Dynamic PGAM5 multimers dephosphorylate BCL-xL or FUNDC1 to regulate mitochondrial and cellular fate

Mitophagy in acute central nervous system injuries: regulatory mechanisms and therapeutic potentials

Acute central nervous system injuries, including ischemic stroke, intracerebral hemorrhage, subarachnoid hemorrhage, traumatic brain injury, and spinal cord injury, are a major global health challenge. Identifying optimal therapies and improving the long-term neurological functions of patients with acute central nervous system injuries are urgent priorities. Mitochondria are susceptible to damage after acute central nervous system injury, and this leads to the release of toxic levels of reactive oxygen species, which induce cell death. Mitophagy, a selective form of autophagy, is crucial in eliminating redundant or damaged mitochondria during these events. Recent evidence has highlighted the significant role of mitophagy in acute central nervous system injuries. In this review, we provide a comprehensive overview of the process, classification, and related mechanisms of mitophagy. We also highlight the recent developments in research into the role of mitophagy in various acute central nervous system injuries and drug therapies that regulate mitophagy. In the final section of this review, we emphasize the potential for treating these disorders by focusing on mitophagy and suggest future research paths in this area.

Met-Exo attenuates pyroptosis in miniature pig liver IRI by improving mitochondrial quality control

Metformin(Met) and adipose-derived stem cell exosomes(ADSCs-Exo) both demonstrate therapeutic effects on mitochondrial dysfunction and pyroptosis. There is also a phenomenon of mutual promotion between these two pathological states. The synergistic effect of metformin-loaded exosomes (Met-Exo) via electroporation in a miniature pig liver ischemia-reperfusion injury (IRI) model remains unexplored. This study established a liver IRI model in miniature pigs to compare the effects of ADSCs-Exo and Met-Exo. We found that Met-Exo intervention better activated the Adenosine 5'-monophosphate activated protein kinase (AMPK)/NAD-dependent deacetylase sirtuin-1(SIRT1) axis, improved mitochondrial dynamics, promoted mitochondrial biogenesis, and inhibited the sustained excessive autophagy of mitochondria after liver IRI. It was then demonstrated that by improving mitochondrial dysfunction, ATP production in liver tissue could be ensured, and ROS generation could be suppressed. This also further inhibited the occurrence of pyroptosis and ensured that mitochondria were protected from gasdermin D-N(GSDMD-N) attack. Met-Exo inhibited the occurrence of pyroptosis through the above pathways, reducing the release of inflammatory factors such as IL-1β and IL-18, and alleviating inflammation. This provides a new therapeutic approach for clinical treatment of liver IRI and improving the success rate of liver transplantation.

Organellophagy regulates cell death:A potential therapeutic target for inflammatory diseases

BACKGROUND

Dysregulated alterations in organelle structure and function have a significant connection with cell death, as well as the occurrence and development of inflammatory diseases. Maintaining cell viability and inhibiting the release of inflammatory cytokines are essential measures to treat inflammatory diseases. Recently, many studies have showed that autophagy selectively targets dysfunctional organelles, thereby sustaining the functional stability of organelles, alleviating the release of multiple cytokines, and maintaining organismal homeostasis. Organellophagy dysfunction is critically engaged in different kinds of cell death and inflammatory diseases.

AIM OF REVIEW

We summarized the current knowledge of organellophagy (e.g., mitophagy, reticulophagy, golgiphagy, lysophagy, pexophagy, nucleophagy, and ribophagy) and the underlying mechanisms by which organellophagy regulates cell death.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We outlined the potential role of organellophagy in the modulation of cell fate during the inflammatory response to develop an intervention strategy for the organelle quality control in inflammatory diseases.

Mitochondrial quality control: A promising target of traditional Chinese medicine in the treatment of cardiovascular disease

Cardiovascular disease remains the leading cause of death globally, and drugs for new targets are urgently needed. Mitochondria are the primary sources of cellular energy, play crucial roles in regulating cellular homeostasis, and are tightly associated with pathological processes in cardiovascular disease. In response to physiological signals and external stimuli in cardiovascular disease, mitochondrial quality control, which mainly includes mitophagy, mitochondrial dynamics, and mitochondrial biogenesis, is initiated to meet cellular requirements and maintain cellular homeostasis. Traditional Chinese Medicine (TCM) has been shown to have pharmacological effects on alleviating cardiac injury in various cardiovascular diseases, including myocardial ischemia/reperfusion, myocardial infarction, and heart failure, by regulating mitochondrial quality control. Recently, several molecular mechanisms of TCM in the treatment of cardiovascular disease have been elucidated. However, mitochondrial quality control by TCM for treating cardiovascular disease has not been investigated. In this review, we aim to decipher the pharmacological effects and molecular mechanisms of TCM in regulating mitochondrial quality in various cardiovascular diseases. We also present our perspectives regarding future research in this field.

Mitochondrial PGAM5 modulates methionine metabolism and feather follicle development by targeting Wnt/β-catenin signaling pathway in broiler chickens

BACKGROUND

Poor feather growth not only affects the appearance of the organism but also decreases the feed efficiency. Methionine (Met) is an essential amino acid required for feather follicle development; yet the exact mechanism involved remains insufficiently understood.

METHODS

A total of 180 1-day-old broilers were selected and randomly divided into 3 treatments: control group (0.45% Met), Met-deficiency group (0.25% Met), and Met-rescue group (0.45% Met in the pre-trial period and 0.25% Met in the post-trial period). The experimental period lasted for 56 d, with a pre-trial period of 1-28 d and a post-trial period of 29-56 d. In addition, Met-deficiency and Met-rescue models were constructed in feather follicle epidermal stem cell by controlling the supply of Met in the culture medium.

RESULTS

Dietary Met-deficiency significantly (P < 0.05) reduced the ADG, ADFI and F/G, and inhibited feather follicle development. Met supplementation significantly (P < 0.05) improved growth performance and the feather growth in broilers. Met-rescue may promote feather growth in broilers by activating the Wnt/β-catenin signaling pathway (GSK-3β, CK1, Axin1, β-catenin, Active β-catenin, TCF4, and Cyclin D1). Compared with Met-deficiency group, Met-rescue significantly (P < 0.05) increased the activity of feather follicle epidermal stem cell and mitochondrial membrane potential, activated Wnt/β-catenin signaling pathway, and decreased the content of reactive oxygen species (P < 0.05). CO-IP confirmed that mitochondrial protein PGAM5 interacted with Axin1, the scaffold protein of the disruption complex of the Wnt/β-catenin signaling pathway, and directly mediated Met regulation of Wnt/β-catenin signaling pathway and feather follicle development.

CONCLUSIONS

PGAM5 binding to Axin1 mediates the regulation of Wnt/β-catenin signaling pathway, and promotes feather follicle development and feather growth of broiler chickens through Met supplementation. These results provide theoretical support for the improvement of economic value and production efficiency of broiler chickens.

Physiological and pathological roles of PGAM5: An update and future trend

PGAM5, a phosphatase found in mitochondria, is crucial for mitochondrial quality control (MQC) through its regulation on mitochondrial dynamics, biogenesis, and mitophagy. Previous studies have shown its involvement in multiple regulated cell deaths (RCDs), including apoptosis, necroptosis, and pyroptosis. The objective of this review is to enhance our comprehension of the involvement of PGAM5 in MQC and RCDs. Additionally, we summarize some novel roles of PGAM5 in cellular senescence, lipid metabolism, and immune response modulation in recent studies. Finally, we discuss PGAM5's contribution to the pathological state of cardiovascular, hepatic, neurological, and neoplastic diseases, offering potential perspectives for future research.

The dual role of PGAM5 in inflammation

In recent years, the focus on human inflammation in research has increased, with aging-related inflammation widely recognized as a defining characteristic of aging. Inflammation is strongly correlated with mitochondrial dysfunction. Phosphoglycerate mutase family member 5 (PGAM5) is a novel modulator of mitochondrial homeostasis in response to mechanical stimulation. Here we review the structure and sublocalization of PGAM5, introduce its importance in programmed cell death and summarize its crucial roles in the development and progression of inflammatory diseases such as pneumonia, hepatitis, neuroinflammation and aging. Notably, PGAM5 has dual effects on controlling inflammation: distinct PGAM5-mediated mitochondrial functions exhibit cellular heterogeneity, leading to its dual functions in inflammation control. We therefore highlight the double-edged sword nature of PGAM5 as a potential critical regulator and innovative therapeutic target in inflammation. Finally, the challenges and future directions of the use of PGAM5, which has dual properties, as a target molecule in the clinic are discussed. This review provides crucial insights to guide the development of intelligent therapeutic strategies targeting PGAM5-specific regulation to treat intractable inflammatory conditions, as well as the potential extension of its broader application to other diseases to achieve more precise and effective treatment outcomes.

Ferroptosis triggers mitochondrial fragmentation via Drp1 activation

Constitutive mitochondrial dynamics ensure quality control and metabolic fitness of cells, and their dysregulation has been implicated in various human diseases. The large GTPase Dynamin-related protein 1 (Drp1) is intimately involved in mediating constitutive mitochondrial fission and has been implicated in mitochondrial cell death pathways. During ferroptosis, a recently identified type of regulated necrosis driven by excessive lipid peroxidation, mitochondrial fragmentation has been observed. Yet, how this is regulated and whether it is involved in ferroptotic cell death has remained unexplored. Here, we provide evidence that Drp1 is activated upon experimental induction of ferroptosis and promotes cell death execution and mitochondrial fragmentation. Using time-lapse microscopy, we found that ferroptosis induced mitochondrial fragmentation and loss of mitochondrial membrane potential, but not mitochondrial outer membrane permeabilization. Importantly, Drp1 accelerated ferroptotic cell death kinetics. Notably, this function was mediated by the regulation of mitochondrial dynamics, as overexpression of Mitofusin 2 phenocopied the effect of Drp1 deficiency in delaying ferroptosis cell death kinetics. Mechanistically, we found that Drp1 is phosphorylated and activated after induction of ferroptosis and that it translocates to mitochondria. Further activation at mitochondria through the phosphatase PGAM5 promoted ferroptotic cell death. Remarkably, Drp1 depletion delayed mitochondrial and plasma membrane lipid peroxidation. These data provide evidence for a functional role of Drp1 activation and mitochondrial fragmentation in the acceleration of ferroptotic cell death, with important implications for targeting mitochondrial dynamics in diseases associated with ferroptosis.

Molecular regulation of mitophagy signaling in tumor microenvironment and its targeting for cancer therapy

Aberrations emerging in mitochondrial homeostasis are restrained by mitophagy to control mitochondrial integrity, bioenergetics signaling, metabolism, oxidative stress, and apoptosis. The mitophagy-accompanied mitochondrial processes that occur in a dysregulated condition act as drivers for cancer occurrence. In addition, the enigmatic nature of mitophagy in cancer cells modulates the cellular proteome, creating challenges for therapeutic interventions. Several reports found the role of cellular signaling pathways in cancer to modulate mitophagy to mitigate stress, immune checkpoints, energy demand, and cell death. Thus, targeting mitophagy to hinder oncogenic intracellular signaling by promoting apoptosis, in hindsight, might have an edge against cancer. This review highlights the receptors and adaptors, and the involvement of many proteins in mitophagy and their role in oncogenesis. It also provides insight into using mitophagy as a potential target for therapeutic intervention in various cancer types.

Disruption of tumor-intrinsic PGAM5 increases anti-PD-1 efficacy through the CCL2 signaling pathway

BACKGROUND

Immunosuppressive phenotype compromised immunotherapy efficacy of hepatocellular carcinoma. Tumor cells intrinsic mitochondria dynamics could pass effects on the extracellular microenvironment through mtDNA stress. PGAM5 anchors at mitochondria and regulates mitochondria functions. We aim to explore whether the regulation of tumor-intrinsic PGAM5 on mitochondria affects tumor-infiltrating immune cells in the microenvironment and whether tumor-intrinsic PGAM5 can be a therapeutic target to enhance the immunotherapy efficacy of hepatocellular carcinoma (HCC).

METHODS

We analyzed the correlation of PGAM5 expression and immune cells infiltration using Gene Expression Omnibus (GEO) and The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) data sets based on cibersort algorithm and tumor-tissue arrays from two independent cohorts. To further validate our findings, we established subcutaneous and orthotopic mouse HCC models with tumor-intrinsic Pgam5 deficiency and analyzed tumor-infiltrating immune cells by flow cytometry and single-cell RNA sequencing. Mechanistically, we established an in vitro co-culture system and analyzed proteomics data to find out the bridge between tumor cell PGAM5 and tumor-associated macrophages (TAMs) in the microenvironment. Immunofluorescence, chromatin-immunoprecipitation, ELISA, mass spectrometry were conducted to explore the molecular pathway. Macrophages were depleted to investigate whether the effects of tumor-intrinsic PGAM5 on TAMs could affect immunotherapy efficacy in HCC orthotopic and subcutaneous mouse models.

RESULTS

PGAM5 expression in tumor was positively correlated with M2-phenotype TAM infiltration in patients with both HCC and mouse HCC tumor models. High tumor-intrinsic PGAM5 expression promoting M2 TAMs infiltration correlated with poor clinical-pathological characteristics and prognosis in patients with HCC. Disruption of tumor-intrinsic Pgam5 reduced TAM M2 polarization and inhibited HCC tumor growth in tumor-bearing mice. Mechanistically, in HCC cells PGAM5 deficiency inhibited mitochondria fission by promoting TRIM28 binding with DRP1, which increased ubiquitination and degradation of DRP1. Tumor-intrinsic PGAM5 deficiency mediated mitochondria fusion and reduced cytosolic mtDNA stress which attenuated TLR9 activation and downstream NF-κB-regulated CCL2 secretion. Furthermore, disruption of tumor-intrinsic Pgam5 significantly facilitated CD8+ T cells activation and improved anti-programmed cell death protein-1 therapeutic efficacy with macrophages depletion compromising synergistic antitumor immune response.

CONCLUSION

Our results shed light on the effect of tumor mitochondria dynamics on TAMs in tumor microenvironment. Tumor-intrinsic PGAM5 can be a therapeutic target to improve immunotherapy efficacy in patients with HCC.

Unveiling a novel signalling pathway involving NRF2 and PGAM5 in regulating the mitochondrial unfolded protein response in stressed cardiomyocytes

The mitochondrial unfolded protein response (UPRmt) is a conserved signalling pathway that initiates a specific transcriptional programme to maintain mitochondrial and cellular homeostasis under stress. Previous studies have demonstrated that UPRmt activation has protective effects in the pressure-overloaded human heart, suggesting that robust UPRmt stimulation could serve as an intervention strategy for cardiovascular diseases. However, the precise mechanisms of UPRmt regulation remain unclear. In this study, we present evidence that the NRF2 transcription factor is involved in UPRmt activation in cardiomyocytes during conditions of mitochondrial stress. Silencing NRF2 partially reduces UPRmt activation, highlighting its essential role in this pathway. However, constitutive activation of NRF2 via inhibition of its cytosolic regulator KEAP1 does not increase levels of UPRmt activation markers, suggesting an alternative regulatory mechanism independent of the canonical KEAP1-NRF2 axis. Further analysis revealed that NRF2 likely affects UPRmt activation through its interaction with PGAM5 at the mitochondrial membrane. Disruption of PGAM5 in cardiomyocytes subjected to mitochondrial stress reduces the interaction between PGAM5 and NRF2, enhancing nuclear translocation of NRF2 and significantly upregulating the UPRmt in an NRF2-dependent manner. This NRF2-regulated UPRmt amplification improves mitochondrial respiration, reflecting an enhanced capacity for cardiomyocytes to meet elevated energetic demands during mitochondrial stress. Our findings highlight the therapeutic potential of targeting the NRF2-PGAM5-KEAP1 signalling complex to amplify the UPRmt in cardiomyocytes for cardiovascular and other diseases associated with mitochondrial dysfunction. Future studies should aim to elucidate the mechanisms via which NRF2 enhances the protective effects of UPRmt, thereby contributing to more targeted therapeutic approaches.

Mitochondrial quality control: the real dawn of intervertebral disc degeneration?

Intervertebral disc degeneration is the most common disease in chronic musculoskeletal diseases and the main cause of low back pain, which seriously endangers social health level and increases people's economic burden. Disc degeneration is characterized by NP cell apoptosis, extracellular matrix degradation and disc structure changes. It progresses with age and under the influence of mechanical overload, oxidative stress and genetics. Mitochondria are not only the energy factories of cells, but also participate in a variety of cellular functions such as calcium homeostasis, regulation of cell proliferation, and control of apoptosis. The mitochondrial quality control system involves many mechanisms such as mitochondrial gene regulation, mitochondrial protein import, mitophagy, and mitochondrial dynamics. A large number of studies have confirmed that mitochondrial dysfunction is a key factor in the pathological mechanism of aging and intervertebral disc degeneration, and balancing mitochondrial quality control is extremely important for delaying and treating intervertebral disc degeneration. In this paper, we first demonstrate the molecular mechanism of mitochondrial quality control in detail by describing mitochondrial biogenesis and mitophagy. Then, we describe the ways in which mitochondrial dysfunction leads to disc degeneration, and review in detail the current research on targeting mitochondria for the treatment of disc degeneration, hoping to draw inspiration from the current research to provide innovative perspectives for the treatment of disc degeneration.

Nuclear translocation of SIRT4 mediates deacetylation of U2AF2 to modulate renal fibrosis through alternative splicing-mediated upregulation of CCN2

TGF-β stimulates CCN2 expression which in turn amplifies TGF-β signaling. This process promotes extracellular matrix production and accelerates the pathological progression of fibrotic diseases. Alternative splicing plays an important role in multiple disease development, while U2 small nuclear RNA auxiliary factor 2 (U2AF2) is an essential factor in the early steps of pre-mRNA splicing. However, the molecular mechanism underlying abnormal CCN2 expression upon TGF-β stimulation remains unclear. This study elucidates that SIRT4 acts as a master regulator for CCN2 expression in response to TGF-β by modulating U2AF2-mediated alternative splicing. Analyses of renal biopsy specimens from patients with CKD and mouse fibrotic kidney tissues revealed marked nuclear accumulation of SIRT4. The tubulointerstitial fibrosis was alleviated by global deletion or tubular epithelial cell (TEC)-specific knockout of Sirt4, and aggravated by adeno-associated virus-mediated SIRT4 overexpression in TECs. Furthermore, SIRT4 was found to translocate from the mitochondria to the cytoplasm through the BAX/BAK pore under TGF-β stimulation. In the cytoplasm, TGF-β activated the ERK pathway and induced the phosphorylation of SIRT4 at Ser36, which further promoted its interaction with importin α1 and subsequent nuclear translocation. In the nucleus, SIRT4 was found to deacetylate U2AF2 at K413, facilitating the splicing of CCN2 pre-mRNA to promote CCN2 protein expression. Importantly, exosomes containing anti-SIRT4 antibodies were found to effectively mitigate the UUO-induced kidney fibrosis in mice. Collectively, these findings indicated that SIRT4 plays a role in kidney fibrosis by regulating CCN2 expression via the pre-mRNA splicing.

Mitochondrial proteases modulate mitochondrial stress signalling and cellular homeostasis in health and disease

Maintenance of mitochondrial homeostasis requires a plethora of coordinated quality control and adaptations' mechanisms in which mitochondrial proteases play a key role. Their activation or loss of function reverberate beyond local mitochondrial biochemical and metabolic remodelling into coordinated cellular pathways and stress responses that feedback onto the mitochondrial functionality and adaptability. Mitochondrial proteolysis modulates molecular and organellar quality control, metabolic adaptations, lipid homeostasis and regulates transcriptional stress responses. Defective mitochondrial proteolysis results in disease conditions most notably, mitochondrial diseases, neurodegeneration and cancer. Here, it will be discussed how mitochondrial proteases and mitochondria stress signalling impact cellular homeostasis and determine the cellular decision to survive or die, how these processes may impact disease etiopathology, and how modulation of proteolysis may offer novel therapeutic strategies.

Melatonin attenuates liver ischemia-reperfusion injury via inhibiting the PGAM5-mPTP pathway

Phosphoglycerate mutase/protein phosphatase (PGAM5)-mediated cell death plays an important role in multiple liver diseases. However, few studies have confirmed the regulatory mechanism of melatonin acting on PGAM5-mediated cell death in the context of liver ischemia-reperfusion (I/R) injury. The liver I/R injury model and cell hypoxia-reoxygenation model were established after melatonin pretreatment. Liver injury, cell activity, cell apoptosis, oxidative stress index, and PGAM5 protein expression were detected. To investigate the role of PGAM5 in melatonin-mediated liver protection during I/R injury, PGAM5 silencing, and overexpression were performed before melatonin pretreatment. Our results indicated that PGAM5 was significantly elevated by I/R injury, and predominantly localized in the necrosis area. However, treatment with melatonin blocked PGAM5 activation and conferred a survival advantage of hepatocytes in liver I/R injury, similar to the results achieved by silencing PGAM5. In terms of mechanism, we illustrated that activated PGAM5 promoted mitochondrial permeability transition pore (mPTP) opening, and administration of melatonin inhibited mPTP opening and interrupted hepatocytes death via blocking PGAM5. Our data indicated that the PGAM5-mPTP axis is responsible for I/R-induced liver injury. In contrast, melatonin supplementation blocked the PGAM5-mPTP axis and thus decreased cell death, providing a protective advantage to hepatocytes in I/R. These results established a new paradigm in melatonin-mediated hepatocyte protection under the burden of I/R attack.

Mitophagy in Cell Death Regulation: Insights into Mechanisms and Disease Implications

Mitophagy, a selective form of autophagy, plays a crucial role in maintaining optimal mitochondrial populations, normal function, and intracellular homeostasis by monitoring and removing damaged or excess mitochondria. Furthermore, mitophagy promotes mitochondrial degradation via the lysosomal pathway, and not only eliminates damaged mitochondria but also regulates programmed cell death-associated genes, thus preventing cell death. The interaction between mitophagy and various forms of cell death has recently gained increasing attention in relation to the pathogenesis of clinical diseases, such as cancers and osteoarthritis, neurodegenerative, cardiovascular, and renal diseases. However, despite the abundant literature on this subject, there is a lack of understanding regarding the interaction between mitophagy and cell death. In this review, we discuss the main pathways of mitophagy, those related to cell death mechanisms (including apoptosis, ferroptosis, and pyroptosis), and the relationship between mitophagy and cell death uncovered in recent years. Our study offers potential directions for therapeutic intervention and disease diagnosis, and contributes to understanding the molecular mechanism of mitophagy.

Multiple roles of mitochondrial autophagy receptor FUNDC1 in mitochondrial events and kidney disease

This article reviews the latest research progress on the role of mitochondrial autophagy receptor FUN14 domain containing 1 (FUNDC1) in mitochondrial events and kidney disease. FUNDC1 is a protein located in the outer membrane of mitochondria, which maintains the function and quality of mitochondria by regulating mitochondrial autophagy, that is, the selective degradation process of mitochondria. The structural characteristics of FUNDC1 enable it to respond to intracellular signal changes and regulate the activity of mitochondrial autophagy through phosphorylation and dephosphorylation. During phosphorylation, unc-51-like kinase 1 (ULK1) promotes the activation of mitophagy by phosphorylating Ser17 of FUNDC1. In contrast, Src and CK2 kinases inhibit the interaction between FUNDC1 and LC3 by phosphorylating Tyr18 and Ser13, thereby inhibiting mitophagy. During dephosphorylation, PGAM5 phosphatase enhances the interaction between FUNDC1 and LC3 by dephosphorylating Ser13, thereby activating mitophagy. BCL2L1 inhibits the activity of PGAM5 by interacting with PGAM5, thereby preventing the dephosphorylation of FUNDC1 and inhibiting mitophagy. FUNDC1 plays an important role in mitochondrial events, participating in mitochondrial fission, maintaining the homeostasis of iron and proteins in mitochondrial matrix, and mediating crosstalk between mitochondria, endoplasmic reticulum and lysosomes, which have important effects on cell energy metabolism and programmed death. In the aspect of kidney disease, the abnormal function of FUNDC1 is closely related to the occurrence and development of many diseases. In acute kidney injury (AKI), cardiorenal syndrome (CRS), diabetic nephropathy (DN), chronic kidney disease (CKD) ,renal fibrosis (RF) and renal anemia, FUNDC1-mediated imbalance of mitophagy may be one of the key factors in disease progression. Therefore, in-depth study of the regulatory mechanism and function of FUNDC1 is of great significance for understanding the pathogenesis of renal disease and developing new treatment strategies.

Iron chelators as mitophagy agents: Potential and limitations

Mitochondrial autophagy (mitophagy) is very important process for the maintenance of cellular homeostasis, functionality and survival. Its dysregulation is associated with high risk and progression numerous serious diseases (e.g., oncological, neurodegenerative and cardiovascular ones). Therefore, targeting mitophagy mechanisms is very hot topic in the biological and medicinal research. The interrelationships between the regulation of mitophagy and iron homeostasis are now becoming apparent. In short, mitochondria are central point for the regulation of iron homeostasis, but change in intracellular cheatable iron level can induce/repress mitophagy. In this review, relationships between iron homeostasis and mitophagy are thoroughly discussed and described. Also, therapeutic applicability of mitophagy chelators in the context of individual diseases is comprehensively and critically evaluated.

Exploring the Mechanism of Ferroptosis Induction by Sappanone A in Cancer: Insights into the Mitochondrial Dysfunction Mediated by NRF2/xCT/GPX4 Axis

Non-small cell lung cancer (NSCLC), a major subtype of lung cancer, encompasses squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. Compared to small cell lung cancer, NSCLC cells grow and divide more slowly, and their metastasis occurs at a later stage. Currently, chemotherapy is the primary treatment for this disease. Sappanone A (SA) is a flavonoid compound extracted from the plant Caesalpinia sappan, known for its antitumor, redox-regulating, and anti-inflammatory properties. Recent studies have investigated the interaction of SA with mitochondrial pathways in regulating cell death through the Nrf-2/GPX-4/xCT axis. This study specifically explores the mechanism by which SA affects mitochondrial morphology and structure through the regulation of mitophagy and mitochondrial biogenesis in tumor cells. The study primarily utilizes second-generation transcriptomic sequencing data and molecular docking techniques to elucidate the role of SA in regulating programmed cell death in tumor cells. The omics results indicate that SA treatment significantly targets genes involved in oxidative phosphorylation, mitophagy, mitochondrial dynamics, and oxidative stress. Further findings confirmed that the Nrf-2/GPX4/xCT pathway serves as a crucial target of SA in the treatment of NSCLC. Knockdown of Nrf-2 (si-Nrf-2) and Nrf-2 overexpression (ad-Nrf-2) were shown to modulate the therapeutic efficacy of SA to varying degrees. Additionally, modifications to the GPX4/xCT genes significantly affected the regulatory effects of SA on mitochondrial autophagy, biogenesis, and energy metabolism. These regulatory mechanisms may be mediated through the caspase pathway and ferroptosis-related signaling. Molecular biology experiments have demonstrated that SA intervention further inhibits the phosphorylation of FUNDC1 at Tyr18 and downregulates TOM20 expression. SA treatment was found to reduce the expression of PGC1α, Nrf-1, and Tfam, resulting in a decrease in mitochondrial respiration and energy metabolism. Overexpression of Nrf-2 was shown to counteract the regulatory effects of SA on mitophagy and mitochondrial biogenesis. Confocal microscopy experiments further revealed that SA treatment increases mitochondrial fragmentation, subsequently inducing mitochondrial pathway-mediated programmed cell death. However, genetic modification of the Nrf-2/GPX4/xCT pathway significantly altered the regulatory effects of SA on tumor cells. In conclusion, SA has been identified as a promising therapeutic agent for NSCLC. The mitochondrial pathway-mediated apoptosis and ferroptosis may represent key mechanisms in regulating tumor cell death. Targeting the Nrf-2/GPX-4/xCT axis offers a novel therapeutic approach for maintaining mitochondrial homeostasis within the cellular microenvironment.

Therapeutic effects of natural compounds against diabetic complications via targeted modulation of ferroptosis

Diabetes mellitus, a chronic metabolic disorder, can result in serious tissue and organ damage due to long-term metabolic dysfunction, leading to various complications. Therefore, exploring the pathogenesis of diabetic complications and developing effective prevention and treatment drugs is crucial. The role of ferroptosis in diabetic complications has emerged as a significant area of research in recent years. Ferroptosis, a recently discovered form of regulated cell death closely linked to iron metabolism imbalance and lipid peroxidation, has garnered increasing attention in studies exploring the potential role of natural products in its regulation. This review provides an overview of the mechanisms underlying ferroptosis, outlines detection methods, and synthesizes information from natural product databases. It also summarizes current research on how natural products may regulate ferroptosis in diabetic complications. Studies have shown that these products can modulate the ferroptosis process by influencing iron ion balance and combating oxidative stress. This highlights the potential of natural products in treating diabetic complications by regulating ferroptosis, offering a new strategy for managing such complications.

The bioenergetics of traumatic brain injury and its long-term impact for brain plasticity and function

Mitochondria provide the energy to keep cells alive and functioning and they have the capacity to influence highly complex molecular events. Mitochondria are essential to maintain cellular energy homeostasis that determines the course of neurological disorders, including traumatic brain injury (TBI). Various aspects of mitochondria metabolism such as autophagy can have long-term consequences for brain function and plasticity. In turn, mitochondria bioenergetics can impinge on molecular events associated with epigenetic modifications of DNA, which can extend cellular memory for a long time. Mitochondrial dysfunction leads to pathological manifestations such as oxidative stress, inflammation, and calcium imbalance that threaten brain plasticity and function. Hence, targeting mitochondrial function may have great potential to lessen the outcomes of TBI.

The interplay between mitochondrial dynamics and autophagy: From a key homeostatic mechanism to a driver of pathology

The complex relationship between mitochondrial dynamics and autophagy illustrates how two cellular housekeeping processes are intimately linked, illuminating fundamental principles of cellular homeostasis and shedding light on disparate pathological conditions including several neurodegenerative disorders. Here we review the basic tenets of mitochondrial dynamics i.e., the concerted balance between fusion and fission of the organelle, and its interplay with macroautophagy and selective mitochondrial autophagy, also dubbed mitophagy, in the maintenance of mitochondrial quality control and ultimately in cell viability. We illustrate how conditions of altered mitochondrial dynamics reverberate on autophagy and vice versa. Finally, we illustrate how altered interplay between these two key cellular processes participates in the pathogenesis of human disorders affecting multiple organs and systems.

Src inhibition rescues FUNDC1-mediated neuronal mitophagy in ischaemic stroke

BACKGROUND

Ischaemic stroke triggers neuronal mitophagy, while the involvement of mitophagy receptors in ischaemia/reperfusion (I/R) injury-induced neuronal mitophagy remain not fully elucidated. Here, we aimed to investigate the involvement of mitophagy receptor FUN14 domain-containing 1 (FUNDC1) and its modulation in neuronal mitophagy induced by I/R injury.

METHODS

Wild-type and FUNDC1 knockout mice were generated to establish models of neuronal I/R injury, including transient middle cerebral artery occlusion (tMCAO) in vivo and oxygen glucose deprivation/reperfusion in vitro. Stroke outcomes of mice with two genotypes were assessed. Neuronal mitophagy was analysed both in vivo and in vitro. Activities of FUNDC1 and its regulator Src were evaluated. The impact of Src on FUNDC1-mediated mitophagy was assessed through administration of Src antagonist PP1.

RESULTS

To our surprise, FUNDC1 knockout mice subjected to tMCAO showed stroke outcomes comparable to those of their wild-type littermates. Although neuronal mitophagy could be activated by I/R injury, FUNDC1 deletion did not disrupt neuronal mitophagy. Transient activation of FUNDC1, represented by dephosphorylation of Tyr18, was detected in the early stages (within 3 hours) of neuronal I/R injury; however, phosphorylated Tyr18 reappeared and even surpassed baseline levels in later stages (after 6 hours), accompanied by a decrease in FUNDC1-light chain 3 interactions. Spontaneous inactivation of FUNDC1 was associated with Src activation, represented by phosphorylation of Tyr416, which changed in parallel with the level of phosphorylated FUNDC1 (Tyr18) during neuronal I/R injury. Finally, FUNDC1-mediated mitophagy in neurons under I/R conditions can be rescued by pharmacological inhibition of Src.

CONCLUSIONS

FUNDC1 is inactivated by Src during the later stage (after 6 hours) of neuronal I/R injury, and rescue of FUNDC1-mediated mitophagy may serve as a potential therapeutic strategy for treating ischaemic stroke.

Crosstalk among mitophagy, pyroptosis, ferroptosis, and necroptosis in central nervous system injuries

Central nervous system injuries have a high rate of resulting in disability and mortality; however, at present, effective treatments are lacking. Programmed cell death, which is a genetically determined form of active and ordered cell death with many types, has recently attracted increasing attention due to its functions in determining the fate of cell survival. A growing number of studies have suggested that programmed cell death is involved in central nervous system injuries and plays an important role in the progression of brain damage. In this review, we provide an overview of the role of programmed cell death in central nervous system injuries, including the pathways involved in mitophagy, pyroptosis, ferroptosis, and necroptosis, and the underlying mechanisms by which mitophagy regulates pyroptosis, ferroptosis, and necroptosis. We also discuss the new direction of therapeutic strategies targeting mitophagy for the treatment of central nervous system injuries, with the aim to determine the connection between programmed cell death and central nervous system injuries and to identify new therapies to modulate programmed cell death following central nervous system injury. In conclusion, based on these properties and effects, interventions targeting programmed cell death could be developed as potential therapeutic agents for central nervous system injury patients.

Translational selenium nanoparticles boost GPx1 activation to reverse HAdV-14 virus-induced oxidative damage

Human adenovirus (HAdV) can cause severe respiratory infections in immunocompromised patients, but its clinical treatment is seriously limited by side effects of drugs such as poor efficacy, low bioavailability and severe nephrotoxicity. Trace element selenium (Se) has been found will affect the disease progression of pneumonia, but its antivirus efficacy could be improved by speciation optimization. Therefore, herein we performed anti-HAdV effects of different Se speciation and found that lentinan (LNT)-decorated selenium nanoparticles (SeNPs) exhibited low cytotoxicity and excellent anti-HAdV antiviral activity. Furthermore, SeNPs@LNT reduced the HAdV infection-induced mitochondrial damage and excessive production of reactive oxygen species (ROS). It was also involved in the repair of host cell DNA damage and inhibition of viral DNA replication. SeNPs@LNT inhibited HAdV-induced apoptosis mainly by modulating the p53/Bcl-2 apoptosis signaling pathway. In vivo, SeNPs@LNT replenished Se by targeting the infected site through the circulatory system and was involved in the synthesis of Glutathione peroxidase 1 (GPx1). More importantly, GPx1 played an antioxidant and immunomodulatory role in alleviating HAdV-induced inflammatory cytokine storm and alleviating adenovirus pneumonia in Se-deficient mice. Collectively, this study provides a Se speciation of SeNPs@LNT with anti-HAdV activity, and demonstrate that SeNPs@LNT is a promising pharmaceutical candidate for the treatment of HAdV.

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

The structure and function of FUN14 domain-containing protein 1 and its contribution to cardioprotection by mediating mitophagy

Cardiovascular disease (CVD) is a serious public health risk, and prevention and treatment efforts are urgently needed. Effective preventive and therapeutic programs for cardiovascular disease are still lacking, as the causes of CVD are varied and may be the result of a multifactorial combination. Mitophagy is a form of cell-selective autophagy, and there is increasing evidence that mitophagy is involved in cardioprotective processes. Recently, many studies have shown that FUN14 domain-containing protein 1 (FUNDC1) levels and phosphorylation status are highly associated with many diseases, including heart disease. Here, we review the structure and functions of FUNDC1 and the path-ways of its mediated mitophagy, and show that mitophagy can be effectively activated by dephosphorylation of Ser13 and Tyr18 sites, phosphorylation of Ser17 site and ubiquitination of Lys119 site in FUNDC1. By effectively activating or inhibiting excessive mitophagy, the quality of mitochondria can be effectively controlled. The main reason is that, on the one hand, improper clearance of mitochondria and accumulation of damaged mitochondria are avoided, and on the other hand, excessive mitophagy causing apoptosis is avoided, both serving to protect the heart. In addition, we explore the possible mechanisms by which FUNDC1-mediated mitophagy is involved in exercise preconditioning (EP) for cardioprotection. Finally, we also point out unresolved issues in FUNDC1 and its mediated mitophagy and give directions where further research may be needed.

The mechanisms of natural products for eye disorders by targeting mitochondrial dysfunction

The human eye is susceptible to various disorders that affect its structure or function, including glaucoma, age-related macular degeneration (AMD) and diabetic retinopathy (DR). Mitochondrial dysfunction has been identified as a critical factor in the pathogenesis and progression of eye disorders, making it a potential therapeutic target in the clinic. Natural products have been used in traditional medicine for centuries and continue to play a significant role in modern drug development and clinical therapeutics. Recently, there has been a surge in research exploring the efficacy of natural products in treating eye disorders and their underlying physiological mechanisms. This review aims to discuss the involvement of mitochondrial dysfunction in eye disorders and summarize the recent advances in the application of natural products targeting mitochondria. In addition, we describe the future perspective and challenges in the development of mitochondria-targeting natural products.

CLPB disaggregase dysfunction impacts the functional integrity of the proteolytic SPY complex

CLPB is a mitochondrial intermembrane space AAA+ domain-containing disaggregase. CLPB mutations are associated with 3-methylglutaconic aciduria and neutropenia; however, the molecular mechanism underscoring disease and the contribution of CLPB substrates to disease pathology remains unknown. Interactions between CLPB and mitochondrial quality control (QC) factors, including PARL and OPA1, have been reported, hinting at dysregulation of organelle QC in disease. Utilizing proteomic and biochemical approaches, we show a stress-specific aggregation phenotype in a CLPB-null environment and define the CLPB substrate profile. We illustrate an interplay between intermembrane space proteins including CLPB, HAX1, HTRA2, and the inner membrane quality control proteins (STOML2, PARL, YME1L1; SPY complex), with CLPB deficiency impeding SPY complex function by virtue of protein aggregation in the intermembrane space. We conclude that there is an interdependency of mitochondrial QC components at the intermembrane space/inner membrane interface, and perturbations to this network may underscore CLPB disease pathology.

Targeted knockdown of PGAM5 in synovial macrophages efficiently alleviates osteoarthritis

Osteoarthritis (OA) is a common degenerative disease worldwide and new therapeutics that target inflammation and the crosstalk between immunocytes and chondrocytes are being developed to prevent and treat OA. These attempts involve repolarizing pro-inflammatory M1 macrophages into the anti-inflammatory M2 phenotype in synovium. In this study, we found that phosphoglycerate mutase 5 (PGAM5) significantly increased in macrophages in OA synovium compared to controls based on histology of human samples and single-cell RNA sequencing results of mice models. To address the role of PGAM5 in macrophages in OA, we found conditional knockout of PGAM5 in macrophages greatly alleviated OA symptoms and promoted anabolic metabolism of chondrocytes in vitro and in vivo. Mechanistically, we found that PGAM5 enhanced M1 polarization via AKT-mTOR/p38/ERK pathways, whereas inhibited M2 polarization via STAT6-PPARγ pathway in murine bone marrow-derived macrophages. Furthermore, we found that PGAM5 directly dephosphorylated Dishevelled Segment Polarity Protein 2 (DVL2) which resulted in the inhibition of β-catenin and repolarization of M2 macrophages into M1 macrophages. Conditional knockout of both PGAM5 and β-catenin in macrophages significantly exacerbated osteoarthritis compared to PGAM5-deficient mice. Motivated by these findings, we successfully designed mannose modified fluoropolymers combined with siPGAM5 to inhibit PGAM5 specifically in synovial macrophages via intra-articular injection, which possessed desired targeting abilities of synovial macrophages and greatly attenuated murine osteoarthritis. Collectively, these findings defined a key role for PGAM5 in orchestrating macrophage polarization and provides insights into novel macrophage-targeted strategy for treating OA.

Phosphoglycerate mutase 5 aggravates alcoholic liver disease through disrupting VDAC-1-dependent mitochondrial integrity

Alcoholic liver disease (ALD) poses a substantial global health challenge, with its pathogenesis deeply rooted in mitochondrial dysfunction. Our study explores the pivotal roles of Phosphoglycerate mutase family member 5 (Pgam5) and Voltage-Dependent Anion Channel 1 (VDAC1) in the progression of ALD, providing novel insights into their interplay and impact on mitochondrial integrity. We demonstrate that Pgam5 silencing preserves hepatocyte viability and attenuates ethanol-induced apoptosis, underscoring its detrimental role in exacerbating hepatocyte dysfunction. Pgam5's influence extends to the regulation of VDAC1 oligomerization, a key process in mitochondrial permeability transition pore (mPTP) opening, mitochondrial swelling, and apoptosis initiation. Notably, the inhibition of VDAC1 oligomerization through Pgam5 silencing or pharmacological intervention (VBIT-12) significantly preserves mitochondrial function, evident in the maintenance of mitochondrial membrane potential and reduced reactive oxygen species (ROS) production. In vivo experiments using hepatocyte-specific Pgam5 knockout (Pgam5hKO) and control mice reveal that Pgam5 deficiency mitigates ethanol-induced liver histopathology, inflammation, lipid peroxidation, and metabolic disorder, further supporting its role in ALD progression. Our findings highlight the critical involvement of Pgam5 and VDAC1 in mitochondrial dysfunction in ALD, suggesting potential therapeutic targets. While promising, these findings necessitate further research, including human studies, to validate their clinical applicability and explore broader implications in liver diseases. Overall, our study provides a significant advancement in understanding ALD pathophysiology, paving the way for novel therapeutic strategies targeting mitochondrial pathways in ALD.

PGAM5 knockout causes depressive-like behaviors in mice via ATP deficiency in the prefrontal cortex

INTRODUCTION

Major depressive disorder (MDD) affects about 17% population in the world. Although abnormal energy metabolism plays an important role in the pathophysiology of MDD, however, how deficiency of adenosine triphosphate (ATP) products affects emotional circuit and what regulates ATP synthesis are still need to be elaborated.

AIMS

Our study aimed to investigate how deficiency of PGAM5-mediated depressive behavior.

RESULTS

We firstly discovered that PGAM5 knockout (PGAM5-/- ) mice generated depressive-like behaviors. The phenotype was reinforced by the observation that chronic unexpected mild stress (CUMS)-induced depressive mice exhibited lowered expression of PGAM5 in prefrontal cortex (PFC), hippocampus (HIP), and striatum. Next, we found, with the using of functional magnetic resonance imaging (fMRI), that the functional connectivity between PFC reward system and the PFC volume were reduced in PGAM5-/- mice. PGAM5 ablation resulted in the loss of dendritic spines and lowered density of PSD95 in PFC, but not in HIP. Finally, we found that PGAM5 ablation led to lowered ATP concentration in PFC, but not in HIP. Coimmunoprecipitation study showed that PGAM5 directly interacted with the ATP F1 F0 synthase without influencing the interaction between ATP F1 F0 synthase and Bcl-xl. We then conducted ATP administration to PGAM5-/- mice and found that ATP could rescue the behavioral and neuronal phenotypes of PGAM5-/- mice.

CONCLUSIONS

Our findings provide convincing evidence that PGAM5 ablation generates depressive-like behaviors via restricting neuronal ATP production so as to impair the number of neuronal spines in PFC.

S-9-PAHSA's neuroprotective effect mediated by CAIII suppresses apoptosis and oxidative stress in a mouse model of type 2 diabetes

BACKGROUND

With the rapidly increasing prevalence of metabolic diseases such as type 2 diabetes mellitus (T2DM), neuronal complications associated with these diseases have resulted in significant burdens on healthcare systems. Meanwhile, effective therapies have remained insufficient. A novel fatty acid called S-9-PAHSA has been reported to provide metabolic benefits in T2DM by regulating glucose metabolism. However, whether S-9-PAHSA has a neuroprotective effect in mouse models of T2DM remains unclear.

METHODS

This in vivo study in mice fed a high-fat diet (HFD) for 5 months used fasting blood glucose, glucose tolerance, and insulin tolerance tests to examine the effect of S-9-PAHSA on glucose metabolism. The Morris water maze test was also used to assess the impact of S-9-PAHSA on cognition in the mice, while the neuroprotective effect of S-9-PAHSA was evaluated by measuring the expression of proteins related to apoptosis and oxidative stress. In addition, an in vitro study in PC12 cells assessed apoptosis, oxidative stress, and mitochondrial membrane potential with or without CAIII knockdown to determine the role of CAIII in the neuroprotective effect of S-9-PAHSA.

RESULTS

S-9-PAHSA reduced fasting blood glucose levels significantly, increased insulin sensitivity in the HFD mice and also suppressed apoptosis and oxidative stress in the cortex of the mice and PC12 cells in a diabetic setting. By suppressing oxidative stress and apoptosis, S-9-PAHSA protected both neuronal cells and microvascular endothelial cells in in vivo and in vitro diabetic environments. Interestingly, this protective effect of S-9-PAHSA was reduced significantly when CAIII was knocked down in the PC12 cells, suggesting that CAIII has a major role in the neuroprotective effect of S-9-PAHSA. However, overexpression of CAIII did not significantly enhance the protective effect of S-9-PAHSA.

CONCLUSION

S-9-PAHSA mediated by CAIII has the potential to exert a neuroprotective effect by suppressing apoptosis and oxidative stress in neuronal cells exposed to diabetic conditions. Furthermore, S-9-PAHSA has the capability to reduce fasting blood glucose and LDL levels and enhance insulin sensitivity in mice fed with HFD.

PGAM5 expression levels in heart failure and protection ROS-induced oxidative stress and ferroptosis by Keap1/Nrf2

OBJECTIVES

As a common and frequently occurring disease, heart failure has been paid more and more attention, but the mechanism of its occurrence and development is still unclear. This study investigated that PGAM5 expression levels in heart failure and its underlying mechanisms in vivo and in vitro.

METHODS

The inhibition of PGAM5 mRNA expression levels in patients with heart failure was compared with the normal group.

RESULTS

The serum of PGAM5 mRNA expression was negative correlation with collagen I and collagen III in patients with heart failure. PGAM5 mRNA and protein expression in the heart tissue of mice with heart failure were down-regulated at a time-dependent rate. The inhibition of PGAM5 presented heart failure in the model. PGAM5 reduced inflammation and inhibited ROS-induced oxidative stress in models of heart failure. PGAM5 reduced Ferroptosis in models of heart failure. PGAM5 regulated Keap1/Nrf2 signaling pathway. IP also showed that PGAM5 protein combined with the Keap1 protein. PGAM5 could increase Keap1 protein ubiquitination. Keap1 inhibition affected the effects of PGAM5 in model of heart failure.

CONCLUSIONS

We conclude that the protection of PGAM5 reduced ROS-induced oxidative stress and ferroptosis by the Keap1/Nrf2 signaling pathway in heart failure, suggesting that targeting this mechanism of PGAM5 may be a feasible strategy to treat heart failure.

The SARS-CoV-2 protein ORF3c is a mitochondrial modulator of innate immunity

The SARS-CoV-2 genome encodes a multitude of accessory proteins. Using comparative genomic approaches, an additional accessory protein, ORF3c, has been predicted to be encoded within the ORF3a sgmRNA. Expression of ORF3c during infection has been confirmed independently by ribosome profiling. Despite ORF3c also being present in the 2002-2003 SARS-CoV, its function has remained unexplored. Here we show that ORF3c localizes to mitochondria, where it inhibits innate immunity by restricting IFN-β production, but not NF-κB activation or JAK-STAT signaling downstream of type I IFN stimulation. We find that ORF3c is inhibitory after stimulation with cytoplasmic RNA helicases RIG-I or MDA5 or adaptor protein MAVS, but not after TRIF, TBK1 or phospho-IRF3 stimulation. ORF3c co-immunoprecipitates with the antiviral proteins MAVS and PGAM5 and induces MAVS cleavage by caspase-3. Together, these data provide insight into an uncharacterized mechanism of innate immune evasion by this important human pathogen.

Methylcrotonyl-CoA carboxylase subunit 1 (MCCA) regulates multidrug resistance in multiple myeloma

AIMS

This study aimed to investigate the effect and mechanism of methylcrotonyl-CoA carboxylase subunit 1 (MCCA) on multidrug resistance in multiple myeloma (MM).

MATERIALS AND METHODS

The apoptosis kit and CCK-8 reagent were used to detect drug-induced cell apoptosis and viability. Immunoprecipitation, immunofluorescence staining, and protein structural simulation were used to detect the interaction between MCCA and Bad. Immunodeficient mice were injected with ARD cells and treated with bortezomib. Changes in tumor burden were recorded by bioluminescence imaging, and κ light chain content in the blood of mice was detected by enzyme-linked immunoassay.

KEY FINDINGS

Patients with high MCCA expression from a primary MM dataset had superior overall survival. After treatment with different anti-MM drugs, MCCA knockdown MM (MCCA-KD) cells had higher survival rates than control knockdown (CTR-KD) cells (p < 0.05). Mechanistic studies have revealed that MCCA-KD cells had dysfunctional mitochondria with decreased Bax and Bad levels and increased Bcl-xl and Mcl-1 levels. Furthermore, that MCCA and Bad demonstrated protein-protein interactions. The half-life of Bad in MCCA-KD cells is significantly shorter than that in CTR-KD cells (7.34 vs. 2.42 h, p < 0.05). In a human MM xenograft mouse model, we confirmed that MCCA-KD tumors had a poor response to anti-MM drugs in vivo. Finally, we showed that MCCA might contribute to multidrug resistance in different human cancers, particularly in solid tumors.

SIGNIFICANCE

Our findings demonstrated a novel function of MCCA in multidrug resistance. The lack of MCCA expression promoted antiapoptotic cell signaling in MM cells.

Contribution and therapeutic value of mitophagy in cerebral ischemia-reperfusion injury after cardiac arrest

Cardiopulmonary resuscitation and related life support technologies have improved substantially in recent years; however, mortality and disability rates from cardiac arrest (CA) remain high and are closely associated with the high incidence of cerebral ischemia-reperfusion injury (CIRI), which is explained by a "double-hit" model (i.e., resulting from both ischemia and reperfusion). Mitochondria are important power plants in the cell and participate in various biochemical processes, such as cell differentiation and signaling in eukaryotes. Various mitochondrial processes, including energy metabolism, calcium homeostasis, free radical production, and apoptosis, are involved in several important stages of the progression and development of CIRI. Mitophagy is a key mechanism of the endogenous removal of damaged mitochondria to maintain organelle function and is a critical target for CIRI treatment after CA. Mitophagy also plays an essential role in attenuating ischemia-reperfusion in other organs, particularly during post-cardiac arrest myocardial dysfunction. Regulation of mitophagy may influence necroptosis (a programmed cell death pathway), which is the main endpoint of organ ischemia-reperfusion injury. In this review, we summarize the main signaling pathways related to mitophagy and their associated regulatory proteins. New therapeutic methods and drugs targeting mitophagy in ischemia-reperfusion animal models are also discussed. In-depth studies of the mechanisms underlying the regulation of mitophagy will enhance our understanding of the damage and repair processes in CIRI after CA, thereby contributing to the development of new therapeutic strategies.

Focused low-intensity pulsed ultrasound alleviates osteoarthritis via restoring impaired FUNDC1-mediated mitophagy

Mitophagy is critical for maintaining proper cellular functions, and it contributes to the onset and progression of osteoarthritis (OA). A recent study showed that focused low-intensity pulsed ultrasound (FLIPUS) could activate mitophagy, but the molecular mechanism remains unclear. This study aimed to elucidate the chondroprotective effects of FLIPUS in OA and the regulatory effects on FUN14-domain containing 1 (FUNDC1-mediated mitophagy. In vitro, FLIPUS improved inflammatory response, anabolism, and catabolism in interleukin (IL)-1β-induced OA chondrocytes. The chondroprotective effects of FLIPUS were attributed to promoting the expression of phosphoglycerate mutase 5 (PGAM5) and the dephosphorylation of FUNDC1 at serine 13 (Ser13), as well as promoting the mitophagy process. In vivo, FLIPUS reduced the cartilage degeneration and apoptosis and reversed the change of anabolic- and catabolic-related proteins in destabilized medial meniscus (DMM)-induced mouse model. Thus, the study indicates that FLIPUS exhibits a chondroprotective effect via activating impaired FUNDC1-mediated mitophagy.

Crosstalk between mitochondrial biogenesis and mitophagy to maintain mitochondrial homeostasis

Mitochondrial mass and quality are tightly regulated by two essential and opposing mechanisms, mitochondrial biogenesis (mitobiogenesis) and mitophagy, in response to cellular energy needs and other cellular and environmental cues. Great strides have been made to uncover key regulators of these complex processes. Emerging evidence has shown that there exists a tight coordination between mitophagy and mitobiogenesis, and their defects may cause many human diseases. In this review, we will first summarize the recent advances made in the discovery of molecular regulations of mitobiogenesis and mitophagy and then focus on the mechanism and signaling pathways involved in the simultaneous regulation of mitobiogenesis and mitophagy in the response of tissue or cultured cells to energy needs, stress, or pathophysiological conditions. Further studies of the crosstalk of these two opposing processes at the molecular level will provide a better understanding of how the cell maintains optimal cellular fitness and function under physiological and pathophysiological conditions, which holds promise for fighting aging and aging-related diseases.

Mitochondria in health, disease, and aging

Mitochondria are well known as organelles responsible for the maintenance of cellular bioenergetics through the production of ATP. Although oxidative phosphorylation may be their most important function, mitochondria are also integral for the synthesis of metabolic precursors, calcium regulation, the production of reactive oxygen species, immune signaling, and apoptosis. Considering the breadth of their responsibilities, mitochondria are fundamental for cellular metabolism and homeostasis. Appreciating this significance, translational medicine has begun to investigate how mitochondrial dysfunction can represent a harbinger of disease. In this review, we provide a detailed overview of mitochondrial metabolism, cellular bioenergetics, mitochondrial dynamics, autophagy, mitochondrial damage-associated molecular patterns, mitochondria-mediated cell death pathways, and how mitochondrial dysfunction at any of these levels is associated with disease pathogenesis. Mitochondria-dependent pathways may thereby represent an attractive therapeutic target for ameliorating human disease.

Deletion of PGAM5 Downregulates FABP1 and Attenuates Long-Chain Fatty Acid Uptake in Hepatocellular Carcinoma

Phosphoglycerate mutase 5 (PGAM5) is a Ser/His/Thr phosphatase responsible for regulating mitochondrial homeostasis. Overexpression of PGAM5 is correlated with a poor prognosis in hepatocellular carcinoma, colon cancer, and melanoma. In hepatocellular carcinoma, silencing of PGAM5 reduces growth, which has been attributed to decreased mitophagy and enhanced apoptosis. Yet in colon cancer, PGAM5's pro-tumor survival effect is correlated to lipid metabolism. We sought to identify whether deletion of PGAM5 modulated lipid droplet accrual in hepatocellular carcinoma. HepG2 and Huh7 PGAM5 knockout cell lines generated using CRISPR/Cas9 technology were used to measure cell growth, cellular ATP, and long-chain fatty acid uptake. Expression of hepatocellular fatty acid transporters, cluster of differentiation 36 (CD36), solute carrier family 27 member 2 (SLC27A2), solute carrier family 27 member 5 (SLC27A5), and fatty acid binding protein 1 (FABP1) was measured by quantitative PCR and Western blot. We found that deletion of PGAM5 attenuates hepatocellular carcinoma cell growth and ATP production. Further, PGAM5 knockout ameliorates palmitate-induced steatosis and reduces expression of FABP1 in HepG2 and Huh7 cell lines. PGAM5's role in hepatocellular carcinoma includes regulation of fatty acid metabolism, which may be related to expression of the fatty acid transporter, FABP1.

PGAM5 is an MFN2 phosphatase that plays an essential role in the regulation of mitochondrial dynamics

Mitochondrial morphology is regulated by the post-translational modifications of the dynamin family GTPase proteins including mitofusin 1 (MFN1), MFN2, and dynamin-related protein 1 (DRP1). Mitochondrial phosphatase phosphoglycerate mutase 5 (PGAM5) is emerging as a regulator of these post-translational modifications; however, its precise role in the regulation of mitochondrial morphology is unknown. We show that PGAM5 interacts with MFN2 and DRP1 in a stress-sensitive manner. PGAM5 regulates MFN2 phosphorylation and consequently protects it from ubiquitination and degradation. Further, phosphorylation and dephosphorylation modification of MFN2 regulates its fusion ability. Phosphorylation enhances fission and degradation, whereas dephosphorylation enhances fusion. PGAM5 dephosphorylates MFN2 to promote mitochondrial network formation. Further, using a Drosophila genetic model, we demonstrate that the MFN2 homolog Marf and dPGAM5 are in the same biological pathway. Our results identify MFN2 dephosphorylation as a regulator of mitochondrial fusion and PGAM5 as an MFN2 phosphatase.

The mitophagy pathway and its implications in human diseases

Mitochondria are dynamic organelles with multiple functions. They participate in necrotic cell death and programmed apoptotic, and are crucial for cell metabolism and survival. Mitophagy serves as a cytoprotective mechanism to remove superfluous or dysfunctional mitochondria and maintain mitochondrial fine-tuning numbers to balance intracellular homeostasis. Growing evidences show that mitophagy, as an acute tissue stress response, plays an important role in maintaining the health of the mitochondrial network. Since the timely removal of abnormal mitochondria is essential for cell survival, cells have evolved a variety of mitophagy pathways to ensure that mitophagy can be activated in time under various environments. A better understanding of the mechanism of mitophagy in various diseases is crucial for the treatment of diseases and therapeutic target design. In this review, we summarize the molecular mechanisms of mitophagy-mediated mitochondrial elimination, how mitophagy maintains mitochondrial homeostasis at the system levels and organ, and what alterations in mitophagy are related to the development of diseases, including neurological, cardiovascular, pulmonary, hepatic, renal disease, etc., in recent advances. Finally, we summarize the potential clinical applications and outline the conditions for mitophagy regulators to enter clinical trials. Research advances in signaling transduction of mitophagy will have an important role in developing new therapeutic strategies for precision medicine.

To eat or not to eat mitochondria? How do host cells cope with mitophagy upon bacterial infection?

Mitochondria fulfil a plethora of cellular functions ranging from energy production to regulation of inflammation and cell death control. The fundamental role of mitochondria makes them a target of choice for invading pathogens, with either an intracellular or extracellular lifestyle. Indeed, the modulation of mitochondrial functions by several bacterial pathogens has been shown to be beneficial for bacterial survival inside their host. However, so far, relatively little is known about the importance of mitochondrial recycling and degradation pathways through mitophagy in the outcome (success or failure) of bacterial infection. On the one hand, mitophagy could be considered as a defensive response triggered by the host upon infection to maintain mitochondrial homeostasis. However, on the other hand, the pathogen itself may initiate the host mitophagy to escape from mitochondrial-mediated inflammation or antibacterial oxidative stress. In this review, we will discuss the diversity of various mechanisms of mitophagy in a general context, as well as what is currently known about the different bacterial pathogens that have developed strategies to manipulate the host mitophagy.

Inflammatory, mitochondrial, and senescence-related markers: Underlying biological pathways of muscle aging and new therapeutic targets

The maintenance of functional health is pivotal for achieving independent life in older age. The aged muscle is characterized by ultrastructural changes, including loss of type I and type II myofibers and a greater proportion of cytochrome c oxidase deficient and succinate dehydrogenase positive fibers. Both intrinsic (e.g., altered proteostasis, DNA damage, and mitochondrial dysfunction) and extrinsic factors (e.g., denervation, altered metabolic regulation, declines in satellite cells, and inflammation) contribute to muscle aging. Being a hub for several cellular activities, mitochondria are key to myocyte viability and mitochondrial dysfunction has been implicated in age-associated physical decline. The maintenance of functional organelles via mitochondrial quality control (MQC) processes is, therefore, crucial to skeletal myofiber viability and organismal health. The autophagy-lysosome pathway has emerged as a critical step of MQC in muscle by disposing organelles and proteins via their tagging for autophagosome incorporation and delivery to the lysosome for clearance. This pathway was found to be altered in muscle of physically inactive older adults. A relationship between this pathway and muscle tissue composition of the lower extremities as well as physical performance was also identified. Therefore, integrating muscle structure and myocyte quality control measures in the evaluation of muscle health may be a promising strategy for devising interventions fostering muscle health.

Mitochondrial Protease Targeting Chimeras for Mitochondrial Matrix Protein Degradation

Targeted protein degradation (TPD) is an emerging technique for protein regulation. Currently, all TPD developed in eukaryotic cells relies on either ubiquitin-proteasome or lysosomal systems, thus are powerless against target proteins in membrane organelles lacking proteasomes and lysosomes, such as mitochondria. Here, we developed a mitochondrial protease targeting chimera (MtPTAC) to address this issue. MtPTAC is a bifunctional small molecule that can bind to mitochondrial caseinolytic protease P (ClpP) at one end and target protein at the other. Mechanistically, MtPTAC activates the hydrolase activity of ClpP while simultaneously bringing target proteins into proximity with ClpP. Taking mitochondrial RNA polymerase (POLRMT) as a model protein, we have demonstrated the powerful proteolytic ability and antitumor application prospects of MtPTAC, both in vivo and in vitro. This is the first modularly designed TPD that can specifically hydrolyze target proteins inside mitochondria.

Akkermansia muciniphila-Nlrp3 is involved in the neuroprotection of phosphoglycerate mutase 5 deficiency in traumatic brain injury mice

INTRODUCTION

Gut-microbiota-brain axis is a potential treatment to decrease the risk of chronic traumatic encephalopathy following traumatic brain injury (TBI). Phosphoglycerate mutase 5 (PGAM5), a mitochondrial serine/threonine protein phosphatase, resides in mitochondrial membrane and regulates mitochondrial homeostasis and metabolism. Mitochondria mediates intestinal barrier and gut microbiome.

OBJECTIVES

This study investigated the association between PGAM5 and gut microbiota in mice with TBI.

METHODS

The controlled cortical impact injury was established in mice with genetically-ablated Pgam5 (Pgam5-/-) or wild type, and WT male mice were treated with fecal microbiota transplantation (FMT) from male Pgam5-/- mice or Akkermansia muciniphila (A. muciniphila). Then the gut microbiota abundance, blood metabolites, neurological function, and nerve injury were detected.

RESULTS

Treated with antibiotics for suppressing gut microbiota in Pgam5-/- mice partially relieved the role of Pgam5 deficiency in the improvement of initial inflammatory factors and motor dysfunction post-TBI. Pgam5 knockout exhibited an increased abundance of A. muciniphila in mice. FMT from male Pgam5-/- mice enabled better maintenance of amino acid metabolism and peripherial environment than that in TBI-vehicle mice, which suppressed neuroinflammation and improved neurological deficits, and A. muciniphila was negatively associated with intestinal mucosal injury and neuroinflammation post-TBI. Moreover, A. muciniphila treatment ameliorated neuroinflammation and nerve injury by regulating Nlrp3 inflammasome activation in cerebral cortex with TBI.

CONCLUSION

Thus, the present study provides evidence that Pgam5 is involved in gut microbiota-mediated neuroinflammation and nerve injury, with A. muciniphila-Nlrp3 contributing to peripheral effects.

LncRNA FAS-AS1 upregulated by its genetic variation rs6586163 promotes cell apoptosis in nasopharyngeal carcinoma through regulating mitochondria function and Fas splicing

Nasopharyngeal carcinoma (NPC) is a common head and neck malignant with a high incidence in Southern China. Genetic aberrations play a vital role in the pathogenesis, progression and prognosis of NPC. In the present study, we elucidated the underlying mechanism of FAS-AS1 and its genetic variation rs6586163 in NPC. We demonstrated that FAS-AS1 rs6586163 variant genotype carriers were associated with lower risk of NPC (CC vs. AA, OR = 0.645, P = 0.006) and better overall survival (AC + CC vs. AA, HR = 0.667, P = 0.030). Mechanically, rs6586163 increased the transcriptional activity of FAS-AS1 and contributed to ectopic overexpression of FAS-AS1 in NPC. rs6586163 also exhibited an eQTL trait and the genes affected by rs6586163 were enriched in apoptosis related signaling pathway. FAS-AS1 was downregulated in NPC tissues and over-expression of FAS-AS1 was associated with early clinical stage and better short-term treatment efficacy for NPC patients. Overexpression of FAS-AS1 inhibited NPC cell viability and promoted cell apoptosis. GSEA analysis of RNA-seq data suggested FAS-AS1 participate in mitochondria regulation and mRNA alternative splicing. Transmission electron microscopic examination verified that the mitochondria was swelled, the mitochondrial cristae was fragmented or disappeared, and their structures were destroyed in FAS-AS1 overexpressed cells. Furthermore, we identified HSP90AA1, CS, BCL2L1, SOD2 and PPARGC1A as the top 5 hub genes of FAS-AS1 regulated genes involved in mitochondria function. We also proved FAS-AS1 could affect Fas splicing isoform sFas/mFas expression ratio, and apoptotic protein expression, thus leading to increased apoptosis. Our study provided the first evidence that FAS-AS1 and its genetic polymorphism rs6586163 triggered apoptosis in NPC, which might have a potential as new biomarkers for NPC susceptibility and prognosis.

Mitophagy in atherosclerosis: from mechanism to therapy

Mitophagy is a type of autophagy that can selectively eliminate damaged and depolarized mitochondria to maintain mitochondrial activity and cellular homeostasis. Several pathways have been found to participate in different steps of mitophagy. Mitophagy plays a significant role in the homeostasis and physiological function of vascular endothelial cells, vascular smooth muscle cells, and macrophages, and is involved in the development of atherosclerosis (AS). At present, many medications and natural chemicals have been shown to alter mitophagy and slow the progression of AS. This review serves as an introduction to the field of mitophagy for researchers interested in targeting this pathway as part of a potential AS management strategy.

TIPE3 represses head and neck squamous cell carcinoma progression via triggering PGAM5 mediated mitochondria dysfunction

Mitochondria are essential organelles in balancing oxidative stress and cell death during cancer cell proliferation. Rapid tumor growth induces tremendous stress on mitochondria. The mammalian tumor necrosis factor-α-induced protein 8-likes (TIPEs) family plays critical roles in balancing cancer cell death and survival. Yet, the roles of TIPEs in HNSCC tumorigenesis and mitochondria stress maintenance is unclear. Based on an integrative analysis of public HNSCC datasets, we identified that the downregulation of TIPE3 via its promoter hypermethylation modification is the major event of TIPEs alterations during HNSCC tumorigenesis. Low expression levels of TIPE3 were correlated with high malignancy and poor clinical outcomes of HNSCC patients. Restoring TIPE3 represses HNSCC proliferation, migration, and invasion in vitro and in vivo, while silencing TIPE3 acted on an opposite way. Mechanistically, TIPE3 band to the PGAM5 and electron transport chain (ETC) complex. Restoring TIPE3 promoted PGAM5 recruiting BAX and dephosphorylating p-DRP1(Ser637), which triggered mitochondrial outer membrane permeabilization and fragmentation. Ultimately, TIPE3 induced ETC damage and oxygen consumption rate decrease, ROS accumulation, mitochondrial membrane potential depolarization, and cell apoptosis. Collectively, our work reveals that TIPE3 plays critical role in maintaining mitochondrial stress and cancer cell progression in HNSCC, which might be a potential therapeutic target for HNSCC patients.