PINK1 is selectively stabilized on impaired mitochondria to activate Parkin

Improving mitochondria-associated endoplasmic reticulum membranes integrity as converging therapeutic strategy for rare neurodegenerative diseases and cancer

Membrane contact sites harbor a distinct set of proteins with varying biological functions, thereby emerging as hubs for localized signaling nanodomains underlying adequate cell function. Here, we will focus on mitochondria-associated endoplasmic reticulum membranes (MAMs), which serve as hotspots for Ca2+ signaling, redox regulation, lipid exchange, mitochondrial quality and unfolded protein response pathway. A network of MAM-resident proteins contributes to the structural integrity and adequate function of MAMs. Beyond endoplasmic reticulum (ER)-mitochondrial tethering proteins, MAMs contain several multi-protein complexes that mediate the transfer of or are influenced by Ca2+, reactive oxygen species and lipids. Particularly, IP3 receptors, intracellular Ca2+-release channels, and Sigma-1 receptors (S1Rs), ligand-operated chaperones, serve as important platforms that recruit different accessory proteins and intersect with these local signaling processes. Furthermore, many of these proteins are directly implicated in pathophysiological conditions, where their dysregulation or mutation is not only causing diseases such as cancer and neurodegeneration, but also rare genetic diseases, for example familial Parkinson's disease (PINK1, Parkin, DJ-1), familial Amyotrophic lateral sclerosis (TDP43), Wolfram syndrome1/2 (WFS1 and CISD2), Harel-Yoon syndrome (ATAD3A). In this review, we will discuss the current state-of-the-art regarding the molecular components, protein platforms and signaling networks underlying MAM integrity and function in cell function and how their dysregulation impacts MAMs, thereby driving pathogenesis and/or impacting disease burden. We will highlight how these insights can generate novel, potentially therapeutically relevant, strategies to tackle disease outcomes by improving the integrity of MAMs and the signaling processes occurring at these membrane contact sites.

Synaptic-mitochondrial transport: mechanisms in neural adaptation and degeneration

Synaptic plasticity is the basis for the proper functioning of the central nervous system. Synapses are the contact points between neurons and are crucial for information transmission, the structure and function of synapses change adaptively based on the different activities of neurons, thus affecting processes such as learning, memory, and neural development and repair. Synaptic activity requires a large amount of energy provided by mitochondria. Mitochondrial transport proteins regulate the positioning and movement of mitochondria to maintain normal energy metabolism. Recent studies have shown a close relationship between mitochondrial transport proteins and synaptic plasticity, providing a new direction for the study of adaptive changes in the central nervous system and new targets for the treatment of neurodegenerative diseases.

Actinomyces viscosus promotes neuroprotection in C. elegans models of Parkinson's disease

Parkinson's Disease is characterized by selective degeneration of dopaminergic neurons, primarily in the substantia nigra pars compacta, as well as accumulation of alpha-synuclein enriched protein aggregates within neurons. The pathogenesis of PD is still not completely understood, and no treatments exist that alter disease progression. Obvious genetic causes are detected in only a small number of PD patients (5-10 %), suggesting that environmental factors play a significant role the development of PD. Correlative studies suggest that the microbiota could be an important environmental modifier of neurodegeneration. We identified a microbiotal isolate, Actinomyces viscosus, that reduced neurodegeneration in C. elegans expressing a pathological mutant form (G2019S) of leucine-rich repeat kinase 2 (LRRK2) in dopaminergic neurons. A. viscosus also suppressed autophagic dysfunction in these animals and reduced alpha-synuclein aggregation in a synucleinopathy model. Global gene expression analysis revealed increased expression of aspartic cathepsins in response to A. viscosus. Consistent with the involvement of these proteins in neuroprotection, we found that reducing aspartic cathepsin function increased neurodegeneration in the LRRK2 transgenic model. Our findings contribute to the current understanding of how the gut microbiota may influence PD, elucidating one potential mechanism of microbiota-mediated neuroprotection.

Kaposi's sarcoma-associated herpesvirus induces mitochondrial fission to evade host immune responses and promote viral production

Mitochondrial dynamics are pivotal for host immune responses upon infection, yet how viruses manipulate these processes to impair host defence and enhance viral fitness remains unclear. Here we show that Kaposi's sarcoma-associated herpesvirus (KSHV), an oncogenic virus also known as human herpesvirus 8, encodes Bcl-2 (vBcl-2), which reprogrammes mitochondrial architecture. It binds with NM23-H2, a host nucleoside diphosphate (NDP) kinase, to stimulate GTP loading of the dynamin-related protein (DRP1) GTPase, which triggers mitochondrial fission, inhibits mitochondrial antiviral signalling protein (MAVS) aggregation and impairs interferon responses in cell lines. An NM23-H2-binding-defective vBcl-2 mutant fails to evoke fission, leading to defective virion assembly due to activated MAVS-IFN signalling. Notably, we identify two key interferon-stimulated genes restricting vBcl-2-dependent virion morphogenesis. Using a high-throughput drug screening, we discover an inhibitor targeting vBcl-2-NM23-H2 interaction that blocks virion production in vitro. Our study identifies a mechanism in which KSHV manipulates mitochondrial dynamics to allow for virus assembly and shows that targeting the virus-mitochondria interface represents a potential therapeutic strategy.

The regulation of microglia by aging and autophagy in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory disease that is often characterized by the development of irreversible clinical disability. Age is a strong risk factor that is strongly associated with the clinical course and progression of MS. Several lines of evidence suggest that with aging, microglia have an aging-related gene expression signature and are close to disease-associated microglia (DAM), which exhibit decreased phagocytosis but increased production of inflammatory factors. The gene expression signatures of microglia in MS overlap with those in aging, inflammation and DAM. Moreover, the clearance of damaged myelin by microglia is impaired in the aged brain. Autophagy is a cellular process that decreases in activity with age. In this review, we provide an overview of the role of autophagy and aging in MS. We describe the impact of autophagy and aging on microglial activation in MS and the molecules involved in autophagy and aging, which are related to the phagocytosis and activation of microglia. We propose that a decrease in autophagy in microglia occurs with aging, leading to a decrease in phagocytosis. Decreases in phagocytosis and increases in the production of inflammatory factors by microglia contribute to chronic inflammation in the aged brain and disease progression in MS. Thus, the modulation of autophagy in microglia serves as a potential therapeutic target for MS.

Autophagy dysfunction and neurodegeneration: Where does it go wrong?

An infamous hallmark of neurodegenerative diseases is the accumulation of misfolded or unfolded proteins forming inclusions in the brain. The accumulation of these abnormal structures is a mysterious one, given that cells devote significant resources to integrate complementary pathways to ensure proteome integrity and proper protein folding. Aberrantly folded protein species are rapidly targeted for disposal by the ubiquitin-proteasome system (UPS), and even if this should fail, and the species accumulates, the cell can also rely on the lysosome-mediated degradation pathways of autophagy. Despite the many safeguards in place, failure to maintain protein homeostasis commonly occurs during, or preceding, the onset of disease. Over the last decade and a half, studies suggest that the failure of autophagy may explain the disruption in protein homeostasis observed in disease. In this review, we will examine how the highly complex cells of the brain can become vulnerable to failure of aggregate clearance at specific points during the processive pathway of autophagy, contributing to aggregate accumulation in brains with neurodegenerative disease.

Kinome screening identifies integrated stress response kinase EIF2AK1/HRI as a negative regulator of PINK1 mitophagy signaling

Loss-of-function mutations in the PINK1 kinase lead to early-onset Parkinson's disease (PD). PINK1 is activated by mitochondrial damage to phosphorylate ubiquitin and Parkin, triggering mitophagy. PINK1 also indirectly phosphorylates Rab GTPases, such as Rab8A. Using an siRNA library targeting human Ser/Thr kinases in HeLa cells, we identified EIF2AK1 [heme-regulated inhibitor (HRI) kinase], a branch of the integrated stress response (ISR), as a negative regulator of PINK1. EIF2AK1 knockdown enhances mitochondrial depolarization-induced PINK1 stabilization and phosphorylation of ubiquitin and Rab8A. These results were confirmed in SK-OV-3, U2OS, and ARPE-19 cells. Knockdown of DELE1, an activator of EIF2AK1, produced similar effects. Notably, the ISR inhibitor ISRIB also enhanced PINK1 activation. In human cells with mito-QC mitophagy reporters, EIF2AK1 knockdown or ISRIB treatment increased PINK1-dependent mitophagy without affecting deferiprone-induced mitophagy. These findings suggest that the DELE1-EIF2AK1 ISR pathway is a negative regulator of PINK1-dependent mitophagy. Further evaluation in PD-relevant models is needed to assess the therapeutic potential of targeting this pathway.

Mitochondrial Dysfunction in Genetic and Non-Genetic Parkinson's Disease

Mitochondrial dysfunction is a hallmark of Parkinson's disease (PD) pathogenesis, contributing to increased oxidative stress and impaired endo-lysosomal-proteasome system efficiency underlying neuronal injury. Genetic studies have identified 19 monogenic mutations-accounting for ~10% of PD cases-that affect mitochondrial function and are associated with early- or late-onset PD. Early-onset forms typically involve genes encoding proteins essential for mitochondrial quality control, including mitophagy and structural maintenance, while late-onset mutations impair mitochondrial dynamics, bioenergetics, and trafficking. Atypical juvenile genetic syndromes also exhibit mitochondrial abnormalities. In idiopathic PD, environmental neurotoxins such as pesticides and MPTP act as mitochondrial inhibitors, disrupting complex I activity and increasing reactive oxygen species. These converging pathways underscore mitochondria as a central node in PD pathology. This review explores the overlapping and distinct mitochondrial mechanisms in genetic and non-genetic PD, emphasizing their role in neuronal vulnerability. Targeting mitochondrial dysfunction finally offers a promising therapeutic avenue to slow or modify disease progression by intervening at a key point of neurodegenerative convergence.

Chimeric deubiquitinase engineering reveals structural basis for specific inhibition of the mitophagy regulator USP30

The mitochondrial deubiquitinase ubiquitin-specific protease (USP) 30 negatively regulates PINK1-parkin-driven mitophagy. Whether enhanced mitochondrial quality control through inhibition of USP30 can protect dopaminergic neurons is currently being explored in a clinical trial for Parkinson's disease. However, the molecular basis for specific inhibition of USP30 by small molecules has remained elusive. Here we report the crystal structure of human USP30 in complex with a specific inhibitor, enabled by chimeric protein engineering. Our study uncovers how the inhibitor extends into a cryptic pocket facilitated by a compound-induced conformation of the USP30 switching loop. Our work underscores the potential of exploring induced pockets and conformational dynamics to obtain deubiquitinase inhibitors and identifies residues facilitating specific inhibition of USP30. More broadly, we delineate a conceptual framework for specific USP deubiquitinase inhibition based on a common ligandability hotspot in the Leu73 ubiquitin binding site and on diverse compound extensions. Collectively, our work establishes a generalizable chimeric protein-engineering strategy to aid deubiquitinase crystallization and enables structure-based drug design with relevance to neurodegeneration.

Mitochondrial Maintenance in Skeletal Muscle

Skeletal muscle is one of the tissues with the highest range of variability in metabolic rate, which, to a large extent, is critically dependent on tightly controlled and fine-tuned mitochondrial activity. Besides energy production, other mitochondrial processes, including calcium buffering, generation of heat, redox and reactive oxygen species homeostasis, intermediate metabolism, substrate biosynthesis, and anaplerosis, are essential for proper muscle contractility and performance. It is thus not surprising that adequate mitochondrial function is ensured by a plethora of mechanisms, aimed at balancing mitochondrial biogenesis, proteostasis, dynamics, and degradation. The fine-tuning of such maintenance mechanisms ranges from proper folding or degradation of individual proteins to the elimination of whole organelles, and in extremis, apoptosis of cells. In this review, the present knowledge on these processes in the context of skeletal muscle biology is summarized. Moreover, existing gaps in knowledge are highlighted, alluding to potential future studies and therapeutic implications.

SIRT5 modulates mitochondria function via mitophagy and antioxidant mechanisms to facilitate oocyte maturation in mice

Mitochondrial homeostasis, closely associated with mitophagy and antioxidant mechanisms, is essential for proper meiotic spindle assembly and chromosome segregation during oocyte maturation. SIRT5, known to modulate mitochondrial function under various conditions, has been shown to impact oocyte quality when inhibited, however, the precise mechanisms linking SIRT5 to mitochondrial homeostasis during meiotic progression remain unclear. In this study, we demonstrate that SIRT5 localizes predominantly at the periphery of the meiotic spindle and is enriched on chromosomes during oocyte maturation. Inhibition of SIRT5 led to significant meiotic defects, including disrupted spindle organization and chromosome misalignment. These defects were associated with increased histone acetylation, which impaired kinetochore-microtubule attachments. Moreover, SIRT5 inhibition resulted in mitochondrial dysfunction, subsequently elevating ROS levels and triggering oxidative stress, which further exacerbated meiotic abnormalities. Mechanistically, SIRT5 inhibition disrupted the balance of Parkin-dependent mitophagy by inducing ULK phosphorylation. Additionally, it activated the PI3K/Akt signaling pathway, which increased NADPH consumption and reduced GSH levels. Collectively, these findings reveal that SIRT5 plays dual roles in maintaining mitochondrial homeostasis during oocyte maturation: (1) by regulating Parkin-dependent mitophagy to prevent excessive mitochondrial clearance, and (2) by preserving the NADPH/GSH antioxidant system to ensure redox balance. These insights provide potential targets for improving oocyte quality and addressing mitochondrial dysfunction-related reproductive disorders in females.

Mitochondrial Quality Control in Ovarian Function: From Mechanisms to Therapeutic Strategies

Mitochondrial quality control plays a critical role in cytogenetic development by regulating various cell-death pathways and modulating the release of reactive oxygen species (ROS). Dysregulated mitochondrial quality control can lead to a broad spectrum of diseases, including reproductive disorders, particularly female infertility. Ovarian insufficiency is a significant contributor to female infertility, given its high prevalence, complex pathogenesis, and profound impact on women's health. Understanding the pathogenesis of ovarian insufficiency and devising treatment strategies based on this understanding are crucial. Oocytes and granulosa cells (GCs) are the primary ovarian cell types, with GCs regulated by oocytes, fulfilling their specific energy requirements prior to ovulation. Dysregulation of mitochondrial quality control through gene knockout or external stimuli can precipitate apoptosis, inflammatory responses, or ferroptosis in both oocytes and GCs, exacerbating ovarian insufficiency. This review aimed to delineate the regulatory mechanisms of mitochondrial quality control in GCs and oocytes during ovarian development. This study highlights the adverse consequences of dysregulated mitochondrial quality control on GCs and oocyte development and proposes therapeutic interventions for ovarian insufficiency based on mitochondrial quality control. These insights provide a foundation for future clinical approaches for treating ovarian insufficiency.

Umbilical cord mesenchymal stem cell-derived extracellular vesicles improve excessive autophagy of granulosa cells through METTL3

Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder impacting women's fertility. We assessed the effect of umbilical cord mesenchymal stem cell-derived extracellular vesicles (UC-MSC-EVs) on PTEN-induced kinase 1 (PINK1)/Parkin-mediated excessive autophagy of ovarian granulosa cells (GCs) through methyltransferase-like 3 (METTL3). Human ovarian GC line KGN was cultured and treated with dehydroepiandrosterone (DHEA) and UC-MSC-EVs. Cell apoptosis and viability, autophagy-related protein levels, adenosine triphosphate (ATP) and mitochondrial membrane potential (MMP) level, and microtubule-associated protein 1 light chain 3 β (LC3B) and translocase of outer mitochondrial membrane 20 (TOMM20) colocalization were assessed by flow cytometry, CCK-8, Western blot, kit, and immunofluorescence. PINK1 N6-methyladenosine (m6A) modification, METTL3 levels, and PINK1 mRNA stability were determined by methylated RNA immunoprecipitation, reverse transcription quantitative polymerase chain reaction, and Western blot. The PCOS mouse model was established and treated with UC-MSC-EVs. Serum hormone and ovarian tissue autophagy-related protein levels were determined by enzyme-linked immunosorbent assay. DHEA decreased KGN cell viability and p62 level, increased PINK1, Parkin, LC3BII/I, and Beclin-1 protein levels, ATP content, MMP level, TOMM20+LC3B+ cell number, and apoptosis, which were partly abrogated by UC-MSC-EV treatment. PINK1 had m6A modification sites. METTL3 was a PINK1 m6A-modified writer protein. After DHEA treatment, KGN cells showed elevated METTL3 and PINK1 m6A modification levels and mRNA stability, whereas UC-MSC-EV treatment caused the opposite results. METTL3 overexpression partly averted UC-MSC-EVs-improved PINK1/Parkin-mediated mitophagy. UC-MSC-EVs curbed PINK1/Parkin-mediated excessive autophagy through METTL3 and improved ovarian function in PCOS mice. In conclusion, UC-MSC-EVs suppressed PINK1/Parkin-mediated mitophagy of ovarian GCs through METTL3, thereby improving PCOS.NEW & NOTEWORTHY Polycystic ovary syndrome (PCOS) is a prevalent endocrine disorder impacting women's fertility. The authors in this study using DHEA-induced granulosa cells (GCs) demonstrated that umbilical cord mesenchymal stem cell-derived extracellular vesicles (UC-MSC-EVs) suppressed PINK1/Parkin-mediated mitophagy of ovarian GCs through METTL3, thereby improving PCOS.

Quality control of un-imported mitochondrial proteins at a glance

Mitochondria are metabolic hubs that are essential for cellular homeostasis. Most mitochondrial proteins are translated in the cytosol and imported into the organelle. However, import machineries can become overwhelmed or disrupted by physiological demands, mitochondrial damage or diseases, such as metabolic and neurodegenerative disorders. Impaired import affects mitochondrial function and causes un-imported pre-proteins to accumulate not only in the cytosol but also in other compartments, including the endoplasmic reticulum and nucleus. Quality control pathways have evolved to mitigate the accumulation of these mistargeted proteins and prevent proteotoxicity. In this Cell Science at a Glance article and the accompanying poster, we summarize the fate of un-imported mitochondrial proteins and the compartment-specific quality control pathways that regulate them.

The Involvement of Mitochondrial Dysfunction during the Development of Adenomyosis

The etiology of adenomyosis remains unclear. The association between epithelial-mesenchymal transition (EMT) and mitochondrial dysfunction is involved in fibrotic diseases. Adenomyosis is defined as the existence of endometrial glands and stroma in the myometrium with EMT and ultimate fibrosis. This study was designed to investigate the involvement of mitochondrial dysfunction in fibrotic adenomyosis. Mitochondrial integrity was examined in mouse and human adenomyotic tissues. Control and tamoxifen-treated mice were treated with 3-nitropropionic acid (a mitochondrial dysfunction inducer) and NG-nitro-L-arginine methyl ester (a mitochondrial dysfunction inhibitor), respectively, at postnatal day 21, followed by an evaluation of adenomyosis, EMT, and fibrosis as well as the expression of mitophagy, oxidative stress, and transforming growth factor-β1 (TGF-β1). The gene profiles of adenomyotic uteri were examined at postnatal day 42. Adenomyotic mice exhibited increased development of EMT and fibrosis. Adenomyotic tissues showed consistent mitochondrial destruction with increased fission, mitophagosomes, and lysosomes. Besides, mitophagy, oxidative stress, and TGF-β1 levels were consistently increased. The mitochondrial dysfunction, the development of mitophagy and fibrosis, and TGF-β1 expression were induced by 3-nitropropionic acid in control uteri. In contrast, NG-nitro-L-arginine methyl ester attenuated mitochondrial dysfunction, mitophagy, fibrosis, and TGF-β1 in adenomyotic uteri. Gene profiling demonstrated increased expression of mitochondrial dysfunction-related genes in adenomyotic uteri. This indicates that mitochondrial dysfunction-induced TGF-β1 dysregulation and fibrosis are associated with the development of adenomyosis.

The Unified Theory of Neurodegeneration Pathogenesis Based on Axon Deamidation

Until now, neurodegenerative diseases like Alzheimer's and Parkinson's have been studied separately in biochemistry and therapeutic drug development, and no causal link has ever been established between them. This study has developed a Unified Theory, which establishes that the regulation of axon and dendrite-specific 4E-BP2 deamidation rates controls the occurrence and progression of neurodegenerative diseases. This is based on identifying axon-specific 4E-BP2 deamidation as a universal denominator for the biochemical processes of deamidation, translational control, oxidative stress, and neurodegeneration. This was achieved by conducting a thorough and critical review of 224 scientific publications regarding (a) deamidation, (b) translational control in protein synthesis initiation, (c) neurodegeneration and (d) oxidative stress, and by applying my discovery of the fundamental neurobiological mechanism behind neuron-specific 4E-BP2 deamidation to practical applications in medicine. Based on this newly developed Unified Theory and my critical review of the scientific literature, I also designed three biochemical flowsheets of (1) in-vivo deamidation, (2) protein synthesis initiation and translational control, and (3) 4E-BP2 deamidation as a control system of the four biochemical processes. The Unified Theory of Neurodegeneration Pathogenesis based on axon deamidation, developed in this work, paves the way to controlling the occurrence and progression of neurodegenerative diseases such as Alzheimer's and Parkinson's through a unique, neuron-specific regulatory system that is 4E-BP2 deamidation, caused by the proteasome-poor environment in neuronal projections, consisting mainly of axons.

Vital Role of PINK1/Parkin-Mediated Mitophagy of Pulmonary Epithelial Cells in Severe Pneumonia Induced by IAV and Secondary Staphylococcus aureus Infection

Influenza A virus (IAV) infection causes considerable morbidity and mortality worldwide, and the secondary bacterial infection further exacerbates the severity and fatality of the initial viral infection. Mitophagy plays an important role in host resistance to pathogen infection and immune response, while its role on pulmonary epithelial cells with viral and bacterial co-infection remains unclear. The present study reveals that the secondary Staphylococcus aureus infection significantly increased the viral and bacterial loads in human lung epithelial cells (A549) during the initial H1N1 infection. Meanwhile, the secondary S. aureus infection triggered more intense mitophagy in A549 cells by activating the PINK1/Parkin signaling pathway. Notably, mitophagy could contribute to the proliferation of pathogens in A549 cells via the inhibition of cell apoptosis. Furthermore, based on an influenza A viral and secondary bacterial infected mouse model, we showed that activation of mitophagy was conducive to the proliferation of virus and bacteria in the lungs, aggravated the inflammatory damage and severe pneumonia at the same time, and eventually decreased the survival rate. The results elucidated the effect and the related molecular mechanism of mitophagy in pulmonary epithelial cells following IAV and secondary S. aureus infection for the first time, which will provide valuable information for the pathogenesis of virus/bacteria interaction and new ideas for the treatment of severe pneumonia.

An Insight into Neuronal Processing of Ghrelin: Effects of a Bioactive Ghrelin Derivative on Proteolytic Pathways and Mitophagy

Protein homeostasis (proteostasis) is preserved by an orchestrated network of molecular mechanisms that regulate protein synthesis, folding, and degradation, ensuring cellular integrity and function. Proteostasis declines with age and is related to pathologies such as neurodegenerative diseases and cardiac disorders, which are accompanied by the accumulation of toxic protein aggregates. In this context, therapeutic strategies enhancing the two primary degradative systems involved in the cellular clearance of those abnormal proteins, namely ubiquitin-proteasome system and autophagy-lysosomal pathway, represent a promising approach to counteract the collapse of proteostasis in such pathological conditions. In this work, we explored the processing of ghrelin, a pleiotropic peptide hormone linked to energy metabolism and higher brain functions, which is reported to modulate the protein degradative mechanisms. According to our data, ghrelin is processed by serine hydrolases secreted into the conditioned medium of SH-SY5Y neuroblastoma cell line, commonly used in neurotoxicology and neuroscience research. Ghrelin processing leads to the formation of a shorter peptide (ghrelin(1-11)) that stimulates both the cell proteasome system and autophagy-lysosomal pathway, encompassing the selective autophagy of mitochondria. Our findings suggest that ghrelin processing may contribute to the maintenance of neuronal proteostasis.

Cold storage effects on mitochondrial bioenergetics and protein expression in human mesenchymal stromal cells

BACKGROUND

A ready-to-use format for cell therapy products, human mesenchymal stromal cells (MSCs) or other progenitor cells, would make their use in acute trauma feasible by the military or in rural community hospitals. In designing a strategy to package MSCs, it was noted that vitality (adenosine triphosphate [ATP] content) fell prior to viability. This study investigated the effects of cold storage on mitochondrial bioenergetics and protein in MSCs.

METHODS

Commercial MSCs were harvested and resuspended in either a balanced salt solution (PlasmaLyte A) or xeno-free medium (XFM) and then stored at 4°C. Cells were assayed on Days 0, 4, 7, 14, and 21 for cell count, viability, and ATP content, mitochondrial bioenergetics by Seahorse XF24 and Oroboros, and mitochondrial membrane potential by JC1 staining. Levels of proteins involved in mitochondrial function were assayed by Western blots. Proteins assessed included those involved in mitochondrial fusion (OPA1, MFN1, MFN2), fission (FIS1, DRP1, and DRP1 phosphoserine 637), regulation (PINK1 kinase and Parkin ubiquitin-ligase), mitophagy (NDP52 and optineurin), and electron transport chain function (COX IV, SDHB, cytochrome C, and NDUFS1).

RESULTS

Total counts for cells stored in PlasmaLyte A and XFM were similar through Day 21. However, by Day 4, while viability was modestly decreased for cells stored in PlasmaLyte A compared with those in XFM (68% vs. 83%), ATP content plummeted for cells stored in PlasmaLyte A, with only 9.5% of the initial ATP compared with 86% of the initial ATP levels for cells stored in XFM. Both the Seahorse assays and JC1 staining identified further differences between media. JC1 staining revealed that mitochondria were almost completely depolarized by Day 7 following storage in PlasmaLyte A whereas polarized mitochondria were still evident at Day 21 for cells stored in XFM. By Western blot analyses, significant changes in fusion, fission, and mitophagy proteins were observed both for media and over time whereas the electron transport proteins were generally stable. Significant changes in the phosphorylated form of the fission protein DRP1S637 most closely correlated with the ATP data. All parameters were better preserved over time in the XFM.

CONCLUSIONS

This study highlighted changes that occur during 4°C storage in the areas of vitality, mitochondrial membrane polarization, and fission. With these targets, research into treatments or additives to a media to improve cold storage and maintain functional cells at 4°C could result in a product that greatly extends the therapeutic use of cellular therapies.

Mitophagy in Neurons: Mechanisms Regulating Mitochondrial Turnover and Neuronal Homeostasis

Mitochondrial quality control is instrumental in regulating neuronal health and survival. The receptor-mediated clearance of damaged mitochondria by autophagy, known as mitophagy, plays a key role in controlling mitochondrial homeostasis. Mutations in genes that regulate mitophagy are causative for familial forms of neurological disorders including Parkinson's disease (PD) and Amyotrophic lateral sclerosis (ALS). PINK1/Parkin-dependent mitophagy is the best studied mitophagy pathway, while more recent work has brought to light additional mitochondrial quality control mechanisms that operate either in parallel to or independent of PINK1/Parkin mitophagy. Here, we discuss our current understanding of mitophagy mechanisms operating in neurons to govern mitochondrial homeostasis. We also summarize progress in our understanding of the links between mitophagic dysfunction and neurodegeneration, and highlight the potential for therapeutic interventions to maintain mitochondrial health and neuronal function.

The role and machine learning analysis of mitochondrial autophagy-related gene expression in lung adenocarcinoma

Objective

Lung adenocarcinoma (LUAD) continues to be a primary cause of cancer-related mortality globally, highlighting the urgent need for novel insights finto its molecular mechanisms. This study aims to investigate the relationship between gene expression and mitophagy in LUAD, with an emphasis on identifying key biomarkers and elucidating their roles in tumorigenesis and immune cell infiltration.

Methods

We utilized datasets GSE151101 and GSE203609 from the Gene Expression Omnibus (GEO) database to identify differentially expressed genes (DEGs) associated with lung cancer and mitophagy. DEGs were identified using GEO2R, filtered based on criteria of P < 0.05 and log2 fold change ≥ 1. Subsequently, Weighted Gene Co-expression Network Analysis (WGCNA) was conducted to classify DEGs into modules. Functional annotation of these modules was performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Gene Set Enrichment Analysis (GSEA) was applied to the most relevant module, designated as the greenyellow module. To identify critical biomarkers, machine learning algorithms including Random Forest, Least Absolute Shrinkage and Selection Operator (LASSO) regression, and Support Vector Machine (SVM) were employed. Validation of the findings was conducted using The Cancer Genome Atlas (TCGA) database, Human Protein Atlas (HPA), quantitative PCR (qPCR), and immune cell infiltration analysis via CIBERSORTx.

Results

Our analysis identified 11,012 overlapping DEGs between the two datasets. WGCNA revealed 11 modules, with the green-yellow module exhibiting the highest correlation. Functional enrichment analysis highlighted significant associations with FOXM1 signaling pathways and retinoblastoma in cancer. Machine learning algorithms identified COASY, FTSJ1, and MOGS as pivotal genes. These findings were validated using TCGA data, qPCR experiments, which demonstrated high expression levels in LUAD samples. Immunohistochemistry from HPA confirmed consistency between protein levels and RNA-seq data. Furthermore, pan-cancer analysis indicated that these genes are highly expressed across various cancer types. Immune infiltration analysis suggested significant correlations between these genes and specific immune cell populations.

Conclusion

COASY, FTSJ1 and MOGS have emerged as critical biomarkers in LUAD, potentially influencing tumorigenesis through mitophagy-related mechanisms and immune modulation. These findings provide promising avenues for future research into targeted therapies and diagnostic tools, thereby enhancing LUAD management.

Mitochondrial quality control and stress signaling pathways in the pathophysiology of cardio-renal diseases

Mitochondria are essential organelles for cellular function and have become a broad field of study. In cardio-renal diseases, it has been established that mitochondrial dysfunction is a primary mechanism leading to these pathologies. Under stress, mitochondria can develop stress response mechanisms to maintain mitochondrial quality control (MQC) and functions. In contrast, the perturbation of these mechanisms has been associated with the pathogenesis of several diseases. Thus, targeting specific pathways within MQC could offer a therapeutic avenue for protecting mitochondrial integrity. However, the mechanisms related to MQC and mitochondrial stress signaling in the cardio-renal axis have been poorly explored. The primary limitations include the lack of reproducibility in the experimental models of cardio-renal disease, the incomplete knowledge of molecules that generate bidirectional damage, and the temporality of the study models. Therefore, we believe that integration of all of those limitations, along with recent advances in MQC mechanisms (i.e., mitophagy), stress signaling pathways (e.g., integrated stress response, mitochondrial unfolded protein response, and mitochondrial protein import), associated pharmacology, and targeted therapeutic approaches could reveal what the deregulation of these mechanisms is like and provide ideas for generating strategies that seek to avoid the progression of cardio-renal diseases.

The African swine fever virus gene MGF_360-4L inhibits interferon signaling by recruiting mitochondrial selective autophagy receptor SQSTM1 degrading MDA5 antagonizing innate immune responses

Multigene family (MGF) 360 genes, which are African swine fever virus (ASFV) virulence genes, primarily target key host immune molecules to suppress host interferon (IFN) production and interferon-stimulated gene (ISG) transcription, impairing host innate immune responses for efficient viral replication. However, the interactions between MGF 360 virulence genes and host molecules, as well as the mechanisms through which MGF 360 genes regulate host immune responses and IFN signaling, require further elucidation. In this study, we discovered that ASFV MGF_360-4L interacts with MDA5 and recruits the mitochondrial selective autophagy receptor SQSTM1 to degrade MDA5, thus impairing IFN signaling and compromising host innate immune responses. Furthermore, MGF_360-4L inhibits the interaction between MDA5 and MAVS, blocking ISG15-mediated ISGylation of MDA5. MGF_360-4L deficiency significantly attenuated virus-induced mitochondrial autophagy in vitro. Additionally, OAS1 ubiquitinates MGF_360-4L at residues K290, K295, and K327. Finally, a recombinant ASFV lacking the MGF_360-4L gene (ASFV-∆MGF_360-4L) was generated using ASFV-CN/SC/2019 as the backbone, which demonstrated that the replication kinetics of ASFV-∆MGF_360-4L in PAM cells were like those of the highly virulent parental ASFV-WT in vitro. Domestic pigs infected with ASFV-∆MGF_360-4L exhibited milder symptoms than those infected with parental ASFV-WT, and ASFV-∆MGF_360-4L-infected pigs presented with enhanced host innate antiviral immune response, confirming that the deletion of the MGF_360-4L gene from the ASFV genome highly attenuated virulence in pigs and provided effective protection against parental ASFV challenge. In conclusion, we identified a novel ASFV virulence gene, MGF_360-4L, further elucidating ASFV infection mechanisms and providing a new candidate for vaccine development.IMPORTANCEAfrican swine fever virus (ASFV) infection causes acute death in pigs, and there is currently no effective vaccine available for prevention. Multigene family (MGF) virulence genes have been shown to be crucial for ASFV's ability to evade host innate immune responses. However, the functions of most MGF genes remain unknown, which poses significant challenges for the development of ASFV vaccines and antiviral drugs. In this study, we identified a virulence gene of ASFV, MGF_360-4L, that targets and recruits the selective autophagy receptor p62 to mediate the degradation of the dsRNA sensor MDA5, thereby blocking interferon signaling. Additionally, it inhibits the ISG15-mediated ISGylation activation of MDA5. ASFV lacking MGF_360-4L showed reduced virulence and provided protection in pigs. Our data identify a novel virulence gene and provide new insights for ASFV vaccine development.

The role of autophagy in cancer: from molecular mechanism to therapeutic window

Autophagy is a cellular degradation process that plays a crucial role in maintaining metabolic homeostasis under conditions of stress or nutrient deprivation. This process involves sequestering, breaking down, and recycling intracellular components such as proteins, organelles, and cytoplasmic materials. Autophagy also serves as a mechanism for eliminating pathogens and engulfing apoptotic cells. In the absence of stress, baseline autophagy activity is essential for degrading damaged cellular components and recycling nutrients to maintain cellular vitality. The relationship between autophagy and cancer is well-established; however, the biphasic nature of autophagy, acting as either a tumor growth inhibitor or promoter, has raised concerns regarding the regulation of tumorigenesis without inadvertently activating harmful aspects of autophagy. Consequently, elucidating the mechanisms by which autophagy contributes to cancer pathogenesis and the factors determining its pro- or anti-tumor effects is vital for devising effective therapeutic strategies. Furthermore, precision medicine approaches that tailor interventions to individual patients may enhance the efficacy of autophagy-related cancer treatments. To this end, interventions aimed at modulating the fate of tumor cells by controlling or inducing autophagy substrates necessitate meticulous monitoring of these mediators' functions within the tumor microenvironment to make informed decisions regarding their activation or inactivation. This review provides an updated perspective on the roles of autophagy in cancer, and discusses the potential challenges associated with autophagy-related cancer treatment. The article also highlights currently available strategies and identifies questions that require further investigation in the future.

Targeting the NLRP3 inflammasome in Parkinson's disease: From molecular mechanism to therapeutic strategy

Parkinson's disease is the second most common neurodegenerative disease, characterized by substantial loss of dopaminergic (DA) neurons, the formation of Lewy bodies (LBs) in the substantia nigra, and pronounced neuroinflammation. The nucleotide-binding domain like leucine-rich repeat- and pyrin domain-containing protein 3 (NLRP3) inflammasome is one of the pattern recognition receptors (PRRs) that function as intracellular sensors in response to both pathogenic microbes and sterile triggers associated with Parkinson's disease. These triggers include reactive oxygen species (ROS), misfolding protein aggregation, and potassium ion (K+) efflux. Upon activation, it recruits and activates caspase-1, then processes the pro-inflammatory cytokines interleukin-1β (IL-1β) and IL-18, which mediate neuroinflammation in Parkinson's disease. In this review, we provide a comprehensive overview of NLRP3 inflammasome, detailing its structure, activation pathways, and the factors that trigger its activation. We also explore the pathological mechanisms by which NLRP3 contributes to Parkinson's disease and discuss potential strategies for targeting NLRP3 as a therapeutic approach.

Deubiquitinating Enzymes Regulate Skeletal Muscle Mitochondrial Quality Control and Insulin Sensitivity in Patients With Type 2 Diabetes

BACKGROUND

Activation of mitochondrial fission and quality control occur early in the onset of insulin resistance in human skeletal muscle. We hypothesized that differences in mitochondrial dynamics, structure and bioenergetics in humans would explain the onset and progression of type 2 diabetes (T2D).

METHODS

Fifty-eight sedentary adults (37 ± 12 years) were enrolled into one of three groups: (1) healthy weight (HW), (2) overweight and obesity (Ow/Ob), or (3) T2D. Body composition, aerobic capacity, and insulin sensitivity were assessed during a 3-day inpatient stay. A fasted skeletal muscle biopsy was obtained to assess mitochondrial functions. C2C12 myoblasts were transfected with FLAG-HA-USP15 and FLAG-HA-USP30 and harvested to assess mitochondrial dynamics and cellular insulin action.

RESULTS

Insulin sensitivity and aerobic capacity were lower in Ow/Ob (132% and 28%, respectively) and T2D (1024% and 83%, respectively) relative to HW. Patients with T2D presented with elevated skeletal muscle mitochondrial fission (3.2 fold relative to HW and Ow/Ob), decreased fusion, and impairments in quality control. Mitochondrial content was lower in Ow/Ob (26%) and T2D (56%). USP13 (84%), USP15 (96%) and USP30 (53%) expression were increased with decreased Parkin and Ub activation in T2D alone. USP15 (R2 = 0.55, p < 0.0001) and USP30 (R2 = 0.40, p < 0.0001) expression negatively correlated with peripheral insulin sensitivity. USP15 and USP30 overexpression activated DRP1 (3.6 and 3.7 fold, respectively) while inhibiting AKT (96% and 81%, respectively) and AS160 (2.1 and 3.5 fold, respectively) phosphorylation.

CONCLUSION

Mitochondrial fragmentation bypasses defects in mitophagy to sustain skeletal muscle quality control in patients with T2D.

Region-specific mitophagy in nucleus pulposus, annulus fibrosus, and cartilage endplate of intervertebral disc degeneration: mechanisms and therapeutic strategies

Intervertebral disc degeneration (IVDD) is a prevalent condition contributing to various spinal disorders, posing a significant global health burden. Mitophagy plays a crucial role in maintaining mitochondrial quantity and quality and is closely associated with the onset and progression of IVDD. Well-documented region-specific mitophagy mechanisms in IVDD are guiding the development of therapeutic strategies. In the nucleus pulposus (NP), impaired mitochondria lead to apoptosis, oxidative stress, senescence, extracellular matrix degradation and synthesis, excessive autophagy, inflammation, mitochondrial instability, and pyroptosis, with key regulatory targets including AMPK, PGC-1α, SIRT1, SIRT3, Progerin, p65, Mfn2, FOXO3, NDUFA4L2, SLC39A7, ITGα5/β1, Nrf2, and NLRP3 inflammasome. In the annulus fibrosus (AF), mitochondrial damage induces apoptosis and oxidative stress mediated by PGC-1α, while in the cartilage endplate (CEP), mitochondrial dysfunction similarly triggers apoptosis and oxidative stress. These mechanistic insights highlight therapeutic strategies such as activating Parkin-dependent and Ub-independent mitophagy pathways for NP, enhancing Parkin-dependent mitophagy for AF, and targeting Parkin-mediated mitophagy for CEP. These strategies include the use of natural ingredients, hormonal modulation, gene editing technologies, targeted compounds, and manipulation of related proteins. This review summarizes the mechanisms of mitophagy in different regions of the intervertebral disc and highlights therapeutic approaches using mitophagy modulators to ameliorate IVDD. It discusses the complex mechanisms of mitophagy and underscores its potential as a therapeutic target. The objective is to provide valuable insights and a scientific basis for the development of mitochondrial-targeted drugs for anti-IVDD.

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.

Novel Parkin agonists from Poria cocos against dyslipidemia

Parkin, a cytosolic E3 ubiquitin ligase, plays a crucial role in targeting damaged mitochondria. The dysfunction of Parkin has been implicated in various diseases, including dyslipidemia, highlighting the significance of regulating Parkin activity for therapeutic interventions. Poria cocos (PC), a traditional Chinese medicine with a history spanning over two thousand years, has shown promising effects in regulating dyslipidemia. However, the scarcity of Parkin ligands, particularly from PC, remains a significant drawback in the field. This study identified two novel Parkin ligands from PC using a Parkin-based centrifugal ultrafiltration/liquid chromatography/mass spectrometry method. Molecular docking analysis, molecular dynamic simulations, and autoubiquitination assays confirmed their abilities to activate Parkin. Furthermore, their mitophagy promotion and dyslipidemia mitigation capacities were validated in fat emulsion-induced human liver L02 cells and high-fat diet-induced mice. The results revealed that the two ligands, tumulosic acid and polyporenic acid C, from PC activated Parkin and further promoted mitophagy to alleviate dyslipidemia. These findings will contribute to developing new drugs and enhance our understanding of the PC anti-dyslipidemia mechanisms.

Heavy metal-induced disruption of the autophagy-lysosomal pathway: implications for aging and neurodegenerative disorders

Heavy metals such as lead, mercury, cadmium, magnesium, manganese, arsenic, copper pose considerable threats to neuronal health and are increasingly recognized as factors contributing to aging-related neurodegeneration. Exposure to these environmental toxins disrupts cellular homeostasis, resulting in oxidative stress and compromising critical cellular processes, particularly the autophagy-lysosomal pathway. This pathway is vital for preserving cellular integrity by breaking down damaged proteins and organelles; however, toxicity from heavy metals can hinder this function, leading to the buildup of harmful substances, inflammation, and increased neuronal injury. As individuals age, the consequences of neurodegeneration become more significant, raising the likelihood of developing disorders like Alzheimer's and Parkinson's disease. This review explores the intricate relationship between heavy metal exposure, dysfunction of the autophagy-lysosomal pathway, and aging-related neurodegeneration, emphasizing the urgent need for a comprehensive understanding of these mechanisms. The insights gained from this analysis are crucial for creating targeted therapeutic approaches aimed at alleviating the harmful effects of heavy metals on neuronal health and improving cellular resilience in aging populations.

In situ cryo-ET visualization of mitochondrial depolarization and mitophagic engulfment

Defective mitochondrial quality control in response to loss of mitochondrial membrane polarization is implicated in Parkinson's disease by mutations in PINK1 and PRKN. Application of in situ cryo-electron tomography (cryo-ET) made it possible to visualize the consequences of mitochondrial depolarization at higher resolution than heretofore attainable. Parkin-expressing U2OS cells were treated with the depolarizing agents oligomycin and antimycin A (OA), subjected to cryo-FIB milling, and mitochondrial structure was characterized by in situ cryo-ET. Phagophores were visualized in association with mitochondrial fragments. Bridge-like lipid transporter (BLTP) densities potentially corresponding to ATG2A were seen connected to mitophagic phagophores. Mitochondria in OA-treated cells were fragmented and devoid of matrix calcium phosphate crystals. The intermembrane gap of cristae was narrowed and the intermembrane volume reduced, and some fragments were devoid of cristae. A subpopulation of ATP synthases re-localized from cristae to the inner boundary membrane (IBM) apposed to the outer membrane (OMM). The structure of the dome-shaped prohibitin complex, a dodecamer of PHB1-PHB2 dimers, was determined in situ by sub-tomogram averaging in untreated and treated cells and found to exist in open and closed conformations, with the closed conformation is enriched by OA treatment. These findings provide a set of native snapshots of the manifold nano-structural consequences of mitochondrial depolarization and provide a baseline for future in situ dissection of Parkin-dependent mitophagy.

Mitochondrial quality control in cardiomyocytes: safeguarding the heart against disease and ageing

Mitochondria are multifunctional organelles that are important for many different cellular processes, including energy production and biosynthesis of fatty acids, haem and iron-sulfur clusters. Mitochondrial dysfunction leads to a disruption in these processes, the generation of excessive reactive oxygen species, and the activation of inflammatory and cell death pathways. The consequences of mitochondrial dysfunction are particularly harmful in energy-demanding organs such as the heart. Loss of terminally differentiated cardiomyocytes leads to cardiac remodelling and a reduced ability to sustain contraction. Therefore, cardiomyocytes rely on multilayered mitochondrial quality control mechanisms to maintain a healthy population of mitochondria. Mitochondrial chaperones protect against protein misfolding and aggregation, and resident proteases eliminate damaged proteins through proteolysis. Irreparably damaged mitochondria can also be degraded through mitochondrial autophagy (mitophagy) or ejected from cells inside vesicles. The accumulation of dysfunctional mitochondria in cardiomyocytes is a hallmark of ageing and cardiovascular disease. This accumulation is driven by impaired mitochondrial quality control mechanisms and contributes to the development of heart failure. Therefore, there is a strong interest in developing therapies that directly target mitochondrial quality control in cardiomyocytes. In this Review, we discuss the current knowledge of the mechanisms involved in regulating mitochondrial quality in cardiomyocytes, how these pathways are altered with age and in disease, and the therapeutic potential of targeting mitochondrial quality control pathways in cardiovascular disease.

Deciphering significances of autophagy in the development and metabolism of adipose tissue

The mechanisms of adipose tissue activation and inactivation have been a hot topic of research in the last decade, from which countermeasures have been attempted to be found against obesity as well as other lipid metabolism-related diseases, such as type 2 diabetes mellitus and non-alcoholic fatty liver disease. Autophagy has been shown to be closely related to the regulation of adipocyte activity, which is involved in the whole process including white adipocyte differentiation/maturation and brown or beige adipocyte generation/activation. Dysregulation of autophagy in adipose tissue has been demonstrated to be associated with obesity. On this basis, we summarize the pathways and mechanisms of autophagy involved in the regulation of lipid metabolism and present a review of its pathophysiological roles in lipid metabolism-related diseases, in the hope of providing ideas for the treatment of these diseases.

HTLV-1 Tax induces PINK1-Parkin-dependent mitophagy to mitigate activation of the cGAS-STING pathway

Human T-cell leukemia virus type 1 (HTLV-1) is the causative agent of adult T-cell leukemia/lymphoma (ATLL) and the neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The HTLV-1 Tax regulatory protein plays a critical role in HTLV-1 persistence and pathogenesis; however, the underlying mechanisms are poorly understood. Here we show that Tax dynamically regulates mitochondrial reactive oxygen species (ROS) and membrane potential to trigger mitochondrial dysfunction. Tax is recruited to damaged mitochondria through its interaction with the IKK regulatory subunit NEMO and directly engages the ubiquitin-dependent PINK1-Parkin pathway to induce mitophagy. Tax also recruits autophagy receptors NDP52 and p62/SQSTM1 to damaged mitochondria to induce mitophagy. Furthermore, Tax requires Parkin to limit the extent of cGAS-STING activation and suppress type I interferon (IFN). HTLV-1-transformed T cell lines and PBMCs from HAM/TSP patients exhibit hallmarks of chronic mitophagy which may contribute to immune evasion and pathogenesis. Collectively, our findings suggest that Tax manipulation of the PINK1-Parkin mitophagy pathway represents a new HTLV-1 immune evasion strategy.

A positive feedback loop between SMAD3 and PINK1 in regulation of mitophagy

PTEN-induced kinase-1 (PINK1) is a crucial player in selective clearance of damaged mitochondria via the autophagy-lysosome pathway, a process termed mitophagy. Previous studies on PINK1 mainly focused on its post-translational modifications, while the transcriptional regulation of PINK1 is much less understood. Herein, we reported a novel mechanism in control of PINK1 transcription by SMAD Family Member 3 (SMAD3), an essential component of the transforming growth factor beta (TGFβ)-SMAD signaling pathway. First, we observed that mitochondrial depolarization promotes PINK1 transcription, and SMAD3 is likely to be the nuclear transcription factor mediating PINK1 transcription. Intriguingly, SMAD3 positively transactivates PINK1 transcription independent of the canonical TGFβ signaling components, such as TGFβ-R1, SMAD2 or SMAD4. Second, we found that mitochondrial depolarization activates SMAD3 via PINK1-mediated phosphorylation of SMAD3 at serine 423/425. Therefore, PINK1 and SMAD3 constitute a positive feedforward loop in control of mitophagy. Finally, activation of PINK1 transcription by SMAD3 provides an important pro-survival signal, as depletion of SMAD3 sensitizes cells to cell death caused by mitochondrial stress. In summary, our findings identify a non-canonical function of SMAD3 as a nuclear transcriptional factor in regulation of PINK1 transcription and mitophagy and a positive feedback loop via PINK1-mediated SMAD3 phosphorylation and activation. Understanding this novel regulatory mechanism provides a deeper insight into the pathological function of PINK1 in the pathogenesis of neurodegenerative diseases such as Parkinson's disease.

Nicotinamide mononucleotide combined with PJ-34 protects microglial cells from lipopolysaccharide-induced mitochondrial impairment through NMNAT3-PARP1 axis

Lipopolysaccharide (LPS) is known to induce cell injury and mitochondrial dysfunction, which are pivotal in neuroinflammation and related disorders. Recent studies have demonstrated the potential of nicotinamide mononucleotide (NMN) and poly(ADP-ribose) polymerase-1 (PARP1) inhibitors to enhance mitochondrial function. However, the underlying mechanisms have not been fully elucidated. This study investigates the impact of NMN in conjunction with PJ-34, a PARP1 inhibitor, on LPS-induced mitochondrial damage, focusing on nicotinamide mononucleotide adenylyl transferase 3 (NMNAT3) -PARP1 axis. The results showed that LPS treatment led to down-regulation of NMNAT3 (decreased 58.72% at 1 µM), up-regulation of PARP1 (enhanced 22.78% at 1 µM), thereby impairing mitophagy and mitochondrial function. The negative effects can be mitigated through supplementation with NMN and PJ-34. Specifically, compared to the LPS group, the expression of NMNAT3 increased by 63.29% and PARP1 decreased by 27.94% at a concentration of 400 µM NMN. Additionally, when 400 µM NMN was combined with 5 µM PJ-34, PARP1 expression decreased by 21.99%. Mechanistic studies reveal that NMN and PJ-34 counteracted the detrimental effects by promoting the binding of FoxO1 to the PINK1 promoter to activate the PINK1/Parkin mediated mitophagy pathway. Further experimental results demonstrate that the down-regulation of NMNAT3 can activate PARP1 and inhibit the initiation of autophagic processes. Consequently, targeting the NMNAT3-PARP1 signaling pathway holds promise for the development of novel therapeutic strategies to alleviate mitochondrial damage-related disorders.

Mitophagy in plants: Emerging regulators of mitochondrial targeting for selective autophagy

The degradation and turnover of mitochondria is fundamental to Eukaryotes and is a key homeostatic mechanism for maintaining functional mitochondrial populations. Autophagy is an important pathway by which mitochondria are degraded, involving their sequestration into membrane-bound autophagosomes and targeting to lytic endosomal compartments (the lysosome in animals, the vacuole in plants and yeast). Selective targeting of mitochondria for autophagy, also known as mitophagy, distinguishes mitochondria from other cell components for degradation and is necessary for the regulation of mitochondria-specific cell processes. In mammals and yeast, mitophagy has been well characterised and is regulated by numerous pathways with diverse and important functions in the regulation of cell homeostasis, metabolism and responses to specific stresses. In contrast, we are only just beginning to understand the importance and functions of mitophagy in plants, chiefly as the proteins that target mitochondria for autophagy in plants are only recently emerging. Here, we discuss the current progress of our understanding of mitophagy in plants, the importance of mitophagy for plant life and the regulatory autophagy proteins involved in mitochondrial degradation. In particular, we will discuss the recent emergence of mitophagy receptor proteins that selectively target mitochondria for autophagy, and discuss the missing links in our knowledge of mitophagy-regulatory proteins in plants compared to animals and yeast.

Aging, cellular senescence and Parkinson's disease

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, affecting 1-2% of people over age 65. The risk of developing PD dramatically increases with advanced age, indicating that aging is likely a driving factor in PD neuropathogenesis. Several age-associated biological changes are also hallmarks of PD neuropathology, including mitochondrial dysfunction, oxidative stress, and neuroinflammation. Accumulation of senescent cells is an important feature of aging that contributes to age-related diseases. How age-related cellular senescence affects brain health and whether this phenomenon contributes to neuropathogenesis in PD is not yet fully understood. In this review, we highlight hallmarks of aging, including mitochondrial dysfunction, loss of proteostasis, genomic instability and telomere attrition in relation to well established PD neuropathological pathways. We then discuss the hallmarks of cellular senescence in the context of neuroscience and review studies that directly examine cellular senescence in PD. Studying senescence in PD presents challenges and holds promise for advancing our understanding of disease mechanisms, which could contribute to the development of effective disease-modifying therapeutics. Targeting senescent cells or modulating the senescence-associated secretory phenotype (SASP) in PD requires a comprehensive understanding of the complex relationship between PD pathogenesis and cellular senescence.

Phytochemicals Targeting Mitophagy to Treat Heart Diseases: Retrospective Insights and Prospective Directions

Mitophagy is a process by which cells selectively eliminate damaged or dysfunctional mitochondria through the autophagy-lysosome pathway, thereby maintaining mitochondrial quality and cellular homeostasis. This process is closely linked to the onset and progression of various heart diseases. Modern pharmacological research has demonstrated that phytochemicals can regulate mitochondrial homeostasis in cardiomyocytes through multiple mechanisms, influencing mitophagy and protecting cardiomyocytes, which in turn exerts anti-cardiovascular effects. However, the underlying mechanisms of these effects are not yet fully understood. This study summarizes the pharmacological effects and molecular mechanisms of mitophagy in heart diseases, aiming to provide reference for the research and treatment of phytochemicals targeting mitophagy against heart diseases. The results indicated that phytochemicals (such as Berberine, Ginsenoside Rg1, Quercetin, Resveratrol, Baicalein, and so on) can exert preventive and therapeutic effects on heart diseases (such as cardiac toxicity or damage, myocardial ischemia/reperfusion injury, heart failure, heart aging, cardiac hypertrophy, cardiomyopathy, and so on.) via regulating the PINK1/Parkin and FUNDC1-dependent mitophagy pathway. These compounds mainly exert their effects by regulating mitochondrial homeostasis, mitochondrial dynamics, mitochondrial oxidative stress, mitochondrial apoptosis, and mitochondrial energy metabolism. This study provides a reference that phytochemicals have effect on anti-cardiovascular effects by regulating mitophagy. However, further in-depth mechanistic and clinical research are needed in the future.

Mitochondrial fission and fusion in neurodegenerative diseases:Ca2+ signalling

Neurodegenerative diseases (NDs) are a group of disorders characterized by the progressive loss of neuronal structure and function. The pathogenesis is intricate and involves a network of interactions among multiple causes and systems. Mitochondria and Ca2+ signaling have long been considered to play important roles in the development of various NDs. Mitochondrial fission and fusion dynamics are important processes of mitochondrial quality control, ensuring the stability of mitochondrial structure and function. Mitochondrial fission and fusion imbalance and Ca2+ signaling disorders can aggravate the disease progression of NDs. In this review, we explore the relationship between mitochondrial dynamics and Ca2+ signaling in AD, PD, ALS, and HD, focusing on the roles of key regulatory proteins (Drp1, Fis1, Mfn1/2, and Opa1) and the association structures between mitochondria and the endoplasmic reticulum (MERCs/MAMs). We provide a detailed analysis of their involvement in the pathogenesis of these four NDs. By integrating these mechanisms, we aim to clarify their contributions to disease progression and offer insights into the development of therapeutic strategies that target mitochondrial dynamics and Ca2+ signaling. We also examine the progress in drug research targeting these pathways, highlighting their potential as therapeutic targets in the treatment of NDs.

A long-lived pool of PINK1 imparts a molecular memory of depolarization-induced activity

The Parkinson's disease-linked kinase, PINK1, is a short-lived protein that undergoes cleavage upon mitochondrial import leading to its proteasomal degradation. Under depolarizing conditions, it accumulates on mitochondria where it becomes activated, phosphorylating both ubiquitin and the ubiquitin E3 ligase Parkin, at Ser65. Our experiments reveal that in retinal pigment epithelial cells, only a fraction of PINK1 becomes stabilized after depolarization by electron transport chain inhibitors. Furthermore, the observed accrual of PINK1 cannot be completely accounted for without an accompanying increase in biosynthesis. We have used a ubiquitylation inhibitor TAK-243 to accumulate cleaved PINK1. Under these conditions, generation of unconjugated "free" phospho-ubiquitin serves as a proxy readout for PINK1 activity. This has enabled us to find a preconditioning phenomenon, whereby an initial depolarizing treatment leaves a residual pool of active PINK1 that remains competent to seed the activation of nascent cleaved PINK1 following a 16-hour recovery period.

Roles of Oxidative Stress and Autophagy in Alcohol-Mediated Brain Damage

Excessive alcohol consumption significantly impacts human health, particularly the brain, due to its susceptibility to oxidative stress, which contributes to neurodegenerative conditions. Alcohol metabolism in the brain occurs primarily via catalase, followed by CYP2E1 pathways. Excess alcohol metabolized by CYP2E1 generates reactive oxygen/nitrogen species (ROS/RNS), leading to cell injury via altering many different pathways. Elevated oxidative stress impairs autophagic processes, increasing post-translational modifications and further exacerbating mitochondrial dysfunction and ER stress, leading to cell death. The literature highlights that alcohol-induced oxidative stress disrupts autophagy and mitophagy, contributing to neuronal damage. Key mechanisms include mitochondrial dysfunction, ER stress, epigenetics, and the accumulation of oxidatively modified proteins, which lead to neuroinflammation and impaired cellular quality control. These processes are exacerbated by chronic alcohol exposure, resulting in the suppression of protective pathways like NRF2-mediated antioxidant responses and increased susceptibility to neurodegenerative changes in the brain. Alcohol-mediated neurotoxicity involves complex interactions between alcohol metabolism, oxidative stress, and autophagy regulation, which are influenced by various factors such as drinking patterns, nutritional status, and genetic/environmental factors, highlighting the need for further molecular studies to unravel these mechanisms and develop targeted interventions.

Dysregulation of mitochondrial α-ketoglutarate dehydrogenase leads to elevated lipid peroxidation in CHCHD2-linked Parkinson's disease models

Dysregulation of mitochondrial function has been implicated in Parkinson's disease (PD), but the role of mitochondrial metabolism in disease pathogenesis remains to be elucidated. Using an unbiased metabolomic analysis of purified mitochondria, we identified alterations in α-ketoglutarate dehydrogenase (KGDH) pathway upon loss of PD-linked CHCHD2 protein. KGDH, a rate-limiting enzyme complex in the tricarboxylic acid cycle, was decreased in CHCHD2-deficient male mouse brains and human dopaminergic neurons. This deficiency of KGDH led to elevated α-ketoglutarate and increased lipid peroxidation. Treatment of CHCHD2-deficient dopaminergic neurons with lipoic acid, a KGDH cofactor and antioxidant agent, resulted in decreased levels of lipid peroxidation and phosphorylated α-synuclein. CHCHD10, a close homolog of CHCHD2 that is primarily linked to amyotrophic lateral sclerosis/frontotemporal dementia, did not affect the KGDH pathway or lipid peroxidation. Together, these results identify KGDH metabolic pathway as a targetable mitochondrial mechanism for correction of increased lipid peroxidation and α-synuclein in Parkinson's disease.

Novel reporter of the PINK1-Parkin mitophagy pathway identifies its damage sensor in the import gate

Damaged mitochondria can be cleared from the cell by mitophagy, using a pathway formed by the recessive Parkinson's disease genes PINK1 and Parkin. How mitochondrial damage is sensed by the PINK1-Parkin pathway, however, remains uncertain. Here, using a Parkin substrate-based reporter in genome-wide screens, we identified that diverse forms of mitochondrial damage converge on loss of mitochondrial membrane potential (MMP) to activate PINK1. Consistently, the MMP but not the presequence translocase-associated motor (PAM) import motor provided the essential driving force for endogenous PINK1 import through the inner membrane translocase TIM23. In the absence of TIM23, PINK1 arrested in the translocase of the outer membrane (TOM) during import. The energy-state outside of the mitochondria further modulated the pathway by controlling the rate of new PINK1 synthesis. Our results identify separation of PINK1 from TOM by the MMP, as the key damage-sensing switch in the PINK1-Parkin mitophagy pathway.

Highlights

MFN2-Halo is a quantitative single-cell reporter of PINK1-Parkin activation.Diverse forms of mitochondrial damage, identified in whole-genome screens, activate the PINK1-Parkin pathway by disrupting the mitochondrial membrane potential (MMP).The primary driving force for endogenous PINK1 import through the TIM23 translocase is the MMP with the PAM import motor playing a supporting role.Loss of TIM23 is sufficient to stabilize PINK1 in the TOM complex and activate Parkin.

Mitochondrial alterations and signatures in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer worldwide. Its primary risk factors are chronic liver diseases such as metabolic fatty liver disease, non-alcoholic steatohepatitis, and hepatitis B and C viral infections. These conditions contribute to a specific microenvironment in liver tumors which affects mitochondrial function. Mitochondria are energy producers in cells and are responsible for maintaining normal functions by controlling mitochondrial redox homeostasis, metabolism, bioenergetics, and cell death pathways. HCC involves abnormal mitochondrial functions, such as accumulation of reactive oxygen species, oxidative stress, hypoxia, impairment of the mitochondrial unfolded protein response, irregularities in mitochondrial dynamic fusion/fission mechanisms, and mitophagy. Cell death mechanisms, such as necroptosis, pyroptosis, ferroptosis, and cuproptosis, contribute to hepatocarcinogenesis and play a significant role in chemoresistance. The relationship between mitochondrial dynamics and HCC is thus noteworthy. In this review, we summarize the recent advances in mitochondrial alterations and signatures in HCC and attempt to elucidate its molecular biology. Here, we provide an overview of the mitochondrial processes involved in hepatocarcinogenesis and offer new insights into the molecular pathology of the disease. This may help guide future research focused on improving patient outcomes using innovative therapies.

Insights on the crosstalk among different cell death mechanisms

The phenomenon of cell death has garnered significant scientific attention in recent years, emerging as a pivotal area of research. Recently, novel modalities of cellular death and the intricate interplay between them have been unveiled, offering insights into the pathogenesis of various diseases. This comprehensive review delves into the intricate molecular mechanisms, inducers, and inhibitors of the underlying prevalent forms of cell death, including apoptosis, autophagy, ferroptosis, necroptosis, mitophagy, and pyroptosis. Moreover, it elucidates the crosstalk and interconnection among the key pathways or molecular entities associated with these pathways, thereby paving the way for the identification of novel therapeutic targets, disease management strategies, and drug repurposing.

Compensatory synaptotagmin-11 expression conceals parkinson's disease-like phenotypes in parkin knockout mice

Animal models are crucial for elucidating the pathological mechanisms underlying Parkinson's disease (PD). Unfortunately, most of transgenic mouse models fail to manifest pathological changes observed in PD patients, pending the advancement of PD research. However, the mechanism underlying this discrepancy remains elusive. Here, we provide compelling evidence that the compensatory expression of synaptotagmin-11 (Syt11) plays a key role in concealing PD-associated phenotypes in parkin knockout (KO) mouse models. Unlike the normal dopamine (DA) release and motor behaviors observed in parkin KO mice, parkin knockdown (KD) in the substantia nigra pars compacta (SNpc) in adult mice led to both the impaired DA release and the pronounced motor deficits. Interestingly, Syt11, a well-established parkin substrate involved in PD, was specifically upregulated in parkin KD mice and in parkin KO mice during the suckling stage, but not in adult parkin KO mice. Importantly, the overexpression of Syt11 alone is capable of inducing PD-like motor and non-motor impairments, as well as the impaired DA release and reuptake, which is essential for parkin-associated pathogenesis of PD. Therefore, this work not only elucidate a compensatory mechanism that accounts for the absence of overt PD phenotypes in parkin KO mice, but also contribute to the comprehensive understanding of the progression of PD, opening new avenues for the therapeutic treatment of PD.

Calcium-mediated regulation of mitophagy: implications in neurodegenerative diseases

Calcium signaling plays a pivotal role in diverse cellular processes through precise spatiotemporal regulation and interaction with effector proteins across distinct subcellular compartments. Mitochondria, in particular, act as central hubs for calcium buffering, orchestrating energy production, redox balance and apoptotic signaling, among others. While controlled mitochondrial calcium uptake supports ATP synthesis and metabolic regulation, excessive accumulation can trigger oxidative stress, mitochondrial membrane permeabilization, and cell death. Emerging findings underscore the intricate interplay between calcium homeostasis and mitophagy, a selective type of autophagy for mitochondria elimination. Although the literature is still emerging, this review delves into the bidirectional relationship between calcium signaling and mitophagy pathways, providing compelling mechanistic insights. Furthermore, we discuss how disruptions in calcium homeostasis impair mitophagy, contributing to mitochondrial dysfunction and the pathogenesis of common neurodegenerative diseases.

Electroacupuncture alleviates damage to myopic RGCs probably through lncRNA-XR_002789763.1-mediated mitophagy

BACKGROUND

Mitophagy is closely related to the regulation of retinal ganglion cell (RGC) structure and function. Our previous study suggested that long noncoding RNAs (lncRNAs) can cause damage to myopic RGCs. However, whether electroacupuncture (EA) treatment can delay myopia progression through lncRNA-mediated mitophagy in RGCs is currently unknown. This study aimed to investigate the effect of EA on lncRNA-mediated mitophagy in myopic RGCs.

METHODS

Our study investigated the modulatory effect of EA on mitophagy in RGCs of guinea pigs with form-deprived myopia (FDM). RNA sequencing was performed to further analyze the expression profiles of lncRNAs and mRNAs in RGCs of guinea pigs with FDM after EA treatment, and the related competing endogenous RNA (ceRNA) network was constructed. Importantly, PINK1, a mitophagy-related gene, was included in the core ceRNA network to explore the relationship between lncRNAs and mitophagy in myopic RGCs regulated by EA. We also collected eyeballs from myopic and highly myopic adults to further verify the mechanistic results.

RESULTS

This study demonstrated that EA treatment delayed the reduction in refraction and increase in axial length and alleviated RGC damage in guinea pigs with FDM. We further found that EA could induce mitophagy in guinea pig RGCs with FDM by promoting the mitophagy-related PINK1/Parkin signaling pathway. Moreover, mitophagy is inhibited in the retina of highly myopic adults. RNA sequencing revealed that 599 lncRNAs and 455 mRNAs were differentially expressed in guinea pig RGCs with FDM after EA treatment. A core ceRNA network was constructed by incorporating PINK1 and verified by related molecular experiments, and we found that EA treatment may induce mitophagy and attenuated RGC injury in guinea pigs with FDM by sponging miR-342-5p through lncRNA-XR_002789763.1 to activate the PINK1/Parkin signaling pathway and promote Mfn2 ubiquitination.

CONCLUSION

EA treatment might regulate lncRNA-XR_002789763.1/miR-342-5p axis and activate the mitophagy-related PINK1/Parkin signaling pathway, and promote Mfn2 ubiquitination, thereby alleviating RGC damage and delaying myopia progression.

Functional transformation of macrophage mitochondria in cardiovascular diseases

Mitochondria are pivotal in the modulation of macrophage activation, differentiation, and survival. Furthermore, macrophages are instrumental in the onset and progression of cardiovascular diseases. Hence, it is imperative to investigate the role of mitochondria within macrophages in the context of cardiovascular disease. In this review, we provide an updated description of the origin and classification of cardiac macrophages and also focused on the relationship between macrophages and mitochondria in cardiovascular diseases with respect to (1) proinflammatory or anti-inflammatory macrophages, (2) macrophage apoptosis, (3) macrophage pyroptosis, and (4) macrophage efferocytosis. Clarifying the relationship between mitochondria and macrophages can aid the exploration of novel therapeutic strategies for cardiovascular disease.