Bcl-2-associated athanogene 5 (BAG5) regulates Parkin-dependent mitophagy and cell death

TDCPP and TiO2 NPs aggregates synergistically induce SH-SY5Y cell neurotoxicity by excessive mitochondrial fission and mitophagy inhibition

Tris (1,3-dichloro-2-propyl) phosphate (TDCPP), a halogen-containing phosphorus flame retardant, is widely used and has been shown to possess health risks to humans. The sustained release of artificial nanomaterials into the environment increases the toxicological risks of their coexisting pollutants. Nanomaterials may seriously change the environmental behavior and fate of pollutants. In this study, we investigated this combined toxicity and the potential mechanisms of toxicity of TDCPP and titanium dioxide nanoparticles (TiO2 NPs) aggregates on human neuroblastoma SH-SY5Y cells. TDCPP and TiO2 NPs aggregates were exposed in various concentration combinations, revealing that TDCPP (25 μg/mL) reduced cell viability, while synergistic exposure to TiO2 NPs aggregates exacerbated cytotoxicity. This combined exposure also disrupted mitochondrial function, leading to dysregulation in the expression of mitochondrial fission proteins (DRP1 and FIS1) and fusion proteins (OPA1 and MFN1). Consequently, excessive mitochondrial fission occurred, facilitating the translocation of cytochrome C from mitochondria to activate apoptotic signaling pathways. Furthermore, exposure of the combination of TDCPP and TiO2 NPs aggregates activated upstream mitochondrial autophagy but disrupted downstream Parkin recruitment to damaged mitochondria, preventing autophagosome-lysosome fusion and thereby disrupting mitochondrial autophagy. Altogether, our findings suggest that TDCPP and TiO2 NPs aggregates may stimulate apoptosis in neuronal SH-SY5Y cells by inducing mitochondrial hyperfission and inhibiting mitochondrial autophagy.

BAG5 regulates HSPA8-mediated protein folding required for sperm head-tail coupling apparatus assembly

Teratozoospermia is a significant cause of male infertility, but the pathogenic mechanism of acephalic spermatozoa syndrome (ASS), one of the most severe teratozoospermia, remains elusive. We previously reported Spermatogenesis Associated 6 (SPATA6) as the component of the sperm head-tail coupling apparatus (HTCA) required for normal assembly of the sperm head-tail conjunction, but the underlying molecular mechanism has not been explored. Here, we find that the co-chaperone protein BAG5, expressed in step 9-16 spermatids, is essential for sperm HTCA assembly. BAG5-deficient male mice show abnormal assembly of HTCA, leading to ASS and male infertility, phenocopying SPATA6-deficient mice. In vivo and in vitro experiments demonstrate that SPATA6, cargo transport-related myosin proteins (MYO5A and MYL6) and dynein proteins (DYNLT1, DCTN1, and DNAL1) are misfolded upon BAG5 depletion. Mechanistically, we find that BAG5 forms a complex with HSPA8 and promotes the folding of SPATA6 by enhancing HSPA8's affinity for substrate proteins. Collectively, our findings reveal a novel protein-regulated network in sperm formation in which BAG5 governs the assembly of the HTCA by activating the protein-folding function of HSPA8.

Mechanism and role of mitophagy in the development of severe infection

Mitochondria produce adenosine triphosphate and potentially contribute to proinflammatory responses and cell death. Mitophagy, as a conservative phenomenon, scavenges waste mitochondria and their components in the cell. Recent studies suggest that severe infections develop alongside mitochondrial dysfunction and mitophagy abnormalities. Restoring mitophagy protects against excessive inflammation and multiple organ failure in sepsis. Here, we review the normal mitophagy process, its interaction with invading microorganisms and the immune system, and summarize the mechanism of mitophagy dysfunction during severe infection. We highlight critical role of normal mitophagy in preventing severe infection.

Human proteins curing yeast prions

Recognition that common human amyloidoses are prion diseases makes the use of the Saccharomyces cerevisiae prion model systems to screen for possible anti-prion components of increasing importance. [PSI+] and [URE3] are amyloid-based prions of Sup35p and Ure2p, respectively. Yeast has at least six anti-prion systems that together cure nearly all [PSI+] and [URE3] prions arising in their absence. We made a GAL-promoted bank of 14,913 human open reading frames in a yeast shuttle plasmid and isolated 20 genes whose expression cures [PSI+] or [URE3]. PRPF19 is an E3 ubiquitin ligase that cures [URE3] if its U-box is intact. DNAJA1 is a J protein that cures [PSI+] unless its interaction with Hsp70s is defective. Human Bag5 efficiently cures [URE3] and [PSI+]. Bag family proteins share a 110 to 130 residue "BAG domain"; Bag 1, 2, 3, 4, and 6 each have one BAG domain while Bag5 has five BAG domains. Two BAG domains are necessary for curing [PSI+], but one can suffice to cure [URE3]. Although most Bag proteins affect autophagy in mammalian cells, mutations blocking autophagy in yeast do not affect Bag5 curing of [PSI+] or [URE3]. Curing by Bag proteins depends on their interaction with Hsp70s, impairing their role, with Hsp104 and Sis1, in the amyloid filament cleavage necessary for prion propagation. Since Bag5 curing is reduced by overproduction of Sis1, we propose that Bag5 cures prions by blocking Sis1 access to Hsp70s in its role with Hsp104 in filament cleavage.

Low expression of PINK1 and PARK2 predicts poor prognosis in patients with esophageal squamous cell carcinoma

BACKGROUND

The Parkinson's disease (PD) gene family expression is strongly linked to tumor development and progression; PINK1 and PARK2 are essential members of the PD gene family. However, the relationship between PINK1 and PARK2 and esophageal squamous cell carcinoma (ESCC) remains unknown. This research aims to clarify the prognostic value of PINK1 and PARK2 in ESCC.

METHODS

PINK1 and PARK2 protein levels in 232 ESCC specimens, and 125 matched adjacent normal tissues were detected by immunohistochemistry. The relationship between PINK1 and PARK2 protein expression and clinicopathological features were analyzed. Kaplan-Meier survival analysis was performed to estimate the prognostic value of the PINK1 and PARK2 proteins in patients. Cox univariate and multivariate analyses were used to assess the risk factors affecting the OS for patients with ESCC.

RESULTS

PINK1 and PARK2 had low expression in ESCC. Patients with low PINK1 had worse differentiation and advanced T and TNM stages. Lower PARK2 expression was linked to lymph node metastases and an advanced TNM stage. Furthermore, reduced PINK1 and PARK2 levels were associated with a poor prognosis for ESCC. Cox univariate and multivariate analyses revealed that PINK1, PARK2, and tumor size were closely associated with the prognosis of patients with ESCC, and PARK2 was an independent risk factor for patients with ESCC. Finally, the PINK1 and PARK2 proteins were closely related and shared the same signal pathway.

CONCLUSIONS

PINK1 and PARK2 could work as tumor suppressors in ESCC and are likely to become new treatment targets for ESCC.

Combined analysis of microRNA and mRNA profiles provides insights into the pathogenic resistant mechanisms of the lotus rhizome rot

Lotus rhizome rot caused by Fusarium oxysporum is a common vascular fungal disease in plants that significantly impacts the yield. However, only a few studies have studied the mechanism of Nelumbo nucifera responding to lotus rhizome rot. Here, we investigated the pathogenic genes and miRNAs in lotus rhizome rot to uncover the pathogenic resistant mechanisms by transcriptome and small RNA sequencing of lotus roots after inoculation with Fusarium oxysporum. GO and KEGG functional enrichment analysis showed that differential miRNAs were mostly enriched in starch and sucrose metabolism, biosynthesis of secondary metabolites, glutathione metabolism, brassinosteroid biosynthesis and flavonoid biosynthesis pathways. Twenty-seven upregulated miRNAs, 19 downregulated miRNAs and their target genes were identified. Correlation analysis found that miRNAs negatively regulate target genes, which were also enriched in starch and sucrose metabolism and glutathione metabolism pathways. Their expression was measured by reverse transcription quantitative PCR (qRT-PCR), and the results were consistent with the transcriptome analysis, thus verifying the reliability of transcriptome data. We selected three miRNAs (miRNA858-y, miRNA171-z and a novel miRNA novel-m0005-5p) to test the relationship between miRNAs and their target genes. The activity of the GUS testing assay indicated that miRNA could decrease the GUS activity by inhibiting the expression of their target genes. Collectively, this study provides a comprehensive analysis of transcriptome and small RNA sequencing of lotus root after inoculation with Fusarium oxysporum, and we identified candidate miRNAs and their target genes for breeding strategies of Nelumbo nucifera.

Identification of candidate mitochondrial inheritance determinants using the mammalian cell-free system

The degradation of sperm-borne mitochondria after fertilization is a conserved event. This process known as post-fertilization sperm mitophagy, ensures exclusively maternal inheritance of the mitochondria-harbored mitochondrial DNA genome. This mitochondrial degradation is in part carried out by the ubiquitin-proteasome system. In mammals, ubiquitin-binding pro-autophagic receptors such as SQSTM1 and GABARAP have also been shown to contribute to sperm mitophagy. These systems work in concert to ensure the timely degradation of the sperm-borne mitochondria after fertilization. We hypothesize that other receptors, cofactors, and substrates are involved in post-fertilization mitophagy. Mass spectrometry was used in conjunction with a porcine cell-free system to identify other autophagic cofactors involved in post-fertilization sperm mitophagy. This porcine cell-free system is able to recapitulate early fertilization proteomic interactions. Altogether, 185 proteins were identified as statistically different between control and cell-free-treated spermatozoa. Six of these proteins were further investigated, including MVP, PSMG2, PSMA3, FUNDC2, SAMM50, and BAG5. These proteins were phenotyped using porcine in vitro fertilization, cell imaging, proteomics, and the porcine cell-free system. The present data confirms the involvement of known mitophagy determinants in the regulation of mitochondrial inheritance and provides a master list of candidate mitophagy co-factors to validate in the future hypothesis-driven studies.

Nucleotide Exchange Factors for Hsp70 Molecular Chaperones: GrpE, Hsp110/Grp170, HspBP1/Sil1, and BAG Domain Proteins

Molecular chaperones of the Hsp70 family are key components of the cellular protein-folding machinery. Substrate folding is accomplished by iterative cycles of ATP binding, hydrolysis, and release. The ATPase activity of Hsp70 is regulated by two main classes of cochaperones: J-domain proteins stimulate ATPase hydrolysis by Hsp70, while nucleotide exchange factors (NEFs) facilitate the conversion from the ADP-bound to the ATP-bound state, thus closing the chaperone folding cycle. NEF function can additionally be antagonized by ADP dissociation inhibitors. Beginning with the discovery of the prototypical bacterial NEF, GrpE, a large diversity of nucleotide exchange factors for Hsp70 have been identified, connecting it to a multitude of cellular processes in the eukaryotic cell. Here we review recent advances toward structure and function of nucleotide exchange factors from the Hsp110/Grp170, HspBP1/Sil1, and BAG domain protein families and discuss how these cochaperones connect protein folding with cellular quality control and degradation pathways.

LncRNA TUG1 Promoted Stabilization of BAG5 by Binding DDX3X to Exacerbate Ketamine-Induced Neurotoxicity

As a clinically widely used anesthetic, ketamine (KET) has been reported to cause neurotoxicity in patients. Our work aimed to probe the function of long-chain non-coding RNA taurine-upregulated gene 1 (lncRNA TUG1) in KET-induced neurotoxicity. HT22 cells were subjected to KET to build the cell model. 3-(4, 5-Dimethylthiazolyl2)-2, 5-diphenyltetrazolium bromide (MTT) assay was employed to determine cell viability. Additionally, cell apoptosis was evaluated by flow cytometry. The binding relationships among TUG1, DEAD-box RNA helicase 3X (DDX3X), and Bcl-2-associated athanogene 5 (BAG5) were verified by RIP and RNA pull-down assays. Cell viability was impaired and cell apoptosis was increased in KET-treated HT22 cells accompanied by increased TUG1, DDX3X, and BAG5 expressions. TUG1 knockdown dramatically enhanced cell viability and repressed the of KET-induced apoptosis in HT22 cells, while TUG1 overexpression presented the opposite effects. In addition, we found that TUG1 promoted DDX3X expression via directly binding with DDX3X. As expected, DDX3X overexpression abolished the palliative effect of TUG1 knockdown on KET-induced neurotoxicity. Further research proved that TUG1 increased the stability of BAG5 through interacting with DDX3X. Finally, as expected, the moderating effect of TUG1 knockdown on KET-induced neuron injury was abolished by BAG5 overexpression. Taken together, TUG1 promoted BAG5 expression by binding DDX3X to exacerbate KET-induced neurotoxicity.

Identification of BAG5 as a Potential Biomarker for Parkinson’s Disease Patients With R492X PINK1 Mutation

Parkinson’s disease (PD) is a degenerative, progressive nervous system disorder with an unknown cause. PINK1 [phosphatase and tensin homolog deleted on chromosome 10 (PTEN)-induced putative kinase 1] causative mutations R492X may cause autosomal recessive early-onset parkinsonism. In this study, we utilized patient samples and cell line system to investigate roles of Bcl2-associated athanogene 5 (BAG5) in PD patients with R492X PINK1 mutation. We show that the expression levels of BAG5 in the skin tissues from PD patients with R492X PINK1 mutation are markedly lower than those from the healthy control subjects in a small cohort of patients, which has not been recognized before. In addition, we demonstrate that BAG5 physically binds to R492X mutated PINK1 protein. Furthermore, we reveal that BAG5 promotes the degradation of R492X mutated PINK1 protein via ubiquitin/proteasome-dependent pathway, suggesting that decreased level of BAG5 may lead to R492X mutated PINK1 protein accumulation. These findings suggest that BAG5 may serve as an early detection biomarker for PD patients with R492X PINK1 mutation and provide important new insights on how BAG5 affects R492X mutated PINK1 protein, highlighting therapeutic targets for this disease.

BAG family proteins contributes to autophagy-mediated multidrug resistance of tumor

Multidrug resistance (MDR) is a significant cause of tumor treatment failure. Accumulating evidence suggests that autophagy plays a significant role in the development of MDR. Autophagy is a conserved mechanism that maintains tumor homeostasis by removing damaged mitochondria. However, the specific regulatory mechanism is unclear. Here, we summarize recent studies on the role of autophagy in the development of MDR and the initiation of mitophagy by Bcl-2-associated athanogene (BAG) family proteins. Additionally, this mini-review emphasizes the regulatory role of BAG family proteins, which maintain mitochondrial homeostasis by regulating the PINK1/Parkin pathway. Elucidation of the regulatory mechanisms of mitophagy may foster the development of clinical therapeutic strategies for MDR tumors.

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.

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.

Precise control of mitophagy through ubiquitin proteasome system and deubiquitin proteases and their dysfunction in Parkinson's disease

Parkinson’s disease (PD) is one of the most common neurodegenerative diseases in the elderly population and is caused by the loss of dopaminergic neurons. PD has been predominantly attributed to mitochondrial dysfunction. The structural alteration of α-synuclein triggers toxic oligomer formation in the neurons, which greatly contributes to PD. In this article, we discuss the role of several familial PD-related proteins, such as α-synuclein, DJ-1, LRRK2, PINK1, and parkin in mitophagy, which entails a selective degradation of mitochondria via autophagy. Defective changes in mitochondrial dynamics and their biochemical and functional interaction induce the formation of toxic α-synuclein-containing protein aggregates in PD. In addition, these gene products play an essential role in ubiquitin proteasome system (UPS)-mediated proteolysis as well as mitophagy. Interestingly, a few deubiquitinating enzymes (DUBs) additionally modulate these two pathways negatively or positively. Based on these findings, we summarize the close relationship between several DUBs and the precise modulation of mitophagy. For example, the USP8, USP10, and USP15, among many DUBs are reported to specifically regulate the K48- or K63-linked de-ubiquitination reactions of several target proteins associated with the mitophagic process, in turn upregulating the mitophagy and protecting neuronal cells from α-synuclein-derived toxicity. In contrast, USP30 inhibits mitophagy by opposing parkin-mediated ubiquitination of target proteins. Furthermore, the association between these changes and PD pathogenesis will be discussed. Taken together, although the functional roles of several PD-related genes have yet to be fully understood, they are substantially associated with mitochondrial quality control as well as UPS. Therefore, a better understanding of their relationship provides valuable therapeutic clues for appropriate management strategies.

Molecular Signaling to Preserve Mitochondrial Integrity against Ischemic Stress in the Heart: Rescue or Remove Mitochondria in Danger

Cardiovascular diseases are one of the leading causes of death and global health problems worldwide, and ischemic heart disease is the most common cause of heart failure (HF). The heart is a high-energy demanding organ, and myocardial energy reserves are limited. Mitochondria are the powerhouses of the cell, but under stress conditions, they become damaged, release necrotic and apoptotic factors, and contribute to cell death. Loss of cardiomyocytes plays a significant role in ischemic heart disease. In response to stress, protective signaling pathways are activated to limit mitochondrial deterioration and protect the heart. To prevent mitochondrial death pathways, damaged mitochondria are removed by mitochondrial autophagy (mitophagy). Mitochondrial quality control mediated by mitophagy is functionally linked to mitochondrial dynamics. This review provides a current understanding of the signaling mechanisms by which the integrity of mitochondria is preserved in the heart against ischemic stress.

Lipoxin A4 methyl ester protects PC12 cells from ketamine-induced neurotoxicity via the miR-22/BAG5 pathway

OBJECTIVE

Ketamine is an anesthetic that induces neurotoxicity when administered at high doses. In this work, we explored the protective effects of lipoxin A₄ methyl ester (LXA₄ ME) against ketamine-induced neurotoxicity and the underlying protective mechanism in pheochromocytoma (PC12) cells.

METHODS

PC12 cells were treated with 50 μM of ketamine and different LXA₄ ME concentrations of LXA4 ME (5-50 nM) for 24 h, and their viability, apoptosis, and oxidative status were assessed.

RESULTS

Quantitative real-time polymerase chain reaction experiments showed that ketamine downregulated miR-22 expression and upregulated Bcl-2-associated athanogene 5 (BAG5) in PC12 cells in a concentration-dependent manner. LXA₄ ME induced the opposite effects, thus attenuating ketamine-induced neurotoxicity. Further in vitro assays showed that miR-22 directly targeted BAG5, thus promoting cell viability by suppressing cell apoptosis and oxidative stress. Under expression miR-22 or upregulation of BAG5 antagonized the effects of LXA₄ ME.

CONCLUSION

LXA₄ ME can protect PC12 cells from ketamine-induced neurotoxicity by activating the miR-22/BAG5 signaling pathway. Thus, LXA₄ ME can be used as a protective drug against ketamine-induced neural damage.

Molecular chaperones and Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive death of dopaminergic neurons in the substantia nigra and the formation of Lewy bodies (LBs). Mutations in PD-related genes lead to neuronal pathogenesis through various mechanisms, with known examples including SNCA/α-synuclein (PAKR1), Parkin (PARK2), PINK1 (PARK6), DJ-1 (PARK7), and LRRK2 (PARK8). Molecular chaperones/co-chaperones are proteins that aid the folding of other proteins into a functionally active conformation. It has been demonstrated that chaperones/co-chaperones interact with PD-related proteins and regulate their function in PD. HSP70, HSP90 and small heat shock proteins can prevent neurodegeneration by regulating α-syn misfolding, oligomerization and aggregation. The function of chaperones is regulated by co-chaperones such as HSP110, HSP40, HOP, CHIP, and BAG family proteins. Parkin, PINK1 and DJ-1 are PD-related proteins which are associated with mitochondrial function. Molecular chaperones regulate mitochondrial function and protein homeostasis by interacting with these PD-related proteins. This review discusses critical molecular chaperones/co-chaperones and PD-related proteins which contribute to the pathogenesis of PD, hoping to provide new molecular targets for therapeutic interventions to thwart the disease progression instead of only bringing symptomatic relief. Moreover, appreciating the critical role of chaperones in PD can also help us screen efficient biomarkers to identify PD at an early stage.

BAG6 promotes PINK1 signaling pathway and is essential for mitophagy

Bcl-2-associated athanogen-6 (BAG6) is a nucleocytoplasmic shuttling protein involved in protein quality control. We previously demonstrated that BAG6 is essential for autophagy by regulating the intracellular localization of the acetyltransferase EP300, and thus, modifying accessibility to its substrates (TP53 in the nucleus and autophagy-related proteins in the cytoplasm). Here, we investigated BAG6 localization and function in the cytoplasm. First, we demonstrated that BAG6 is localized in the mitochondria. Specifically, BAG6 is expressed in the mitochondrial matrix under basal conditions, and translocates to the outer mitochondrial membrane after mitochondrial depolarization with carbonyl cyanide m-chlorophenyl hydrazine, a mitochondrial uncoupler that induces mitophagy. In SW480 cells, the deletion of BAG6 expression abrogates its ability to induce mitophagy and PINK1 accumulation. On the reverse, its ectopic expression in LoVo colon cancer cells, which do not express endogenous BAG6, reduces the size of the mitochondria, induces mitophagy, leads to the activation of the PINK1/PARKIN pathway and to the phospho-ubiquitination of mitochondrial proteins. Finally, BAG6 contains two LIR (LC3-interacting Region) domains specifically found in receptors for selective autophagy and responsible for the interaction with LC3 and for autophagosome selectivity. Site-directed mutagenesis showed that BAG6 requires wild-type LIRs domains for its ability to stimulate mitophagy. In conclusion, we propose that BAG6 is a novel mitophagy receptor or adaptor that induces PINK1/PARKIN signaling and mitophagy in a LIR-dependent manner.

Implication of BAG5 downregulation in metabolic reprogramming of cisplatin-resistant ovarian cancer cells via mTORC2 signaling pathway

Ovarian cancer is the most frequent cause of gynecologic malignancies associated death. Primary or acquired cisplatin resistance is frequently occurred during ovarian cancer therapy. Cancer stem cells (CSC) tend to form minimal residual disease after chemotherapy and are implicated in relapse. The ability of cancer cells to reprogram their metabolism has recently been related with maintenance of CSC and resistance to chemotherapies. The current study found that BAG5 expression was decreased in cisplatin-resistant ovarian cancer cells and clinical tissues. Our data demonstrated that BAG5 knockdown was implicated in metabolic reprogramming and maintenance of cancer stem cell (CSC)-like features of ovarian cancer cells via regulation of Rictor and subsequent mTORC2 signaling pathway. In addition, the current study demonstrated that Bcl6 upregulation was responsible for repression of BAG5 transactivation via recruitment on the BAG5 promoter in cisplatin-resistant ovarian cancer. The current study also demonstrated reverse correlations between BAG5 and Bcl6, BAG5 and Rictor in ovarian serous adenocarcinoma tissues. Collectively, the current study identified the implication of Bcl6/BAG5/Rictor-mTORC2 signaling pathway in metabolic reprograming and maintenance of CSC-like features in cisplatin-resistant ovarian cancer cells. Therefore, further studies on the mechanism underlying regulation of metabolic reprogramming and CSC-like characteristics of cisplatin-resistant ovarian cancer cells may contribute to the establishment of novel therapeutic strategy for cisplatin-resistance.

African Swine Fever Virus Protein E199L Promotes Cell Autophagy through the Interaction of PYCR2

African swine fever virus (ASFV), as a member of the large DNA viruses, may regulate autophagy and apoptosis by inhibiting programmed cell death. However, the function of ASFV proteins has not been fully elucidated, especially the role of autophagy in ASFV infection. One of three Pyrroline-5-carboxylate reductases (PYCR), is primarily involved in conversion of glutamate to proline. Previous studies have shown that depletion of PYCR2 was related to the induction of autophagy. In the present study, we found for the first time that ASFV E199L protein induced a complete autophagy process in Vero and HEK-293T cells. Through co-immunoprecipitation coupled with mass spectrometry (CoIP-MS) analysis, we firstly identified that E199L interact with PYCR2 in vitro. Importantly, our work provides evidence that E199L down-regulated the expression of PYCR2, resulting in autophagy activation. Overall, our results demonstrate that ASFV E199L protein induces complete autophagy through interaction with PYCR2 and down-regulate the expression level of PYCR2, which provide a valuable reference for the role of autophagy during ASFV infection and contribute to the functional clues of PYCR2.

MiRNA-429 alleviates ketamine-induced neurotoxicity through targeting BAG5

Ketamine is a kind of anesthetic broadly applied in clinic. However, growing evidence has indicated that ketamine may induce neurotoxicity. Previous studies showed that mircoRNAs (miRNAs) participate in various aspects of biological regulations. In our work, we aimed to reveal the role of miR-429 in ketamine-induced neurotoxicity. The qRT-PCR was used to measure the miR-429 levels in ketamine-treated PC12 cells. TUNEL staining and caspase 3 activity detection assays were performed to assess cell apoptosis. A Cellular Reactive Oxygen Species Detection Assay Kit was utilized to detect ROS activity. A luciferase reporter assay was conducted in HEK-293T cells to test the binding between miR-429 and BAG5. Herein, we found that ketamine could induce the apoptosis and ROS activity in PC12 cells. The qRT-PCR results showed that miR-429 expression was downregulated by treatment of ketamine in a dose-dependent manner. Overexpression of miR-429 alleviated ketamine-induced neurotoxicity in PC12 cells. Mechanically, BAG5 was identified to be a target of miR-429 and negatively regulated by miR-429. Moreover, BAG5 expression was upregulated after ketamine treatment. Rescue assays revealed that overexpression of BAG5 reversed the suppressive effects of miR-429 upregulation on ketamine-induced neurotoxicity in PC12 cells. In summary, miR-429 attenuates ketamine-induced neurotoxicity in PC12 cells by the downregulation of BAG5.

Identification of BAG5 from orange-spotted grouper (Epinephelus coioides) involved in viral infection

Bcl-2-associated athanogene 5 (BAG5) is a kind of molecular chaperone that can bind to the Bcl-2 and modulate cell survival. However, little is known about the functions of fish BAG5. In this study, we characterized a BAG5 homolog from orange-spotted grouper (Epinephelus coioides) gene (Ec-BAG5) and investigated its roles during viral infection. The Ec-BAG5 protein encoded 468 amino acids with four BAG domains, which shared high identities with reported BAG5. The highest transcriptional level of Ec-BAG5 was found in the peripheral blood lymphocyte (PBL). And the Ec-BAG5 expression were significantly up-regulated after red-spotted grouper nervous necrosis virus (RGNNV) or Lipopolysaccharide (LPS) stimulation in vitro. Furthermore, Ec-BAG5 overexpression could inhibited viral replication and the expression of viral genes (coat protein (CP) and RNA-dependent RNA polymerase (RdRp)). Also, overexpression of Ec-BAG5 significantly increased the expression of interferon pathway-related factors including interferon regulatory factor 3 (IRF3), interferon-stimulated gene 15 (ISG15), interferon-induced protein 35 (IFP35), myxovirus resistance gene 1 (Mx1) and inflammatory-related factors including tumor necrosis factor receptor-associated factor 6 (TRAF6), tumor necrosis factor-α (TNF-α), interleukin-1 beta (IL-1β), as well as the activities of NF-κB, ISRE and IFN-1. These data indicate that Ec-BAG5 can affect viral infection through regulating the expression of IFN- and inflammation-related factors, which provide useful information to better understand the immune response against viral infection.

Plant Mitophagy in Comparison to Mammals: What Is Still Missing?

Mitochondrial homeostasis refers to the balance of mitochondrial number and quality in a cell. It is maintained by mitochondrial biogenesis, mitochondrial fusion/fission, and the clearance of unwanted/damaged mitochondria. Mitophagy represents a selective form of autophagy by sequestration of the potentially harmful mitochondrial materials into a double-membrane autophagosome, thus preventing the release of death inducers, which can trigger programmed cell death (PCD). Recent advances have also unveiled a close interconnection between mitophagy and mitochondrial dynamics, as well as PCD in both mammalian and plant cells. In this review, we will summarize and discuss recent findings on the interplay between mitophagy and mitochondrial dynamics, with a focus on the molecular evidence for mitophagy crosstalk with mitochondrial dynamics and PCD.

Mitophagy impairment in neurodegenerative diseases: Pathogenesis and therapeutic interventions

Neurons are specialized cells, requiring a lot of energy for its proper functioning. Mitochondria are the key cellular organelles and produce most of the energy in the form of ATP, required for all the crucial functions of neurons. Hence, the regulation of mitochondrial biogenesis and quality control is important for maintaining neuronal health. As a part of mitochondrial quality control, the aged and damaged mitochondria are removed through a selective mode of autophagy called mitophagy. However, in different pathological conditions, this process is impaired in neuronal cells and lead to a variety of neurodegenerative disease (NDD). Various studies indicate that specific protein aggregates, the characteristics of different NDDs, affect this process of mitophagy, adding to the severity and progression of diseases. Though, the detailed process of this association is yet to be explored. In light of the significant role of impaired mitophagy in NDDs, further studies have also investigated a large number of therapeutic strategies to target mitophagy in these diseases. Our current review summarizes the abnormalities in different mitophagy pathways and their association with different NDDs. We have also elaborated upon various novel therapeutic strategies and their limitations to enhance mitophagy in NDDs that may help in the management of symptoms and increasing the life expectancy of NDD patients. Thus, our study provides an overview of mitophagy in NDDs and emphasizes the need to elucidate the mechanism of impaired mitophagy prevalent across different NDDs in future research. This will help designing better treatment options with high efficacy and specificity.

Stress-induced p53 drives BAG5 cochaperone expression to control α-synuclein aggregation in Parkinson's disease

Parkinson’s disease (PD) is a common neurodegenerative disorder with the pathological hallmark of α-synuclein aggregation. Dysregulation of α-synuclein homeostasis caused by aging, genetic, and environmental factors underlies the pathogenesis of PD. While chaperones are essential for proteostasis, whether modulation of cochaperones may participate in PD formation has not been fully characterized. Here, we assessed the expression of several HSP70- and HSP90-related factors under various stresses and found that BAG5 expression is distinctively elevated in etoposide- or H₂O₂-treated SH-SY5Y cells. Stress-induced p53 binds to the BAG5 promoter directly to stimulate BAG5. Induced BAG5 binds α-synuclein and HSP70 in both cell cultures and brain lysates from PD patients. Overexpressed BAG5 may result in the loss of its ability to promote HSP70. Importantly, α-synuclein aggregation in SH-SY5Y cells requires BAG5. BAG5 expression is also detected in transgenic SNCA mutant mice and in PD patients. Together, our data reveal stress-induced p53-BAG5-HSP70 regulation that provides a potential therapeutic angle for PD.

Kill one or kill the many: interplay between mitophagy and apoptosis

Mitochondria are key players of cellular metabolism, Ca²⁺ homeostasis, and apoptosis. The functionality of mitochondria is tightly regulated, and dysfunctional mitochondria are removed via mitophagy, a specialized form of autophagy that is compromised in hereditary forms of Parkinson's disease. Through mitophagy, cells are able to cope with mitochondrial stress until the damage becomes too great, which leads to the activation of pro-apoptotic BCL-2 family proteins located on the outer mitochondrial membrane. Active pro-apoptotic BCL-2 proteins facilitate the release of cytochrome c from the mitochondrial intermembrane space (IMS) into the cytosol, committing the cell to apoptosis by activating a cascade of cysteinyl-aspartate specific proteases (caspases). We are only beginning to understand how the choice between mitophagy and the activation of caspases is determined on the mitochondrial surface. Intriguingly in neurons, caspase activation also plays a non-apoptotic role in synaptic plasticity. Here we review the current knowledge on the interplay between mitophagy and caspase activation with a special focus on the central nervous system.

BAG5 Promotes Alpha-Synuclein Oligomer Formation and Functionally Interacts With the Autophagy Adaptor Protein p62

Molecular chaperones are critical to maintaining intracellular proteostasis and have been shown to have a protective role against alpha-synuclein-mediated toxicity. Co-chaperone proteins regulate the activity of molecular chaperones and connect the chaperone network to protein degradation and cell death pathways. Bcl-2 associated athanogene 5 (BAG5) is a co-chaperone that modulates proteostasis by inhibiting the activity of Heat shock protein 70 (Hsp70) and several E3 ubiquitin ligases, resulting in enhanced neurodegeneration in models of Parkinson's disease (PD). Here we identify a novel interaction between BAG5 and p62/sequestosome-1 (SQSTM1), suggesting that BAG5 may bridge the chaperone network to autophagy-mediated protein degradation. We found that BAG5 enhanced the formation of pathogenic alpha-synuclein oligomers and regulated the levels and subcellular distribution of p62. These results extend the role of BAG5 in alpha-synuclein processing and intracellular proteostasis.