Mitochondrial Proteostasis Research Articles

Hypoxia-induced mitochondrial stress granules

Perturbations of mitochondrial proteostasis have been associated with aging, neurodegenerative diseases, and recently with hypoxic injury. While examining hypoxia-induced mitochondrial protein aggregation in C. elegans, we found that sublethal hypoxia, sodium azide, or heat shock-induced abundant ethidium bromide staining mitochondrial granules that preceded evidence of protein aggregation. Genetic manipulations that reduce cellular and organismal hypoxic death block the formation of these mitochondrial stress granules (mitoSG). Knockdown of mitochondrial nucleoid proteins also blocked the formation of mitoSG by a mechanism distinct from the mitochondrial unfolded protein response. Lack of the major mitochondrial matrix protease LONP-1 resulted in the constitutive formation of mitoSG without external stress. Ethidium bromide-staining RNA-containing mitochondrial granules were also observed in rat cardiomyocytes treated with sodium azide, a hypoxia mimetic. Mitochondrial stress granules are an early mitochondrial pathology controlled by LONP and the nucleoid, preceding hypoxia-induced protein aggregation.

75-OR: Cold-Responsive Proteolytic Rewiring of Mitochondria Safeguards White Fat Thermogenic Remodeling

Mitochondrial proteases are emerging as key regulators of mitochondrial plasticity acting both as protein quality surveillance and regulatory enzymes. It remains unclear, however, whether the regulated mitochondrial proteolysis is mechanistically linked to cell identity switch such as white-to-beige conversion of adipocytes. Here we report that cold-responsive mitochondrial proteolysis is a prerequisite for conversion from white-to-beige adipocytes during white adipose tissue (WAT) browning. MitoTimer reporter and chemical thiol probe analysis reveal that thermogenic stimulation selectively promotes mitochondrial proteostasis in WAT via mitochondrial protease LONP1 both in vivo and in vitro. Disruption of LONP1-dependent proteolysis substantially impairs cold or b3-AR agonist induced adipocyte identity programming, evidenced by the remarkably attenuated formation of UCP1+ multilocular adipocytes in IWAT from Lonp1 f/f/Adipoq-Cre (LONP1 AKO) mice. LONP1 AKO mice exposed to cold had lower body temperature, elevated serum TG and FFA levels. Chow-fed LONP1 AKO mice also developed glucose intolerance. “AdipoChaser” system “pulse-chase” lineage tracing experiments confirm that LONP1 ablation markedly blocks the direct cell fate programming of pre-existing mature adipocytes. Importantly, augmented LONP1 expression corrects aging-related impairments in white-to-beige adipocytes conversion. 10-month-old adipocyte-specific Lonp1 overexpression mice had significantly lower body weight and fat mass as a result of elevated energy expenditure. Thus, the identification of LONP1 as a critical safeguard of WAT beiging holds promise for translational applications in enhancing white-to-beige adipocytes conversion capacity relevant to a variety of metabolic disease states and during aging. Disclosure T.Fu: None. W.Sun: None. Z.Zhou: None. Z.Xu: None. M.Yan: None. L.Yang: None. Y.Yin: None. Z.Gan: None.

A cytosolic surveillance mechanism activates the mitochondrial UPR

The mitochondrial unfolded protein response (UPRmt) is essential to safeguard mitochondria from proteotoxic damage by activating a dedicated transcriptional response in the nucleus to restore proteostasis1,2. Yet, it remains unclear how the information on mitochondria misfolding stress (MMS) is signalled to the nucleus as part of the human UPRmt (refs. 3,4). Here, we show that UPRmt signalling is driven by the release of two individual signals in the cytosol—mitochondrial reactive oxygen species (mtROS) and accumulation of mitochondrial protein precursors in the cytosol (c-mtProt). Combining proteomics and genetic approaches, we identified that MMS causes the release of mtROS into the cytosol. In parallel, MMS leads to mitochondrial protein import defects causing c-mtProt accumulation. Both signals integrate to activate the UPRmt; released mtROS oxidize the cytosolic HSP40 protein DNAJA1, which leads to enhanced recruitment of cytosolic HSP70 to c-mtProt. Consequently, HSP70 releases HSF1, which translocates to the nucleus and activates transcription of UPRmt genes. Together, we identify a highly controlled cytosolic surveillance mechanism that integrates independent mitochondrial stress signals to initiate the UPRmt. These observations reveal a link between mitochondrial and cytosolic proteostasis and provide molecular insight into UPRmt signalling in human cells.

Proteolytic rewiring of mitochondria by LONP1 directs cell identity switching of adipocytes.

Mitochondrial proteases are emerging as key regulators of mitochondrial plasticity and acting as both protein quality surveillance and regulatory enzymes by performing highly regulated proteolytic reactions. However, it remains unclear whether the regulated mitochondrial proteolysis is mechanistically linked to cell identity switching. Here we report that cold-responsive mitochondrial proteolysis is a prerequisite for white-to-beige adipocyte cell fate programming during adipocyte thermogenic remodelling. Thermogenic stimulation selectively promotes mitochondrial proteostasis in mature white adipocytes via the mitochondrial protease LONP1. Disruption of LONP1-dependent proteolysis substantially impairs cold- or β3 adrenergic agonist-induced white-to-beige identity switching of mature adipocytes. Mechanistically, LONP1 selectively degrades succinate dehydrogenase complex iron sulfur subunit B and ensures adequate intracellular succinate levels. This alters the histone methylation status on thermogenic genes and thereby enables adipocyte cell fate programming. Finally, augmented LONP1 expression raises succinate levels and corrects ageing-related impairments in white-to-beige adipocyte conversion and adipocyte thermogenic capacity. Together, these findings reveal that LONP1 links proteolytic surveillance to mitochondrial metabolic rewiring and directs cell identity conversion during adipocyte thermogenic remodelling.

Aerobic Exercise Delays Alzheimer's Disease by Regulating Mitochondrial Proteostasis in the Cerebral Cortex and Hippocampus.

In clinical practice, Alzheimer's disease (AD), as one of the main neurodegenerative diseases globally, currently has no cure. Recently, the delaying and improving effects of physical exercise on AD have gradually been confirmed; however, the specific mechanism involved needs further clarification. (1) Objective: Explore the mechanism aerobic exercise plays in delaying AD by regulating mitochondrial proteostasis and provide new theoretical bases for improving and delaying AD through aerobic exercise in the future. (2) Methods: Male APP/PS1 mice were randomly divided into a normal group (NG, n = 20), activation group (AG, n = 20), and inhibition group (SG, n = 20). Then, the mice in each group were randomly divided into control group and exercise group (n = 10 mice each), yielding the normal control group (CNG), normal exercise group (ENG), active control group (CAG), active exercise group (EAG), inhibitive control group (CSG), and inhibitive exercise group (ESG). After adaptive training, the mice in the exercise groups were trained on an aerobic treadmill for 12 weeks; we conducted behavioral tests and sampled the results. Then, quantitative real-time PCR (Q-PCR) and Western blot analysis were performed. (3) Results: In the Morris water maze (MWM) test, the latency was significantly reduced and the number of platform crossings was significantly increased in the CAG and ENG compared with the CNG, while the result of the CSG was contrary to this. Compared with the ENG, latency was significantly reduced and the number of platform crossings was significantly increased in the EAG, while the opposite occurred for ESG. Compared with the CAG, the latency was significantly reduced and the number of platform crossings was significantly increased in the EAG, while the results for CSG were contrary. In the step-down test, compared with the CNG, the latency was significantly increased and the number of errors was significantly reduced in the CAG and ENG, respectively, while the results for CSG were contrary. Compared with the ENG, the latency was significantly increased and the number of errors was significantly reduced in the EAG, while the results for ESG were contrary. Compared with the CAG, the latency was significantly increased and the number of errors was significantly reduced in the EAG, while the results for CSG were contrary. Mitochondrial unfolded protein reactions (UPRmt), mitochondrial autophagy, and mitochondrial protein import levels in each group of mice were detected using Q-PCR and Western blot experiments. Compared with the CNG, the UPRmt and mitochondrial autophagy levels in the CAG and ENG were significantly increased and the mitochondrial protein import levels were significantly reduced, while the results for the CSG were contrary. Compared with the ENG, the UPRmt and mitochondrial autophagy levels in the EAG were significantly increased and the mitochondrial protein import levels were significantly reduced, while the results for ESG were contrary. Compared with the CAG, the UPRmt and mitochondrial autophagy levels in the EAG were significantly increased and the mitochondrial protein import levels were significantly reduced, while the results for CSG were contrary. (4) Conclusions: Aerobic exercise can improve cognitive function levels and delay the symptoms of AD in APP/PS1 mice by regulating mitochondrial proteostasis.

The Role of Exercise in Maintaining Mitochondrial Proteostasis in Parkinson's Disease.

Parkinson's disease (PD) is the second most common rapidly progressive neurodegenerative disease and has serious health and socio-economic consequences. Mitochondrial dysfunction is closely related to the onset and progression of PD, and the use of mitochondria as a target for PD therapy has been gaining traction in terms of both recognition and application. The disruption of mitochondrial proteostasis in the brain tissue of PD patients leads to mitochondrial dysfunction, which manifests as mitochondrial unfolded protein response, mitophagy, and mitochondrial oxidative phosphorylation. Physical exercise is important for the maintenance of human health, and has the great advantage of being a non-pharmacological therapy that is non-toxic, low-cost, and universally applicable. In this review, we investigate the relationships between exercise, mitochondrial proteostasis, and PD and explore the role and mechanisms of mitochondrial proteostasis in delaying PD through exercise.

NAD depletion mediates cytotoxicity in human neurons with autophagy deficiency

Autophagy is a homeostatic process critical for cellular survival, and its malfunction is implicated in human diseases including neurodegeneration. Loss of autophagy contributes to cytotoxicity and tissue degeneration, but the mechanistic understanding of this phenomenon remains elusive. Here, we generated autophagy-deficient (ATG5-/-) human embryonic stem cells (hESCs), from which we established a human neuronal platform to investigate how loss of autophagy affects neuronal survival. ATG5-/- neurons exhibit basal cytotoxicity accompanied by metabolic defects. Depletion of nicotinamide adenine dinucleotide (NAD) due to hyperactivation of NAD-consuming enzymes is found to trigger cell death via mitochondrial depolarization in ATG5-/- neurons. Boosting intracellular NAD levels improves cell viability by restoring mitochondrial bioenergetics and proteostasis in ATG5-/- neurons. Our findings elucidate a mechanistic link between autophagy deficiency and neuronal cell death that can be targeted for therapeutic interventions in neurodegenerative and lysosomal storage diseases associated with autophagic defect.

Abstract 4834: Mitochondrial ClpXP degrades serine phosphorylated protein aggregates

Abstract ClpXP is a serine protease localized to the mitochondrial matrix and maintains mitochondrial proteostasis by degrading damaged/aggregated respiratory chain complex proteins. Both inhibition and hyperactivation of ClpP lead to impaired OXPHOS function and kill leukemic cells in vitro and in vivo. Yet, the marks that tag proteins for degradation by ClpXP remain unknown. The bacterial homologue of ClpXP degrades damaged proteins with arginine phosphorylation. Therefore, we assessed how phosphorylation affects ClpXP protease activity. Recombinant ClpXP was incubated with its unnatural substrate, FITC-tagged casein, in the presence of increasing concentrations of phospho-serine (pSer), phospho-threonine (pThr), phospho-arginine (pArg), or phospho-tyrosine (pTyr). In a dose-dependent manner, pSer and pThr free amino acids and short peptides inhibited casein degradation by ClpXP. In contrast, free Ser, Thr, phosphate, pArg and pTyr did not inhibit ClpXP protease activity. In addition, we characterized ClpP peptidase activity and ClpX ATPase activity using the Ac-Trp-Leu-Ala-AMC (Ac-WLA-AMC) peptidase activity assay and the Malachite Green ATPase assay. Neither pSer nor pThr inhibited ClpX ATPase activity or ClpP peptidase activity. Thus, pSer and pThr only blocked ClpXP from degrading full-length protein without altering the enzymatic activity of the complex. Next, we characterized pSer and pThr binding to ClpXP by thermal shift binding assay. pSer and pThr free amino acids and short peptides bound to ClpX but not ClpP. All the dephosphorylated counterparts did not bind to ClpX. Therefore, pSer and pThr interact with ClpX outside the ATPase site. cyroEM studies of ClpX and pSer peptides indicated a putative pSer docking site in the central pore of ClpX. Previously, we identified OXPHOS complex II subunit SDHA as a potential ClpXP endogenous substrate. Therefore, we used SDHA as a model to assess whether serine phosphorylation influenced ClpXP protein degradation in intact cells. Using pSer immunoprecipitation, we observed increased serine phosphorylated SDHA in AML cells after ClpP and ClpX knockdown. The increased serine phosphorylated SDHA was specifically found in the insoluble fraction of the mitochondrial proteins. Supporting that serine phosphorylated SDHA represents aggregated protein, treatment of cells with ROS-inducing antimycin or 42°C heat shock also increased levels of serine phosphorylated SDHA in the fraction of insoluble mitochondrial proteins. Finally, adding recombinant ClpXP to mitochondrial lysates specifically degraded SDHA with serine phosphorylation. In summary, mitochondrial ClpXP degrades aggregated mitochondrial proteins marked by serine phosphorylated. Thus, this work identifies new degradation machinery for mitochondrial protease, advances the function of mitochondrial ClpXP, and highlights a new therapeutic strategy to target this protease. Citation Format: Yue Feng, Yulia Jitkova, Alexander Keszei, Jonathan St-Germain, Yongran Yan, Brian Raught, Mohammad Mazhab-Jafari, Aaron Schimmer. Mitochondrial ClpXP degrades serine phosphorylated protein aggregates. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4834.

Exercise Induces an Augmented Skeletal Muscle Mitochondrial Unfolded Protein Response in a Mouse Model of Obesity Produced by a High-Fat Diet.

Increase in body fat contributes to loss of function and changes in skeletal muscle, accelerating sarcopenia, a phenomenon known as sarco-obesity or sarcopenic obesity. Studies suggest that obesity decreases the skeletal muscle (SM)'s ability to oxidize glucose, increases fatty acid oxidation and reactive oxygen species production, due to mitochondrial dysfunction. Exercise improves mitochondrial dysfunction in obesity; however, it is not known if exercise regulates the mitochondrial unfolded protein response (UPRmt) in the SM. Our study aimed to determine the mito-nuclear UPRmt in response to exercise in a model of obesity, and how this response is associated with the improvement in SM functioning after exercise training. C57BL/6 mice were fed a normal diet and high-fat diet (HFD) for 12 weeks. After 8 weeks, animals were subdivided into sedentary and exercised for the remaining 4 weeks. Grip strength and maximal velocity of mice submitted to HFD improved after training. Our results show an increase in the activation of UPRmt after exercise while in obese mice, proteostasis is basally decreased but shows a more pronounced increase with exercise. These results correlate with improvement in the circulating triglycerides, suggesting mitochondrial proteostasis could be protective and could be related to mitochondrial fuel utilization in SM.

Disturb mitochondrial associated proteostasis: Neurodegeneration and imperfect ageing.

The disturbance in mitochondrial functions and homeostasis are the major features of neuron degenerative conditions, like Parkinson's disease, Amyotrophic Lateral Sclerosis, and Alzheimer's disease, along with protein misfolding. The aberrantly folded proteins are known to link with impaired mitochondrial pathways, further contributing to disease pathogenesis. Despite their central significance, the implications of mitochondrial homeostasis disruption on other organelles and cellular processes remain insufficiently explored. Here, we have reviewed the dysfunction in mitochondrial physiology, under neuron degenerating conditions. The disease misfolded proteins impact quality control mechanisms of mitochondria, such as fission, fusion, mitophagy, and proteasomal clearance, to the detriment of neuron. The adversely affected mitochondrial functional roles, like oxidative phosphorylation, calcium homeostasis, and biomolecule synthesis as well as its axes and contacts with endoplasmic reticulum and lysosomes are also discussed. Mitochondria sense and respond to multiple cytotoxic stress to make cell adapt and survive, though chronic dysfunction leads to cell death. Mitochondria and their proteins can be candidates for biomarkers and therapeutic targets. Investigation of internetworking between mitochondria and neurodegeneration proteins can enhance our holistic understanding of such conditions and help in designing more targeted therapies.

Coupling of autophagy and the mitochondrial intrinsic apoptosis pathway modulates proteostasis and ageing in Caenorhabditis elegans

Mitochondria preserve metabolic homeostasis and integrate stress signals, to trigger cytoprotective, or cell death pathways. Mitochondrial homeostasis and function decline with age. The mechanisms underlying the deterioration of mitochondrial homeostasis during ageing, or in age-associated pathologies, remain unclear. Here, we show that CISD-1, a mitochondrial iron-sulfur cluster binding protein, implicated in the pathogenesis of Wolfram neurodegenerative syndrome type 2, modulates longevity in the nematode Caenorhabditis elegans by engaging autophagy and the mitochondrial intrinsic apoptosis pathway. The anti-apoptotic protein CED-9 is the downstream effector that mediates CISD-1-dependent effects on proteostasis, neuronal integrity and lifespan. Moreover, intracellular iron abundance is critical for CISD-1 function, since mild iron supplementation is sufficient to decelerate ageing and partly ameliorate the disturbed mitochondrial bioenergetics and proteostasis of CISD-1 deficient animals. Our findings reveal that CISD-1 serves as a mechanistic link between autophagy and the apoptotic pathway in mitochondria to differentially modulate organismal proteostasis and ageing, and suggest novel approaches which could facilitate the treatment of Wolfram Syndrome or related diseases.

Functional crosstalk between the TIM22 complex and YME1 machinery maintains mitochondrial proteostasis and integrity.

The TIM22 pathway cargos are essential for sustaining mitochondrial homeostasis as an excess of these proteins leads to proteostatic stress and cell death. Yme1 is an inner membrane metalloprotease that regulates protein quality control with chaperone-like and proteolytic activities. Although the mitochondrial translocase and protease machinery are critical for organelle health, their functional association remains unexplored. The present study unravels a novel genetic connection between the TIM22 complex and YME1 machinery in Saccharomyces cerevisiae required for maintaining mitochondrial health. Our genetic analyses indicate that impairment in the TIM22 complex rescues the respiratory growth defects of cells without Yme1. Further, Yme1 is essential for the stability of the TIM22 complex and regulates the proteostasis of the TIM22 pathway substrates. Moreover, impairment in the TIM22 complex suppressed the mitochondrial structural and functional defects of Yme1 devoid cells. In summary, excessive levels of the TIM22 pathway substrates could be one of the reasons for respiratory growth defects of cells lacking Yme1, and compromising the TIM22 complex can compensate for the imbalance in mitochondrial proteostasis caused by the loss of Yme1.

Mitochondrion-targeting and in situ photocontrolled protein delivery via photocages.

Defects in mitochondrial proteostasis contribute to many disorders, including cancer, neurodegeneration, and metabolic and genetic diseases. A strategy aimed at restoring the damaged mitochondrial proteostasis is the mitochondrion-targeting and carrier-free delivery of exogenous functional proteins that can replace the endogenous dysfunctional proteins. The modification of a protein with a photolabile protecting group (PPG, i.e., photocage group) can be activated in situ by response to illumination, leading to release of the protein from its photocage. Here, the Cys and peptide photocages with coumarin were first prepared and characterized for proof of concept. Then, we designed a pair of photocage groups PPG-RhB and PPG-TPP using coumarin and mitochondrion-targeting Rhodamine B (RhB) and triphenylphosphine (TPP), and another pair of organelle-nontarget photocage groups Br-PPG and NO2-PPG for comparison. The proteins modified with these two pairs of photocage groups undergo photolysis in solutions, and can penetrate cell membrane toward their destinations in the carrier-free fashions. The intracellular protein photocages are in situ activated by illumination at 405nm, and the proteins are released from their photocages in mitochondria and cytoplasm, respectively. This strategy of light-responsive and carrier-free cellular delivery enables mitochondrial and cytoplasmic accumulation of exogenous proteins.

Interaction between host cell mitochondria and Coxiella burnetii.

In order to successfully establish a replicative niche, intracellular bacterial pathogens must influence eukaryotic cell biology. Vesicle and protein traffic, transcription and translation, metabolism and innate immune signaling are all important elements of the host-pathogen interaction that can be manipulated by intracellular bacterial pathogens. The causative agent of Q fever, Coxiella burnetii, is a mammalian adapted pathogen that replicates in a lysosome-derived pathogen-modified vacuole. C. burnetii establishes this replicative niche by using a cohort of novel proteins, termed effectors, to hijack the mammalian host cell. The functional and biochemical roles of a small number of effectors have been discovered and recent studies have demonstrated that mitochondria are a bona fide target for a subset of these effectors. Various approaches have begun to unravel the role these proteins play at mitochondria during infection, with key mitochondrial functions, including apoptosis and mitochondrial proteostasis, likely influenced by mitochondrially localized effectors. Additionally, mitochondrial proteins likely contribute to the host response to infection. Thus, investigating the interplay between host and pathogen elements at this central organelle will uncover important new understanding of the C. burnetii infection process. With the advent of new technologies and sophisticated omics approaches, we are poised to explore the interaction between host cell mitochondria and C. burnetii with unprecedented spatial and temporal resolution.

Sirtuin-3 activates the mitochondrial unfolded protein response and reduces cerebral ischemia/reperfusion injury.

Sirtuin-3 (Sirt3) deacetylates several mitochondrial proteins implicated into cerebral ischemia/reperfusion (I/R) injury. The mitochondrial unfolded protein response (UPRmt) favors mitochondrial proteostasis during various stressors. Here, we used Sirt3 transgenic mice and a transient middle cerebral artery occlusion model to evaluate the molecular basis of Sirt3 on the UPRmt during brain post-ischemic dysfunction. The present study illustrated that Sirt3 abundance was suppressed in the brain after brain ischemic abnormalities. Overexpression of Sirt3 in vivo suppressed the infarction size and attenuated neuroinflammation after brain I/R injury. Sirt3 overexpression restored neural viability by reducing mitochondrial ROS synthesis, maintaining the mitochondrial potential and improving mitochondrial adenosine triphosphate synthesis. Sirt3 overexpression protected neuronal mitochondria against brain post-ischemic malfunction via eliciting the UPRmt by the forkhead box O3 (Foxo3)/sphingosine kinase 1 (Sphk1) pathway. Inhibiting either the UPRmt or the Foxo3/Sphk1 pathway relieved the favorable influence of Sirt3 on neural function and mitochondrial behavior. In contrast, Sphk1 overexpression was sufficient to reduce the infarction size, attenuate neuroinflammation, sustain neuronal viability and prevent mitochondrial abnormalities during brain post-ischemia dysfunction. Thus, the UPRmt protects neural viability and mitochondrial homeostasis, and the Sirt3/Foxo3/Sphk1 pathway is a promosing therapeutic candidate for ischemic stroke.

Dietary cobalt oxide nanoparticles alleviate aging through activation of mitochondrial UPR in Caenorhabditis elegans.

Mitochondrial unfolded protein response (UPRmt), which is a mitochondrial proteostasis pathway, orchestrates an adaptive reprogramming for metabolism homeostasis and organismal longevity. Similar to other defense systems, compromised UPRmt is a feature of several age-related diseases. Here we report that dimercapto succinic acid (DMSA)-modified cobalt oxide nanoparticles (Co3O4 NPs), which have received wide-spread attention in biomedical fields, is a promising UPRmt activator and, more importantly, provides a gate for extending healthy lifespan. Methods: UPRmt activation by Co3O4 NPs was tested in transgenetic Caenorhabditis elegans (C. elegans) specifically expressing UPRmt reporter Phsp-6::GFP, and the underlying mechanism was further validated by mitochondrial morphology, mtDNA/nDNA, metabolism-related genes' expression, mitonuclear protein imbalance, oyxgen assumption and ATP level in C. elegans. Then therapeutic response aganist senescence was monitored by lifespan analysis, lipofusin contents, MDA contents, Fe accumulation, pharyngeal locomotion performance as well as athletic ability (head thrashes and body bends) at different developmental stages of C. elegans. RNAi towards ubl-5 or atfs-1 in UPRmt pathway was applied to clarify the role of UPRmt in Co3O4 NPs -mediated anti-aging effects. Finally, the effect of Co3O4 NPs on mitochondrial homeostasis and D-galactose-induced cell viability decline in mammalian cells were studied. Results: Co3O4 NPs was revealed as a bona fide activator of the UPRmt signaling pathway, through fine-tuning mitochondrial dynamics and inducing a stoichiometric imbalance between OXPHOS subunits encoded by mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) at early life stage of C. elegans. Phenotypically, Co3O4 NPs treatment protect C. elegans from external stresses. More importantly, dietary low level of Co3O4 NPs effectively extend lifespan and alleviate aging-related physiological and functional decline of worms, demonstrating its potential roles in delaying aging. While the protective effect exerted by Co3O4 NPs was compromised in line with atfs-1 or ubl-5 RNAi treatment. Further studies verified the conservation of Co3O4 NPs in activating UPRmt and exerting protective effects in mammalian cells. Conclusions: The results reveal beneficial effects of Co3O4 NPs on mitochondrial metabolic control, thus presenting their potential efficacy in anti-aging care.

Knowledge mapping of research on the mitochondrial unfolded protein response: a bibliometric and visual analysis.

The mitochondrial unfolded protein response (UPRmt) is a mitochondria stress response, which exerts a crucial role in maintaining mitochondrial proteostasis during stress. However, there is no bibliometric analyses systematically studied this field which could comprehensively review research trends, evaluate publication performances and provide future perspectives. Articles investigating UPRmt published between 1994 and 2021 were downloaded from the Core Collection of the Web of Science (WOS). CiteSpace and VOSviewer bibliometric software were applied for bibliometric and visual analyses. A total of 2,073 papers researching UPRmt were retrieved. According to the published number of papers, the field of UPRmt research has gone through its infancy (after 2000) and rapid growth (after 2021) phases. The United States and China contributed the most to UPRmt research. Regarding the distribution of institutions, Harvard University was the most influential institution. The most prolific authors are Johan Auwerx and CM Haynes. PLoS One is the most extensive journal in the field of UPRmt research, while the Cell Death and Differentiation journal had the greatest impact among the most-authored journals. Moreover, biochemistry/molecular biology, and cell biology are the largest subject areas. UPRmt research is mainly categorized as UPRmt, transcription, endoplasmic reticulum (ER) stress, lipotoxicity, mitophagy, inflammation, skeletal muscle, hypoxia, apoptosis, mitochondrial dysfunction, neurodegeneration, mitochondrial permeability transition, and integrated stress response. At present, research on UPRmt is booming. Further strengthening the cooperation and exchanges between countries, institutions, and authors in the future will surely promote the development of this field.

Anti-retroviral treatment with zidovudine alters pyrimidine metabolism, reduces translation, and extends healthy longevity via ATF-4

The human population is aging, and the need for interventions to slow progression of age-related diseases (geroprotective interventions) is growing. Repurposing compounds already used clinically, usually at modified doses, allows rapid implementation of geroprotective pharmaceuticals. Here we find the anti-retroviral nucleoside reverse transcriptase inhibitor (NRTI) zidovudine robustly extends lifespan and health span in C.elegans, independent of electron transport chain impairment or ROS accumulation. Rather, zidovudine treatment modifies pyrimidine metabolism and transcripts related to proteostasis. Testing regulators of mitochondrial stress and proteostasis shows that lifespan extension is dependent on activating transcription factor 4 (ATF-4). ATF-4 regulates longevity induced by mitochondrial stress, specifically communication between mitochondrial and cytosolic translation. Translation is reduced in zidovudine-treated worms, also dependent on ATF-4. Finally, we show ATF-4-dependent lifespan extension induced by didanosine, another NRTI. Altogether, our work elucidates the geroprotective effects of NRTIs such as zidovudine invivo, via reduction of translation and ATF-4.

Mitochondrial Unfolded Protein Response and Integrated Stress Response as Promising Therapeutic Targets for Mitochondrial Diseases

The development and application of high-throughput omics technologies have enabled a more in-depth understanding of mitochondrial biosynthesis metabolism and the pathogenesis of mitochondrial diseases. In accordance with this, a host of new treatments for mitochondrial disease are emerging. As an essential pathway in maintaining mitochondrial proteostasis, the mitochondrial unfolded protein response (UPRmt) is not only of considerable significance for mitochondrial substance metabolism but also plays a fundamental role in the development of mitochondrial diseases. Furthermore, in mammals, the integrated stress response (ISR) and UPRmt are strongly coupled, functioning together to maintain mitochondrial function. Therefore, ISR and UPRmt show great application prospects in the treatment of mitochondrial diseases. In this review, we provide an overview of the molecular mechanisms of ISR and UPRmt and focus on them as potential targets for mitochondrial disease therapy.

Multi-Omics Analysis Reveals Clinical Value and Possible Mechanisms of ATAD1 Down-Regulation in Human Prostate Adenocarcinoma.

Prostate adenocarcinoma (PRAD) is the most common histological subtype of prostate cancer. Post-treatment biochemical recurrence is a challenging issue. ATAD1 (ATPase Family AAA Domain Containing 1) plays a vital role in mitochondrial proteostasis and apoptosis activity, while its clinical value in PRAD and its impact on the tumor microenvironment (TME) remain unanswered. In this study, we aimed to investigate the clinical value and possible mechanisms of ATAD1 in PRAD via multi-omics analysis. Using cBioPortal, we confirmed that ATAD1 alteration was associated with gene expression and unfavorable DFS. Deep deletion predominantly occurred in PRAD. By integrating DriverDBv3 and GEPIA2, we noted ATAD1 downregulation in PRAD tissues compared to normal tissues, associated with unfavorable DFS in PRAD patients. DNA repair genes ATM, PARP1and BRCA2 had positive associations with ATAD1 expression. We found that the generalization value of ATAD1 could be applied to other cancers such as KIRC and UCEC. In addition, LinkedOmics identified that the functional involvement of ATAD1 participates in mitochondrial structure and cell cycle progression. Using TIMER analysis, we demonstrated that ATAD1 downregulation correlated with an immunosuppressive TME. Furthermore, we accessed a GSE55062 dataset on UALCAN and discovered the involvement of ERG-mediated transcriptional repression on ATAD1 downregulation. Cross-association screening of shATAD1 efficacy vs. altered mRNAs identified 190 perturbed mRNAs. Then, functional enrichment analysis using the Metascape omics tool recognized that shATAD1-perturbed mRNAs are primarily in charge of the activation of Wnt/β-catenin pathway and lipid metabolic processes. In conclusion, multi-omics results reveal that ATAD1 downregulation is a clinical biomarker for pathological diagnosis and prognosis for patients with PRAD. Reduced ATAD1 may be involved in the enhanced activity of mitochondria and cell cycle, as well as possibly shaping an immunosuppressive TME. ERG serves as an upstream transcriptional repressor of ATAD1. Downstream mechanisms of ATAD1 are involved in Wnt/β-catenin pathway and lipid metabolic processes.