CLK3.

CONCLUSIONS

Our results uncover a newly identified MFAP2-CLK3 signaling axis, which is a potential therapeutic target for CRC metastasis.

Intersections of Ubiquitin-Proteosome System and Autophagy in Promoting Growth of Glioblastoma Multiforme: Challenges and Opportunities

Glioblastoma multiforme (GBM) is a brain tumor notorious for its propensity to recur after the standard treatments of surgical resection, ionizing radiation (IR), and temozolomide (TMZ). Combined with the acquired resistance to standard treatments and recurrence, GBM is an especially deadly malignancy with hardly any worthwhile treatment options. The treatment resistance of GBM is influenced, in large part, by the contributions from two main degradative pathways in eukaryotic cells: ubiquitin-proteasome system (UPS) and autophagy. These two systems influence GBM cell survival by removing and recycling cellular components that have been damaged by treatments, as well as by modulating metabolism and selective degradation of components of cell survival or cell death pathways. There has recently been a large amount of interest in potential cancer therapies involving modulation of UPS or autophagy pathways. There is significant crosstalk between the two systems that pose therapeutic challenges, including utilization of ubiquitin signaling, the degradation of components of one system by the other, and compensatory activation of autophagy in the case of proteasome inhibition for GBM cell survival and proliferation. There are several important regulatory nodes which have functions affecting both systems. There are various molecular components at the intersections of UPS and autophagy pathways that pose challenges but also show some new therapeutic opportunities for GBM. This review article aims to provide an overview of the recent advancements in research regarding the intersections of UPS and autophagy with relevance to finding novel GBM treatment opportunities, especially for combating GBM treatment resistance.

Biochanin A inhibits lung adenocarcinoma progression by targeting ZEB1

Lung adenocarcinoma is the major subtype of lung cancer, accounting for approximately 40% of lung cancers. During clinical treatment, the emergence of chemotherapy resistance seriously affects the effectiveness of treatment. Thus, finding new chemotherapeutic sensitizers is considered to be one of the effective solutions. Biochanin A, as a naturally occurring isoflavone, has been demonstrated to exhibit anticancer effects in various tumors. However, the potential mechanisms of Biochanin A to inhibit tumor development have not been clarified. In the present study, we found that the combinational treatment of cisplatin and Biochanin A exhibited strong synergistic repression on lung adenocarcinoma growth and progression in vitro and in vivo. Considering that epithelial-mesenchymal transition (EMT) is recognized to be associated with both chemoresistance and metastasis, we examined the EMT-related markers and found that Biochanin A could specifically inhibit the expression of ZEB1. Importantly, Biochanin A chemosensitizes lung adenocarcinoma and inhibits cancer cell metastasis by suppressing ZEB1. At the molecular level, Biochanin A affects the stability of ZEB1 protein through the deubiquitination pathway and thereby influences the progression of lung adenocarcinoma. In conclusion, our finding elucidates the potential efficacy of Bichanin A as a chemosensitizer and provides new strategy for the chemotherapy of advanced lung adenocarcinoma.

Polo-Like Kinase 2 Plays an Essential Role in Cytoprotection against MG132-Induced Proteasome Inhibition via Phosphorylation of Serine 19 in HSPB5

Protein homeostasis, including protein folding, refolding, and degradation, is thought to decline with aging. HSPB5 (also known as αB-crystallin) prevents target protein aggregation as a molecular chaperone and exhibits a cytoprotective function against various cell stresses. To elucidate the effect of HSPB5 on endoplasmic reticulum (ER) stress, we searched for novel binding proteins of HSPB5 using the proximity-dependent biotin labeling method. Proteins presumed to interact with HSPB5 in cells treated with the proteasome inhibitor MG132 were identified by a reversible biotin-binding capacity method combining tamavidin2-REV magnetic beads and mass spectrometry. We discovered a new binding protein for HSPB5, polo-like kinase 2 (PLK2), which is an apoptosis-related enzyme. The expression of PLK2 was upregulated by MG132 treatment, and it was co-localized with HSPB5 near the ER in L6 muscle cells. Inhibition of PLK2 decreased ER stress-induced phosphorylation of serine 19 in HSPB5 and increased apoptosis by activation of caspase 3 under ER stress. Overexpression of HSPB5 (WT) suppressed the ER stress-induced caspase 3 activity, but this was not observed with phospho-deficient HSPB5 (3A) mutants. These results clarify the role of HSPB5 phosphorylation during ER stress and suggest that the PLK2/HSPB5 pathway plays an essential role in cytoprotection against proteasome inhibition-induced ER stress.

Oxidative Stress and Mitochondrial Dysfunction Associated with Peripheral Neuropathy in Type 1 Diabetes

Significance: This review highlights the many intracellular processes generating reactive oxygen species (ROS) in the peripheral nervous system in the context of type 1 diabetes. The major sources of superoxide and hydrogen peroxide (H₂O₂) are described, and scavenging systems are explained. Important roles of ROS in regulating normal redox signaling and in a disease setting, such as diabetes, contributing to oxidative stress and cellular damage are outlined. The primary focus is the role of hyperglycemia in driving elevated ROS production and oxidative stress contributing to neurodegeneration in diabetic neuropathy (within the dorsal root ganglia [DRG] and peripheral nerve). Recent Advances: Contributors to ROS production under high intracellular glucose concentration such as mitochondria and the polyol pathway are discussed. The primarily damaging impact of ROS on multiple pathways including mitochondrial function, endoplasmic reticulum (ER) stress, autophagy, and epigenetic signaling is covered. Critical Issues: There is a strong focus on mechanisms of diabetes-induced mitochondrial dysfunction and how this may drive ROS production (in particular superoxide). The mitochondrial sites of superoxide/H₂O₂ production via mitochondrial metabolism and aerobic respiration are reviewed. Future Directions: Areas for future development are highlighted, including the need to clarify diabetes-induced changes in autophagy and ER function in neurons and Schwann cells. In addition, more clarity is needed regarding the sources of ROS production at mitochondrial sites under high glucose concentration (and lack of insulin signaling). New areas of study should be introduced to investigate the role of ROS, nuclear lamina function, and epigenetic signaling under diabetic conditions in peripheral nerve.

Keeping the beat against time: Mitochondrial fitness in the aging heart

The process of aging strongly correlates with maladaptive architectural, mechanical, and biochemical alterations that contribute to the decline in cardiac function. Consequently, aging is a major risk factor for the development of heart disease, the leading cause of death in the developed world. In this review, we will summarize the classic and recently uncovered pathological changes within the aged heart with an emphasis on the mitochondria. Specifically, we describe the metabolic changes that occur in the aging heart as well as the loss of mitochondrial fitness and function and how these factors contribute to the decline in cardiomyocyte number. In addition, we highlight recent pharmacological, genetic, or behavioral therapeutic intervention advancements that may alleviate age-related cardiac decline.

C-terminal glutamine acts as a C-degron targeted by E3 ubiquitin ligase TRIM7

The exposed N-terminal or C-terminal residues of proteins can act, in cognate sequence contexts, as degradation signals (degrons) that are targeted by specific E3 ubiquitin ligases for proteasome-dependent degradation by N-degron or C-degron pathways. Here, we discovered a distinct C-degron pathway, termed the Gln/C-degron pathway, in which the B30.2 domain of E3 ubiquitin ligase TRIM7 (TRIM7B30.2) mediates the recognition of proteins bearing a C-terminal glutamine. By determining crystal structures of TRIM7B30.2 in complexes with various peptides, we show that TRIM7B30.2 forms a positively charged binding pocket to engage the "U"-shaped Gln/C-degron. The four C-terminal residues of a substrate play an important role in C-degron recognition, with C-terminal glutamine as the principal determinant. In vitro biochemical and cellular experiments were used to further analyze the substrate specificity and selective degradation of the Gln/C-degron by TRIM7.

The different autophagy degradation pathways and neurodegeneration

The term autophagy encompasses different pathways that route cytoplasmic material to lysosomes for degradation and includes macroautophagy, chaperone-mediated autophagy, and microautophagy. Since these pathways are crucial for degradation of aggregate-prone proteins and dysfunctional organelles such as mitochondria, they help to maintain cellular homeostasis. As post-mitotic neurons cannot dilute unwanted protein and organelle accumulation by cell division, the nervous system is particularly dependent on autophagic pathways. This dependence may be a vulnerability as people age and these processes become less effective in the brain. Here, we will review how the different autophagic pathways may protect against neurodegeneration, giving examples of both polygenic and monogenic diseases. We have considered how autophagy may have roles in normal CNS functions and the relationships between these degradative pathways and different types of programmed cell death. Finally, we will provide an overview of recently described strategies for upregulating autophagic pathways for therapeutic purposes.

Role of BAG5 in Protein Quality Control: Double-Edged Sword?

Cardiovascular disorder is the major health burden and cause of death among individuals worldwide. As the cardiomyocytes lack the ability for self-renewal, it is utmost necessary to surveil the protein quality in the cells. The Bcl-2 associated anthanogene protein (BAG) family and molecular chaperones (HSP70, HSP90) actively participate in maintaining cellular protein quality control (PQC) to limit cellular dysfunction in the cells. The BAG family contains a unique BAG domain which facilitates their interaction with the ATPase domain of the heat shock protein 70 (HSP70) to assist in protein folding. Among the BAG family members (BAG1-6), BAG5 protein is unique since it has five domains in tandem, and the binding of BD5 induces certain conformational changes in the nucleotide-binding domain (NBD) of HSP70 such that it loses its affinity for binding to ADP and results in enhanced protein refolding activity of HSP70. In this review, we shall describe the role of BAG5 in modulating mitophagy, endoplasmic stress, and cellular viability. Also, we have highlighted the interaction of BAG5 with other proteins, including PINK, DJ-1, CHIP, and their role in cellular PQC. Apart from this, we have described the role of BAG5 in cellular metabolism and aging.

Metabolism guided optimization of peptidomimetics as non-covalent proteasome inhibitors for cancer treatment

A series of novel non-covalent peptidomimetic proteasome inhibitors possessing bulky group at the C-terminus and N-alkylation at the N-terminus were designed with the aim to increase metabolic stabilities in vivo. All the target compounds were screened for their inhibitory activities against human 20S proteasome, and most analogs exhibited notable potency compared with the positive control bortezomib with IC₅₀ values lower than 10 nM, which also displayed potent cytotoxic activities against multiple myeloma (MM) cell lines and human acute myeloid leukemia (AML) cells. Furthermore, whole blood stability and in vivo proteasome inhibitory activity experiments of selected compounds were conducted for further evaluation, and the representative compound 43 (IC₅₀ = 8.39 ± 2.32 nM, RPMI-8226: IC₅₀ = 15.290 ± 2.281 nM, MM-1S: IC₅₀ = 9.067 ± 3.103 nM, MV-4-11: IC₅₀ = 2.464 ± 0.713 nM) revealed a half-life extension of greater than 9-fold (329.21 min VS 36.79 min) and potent proteasome inhibitory activity in vivo. The positive results confirmed the reliability of the metabolism guided optimization strategy, and the analogs discovered are potential leads for exploring new anti-MM drugs.

N-Acetyltransferase 8 Promotes Viral Replication by Increasing the Stability of Enterovirus 71 Nonstructural Proteins

Enterovirus 71 (EV71) is deemed as a re-emergent pathogen with recent outbreaks worldwide. EV71 infection causes hand, foot and mouth disease (HFMD) and has been associated with severe cardiac and central nervous system complications and even death. Viruses need host factors to complete their life cycle, thus the identification of the host factors for EV71 infection is pivotal to new antiviral research. Emerging evidence has highlighted the importance of protein acetylation during infection of various human viruses. The endoplasmic reticulum, as the prominent organelle of EV71 replication, also has its unique acetylation regulation mechanism. However, the pathogenesis of EV71 and its relationship with the ER-based acetylation machinery are not fully understood. In this study, we demonstrated for the first time that the ER-resident acetyltransferase NAT8 is a host factor for EV71 infection. Inhibiting NAT8 with CRISPR or a small compound significantly suppressed EV71 infection in SK-N-SH cells. NAT8 promoted EV71 replication in an acetyltransferase activity-dependent manner. Additionally, we found NAT8 facilitates EV71 infection through interacting with EV71 2B,3AB and 3C proteins and increasing the stability of these proteins. These results uncovered a novel function of NAT8 and elucidated a new mechanism underlying the regulation of EV71 replication. Importance Enterovirus 71 (EV71) is one of the most common pathogens that cause hand, foot and mouth disease in young children and some patients experience severe or fatal neurologic consequences. To ensure efficient replication, the virus must hijack multiple host factors for its own benefit. Here we show that the ER-resident acetyltransferase NAT8 is a host factor for EV71 infection. EV71 fails to complete its infection in various cells in the absence of NAT8. We further show that NAT8 benefits EV71 replication in an acetyltransferase activity-dependent manner. Finally, we show that NAT8 facilitates EV71 infection through interacting with EV71 2B,3AB and 3C proteins and increasing the stability of these proteins. These results uncovered a novel function of NAT8 in EV71 infection and elucidated a new mechanism underlying the regulation of EV71 replication.

Heat Shock Protein 90 as Therapeutic Target for CVDs and Heart Ageing

Cardiovascular diseases (CVDs) are the leading cause of death globally, representing approximately 32% of all deaths worldwide. Molecular chaperones are involved in heart protection against stresses and age-mediated accumulation of toxic misfolded proteins by regulation of the protein synthesis/degradation balance and refolding of misfolded proteins, thus supporting the high metabolic demand of the heart cells. Heat shock protein 90 (HSP90) is one of the main cardioprotective chaperones, represented by cytosolic HSP90a and HSP90b, mitochondrial TRAP1 and ER-localised Grp94 isoforms. Currently, the main way to study the functional role of HSPs is the application of HSP inhibitors, which could have a different way of action. In this review, we discussed the recently investigated role of HSP90 proteins in cardioprotection, atherosclerosis, CVDs development and the involvements of HSP90 clients in the activation of different molecular pathways and signalling mechanisms, related to heart ageing.

Comparative proteomic profiling reveals a pathogenic role for the O-GlcNAcylated AIMP2-PARP1 complex in aging-related hepatic steatosis in mice

The prevalence of non-alcoholic fatty liver disease (NAFLD) increases with aging. However, the mechanism of aging-related NAFLD remains unclear. Herein, we constructed an aging-related hepatic steatosis model and analyzed the differentially expressed proteins (DEPs) in livers from young and old mice using liquid chromatography-mass spectrometry. Five hundred and eighty-eight aging-related DEPs and novel pathways were identified. Aminoacyl tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2), the most significantly upregulated protein, promoted poly(ADP-ribose) polymerase 1 (PARP1) activation in aging-related hepatic steatosis. Additionally, mice liver-specific O-GlcNAcase knockout promoted AIMP2 and PARP1 expression. O-GlcNAc transferase (OGT) overexpression and O-GlcNAcase inhibition by genetic or pharmaceutical manipulations increased AIMP2 and PARP1 levels in vitro. Mechanistically, O-GlcNAcylation increased AIMP2 protein stability, leading to its aggregation. Our study reveals O-GlcNAcylated AIMP2 as a novel pathogenic regulator of aging-related hepatic steatosis.

Amino Acid Homeostasis in Mammalian Cells with a Focus on Amino Acid Transport

Amino acid homeostasis is maintained by import, export, oxidation, and synthesis of nonessential amino acids, and by the synthesis and breakdown of protein. These processes work in conjunction with regulatory elements that sense amino acids or their metabolites. During and after nutrient intake, amino acid homeostasis is dominated by autoregulatory processes such as transport and oxidation of excess amino acids. Amino acid deprivation triggers processes such as autophagy and the execution of broader transcriptional programs to maintain plasma amino acid concentrations. Amino acid transport plays a crucial role in the absorption of amino acids in the intestine, the distribution of amino acids across cells and organs, the recycling of amino acids in the kidney, and the recycling of amino acids after protein breakdown.

Protein structure and aggregation: a marriage of necessity ruled by aggregation gatekeepers

Protein aggregation propensity is a pervasive and seemingly inescapable property of proteomes. Strikingly, a significant fraction of the proteome is supersaturated, meaning that, for these proteins, their native conformation is less stable than the aggregated state. Maintaining the integrity of a proteome under such conditions is precarious and requires energy-consuming proteostatic regulation. Why then is aggregation propensity maintained at such high levels over long evolutionary timescales? Here, we argue that the conformational stability of the native and aggregated states are correlated thermodynamically and that codon usage strengthens this correlation. As a result, the folding of stable proteins requires kinetic control to avoid aggregation, provided by aggregation gatekeepers. These unique residues are evolutionarily selected to kinetically favor native folding, either on their own or by coopting chaperones.

DAF-16 acts as the "hub" of astaxanthin's anti-aging mechanism to improve aging-related physiological functions in Caenorhabditis elegans

Astaxanthin (AX) is a xanthophyll carotenoid that can effectively inhibit the production of peroxides and thereby protect the body from oxidative damage. In recent years, AX had been shown to have anti-aging properties, both in vivo and in vitro. However, the underlying mechanisms by which AX regulates senescence related proteins and signaling pathways remain unclear. Therefore, we used Caenorhabditis elegans (C. elegans) model binding proteomics to reveal AX anti-aging activity and its molecular mechanism. Our results suggest that AX promotes the health and lifespan of C. elegans by improving mobility, reducing the accumulation of age pigments, and increasing resistance to heat stress. In terms of the underlying mechanism, AX helps prolong the life of worms by regulating AGE-1 in the insulin signaling pathway, promoting the transport of DAF-16 into the nucleus and then up-regulating the expression level of DAF-16's downstream proteins (such as superoxide dismutase [Mn] 2 (SOD-3), heat shock proteins (HSPs), glutathione s-transferase (GST-4), etc.). Furthermore, AX may be a relevant response target for activation of dietary restriction pathways in vivo as a dietary restriction mimic. Meanwhile, proteomics data confirmed that there were 15 proteins enriched in the longevity regulation pathway. AX mainly regulates oxidative stress and the aging process by modulating the insulin signaling pathway around DAF-16 as the "hub". In addition to the insulin signaling pathway, other pathways including dietary restriction, AMP-activated protein kinase (AMPK), and mammal target of rapamycin (mTOR) are also dependent on DAF-16. These findings expand and deepen our knowledge of the underlying mechanism by which AX extends the lifespan of C. elegans.

The ubiquitin-proteasome system and autophagy: self-digestion for metabolic health

Type 2 diabetes mellitus (T2DM) is a global health challenge. Therefore, understanding the molecular mechanisms underlying the pathophysiology of T2DM is key to improving current therapies. Loss of protein homeostasis leads to the accumulation of damaged proteins in cells, which results in tissue dysfunction. The elimination of damaged proteins occurs through the ubiquitin-proteasome system (UPS) and autophagy. In this review, we describe the mutual regulation between the UPS and autophagy and the involvement of these two proteolytic systems in metabolic dysregulation, insulin resistance, and T2DM. We propose that alterations in the UPS or autophagy contribute to triggering insulin resistance and the development of T2DM. In addition, these two pathways emerge as promising therapeutic targets for improving insulin resistance.

Dietary Restriction for Kidney Protection: Decline in Nephroprotective Mechanisms During Aging

Dietary restriction (DR) is believed to be one of the most promising approaches to extend life span of different animal species and to delay deleterious age-related physiological alterations and diseases. Among others, DR was shown to ameliorate acute kidney injury (AKI) and chronic kidney disease (CKD). However, to date, a comprehensive analysis of the mechanisms of the protective effect of DR specifically in kidney pathologies has not been carried out. The protective properties of DR are mediated by a range of signaling pathways associated with adaptation to reduced nutrient intake. The adaptation is accompanied by a number of metabolic changes, such as autophagy activation, metabolic shifts toward lipid utilization and ketone bodies production, improvement of mitochondria functioning, and decreased oxidative stress. However, some studies indicated that with age, the gain of DR-mediated positive remodeling gradually decreases. This may be an obstacle if we seek to translate the DR approach into a clinic for the treatment of kidney diseases as most patients with AKI and CKD are elderly. It is well known that aging is accompanied by impairments in a huge variety of organs and systems, such as hormonal regulation, stress sensing, autophagy and proteasomal activity, gene expression, and epigenome profile, increased damage to macromolecules and organelles including mitochondria. All these age-associated changes might be the reasons for the reduced protective potential of the DR during aging. We summarized the available mechanisms of DR-mediated nephroprotection and described ways to improve the effectiveness of this approach for an aged kidney.

Age-related changes in expression of lysine48 and lysine63 ubiquitin linkages in dopamine neurons of midbrain in mice

Ubiquitination of target proteins is mediated via different ubiquitin lysine (K) linkages and determines the protein fates. In particular, K48 ubiquitin linkage targets proteins for degradation, whereas K63 ubiquitin linkage plays a nondegradative role. Parkinson's disease is an age-onset neurodegenerative disorder, which shows selective loss of dopamine neurons in substantia nigra pars compacta (SNC) and ubiquitinated protein aggregates. However, age-related expression of K48 and K63 ubiquitin linkages in SNC dopamine neurons remains elusive. We thus sought to explore the expression of K48 and K63 ubiquitin linkages in dopamine neurons in SNCs of mice at different ages with morphological and biochemical assays. Here our results indicated that in 5-week-old mice, dopamine neurons presented higher levels of K48 and K63 ubiquitin linkages than nondopamine neural cells. Aging promoted the formation of protein aggregates that are positive for both K48 and K63 ubiquitin linkages, together with tyrosine hydroxylase, a dopamine neuron marker. Moreover, 21-month-old mice showed fewer neural cells and tyrosine hydroxylase positive neurons in the SNCs than younger mice. Through biochemical analysis, the 21-month-old mice were shown to express more K48 ubiquitin linkages and less tyrosine hydroxylase and NeuN than the 5-week-old mice. These results suggest the first time that expression of K48 and K63 ubiquitin lysine linkages in midbrain dopamine neurons is age-related and may be involved in the loss of dopamine neurons.