BAG3 promotes autophagy and glutaminolysis via stabilizing glutaminase

Disruption of BAG3-mediated BACE1 stabilization alleviates neuropathology and memory deficits in a mouse model of Alzheimer's disease

β-Site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) is the rate-limiting enzyme for amyloid-β (Aβ) generation and is considered promising drug target for Alzheimer's disease (AD). The co-chaperone BAG3 (Bcl-2-associated athanogene 3) plays an important role in maintaining intracellular protein homeostasis by regulating heat shock protein 70 (HSP70). Here, we reported that BAG3 expression was significantly elevated in AD. It interacted with and stabilized BACE1 by delaying its degradation through ubiquitin-proteasome and autophagy-lysosomal pathways. BAG3E455K and BAG3R480A mutations reduced their interaction with BACE1. SPOT peptide arrays revealed that BACE1 carboxyl-terminal peptide fragments bound to the RQ domain of BAG3. This interaction can be disrupted by BACE1-derived peptide (Tat-BACE1480-494), leading to decreased BACE1 stability. In APP23/PS45 double transgenic mice, Tat-BACE1480-494 reduced BACE1 levels, decreased Aβ production, and improved synaptic and cognitive deficits. These findings indicate that BAG3 forms complex with HSP70 and BACE1 to stabilize BACE1, suggesting that Tat-BACE1480-494, may represent an ideal class of neuroprotective therapeutics against AD.

Role of ubiquitination-driven metabolisms in oncogenesis and cancer therapy

Ubiquitination represents one of the most critical post-translational modifications, comprising a multi-stage enzyme process that plays a pivotal role in a myriad of cellular biological activities. The deregulation of the processes of ubiquitination and deubiquitination is associated with the development of cancers and other diseases. This typescript reviews the impact of ubiquitination on metabolic processes, elucidating the regulatory functions of ubiquitination on pivotal enzymes within metabolic pathways in pathological contexts. It underscores the role of ubiquitination-driven metabolism disorders in the etiology of cancers, and oncogenesis, and highlights the potential therapeutic efficacy of targeting ubiquitination-driven enzymes in cancer metabolism, their combination with immune checkpoint inhibitors, and their clinical applications.

Endogenous protein S100A14 stabilizes glutaminase to render hepatocellular carcinoma resistant to sorafenib

BACKGROUND

Many cases of advanced hepatocellular carcinoma (HCC) are resistant to the widely used drug sorafenib, which worsens prognosis. While many studies have explored how acquired resistance emerges during drug exposure, the mechanism underlying primary resistance before treatment still remain elusive.

METHODS

Single-cell lineage tracing and RNA sequencing were performed to identify primary sorafenib-resistant lineages in HCC. Differential gene expression analysis was employed to identify the biomarkers of drug-resistant lineage cells. Cell viability and colony formation assays were adopted to assess the involvement of S100A14 on sorafenib resistance. Co-immunoprecipitation (CO-IP) and mass spectrometry analysis were conducted to uncover the downstream targets and regulatory mechanisms of S100A14 in primary resistance to sorafenib. In vivo mouse xenograft experiments were carried out to assess the effect of S100A14 or its interacting protein glutaminase (GLS) on primary resistance to sorafenib in HCC.

RESULTS

Single-cell lineage tracing identified a cluster of sorafenib primary resistant cells, and S100A14, a Ca2+-binding protein, was determined to be a critical biomarker for primary resistance to sorafenib. Knockdown of S100A14 significantly increases sorafenib treatment sensitivity in HCC cells. Mechanistically, S100A14 binds to GLS and blocks its phosphorylation at residues Y308 and S314, which in turn inhibits its ubiquitination and subsequent degradation. By stabilizing GLS, S100A14 reduces oxidative stress in HCC cells, thereby antagonizing sorafenib-induced apoptosis. Inhibiting S100A14 or GLS significantly improved sorafenib efficacy against xenograft tumors in vivo.

CONCLUSIONS

Our results demonstrate that S100A14 plays a pivotal role in promoting primary resistance to sorafenib by stabilizing GLS to reduce oxidative stress, and acts as a potential therapeutic target to enhance the efficacy of sorafenib in HCC patients.

Succinylation of SERCA2a at K352 Promotes Its Ubiquitinoylation and Degradation by Proteasomes in Sepsis-Induced Heart Dysfunction

BACKGROUND

Intracellular Ca2+ cycling governs effective myocardial systolic contraction and diastolic relaxation. SERCA2a (sarco/endoplasmic reticulum Ca2+ ATPase type 2a), which plays a crucial role in controlling intracellular Ca2+ signaling and myocardial cell function, is downregulated and inactivated during sepsis-induced heart dysfunction. However, the cause of this dysregulation remains unclear. In this study, we investigated the effect of lysine succinylation in lipopolysaccharide-induced septic heart dysfunction through global succinylome analysis of myocardial tissues from septic rats.

METHODS

We conducted a succinylome profiling and developed a protein language model-based framework to prioritize succinylation at a functionally important site, and further analysis revealed crosstalk between ubiquitination and succinylation of SERCA2a. The succinylation of SERCA2a in septic rats or lipopolysaccharide-treated cells were detected by co-immunoprecipitation. Thereafter, a desuccinylated SERCA2aK352R was introduced and its function and stability were determined by Ca2+ transient and Western blot, respectively. Meanwhile, the effect on SERCA2aK352R on heart function was assessed in vivo by echocardiography and hemodynamics.

RESULTS

We identified 10 324 succinylated lysine sites in heart tissues, including 1042 differentially succinylated lysine sites, in response to lipopolysaccharide. SERCA2a was hypersuccinylated in the myocardial tissues of septic rats and lipopolysaccharide-treated cardiomyocytes. Increased ubiquitination level, reduced protein level, and activity of SERCA2a were observed, along with increased succinylation of SERCA2a in vivo and in vitro. K352 was essential for SERCA2a succinylation, which reduced SERCA2a protein level by promoting formation of the K48 ubiquitin chain on SERCA2a and its degradation by proteasomes. Co-immunoprecipitation combined with liquid chromatography-tandem mass spectrometry identified that SIRT2 (sirtuin2), a deacylase, exhibited interaction with SERCA2a. Furthermore, SIRT2 decreased K352 succinylation of SERCA2a, suggesting that SIRT2 may function as a desuccinylase for SERCA2a.

CONCLUSIONS

Succinylation of SERCA2a at K352, which was controlled by SIRT2, promotes its ubiquitinoylation and degradation by proteasomes in sepsis-induced heart dysfunction.

Neurofilament accumulation disrupts autophagy in giant axonal neuropathy

Neurofilament accumulation is associated with many neurodegenerative diseases, but it is the primary pathology in giant axonal neuropathy (GAN). This childhood-onset autosomal recessive disease is caused by loss-of-function mutations in gigaxonin, the E3 adaptor protein that enables neurofilament degradation. Using a combination of genetic and RNA interference approaches, we found that dorsal root ganglia from mice lacking gigaxonin have impaired autophagy and lysosomal degradation through 2 mechanisms. First, neurofilament accumulations interfere with the distribution of autophagic organelles, impairing their maturation and fusion with lysosomes. Second, the accumulations attract the chaperone 14-3-3, which is responsible for the proper localization of the key autophagy regulator transcription factor EB (TFEB). We propose that this dual disruption of autophagy contributes to the pathogenesis of other neurodegenerative diseases involving neurofilament accumulations.

The curious case of mitochondrial sirtuin in rewiring breast cancer metabolism: Mr Hyde or Dr Jekyll?

Mammalian sirtuins are class III histone deacetylases involved in the regulation of multiple biological processes including senescence, DNA repair, apoptosis, proliferation, caloric restriction, and metabolism. Among the mammalian sirtuins, SIRT3, SIRT4, and SIRT5 are localized in the mitochondria and collectively termed the mitochondrial sirtuins. Mitochondrial sirtuins are NAD+-dependent deacetylases that play a central role in cellular metabolism and function as epigenetic regulators by performing post-translational modification of cellular proteins. Several studies have identified the role of mitochondrial sirtuins in age-related pathologies and the rewiring of cancer metabolism. Mitochondrial sirtuins regulate cellular functions by contributing to post-translational modifications, including deacetylation, ADP-ribosylation, demalonylation, and desuccinylation of diverse cellular proteins to maintain cellular homeostasis. Here, we review and discuss the structure and function of the mitochondrial sirtuins and their role as metabolic regulators in breast cancer. Altered breast cancer metabolism may promote tumor progression and has been an essential target for therapy. Further, we discuss the potential role of targeting mitochondrial sirtuin and its impact on breast cancer progression using sirtuin inhibitors and activators as anticancer agents.

SIRT5-mediated GLS and GDH desuccinylation attenuates the autophagy of bovine mammary epithelial cells induced by ammonia

Sirtuin 5 (SIRT5) in mitochondria possesses a strong capacity for lysine desuccinylation, involving in various biological processes. Our previous research demonstrated that NH3 regulated autophagy dependent on SIRT5 in bovine mammary epithelial cells (bMECs). Interestingly, we discovered that SIRT5 reduced the content of NH3 and glutamate by inhibiting GLS activity in bMECs, the ratio of ADP/ATP also declined. In this study, we identified that SIRT5 interacted with endogenous GLS and GDH through Co-IP assay, but had no effect on endogenous GLS and GDH expression. SIRT5 made the succinylation levels of GLS and GDH significantly declined and resulted in the reduction of GLS and GDH activity. Next, the content of ammonia and glutamate, as well as the related autophagy markers were measured, we found that SIRT5 affected the glutamine metabolism, which attenuated ammonia release in MAC-T cells, accompanying with cellular autophagy decline, reducing the formation of autophagosome. Deletion of SIRT5 gene in MAC-T cells by means of CRISPR-cas9, we found the content of NH3 and glutamate increased, as well as autophagy promoted, which could be alleviated by SIRT5 overexpression. SIRT5 KO also resulted in increase of succinylation of GLS and GDH, as well as autophagy response in bMECs. Furthermore, SIRT5 promoted the maintenance of mitochondria homeostasis. Mechanistically, SIRT5 reduced ammonia release by modulating the succinylation levels and enzymatic activities of GLS and GDH in mitochondria and promoted the maintenance of mitochondria homeostasis, as well as further attenuated ammonia-stimulated autophagy in bovine mammary epithelial cells.

Bacteria invade the brain following intracortical microelectrode implantation, inducing gut-brain axis disruption and contributing to reduced microelectrode performance

Brain-machine interface performance can be affected by neuroinflammatory responses due to blood-brain barrier (BBB) damage following intracortical microelectrode implantation. Recent findings suggest that certain gut bacterial constituents might enter the brain through damaged BBB. Therefore, we hypothesized that damage to the BBB caused by microelectrode implantation could facilitate microbiome entry into the brain. In our study, we found bacterial sequences, including gut-related ones, in the brains of mice with implanted microelectrodes. These sequences changed over time. Mice treated with antibiotics showed a reduced presence of these bacteria and had a different inflammatory response, which temporarily improved microelectrode recording performance. However, long-term antibiotic use worsened performance and disrupted neurodegenerative pathways. Many bacterial sequences found were not present in the gut or in unimplanted brains. Together, the current study established a paradigm-shifting mechanism that may contribute to chronic intracortical microelectrode recording performance and affect overall brain health following intracortical microelectrode implantation.

HSF1 at the crossroads of chemoresistance: from current insights to future horizons in cell death mechanisms

Heat Shock Factor 1 (HSF1) is a major transcriptional factor regulating the heat shock response and has become a potential target for overcoming cancer chemoresistance. This review comprehensively examines HSF1's role in chemoresistance and its potential as a therapeutic target in cancer. We explore the complex, intricate mechanism that regulates the activation of HSF1, HSF1's function in promoting resistance to chemotherapy, and the strategies used to manipulate HSF1 for therapeutic benefit. In addition, we discuss emerging research implicating HSF1's roles in autophagy, apoptosis, DNA damage repair, drug efflux, and thus chemoresistance. This article highlights the significance of HSF1 in cancer chemoresistance and its potential as a target for enhancing cancer treatment efficacy.

Unlocking the Hidden Potential of Cancer Therapy Targeting Lysine Succinylation

Lysine succinylation is an emerging post-translational modification of proteins. It involves the addition of the succinyl group to lysine residues of target proteins through both enzymatic and non-enzymatic pathways. This modification can alter the structure of the target protein, which, in turn, impacts protein activity and function and is involved in a wide range of diseases. In the field of cancer biology, lysine succinylation has been shown to exert a substantial influence on metabolic reprogramming of tumor cells, regulation of gene expression, and activation of oncogenic signaling pathways. Furthermore, lysine succinylation modulates the activity of immune cells, thereby affecting the immune evasion of tumor cells. Notably, researchers are currently developing inhibitors and activators of lysine succinylation which can inhibit tumor cell proliferation, migration, and metastasis, with potential usefulness in future clinical practice. This article provides an overview of the biological functions of lysine succinylation in cancer and its potential applications in cancer treatment, offering a novel perspective for future cancer management.

HSPB8-BAG3 chaperone complex modulates cell invasion in intrahepatic cholangiocarcinoma by regulating CASA-mediated Filamin A degradation

The incidence of intrahepatic cholangiocarcinoma (ICC) is steadily rising, and it is associated with a high mortality rate. Clinical samples were collected to detect the expression of HSPB8 and BAG3 in ICC tissues. ICC cells were cultured and transfected with plasmids that overexpressed or silenced specific genes to investigate the impact of gene expression alterations on cell function. qPCR and Western blot techniques were utilized to measure gene and protein expression levels. A wound healing assay was conducted to assess cell migration ability. The Transwell assay was used to assess cell invasion ability. Co-IP was used to verify the binding relationship between HSPB8 and BAG3. The effects of HSPB8 and BAG3 on lung metastasis of tumors in vivo were verified by constructing a metastatic tumor model. Through the above experiments, we discovered that the expressions of HSPB8 and BAG3 were up-regulated in ICC tissues and cells, and their expressions were positively correlated. The metastatic ability of ICC cells could be promoted or inhibited by upregulating or downregulating the expression of BAG3. Furthermore, the HSPB8-BAG3 chaperone complex resulted in the abnormal degradation of Filamin A by activating autophagy. Increased expression of Filamin A inhibits the migration and invasion of ICC cells. Overexpression of HSPB8 and BAG3 in vivo promoted the lung metastasis ability of ICC cells. The HSPB8-BAG3 chaperone complex promotes ICC cell migration and invasion by regulating CASA-mediated degradation of Filamin A, offering insights for enhancing ICC therapeutic strategies.

Targeting pivotal amino acids metabolism for treatment of leukemia

Metabolic reprogramming is a crucial characteristic of cancer, allowing cancer cells to acquire metabolic properties that support their survival, immune evasion, and uncontrolled proliferation. Consequently, targeting cancer metabolism has become an essential therapeutic strategy. Abnormal amino acid metabolism is not only a key aspect of metabolic reprogramming but also plays a significant role in chemotherapy resistance and immune evasion, particularly in leukemia. Changes in amino acid metabolism in tumor cells are typically driven by a combination of signaling pathways and transcription factors. Current approaches to targeting amino acid metabolism in leukemia include inhibiting amino acid transporters, blocking amino acid biosynthesis, and depleting specific amino acids to induce apoptosis in leukemic cells. Different types of leukemic cells rely on the exogenous supply of specific amino acids, such as asparagine, glutamine, arginine, and tryptophan. Therefore, disrupting the supply of these amino acids may represent a vulnerability in leukemia. This review focuses on the pivotal role of amino acids in leukemia metabolism, their impact on leukemic stem cells, and their therapeutic potential.

Sirtuins and their influence on autophagy

Sirtuins and autophagy are well-characterized agents that can promote longevity and protect individual organisms from age-associated diseases like neurodegenerative disorders. In recent years, more and more data has been obtained that discerned potential overlaps and crosstalk between Sirtuin proteins and autophagic activity. This review aims to summarize the advances within the field for each individual Sirtuin in mammalian systems. In brief, most Sirtuins have been implicated in promoting autophagy, with Sirtuin 1 and Sirtuin 6 showing the highest immediate involvement, while Sirtuin 4 and Sirtuin 5 only demonstrate occasional influence. The way Sirtuins regulate autophagy, however, is very diverse, as they have been shown to regulate gene expression of autophagy-associated genes and posttranslational modifications of proteins, with consequences for the activity and cellular localization of these proteins. They have also been shown to determine specific proteins for autophagic degradation. Overall, much data has been accumulated over recent years, yet many open questions remain. Especially although the dynamic between Sirtuin proteins and the immediate regulation of autophagic players like Light Chain 3B has been confirmed, many of these proteins have various orthologues in mammalian systems, and research so far has not exceeded the bona fide components of autophagy.

A novel method of Francisella infection of epithelial cells using HeLa cells expressing fc gamma receptor

BACKGROUND

Francisella tularensis, the causative agent of tularemia, is a facultative intracellular bacterium. Although the life cycle of this bacterium inside phagocytic cells (e.g., macrophages, neutrophils) has been well analyzed, the difficulty of gene silencing and editing genes in phagocytic cells makes it difficult to analyze host factors important for the infection. On the other hand, epithelial cell lines, such as HeLa, have been established as cell lines that are easy to perform gene editing. However, the infection efficiency of Francisella into these epithelial cells is extremely low.

METHODS

In order to facilitate the molecular biological analysis of Francisella infection using epithelial cells, we constructed an efficient infection model of F. tularensis subsp. novicida (F. novicida) in HeLa cells expressing mouse FcγRII (HeLa-FcγRII), and the system was applied to evaluate the role of host GLS1 on Francisella infection.

RESULTS

As a result of colony forming unit count, HeLa-FcγRII cells uptake F. novicida in a serum-dependent manner and demonstrated an approximately 100-fold increase in intracellular bacterial infection compared to parental HeLa cells. Furthermore, taking advantage of the gene silencing capability of HeLa-FcγRII cells, we developed GLS1, a gene encoding glutaminase, knockdown cells using lentiviral sh RNA vector and assessed the impact of GLS1 on F. novicida infection. LDH assay revealed that GLS1-knockdown HeLa-FcγRII cells exhibited increased cytotoxicity during infection with F. novicida compared with control HeLa-FcγRII cells. Furthermore, the cell death was inhibited by the addition of ammonia, the metabolite produced through glutaminase activity. These results suggest that ammonia plays an important role in the proliferation of F. novicida.

CONCLUSIONS

In this report, we proposed a new cell-based infection system for Francisella infection using HeLa-FcγRII cells and demonstrated its effectiveness. This system has the potential to accelerate cell-based infection assays, such as large-scale genetic screening, and to provide new insights into Francisella infection in epithelial cells, which has been difficult to analyze in phagocytic cells.

B3GALT4 modulates tumor progression and autophagy by AKT/mTOR signaling pathway in breast cancer

BACKGROUND

β-1,3-Galactosyltransferase-4 (B3GALT4), a member of the β-1,3-galactosyltransferase gene family, is essential to the development of many malignancies. However, its biological function in breast cancer is still unknown.

METHOD

Publically accessible datasets, as well as quantitative real-time PCR, western blot, and immunohistochemistry on our patient cohort were used to investigate the expression levels of B3GALT4 in breast cancer. The correlation of B3GALT4 expression with clinical histopathological data and mortality in breast cancer patients was investigated. The effects of B3GALT4 in breast cancer in vitro and in vivo were investigated. RNA-seq, western blot, autophagolysosomes, and the fluorescence intensity of LC3 were used to explore the effects of B3GALT4 on autophagy. Western blot and gene set enrichment analysis (GSEA) were used to identify the AKT/mTOR pathway.

RESULTS

B3GALT4 was significantly overexpressed in breast cancer tissues and was positively correlated with some aspects of clinicopathological status and poor prognosis. B3GALT4 overexpression significantly promoted cell proliferation, migration, and invasion, both in vitro and in vivo. B3GALT4 inhibition suppressed breast cancer cell proliferation, migration, and invasion in vitro. Suppression of B3GALT4 triggered autophagy and hindered the AKT/mTOR signaling pathway.

CONCLUSION

According to the present research, B3GALT4 blocked autophagy via the AKT/mTOR pathway and accelerated the growth of breast cancer. B3GALT4 may be an effective target for patients with breast cancer.

Corelating the molecular structure of BAG3 to its oncogenic role

BAG3 is a multifaceted protein characterised by having WW domain, PXXP motif and BAG domain. This protein gets upregulated during malignant transformation of cells and has been associated with poorer survival of patients. Procancerous activity of BAG domain of BAG3 is well documented. BAG domain interacts with ATPase domain of Hsp-70 preventing protein delivery to proteasome. This impediment results in enhanced cell survival, proliferation, resistance to apoptosis and chemoresistance. Besides BAG domain other two domains/motifs of BAG3 are under research vigilance to explore its further oncogenic role. This review summarises the role of different structural determinants of BAG3 in elevating oncogenesis. Based on the already existing findings, more interacting partners of BAG3 are anticipated. The anticipated partners of BAG3 can shed a wealth of information into the mechanistic insights of its proproliferative role. Proper insights into the mechanistic details adopted by BAG3 to curtail/elaborate activity of anticipated interacting partners can serve as a potent target for development of therapeutic interventions.

SIRT5-Mediated Desuccinylation of RAB7A Protects Against Cadmium-Induced Alzheimer's Disease-Like Pathology by Restoring Autophagic Flux

Cadmium (Cd) is a neurotoxic contaminant that induces cognitive decline similar to that observed in Alzheimer's disease (AD). Autophagic flux dysfunction is attributed to the pathogenesis of AD, and this study aimed to investigate the effect of autophagy on environmental Cd-induced AD progression and the underlying mechanism. Here, Cd exposure inhibited autophagosome-lysosome fusion and impaired lysosomal function, leading to defects in autophagic clearance and then to APP accumulation and nerve cell death. Proteomic analysis coupled with Ingenuity Pathway Analysis (IPA) identified SIRT5 as an essential molecular target in Cd-impaired autophagic flux. Mechanistically, Cd exposure hampered the expression of SIRT5, thus increasing the succinylation of RAB7A at lysine 31 and inhibiting RAB7A activity, which contributed to autophagic flux blockade. Importantly, SIRT5 overexpression led to the restoration of autophagic flux blockade, the alleviation of Aβ deposition and memory deficits, and the desuccinylation of RAB7A in Cd-exposed FAD4T mice. Additionally, SIRT5 levels decrease mainly in neurons but not in other cell clusters in the brains of AD patients according to single-nucleus RNA sequencing data from the public dataset GSE188545. This study reveals that SIRT5-catalysed RAB7A desuccinylation is an essential adaptive mechanism for the amelioration of Cd-induced autophagic flux blockade and AD-like pathogenesis.

Comprehensive proteomic analysis of the differential expression of 62 proteins following intracortical microelectrode implantation

Intracortical microelectrodes (IMEs) are devices designed to be implanted into the cerebral cortex for various neuroscience and neuro-engineering applications. A critical feature of IMEs is their ability to detect neural activity from individual neurons. Currently, IMEs are limited by chronic failure, largely considered to be caused by the prolonged neuroinflammatory response to the implanted devices. Over the past few years, the characterization of the neuroinflammatory response has grown in sophistication, with the most recent advances focusing on mRNA expression following IME implantation. While gene expression studies increase our broad understanding of the relationship between IMEs and cortical tissue, advanced proteomic techniques have not been reported. Proteomic evaluation is necessary to describe the diverse changes in protein expression specific to neuroinflammation, neurodegeneration, or tissue and cellular viability, which could lead to the further development of targeted intervention strategies designed to improve IME functionality. In this study, we have characterized the expression of 62 proteins within 180 μm of the IME implant site at 4-, 8-, and 16-weeks post-implantation. We identified potential targets for immunotherapies, as well as key pathways that contribute to neuronal dieback around the IME implant.

Glutaminolysis is a Potential Therapeutic Target for Kidney Diseases

Metabolic reprogramming contributes to the progression and prognosis of various kidney diseases. Glutamine is the most abundant free amino acid in the body and participates in more metabolic processes than other amino acids. Altered glutamine metabolism is a prominent feature in different kidney diseases. Glutaminolysis converts glutamine into the TCA cycle metabolite, alpha-ketoglutarate, via a cascade of enzymatic reactions. This metabolic pathway plays pivotal roles in inflammation, maladaptive repair, cell survival and proliferation, redox homeostasis, and immune regulation. Given the crucial role of glutaminolysis in bioenergetics and anaplerotic fluxes in kidney pathogenesis, studies on this cascade could provide a better understanding of kidney diseases, thus inspiring the development of potential methods for targeted therapy. Emerging evidence has shown that targeting glutaminolysis is a promising therapeutic strategy for ameliorating kidney disease. In this narrative review, equation including keywords related to glutamine, glutaminolysis and kidney are subjected to an exhaustive search on Pubmed database, we identified all relevant articles published before 1 April, 2024. Afterwards, we summarize the regulation of glutaminolysis in major kidney diseases and its underlying molecular mechanisms. Furthermore, we highlight therapeutic strategies targeting glutaminolysis and their potential clinical applications.

ABCG2 and SLC1A5 functionally interact to rewire metabolism and confer a survival advantage to cancer cells under oxidative stress

ABCG2, a member of the ABC transporter superfamily, is overexpressed in many human tumors and has long been studied for its ability to export a variety of chemotherapeutic agents, thereby conferring a multidrug resistance (MDR) phenotype. However, several studies have shown that ABCG2 can also confer an MDR-independent survival advantage to tumor cells exposed to stress. While investigating the mechanism by which ABCG2 enhances survival in stressful milieus, we have identified a physical and functional interaction between ABCG2 and SLC1A5, a member of the solute transporter superfamily and the primary transporter of glutamine in cancer cells. This interaction was accompanied by increased glutamine uptake, increased glutaminolysis, and rewired cellular metabolism, as evidenced by an increase in key metabolic enzymes and alteration of glutamine-dependent metabolic pathways. Specifically, we observed an increase in glutamine metabolites shuttled to the TCA cycle, and an increase in the synthesis of glutathione, accompanied by a decrease in basal levels of reactive oxygen species and a marked increase in cell survival in the face of oxidative stress. Notably, the knockdown of SLC1A5 or depletion of exogenous glutamine diminished ABCG2-enhanced autophagy flux, further implicating this solute transporter in ABCG2-mediated cell survival. This is, to our knowledge, the first report of a functionally significant physical interaction between members of the two major transporter superfamilies. Moreover, these observations may underlie the protective role of ABCG2 in cancer cells under duress and suggest a novel role for ABCG2 in the regulation of metabolism in normal and diseased states.

Aging-induced tRNAGlu-derived fragment impairs glutamate biosynthesis by targeting mitochondrial translation-dependent cristae organization

Mitochondrial cristae, infoldings of the mitochondrial inner membrane, undergo aberrant changes in their architecture with age. However, the underlying molecular mechanisms and their contribution to brain aging are largely elusive. Here, we observe an age-dependent accumulation of Glu-5'tsRNA-CTC, a transfer-RNA-derived small RNA (tsRNA), derived from nuclear-encoded tRNAGlu in the mitochondria of glutaminergic neurons. Mitochondrial Glu-5'tsRNA-CTC disrupts the binding of mt-tRNALeu and leucyl-tRNA synthetase2 (LaRs2), impairing mt-tRNALeu aminoacylation and mitochondria-encoded protein translation. Mitochondrial translation defects disrupt cristae organization, leading to damaged glutaminase (GLS)-dependent glutamate formation and reduced synaptosomal glutamate levels. Moreover, reduction of Glu-5'tsRNA-CTC protects aged brains from age-related defects in mitochondrial cristae organization, glutamate metabolism, synaptic structures, and memory. Thus, beyond illustrating a physiological role for normal mitochondrial cristae ultrastructure in maintaining glutamate levels, our study defines a pathological role for tsRNAs in brain aging and age-related memory decline.

Comprehensive Proteomic Analysis of the Differential Expression of 83 Proteins Following Intracortical Microelectrode Implantation

Intracortical microelectrodes (IMEs) are devices designed to be implanted into the cerebral cortex for various neuroscience and neuro-engineering applications. A critical feature of these devices is their ability to detect neural activity from individual neurons. Currently, IMEs are limited by chronic failure, largely considered to be caused by the prolonged neuroinflammatory response to the implanted devices. Over the decades, characterization of the neuroinflammatory response has grown in sophistication, with the most recent advances including advanced genomics and spatially resolved transcriptomics. While gene expression studies increase our broad understanding of the relationship between IMEs and cortical tissue, advanced proteomic techniques have not been reported. Proteomic evaluation is necessary to describe the diverse changes in protein expression specific to neuroinflammation, neurodegeneration, or tissue and cellular viability, which could lead to the development of more targeted intervention strategies designed to improve IME function. In this study, we have characterized the expression of 83 proteins within 180 μm of the IME implant site at 4-, 8-, and 16-weeks post-implantation. We identified potential targets for immunotherapies, as well as key pathways and functions that contribute to neuronal dieback around the IME implant.

Bacteria Invade the Brain Following Sterile Intracortical Microelectrode Implantation

Brain-machine interface performance is largely affected by the neuroinflammatory responses resulting in large part from blood-brain barrier (BBB) damage following intracortical microelectrode implantation. Recent findings strongly suggest that certain gut bacterial constituents penetrate the BBB and are resident in various brain regions of rodents and humans, both in health and disease. Therefore, we hypothesized that damage to the BBB caused by microelectrode implantation could amplify dysregulation of the microbiome-gut-brain axis. Here, we report that bacteria, including those commonly found in the gut, enter the brain following intracortical microelectrode implantation in mice implanted with single-shank silicon microelectrodes. Systemic antibiotic treatment of mice implanted with microelectrodes to suppress bacteria resulted in differential expression of bacteria in the brain tissue and a reduced acute inflammatory response compared to untreated controls, correlating with temporary improvements in microelectrode recording performance. Long-term antibiotic treatment resulted in worsening microelectrode recording performance and dysregulation of neurodegenerative pathways. Fecal microbiome composition was similar between implanted mice and an implanted human, suggesting translational findings. However, a significant portion of invading bacteria was not resident in the brain or gut. Together, the current study established a paradigm-shifting mechanism that may contribute to chronic intracortical microelectrode recording performance and affect overall brain health following intracortical microelectrode implantation.

Exploitation of Autophagy Inducers in the Management of Dementia: A Systematic Review

The social burden of dementia is remarkable since it affects some 57.4 million people all over the world. Impairment of autophagy in age-related diseases, such as dementia, deserves deep investigation for the detection of novel disease-modifying approaches. Several drugs belonging to different classes were suggested to be effective in managing Alzheimer's disease (AD) by means of autophagy induction. Useful autophagy inducers in AD should be endowed with a direct, measurable effect on autophagy, have a safe tolerability profile, and have the capability to cross the blood-brain barrier, at least with poor penetration. According to the PRISMA 2020 recommendations, we propose here a systematic review to appraise the measurable effectiveness of autophagy inducers in the improvement of cognitive decline and neuropsychiatric symptoms in clinical trials and retrospective studies. The systematic search retrieved 3067 records, 10 of which met the eligibility criteria. The outcomes most influenced by the treatment were cognition and executive functioning, pointing at a role for metformin, resveratrol, masitinib and TPI-287, with an overall tolerable safety profile. Differences in sample power, intervention, patients enrolled, assessment, and measure of outcomes prevents generalization of results. Moreover, the domain of behavioral symptoms was found to be less investigated, thus prompting new prospective studies with homogeneous design. PROSPERO registration: CRD42023393456.

Desmin mutations impact the autophagy flux in C2C12 cell in mutation-specific manner

Desmin is the main intermediate filament of striated and smooth muscle cells and plays a crucial role in maintaining the stability of muscle fiber during contraction and relaxation cycles. Being a component of Z-disk area, desmin integrates autophagic pathways, and the disturbance of Z-disk proteins' structure negatively affects chaperone-assisted selective autophagy (CASA). In the present study, we focused on alteration of autophagy flux in myoblasts expressing various Des mutations. We applied Western blotting, immunocytochemistry, RNA sequencing, and shRNA approach to demonstrate that DesS12F, DesA357P, DesL345P, DesL370P, and DesD399Y mutations. Mutation-specific effect on autophagy flux being most severe in aggregate-prone Des mutations such as DesL345P, DesL370P, and DesD399Y. RNA sequencing data confirmed the most prominent effect of these mutations on expression profile and, in particular, on autophagy-related genes. To verify CASA contribution to desmin aggregate formation, we suppressed CASA by knocking down Bag3 and demonstrated that it promoted aggregate formation and lead to downregulation of Vdac2 and Vps4a and upregulation of Lamp, Pink1, and Prkn. In conclusion, Des mutations showed a mutation-specific effect on autophagy flux in C2C12 cells with either a predominant impact on autophagosome maturation or on degradation and recycling processes. Aggregate-prone desmin mutations lead to the activation of basal autophagy level while suppressing the CASA pathway by knocking down Bag3 can promote desmin aggregate formation.

Monitoring and modelling the glutamine metabolic pathway: a review and future perspectives

BACKGROUND

Analysis of the glutamine metabolic pathway has taken a special place in metabolomics research in recent years, given its important role in cell biosynthesis and bioenergetics across several disorders, especially in cancer cell survival. The science of metabolomics addresses the intricate intracellular metabolic network by exploring and understanding how cells function and respond to external or internal perturbations to identify potential therapeutic targets. However, despite recent advances in metabolomics, monitoring the kinetics of a metabolic pathway in a living cell in situ, real-time and holistically remains a significant challenge.

AIM

This review paper explores the range of analytical approaches for monitoring metabolic pathways, as well as physicochemical modeling techniques, with a focus on glutamine metabolism. We discuss the advantages and disadvantages of each method and explore the potential of label-free Raman microspectroscopy, in conjunction with kinetic modeling, to enable real-time and in situ monitoring of the cellular kinetics of the glutamine metabolic pathway.

KEY SCIENTIFIC CONCEPTS

Given its important role in cell metabolism, the ability to monitor and model the glutamine metabolic pathways are highlighted. Novel, label free approaches have the potential to revolutionise metabolic biosensing, laying the foundation for a new paradigm in metabolomics research and addressing the challenges in monitoring metabolic pathways in living cells.

Skeletal Muscle-Specific Bis Depletion Leads to Muscle Dysfunction and Early Death Accompanied by Impairment in Protein Quality Control

Bcl-2-interacting cell death suppressor (BIS), also called BAG3, plays a role in physiological functions such as anti-apoptosis, cell proliferation, autophagy, and senescence. Whole-body Bis-knockout (KO) mice exhibit early lethality accompanied by abnormalities in cardiac and skeletal muscles, suggesting the critical role of BIS in these muscles. In this study, we generated skeletal muscle-specific Bis-knockout (Bis-SMKO) mice for the first time. Bis-SMKO mice exhibit growth retardation, kyphosis, a lack of peripheral fat, and respiratory failure, ultimately leading to early death. Regenerating fibers and increased intensity in cleaved PARP1 immunostaining were observed in the diaphragm of Bis-SMKO mice, indicating considerable muscle degeneration. Through electron microscopy analysis, we observed myofibrillar disruption, degenerated mitochondria, and autophagic vacuoles in the Bis-SMKO diaphragm. Specifically, autophagy was impaired, and heat shock proteins (HSPs), such as HSPB5 and HSP70, and z-disk proteins, including filamin C and desmin, accumulated in Bis-SMKO skeletal muscles. We also found metabolic impairments, including decreased ATP levels and lactate dehydrogenase (LDH) and creatine kinase (CK) activities in the diaphragm of Bis-SMKO mice. Our findings highlight that BIS is critical for protein homeostasis and energy metabolism in skeletal muscles, suggesting that Bis-SMKO mice could be used as a therapeutic strategy for myopathies and to elucidate the molecular function of BIS in skeletal muscle physiology.

Orchestration of Mitochondrial Function and Remodeling by Post-Translational Modifications Provide Insight into Mechanisms of Viral Infection

The regulation of mitochondria structure and function is at the core of numerous viral infections. Acting in support of the host or of virus replication, mitochondria regulation facilitates control of energy metabolism, apoptosis, and immune signaling. Accumulating studies have pointed to post-translational modification (PTM) of mitochondrial proteins as a critical component of such regulatory mechanisms. Mitochondrial PTMs have been implicated in the pathology of several diseases and emerging evidence is starting to highlight essential roles in the context of viral infections. Here, we provide an overview of the growing arsenal of PTMs decorating mitochondrial proteins and their possible contribution to the infection-induced modulation of bioenergetics, apoptosis, and immune responses. We further consider links between PTM changes and mitochondrial structure remodeling, as well as the enzymatic and non-enzymatic mechanisms underlying mitochondrial PTM regulation. Finally, we highlight some of the methods, including mass spectrometry-based analyses, available for the identification, prioritization, and mechanistic interrogation of PTMs.

Ubiquitination Links DNA Damage and Repair Signaling to Cancer Metabolism

Changes in the DNA damage response (DDR) and cellular metabolism are two important factors that allow cancer cells to proliferate. DDR is a set of events in which DNA damage is recognized, DNA repair factors are recruited to the site of damage, the lesion is repaired, and cellular responses associated with the damage are processed. In cancer, DDR is commonly dysregulated, and the enzymes associated with DDR are prone to changes in ubiquitination. Additionally, cellular metabolism, especially glycolysis, is upregulated in cancer cells, and enzymes in this metabolic pathway are modulated by ubiquitination. The ubiquitin-proteasome system (UPS), particularly E3 ligases, act as a bridge between cellular metabolism and DDR since they regulate the enzymes associated with the two processes. Hence, the E3 ligases with high substrate specificity are considered potential therapeutic targets for treating cancer. A number of small molecule inhibitors designed to target different components of the UPS have been developed, and several have been tested in clinical trials for human use. In this review, we discuss the role of ubiquitination on overall cellular metabolism and DDR and confirm the link between them through the E3 ligases NEDD4, APC/C^CDH1, FBXW7, and Pellino1. In addition, we present an overview of the clinically important small molecule inhibitors and implications for their practical use.

FBXW7 promotes autophagy and inhibits proliferation of oral squamous cell carcinoma

BACKGROUND

F-box and WD repeat domain containing 7 (FBXW7) is a critical tumor suppressor. The expression of FBXW7 is decreased in oral squamous cell carcinoma (OSCC) tissues and shows diagnosis value. We aimed to investigate the influence of FBXW7 overexpression on OSCC cell proliferation and autophagy.

METHODS

In Balb/c nude mice, CAL27 xenograft tumor model was established. Western blot was employed to evaluate protein level. Messenger RNA level was analyzed by quantitative reverse transcription-polymerase chain reaction. Colony formation assay and MTT assay were employed to evaluate cell proliferation.

RESULTS

FBXW7 expression was decreased in OSCC cell lines. FBXW7 inhibited cell proliferation of SCC9 and CAL27. FBXW7 increased Autophagy related 7 (Atg7), Beclin1 (BECN1), B-cell lymphoma 2 (BCL2) -associated X (BAX), BCL2 antagonist killer (BAK), and microtubule-associated protein 1 light chain 3 (LC3) levels and decreased MCL1 and BCL2 levels in CAL27 cells. FBXW7 decreased tumor volume and weight in CAL27 xenograft tumor model. FBXW7 increased BECN1, Atg7, and LC3 levels in CAL27 xenograft tumor model.

CONCLUSION

In conclusion, decreased expression of FBXW7 is confirmed in diverse OSCC cell lines. The enhanced FBXW7 expression inhibits cancer cell proliferation and promotes autophagy in both OSCC cells and xenograft tumor model.

The Ubiquitin-Proteasome System in Tumor Metabolism

Metabolic reprogramming, which is considered a hallmark of cancer, can maintain the homeostasis of the tumor environment and promote the proliferation, survival, and metastasis of cancer cells. For instance, increased glucose uptake and high glucose consumption, known as the "Warburg effect," play an essential part in tumor metabolic reprogramming. In addition, fatty acids are harnessed to satisfy the increased requirement for the phospholipid components of biological membranes and energy. Moreover, the anabolism/catabolism of amino acids, such as glutamine, cystine, and serine, provides nitrogen donors for biosynthesis processes, development of the tumor inflammatory environment, and signal transduction. The ubiquitin-proteasome system (UPS) has been widely reported to be involved in various cellular biological activities. A potential role of UPS in the metabolic regulation of tumor cells has also been reported, but the specific regulatory mechanism has not been elucidated. Here, we review the role of ubiquitination and deubiquitination modification on major metabolic enzymes and important signaling pathways in tumor metabolism to inspire new strategies for the clinical treatment of cancer.

BAG3: Nature's Quintessential Multi-Functional Protein Functions as a Ubiquitous Intra-Cellular Glue

BAG3 is a 575 amino acid protein that is found throughout the animal kingdom and homologs have been identified in plants. The protein is expressed ubiquitously but is most prominent in cardiac muscle, skeletal muscle, the brain and in many cancers. We describe BAG3 as a quintessential multi-functional protein. It supports autophagy of both misfolded proteins and damaged organelles, inhibits apoptosis, maintains the homeostasis of the mitochondria, and facilitates excitation contraction coupling through the L-type calcium channel and the beta-adrenergic receptor. High levels of BAG3 are associated with insensitivity to chemotherapy in malignant cells whereas both loss of function and gain of function variants are associated with cardiomyopathy.

A review of the mechanism of succinylation in cancer

Lysine succinylation is a novel, broad-spectrum, dynamic, non-enzymatic protein post-translational modification (PTM). Succinylation is essential for the regulation of protein function and control of various signaling and regulatory pathways. It is involved in several life activities, including glucose metabolism, amino acid metabolism, fatty acid metabolism, ketone body synthesis, and reactive oxygen species clearance, by regulating protease activity and gene expression. The level of succinylation is mainly regulated by succinyl donor, succinyltransferase, and desuccinylase. Many studies have confirmed that succinylation plays a role in tumorigenesis by creating tissue heterogeneity, and can promote or inhibit various cancers via the regulation of different substrate targets or signaling pathways. The mechanism of action of some antineoplastic drugs is related to succinylation. To better understand the role of succinylation modification in cancer development and treatment, the present study reviewed the current research content and latest progress of succinylation modification in cancer, which might provide a new direction and target for the prevention and treatment of cancer.

BAG3 promotes autophagy and suppresses NLRP3 inflammasome activation in Parkinson's disease

Background

Neuroinflammation mediated by microglia plays a key role in the pathogenesis of Parkinson's disease (PD), and our previous studies showed this was significantly inhibited by enhanced autophagy. In the autophagy pathway, Bcl2-associated athanogene (BAG)3 is a prominent co-chaperone, and we have shown BAG3 can regulate autophagy to clear the PD pathogenic protein α-synuclein. However, the connection between BAG3 and microglia mediated neuroinflammation is not clear.

Methods

In this study, we explored whether BAG3 regulated related neuroinflammation and its original mechanism in PD. An inflammatory model of PD was established by injecting adeno-associated virus (AAV)-BAG3 into the bilateral striatum of C57BL/6 male mice to induce overexpression of BAG3, followed by injection of lipopolysaccharide (LPS). The striatum was extracted at 3 days after injection of LPS for Western blotting and reverse transcription quantitative polymerase chain reaction (RT-qPCR), and immunohistochemical staining was performed at 21 days after injection. At the same time, LPS was used to induce activation of BV2 cells to verify the effect of BAG3 in vitro.

Results

Overexpression of BAG3 reduced LPS-induced pyroptosis by reducing activation of caspase-1, the NOD-like receptor family, and the pyrin domain-containing 3 (NLRP3) inflammasome, and by release of interleukin (IL)-1β and tumor necrosis factor (TNF)-α. The LPS-induced inflammatory environment inhibits autophagy, and overexpression of BAG3 can restore autophagy, which may be the mechanism by which BAG3 reduces neuronal inflammation in PD.

Conclusions

Our results demonstrate BAG3 promotes autophagy and suppresses NLRP3 inflammasome formation in PD.

MiR-135a-5p suppresses breast cancer cell proliferation, migration, and invasion by regulating BAG3

BACKGROUND

MicroRNAs (miRNAs) are involved in the progression of diverse human cancers. This work aimed to delve into how microRNA-135a-5p (miR-135a-5p) affects the biological behaviors of Breast Cancer (BC) cells.

METHODS

Gene Expression Omnibus (GEO) datasets were used to analyze the expression differences of miR-135a-5p in cancer tissues of BC patients. Quantitative real-time PCR and western blot were conducted to detect miR-135a-5p and Bcl-2 Associated Athanogene (BAG3) expression levels in BC tissues and cells, respectively. The proliferation, migration, invasion, and cell cycle of BC cells were detected by cell counting kit-8 assay, BrdU assay, wound healing assay, transwell assay, and flow cytometry. The targeted relationship between miR-135a-5p and BAG3 mRNA 3'UTR predicted by bioinformatics was further testified by a dual-luciferase reporter gene assay. Pearson's correlation analysis was adopted to analyze the correlation between miR-135a-5p expression and BAG3 expression. The downstream pathways of BAG3 were analyzed by the LinkedOmics database.

RESULTS

MiR-135a-5p was significantly down-regulated and BAG3 expression was significantly raised in BC tissues. MiR-135a-5p overexpression repressed the viability, migration and invasion of BC cells, and blocked cell cycle progression in G0/G1 phase while inhibiting miR-135a-5p worked oppositely. BAG3 was verified as a target of miR-135a-5p. Overexpression of BAG3 reversed the impacts of miR-135a-5p on the malignant biological behaviors of BC cells. The high expression of BAG3 was associated with the activation of the cell cycle, mTOR and TGF-β signaling pathways.

CONCLUSION

MiR-135a-5p regulates BAG3 to repress the growth, migration, invasion, and cell cycle progression of BC cells.

Glutamine Availability Regulates the Development of Aging Mediated by mTOR Signaling and Autophagy

Glutamine is a conditionally essential amino acid involved in energy production and redox homeostasis. Aging is commonly characterized by energy generation reduction and redox homeostasis dysfunction. Various aging-related diseases have been reported to be accompanied by glutamine exhaustion. Glutamine supplementation has been used as a nutritional therapy for patients and the elderly, although the mechanism by which glutamine availability affects aging remains elusive. Here, we show that chronic glutamine deprivation induces senescence in fibroblasts and aging in Drosophila melanogaster, while glutamine supplementation protects against oxidative stress-induced cellular senescence and rescues the D-galactose-prompted progeria phenotype in mice. Intriguingly, we found that long-term glutamine deprivation activates the Akt-mTOR pathway, together with the suppression of autolysosome function. However, the inhibition of the Akt-mTOR pathway effectively rescued the autophagy impairment and cellular senescence caused by glutamine deprivation. Collectively, our study demonstrates a novel interplay between glutamine availability and the aging process. Mechanistically, long-term glutamine deprivation could evoke mammalian target of rapamycin (mTOR) pathway activation and autophagy impairment. These findings provide new insights into the connection between glutamine availability and the aging process.

BAG Family Members as Mitophagy Regulators in Mammals

The BCL-2-associated athanogene (BAG) family is a multifunctional group of co-chaperones that are evolutionarily conserved from yeast to mammals. In addition to their common BAG domain, these proteins contain, in their sequences, many specific domains/motifs required for their various functions in cellular quality control, such as autophagy, apoptosis, and proteasomal degradation of misfolded proteins. The BAG family includes six members (BAG1 to BAG6). Recent studies reported their roles in autophagy and/or mitophagy through interaction with the autophagic machinery (LC3, Beclin 1, P62) or with the PINK1/Parkin signaling pathway. This review describes the mechanisms underlying BAG family member functions in autophagy and mitophagy and the consequences in physiopathology.

Autophagy in cancer: The cornerstone during glutamine deprivation

Over the past two decades, researchers have revealed the crucial functions of glutamine in supporting the hyperproliferation state of cancer cells. Glutamine acts on maintaining high energy production, supporting redox status and amino acid homeostasis. Therefore, cancer cells exhibit excessive uptake of the extracellular glutamine, synthesize it in some cases, and recycle intracellular and extracellular proteins to provide an additional source of glutamine to satisfy the increasing glutamine demand. On the other hand, autophagy's role is still debated regarding tumor initiation and progression. However, most cancer cells urgently need autophagy to overcome the existential threats during glutamine restriction stress. Downstream to various stress pathways induced during such a condition, autophagy is considered an indispensable cytoprotective tool to maintain cell integrity and survival. However, the overactivation of the autophagy process is related to lethal consequences. This review summarized glutamine pathways to control autophagy and highlighted autophagy's primary activation pathways, and discussed the roles during glutamine deprivation.

HucMSC exosomes promoted imatinib-induced apoptosis in K562-R cells via a miR-145a-5p/USP6/GLS1 axis

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm with increasing incidence worldwide. Growing evidence suggests that ubiquitin-specific proteases (USPs) play a role in cancer treatment. Dysregulation of miR-146a has been found in both adult and pediatric patients with acute leukemia. Knockdown of glutaminase-1 (GLS1) resulted in inhibition of tumor growth. However, the role of miR-146a-5p/USP6/GLS1 in leukemia and chemoresistance of leukemia cells remains to be elucidated. In the current study, USP6 level was increased in bone marrow aspiration specimens of patients with CML and associated with poor prognosis. USP6 was significantly upregulated in imatinib (IM)-resistant clinical samples compared with IM-sensitive samples. USP6 overexpression significantly inhibited IM-induced apoptosis of leukemia cells. Overexpressing USP6 significantly increased GLS1 ubiquitination to decrease GLS protein. A mechanism study indicated that USP6 regulation of IM resistance of CML cells was GLS1 dependent and regulated by miR-146a-5p. Administration of human umbilical cord mesenchymal stem cell (hucMSC) exosomes promoted IM-induced cell apoptosis through miR-145a-5p/USP6. Therefore, hucMSC exosomes promoted IM-induced apoptosis of K562-R cells by suppressing GLS1 ubiquitination to increase GLS protein via miR-146a-5p and its target GLS1. The findings highlight the importance of miR-146a-5p/USP6/GLS1 signaling in chemoresistance of leukemia and provide new insights into therapeutic strategies for chemoresistant leukemia.

The role of BAG3 in health and disease: A "Magic BAG of Tricks"

The multi-domain structure of Bcl-2-associated athanogene 3 (BAG3) facilitates its interaction with many different proteins that participate in regulating a variety of biological pathways. After revisiting the BAG3 literature published over the past ten years with Citespace software, we classified the BAG3 research into several clusters, including cancer, cardiomyopathy, neurodegeneration, and viral propagation. We then highlighted recent key findings in each cluster. To gain greater insight into the roles of BAG3, we analyzed five different published mass spectrometry data sets of proteins that co-immunoprecipitate with BAG3. These data gave us insight into universal, as well as cell-type-specific BAG3 interactors in cancer cells, cardiomyocytes, and neurons. Finally, we mapped variable BAG3 SNPs and also mutation data from previous publications to further explore the link between the domains and function of BAG3. We believe this review will provide a better understanding of BAG3 and direct future studies towards understanding BAG3 function in physiological and pathological conditions.

Knockdown of Bcl-2-Associated Athanogene-3 Can Enhance the Efficacy of BGJ398 via Suppressing Migration and Inducing Apoptosis in Gastric Cancer

BACKGROUND

Gastric cancer (GC) is one of the most common malignancies of the digestive tract worldwide, and cancer cell resistance against anticancer drugs remains a major challenge for GC treatment. Nvp-BGJ398 (BGJ398) is considered as a common drug for cancer treatment; however, Bcl-2-associated athanogene-3 (BAG3) plays an important role in drug resistance.

AIMS

To investigate the function of BAG3 on the sensitivity of GC cells to BGJ398.

METHODS

The expression of BAG3 in GC cells and GC resistance cells was examined by qRT-PCR and western blot. The resistance to BGJ398 was detected by viability assay, and a half-maximal inhibitory concentration (IC50) was calculated. The cell migration and apoptosis were determined by wound-healing assay and flow cytometry assay.

RESULTS

BAG3 was highly expressed in drug-resistant cells Fu97R and Snu16R. BAG3 was also associated with sensitivity of Snu16 cells to BGJ398, promoting migration but inhibiting apoptosis. However, knockdown of heat shock transcription factor 1 (HSF1) suppressed BAG3 expression and lowered the sensitivity to BGJ398 in Snu16R cells. Knockdown of BAG3 inhibited tumor growth and cell apoptosis but induced cell apoptosis and amplified the sensitivity to BGJ398 in Snu16R cells, followed by enhancing BGJ398-induced antitumor function in a Snu16R-derived xenograft mouse model.

CONCLUSION

The mechanism of resistance to BGJ398 in GC is mediated by BAG3/HSF1, and combined treatment with shBAG3 could improve the efficacy of BGJ398 in GC. Thus, BAG3-targeted therapy improves the antitumor efficacy of BGJ398, which might provide a novel therapeutic strategy for GC.

Characterization of Histone Deacetylase Mechanisms in Cancer Development

Over decades of studies, accumulating evidence has suggested that epigenetic dysregulation is a hallmark of tumours. Post-translational modifications of histones are involved in tumour pathogenesis and development mainly by influencing a broad range of physiological processes. Histone deacetylases (HDACs) and histone acetyltransferases (HATs) are pivotal epigenetic modulators that regulate dynamic processes in the acetylation of histones at lysine residues, thereby influencing transcription of oncogenes and tumour suppressor genes. Moreover, HDACs mediate the deacetylation process of many nonhistone proteins and thus orchestrate a host of pathological processes, such as tumour pathogenesis. In this review, we elucidate the functions of HDACs in cancer.

Divalent Metal Transporter 1 Knock-Down Modulates IL-1β Mediated Pancreatic Beta-Cell Pro-Apoptotic Signaling Pathways through the Autophagic Machinery

Pro-inflammatory cytokines promote cellular iron-import through enhanced divalent metal transporter-1 (DMT1) expression in pancreatic β-cells, consequently cell death. Inhibition of β-cell iron-import by DMT1 silencing protects against apoptosis in animal models of diabetes. However, how alterations of signaling networks contribute to the protective action of DMT1 knock-down is unknown. Here, we performed phosphoproteomics using our sequential enrichment strategy of mRNA, protein, and phosphopeptides, which enabled us to explore the concurrent molecular events in the same set of wildtype and DMT1-silenced β-cells during IL-1β exposure. Our findings reveal new phosphosites in the IL-1β-induced proteins that are clearly reverted by DMT1 silencing towards their steady-state levels. We validated the levels of five novel phosphosites of the potential protective proteins using parallel reaction monitoring. We also confirmed the inactivation of autophagic flux that may be relevant for cell survival induced by DMT1 silencing during IL-1β exposure. Additionally, the potential protective proteins induced by DMT1 silencing were related to insulin secretion that may lead to improving β-cell functions upon exposure to IL-1β. This global profiling has shed light on the signal transduction pathways driving the protection against inflammation-induced cell death in β-cells after DMT1 silencing.

Targeting ATF4-dependent pro-survival autophagy to synergize glutaminolysis inhibition

As glutamine plays a central role in cancer metabolism, inhibition of glutaminolysis has become an ideal anticancer therapeutic target. However, glutaminolysis inhibition leads to activation of autophagy, which compromises its antitumor effect. Hence, we investigated the mechanism underlying glutaminolysis inhibition-induced pro-survival autophagy.

Methods: High-throughput sequencing was performed on colorectal cancer (CRC) cells before and after glutaminolysis inhibition to identify differentially expressed genes. Activating transcription factor 4 (ATF4) pathway enrichment in glutaminolysis inhibited cells was identified through gene set enrichment analysis. ATF4 expression was assessed by quantitative real-time PCR (qRT-PCR) and western blotting. The function of ATF4 on mechanistic target of rapamycin (mTOR) regulation was assessed by western blotting. Luciferase reporter assays and chromatin immunoprecipitation were used to confirm the regulation of DNA damage inducible transcript 4 (DDIT4) by ATF4. mRNA half-life assays, RNA immunoprecipitation, qRT-PCR and western blotting were performed to determine the relationship between FTO alpha-ketoglutarate dependent dioxygenase (FTO), YTH N⁶-methyladenosine RNA binding protein 2 (YTHDF2), and ATF4. ATF4 regulation of pro-survival autophagy was measured by tandem monomeric red fluorescent protein-green fluorescent protein fluorescence microscopy. Finally, the synergistic effect of autophagy and glutaminolysis inhibition was analyzed in an azoxymethane/dextran sodium sulfate mouse model.

Results: The ATF4 pathway was activated in CRC cells upon glutaminolysis inhibition. Functionally, ATF4 transcriptionally upregulated DDIT4 to suppress mTOR, which induced pro-survival autophagy during glutaminolysis inhibition. Interestingly, glutaminolysis inhibition promoted ATF4 mRNA expression by abrogating N⁶-methyladenosine (m⁶A) modification and YTHDF2-mediated RNA decay. Finally, inhibition of ATF4-induced autophagy enhanced the antitumor efficacy of glutaminolysis inhibition.

Conclusion: Glutaminolysis inhibition upregulated ATF4 expression in an m⁶A-dependent manner to activate pro-survival autophagy through transcriptional activation of the mTOR inhibitor DDIT4. Targeting ATF4-induced autophagy is a new strategy to synergize glutaminolysis-targeting therapies for cancer treatment.

SIRT4 is the molecular switch mediating cellular proliferation in colorectal cancer through GLS mediated activation of AKT/GSK3β/CyclinD1 pathway

Mitochondria-localized sirtuin 4 (SIRT4) is associated with malignant phenotypes in colorectal cancer (CRC). However, the molecular mechanisms that drive SIRT4-mediated carcinogenesis are unclear. Initially, we confirmed expression of SIRT4 in CRC through public database and in CRC patient tissues using quantitative real-time reverse transcription PCR. We established HCT116 colorectal cells that overexpressed SIRT4 and HT29 cells were transfected with plasmids bearing a small interfering RNA construct to silence SIRT4. Assays to determine the malignant phenotypes (proliferation, invasion and migration) were performed. Xenograft in vivo models were also constructed. A protein interactome network was built using differentially expressed proteins identified using the liquid chromatography/tandem mass spectrophotometry, the findings of which were confirmed using co-immunoprecipitation, western blotting and phenotype rescue experiments. Decreased SIRT4 expression was associated with malignant phenotypes in vitro and in vivo. The ribosomal biogenesis pathway was enriched in the interactome network. SIRT4 suppression activated glutaminase, thereby initiating AKT activation. Our research provided novel insights into the molecular mechanisms underlying CRC, and identified that SIRT4 exerts its antitumor activity in CRC possibly dependent on glutaminase to inhibit proliferation, migration and invasion via the AKT/GSK3β/CyclinD1 pathway.

Neuromodulation of BAG co-chaperones by HIV-1 viral proteins and H2O2: implications for HIV-associated neurological disorders

Despite increasing numbers of aged individuals living with HIV, the mechanisms underlying HIV-associated neurological disorders (HANDs) remain elusive. As HIV-1 pathogenesis and aging are characterized by oxidative stress as well as altered protein quality control (PQC), reactive oxygen species (ROS) themselves might constitute a molecular mediator of neuronal PQC by modulating BCL-2 associated athanogene (BAG) family members. Present results reveal H2O2 replicated and exacerbated a reduction in neuronal BAG3 induced by the expression of HIV-1 viral proteins (i.e., Tat and Nef), while also causing an upregulation of BAG1. Such a reciprocal regulation of BAG3 and BAG1 levels was also indicated in two animal models of HIV, the doxycycline-inducible Tat (iTat) and the Tg26 mouse. Inhibiting oxidative stress via antioxidants in primary culture was capable of partially preserving neuronal BAG3 levels as well as electrophysiological functioning otherwise altered by HIV-1 viral proteins. Current findings indicate HIV-1 viral proteins and H2O2 may mediate neuronal PQC by exerting synergistic effects on complementary BAG family members, and suggest novel therapeutic targets for the aging HIV-1 population.

Succinylation Regulators Promote Clear Cell Renal Cell Carcinoma by Immune Regulation and RNA N6-Methyladenosine Methylation

Succinylation is a newly discovered and multienzyme-regulated post-translational modification (PTM) that is associated with the initiation and progression of cancer. Currently, no systematic analyses on the role of succinylation regulators in tumors have been reported. In this study, we performed a comprehensive pan-cancer analysis on four well-known succinylation regulators (CPT1A, KAT2A, SIRT5, and SIRT7). We found that these regulators played specific and critical roles in the prognosis of clear cell renal cell carcinoma (ccRCC). We constructed a risk score (RS) based on two independent prognostic prediction factors, CPT1A and KAT2A, and subsequently developed a nomogram model containing the RS, which showed good accuracy in the prediction of overall survival (OS) in ccRCC patients. Furthermore, we used the similar expression pattern of four succinylation regulators according to consensus clustering analysis to divide the patients into three clusters that exhibited prominently different OS as well as clinicopathological characteristics. Differently expressed genes (DEGs) and pathway enrichment analyses of three clusters indicated that succinylation regulators might promote malignant progression of ccRCC by regulating the infiltration of immune cells and RNA N6-methyladenosine (m6A) methylation. Importantly, our data suggest that CPT1A and SIRT5 might up-regulate and down-regulate the expression of LRPPRC and EIF3B, respectively. Our study systematically analyzed the prognostic predictive values of four succinylation regulators and revealed their potential mechanisms in ccRCC aggressiveness. These data provide new insight into the understanding of succinylation modification and present clinical evidence for its role in ccRCC treatments.

Sirtuins' control of autophagy and mitophagy in cancer

Mammalian cells use a specialized and complex machinery for the removal of altered proteins or dysfunctional organelles. Such machinery is part of a mechanism called autophagy. Moreover, when autophagy is specifically employed for the removal of dysfunctional mitochondria, it is called mitophagy. Autophagy and mitophagy have important physiological implications and roles associated with cellular differentiation, resistance to stresses such as starvation, metabolic control and adaptation to the changing microenvironment. Unfortunately, transformed cancer cells often exploit autophagy and mitophagy for sustaining their metabolic reprogramming and growth to a point that autophagy and mitophagy are recognized as promising targets for ongoing and future antitumoral therapies. Sirtuins are NAD+ dependent deacylases with a fundamental role in sensing and modulating cellular response to external stresses such as nutrients availability and therefore involved in aging, oxidative stress control, inflammation, differentiation and cancer. It is clear, therefore, that autophagy, mitophagy and sirtuins share many common aspects to a point that, recently, sirtuins have been linked to the control of autophagy and mitophagy. In the context of cancer, such a control is obtained by modulating transcription of autophagy and mitophagy genes, by post translational modification of proteins belonging to the autophagy and mitophagy machinery, by controlling ROS production or major metabolic pathways such as Krebs cycle or glutamine metabolism. The present review details current knowledge on the role of sirtuins, autophagy and mitophagy in cancer to then proceed to discuss how sirtuins can control autophagy and mitophagy in cancer cells. Finally, we discuss sirtuins role in the context of tumor progression and metastasis indicating glutamine metabolism as an example of how a concerted activation and/or inhibition of sirtuins in cancer cells can control autophagy and mitophagy by impinging on the metabolism of this fundamental amino acid.

BAG3 Proteomic Signature under Proteostasis Stress

The multifunctional HSP70 co-chaperone BAG3 (BCL-2-associated athanogene 3) represents a key player in the quality control of the cellular proteostasis network. In response to stress, BAG3 specifically targets aggregation-prone proteins to the perinuclear aggresome and promotes their degradation via BAG3-mediated selective macroautophagy. To adapt cellular homeostasis to stress, BAG3 modulates and functions in various cellular processes and signaling pathways. Noteworthy, dysfunction and deregulation of BAG3 and its pathway are pathophysiologically linked to myopathies, cancer, and neurodegenerative disorders. Here, we report a BAG3 proteomic signature under proteostasis stress. To elucidate the dynamic and multifunctional action of BAG3 in response to stress, we established BAG3 interactomes under basal and proteostasis stress conditions by employing affinity purification combined with quantitative mass spectrometry. In addition to the identification of novel potential BAG3 interactors, we defined proteins whose interaction with BAG3 was altered upon stress. By functional annotation and protein-protein interaction enrichment analysis of the identified potential BAG3 interactors, we confirmed the multifunctionality of BAG3 and highlighted its crucial role in diverse cellular signaling pathways and processes, ensuring cellular proteostasis and cell viability. These include protein folding and degradation, gene expression, cytoskeleton dynamics (including cell cycle and transport), as well as granulostasis, in particular.

The role of ubiquitination and deubiquitination in cancer metabolism

Metabolic reprogramming, including enhanced biosynthesis of macromolecules, altered energy metabolism, and maintenance of redox homeostasis, is considered a hallmark of cancer, sustaining cancer cell growth. Multiple signaling pathways, transcription factors and metabolic enzymes participate in the modulation of cancer metabolism and thus, metabolic reprogramming is a highly complex process. Recent studies have observed that ubiquitination and deubiquitination are involved in the regulation of metabolic reprogramming in cancer cells. As one of the most important type of post-translational modifications, ubiquitination is a multistep enzymatic process, involved in diverse cellular biological activities. Dysregulation of ubiquitination and deubiquitination contributes to various disease, including cancer. Here, we discuss the role of ubiquitination and deubiquitination in the regulation of cancer metabolism, which is aimed at highlighting the importance of this post-translational modification in metabolic reprogramming and supporting the development of new therapeutic approaches for cancer treatment.