PINK1/Parkin Influences Cell Cycle by Sequestering TBK1 at Damaged Mitochondria, Inhibiting Mitosis

Mitophagy at the crossroads of cancer development: Exploring the role of mitophagy in tumor progression and therapy resistance

Preserving a functional mitochondrial network is crucial for cellular well-being, considering the pivotal role of mitochondria in ensuring cellular survival, especially under stressful conditions. Mitophagy, the selective removal of damaged mitochondria through autophagy, plays a pivotal role in preserving cellular homeostasis by preventing the production of harmful reactive oxygen species from dysfunctional mitochondria. While the involvement of mitophagy in neurodegenerative diseases has been thoroughly investigated, it is becoming increasingly evident that mitophagy plays a significant role in cancer biology. Perturbations in mitophagy pathways lead to suboptimal mitochondrial quality control, catalyzing various aspects of carcinogenesis, including establishing metabolic plasticity, stemness, metabolic reconfiguration of cancer-associated fibroblasts, and immunomodulation. While mitophagy performs a delicate balancing act at the intersection of cell survival and cell death, mounting evidence indicates that, particularly in the context of stress responses induced by cancer therapy, it predominantly promotes cell survival. Here, we showcase an overview of the current understanding of the role of mitophagy in cancer biology and its potential as a target for cancer therapy. Gaining a more comprehensive insight into the interaction between cancer therapy and mitophagy has the potential to reveal novel targets and pathways, paving the way for enhanced treatment strategies for therapy-resistant tumors in the near future.

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.

Interplay between α-synuclein and parkin genes: Insights of Parkinson's disease

Parkinson's disease (PD) is a complex and debilitating neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra. The pathogenesis of PD is intimately linked to the roles of two key molecular players, α-synuclein (α-syn) and Parkin. Understanding the intricate interplay between α-syn and Parkin is essential for unravelling the molecular underpinnings of PD. Their roles in synaptic function and protein quality control underscore their significance in neuronal health. Dysregulation of these processes, as seen in PD, highlights the potential for targeted therapeutic strategies aimed at restoring normal protein homeostasis and mitigating neurodegeneration. Investigating the connections between α-syn, Parkin, and various pathological mechanisms provides insights into the complex web of factors contributing to PD pathogenesis and offers hope for the development of more effective treatments for this devastating neurological disorder. The present compilation provides an overview of their structures, regional and cellular locations, associations, physiological functions, and pathological roles in the context of PD.

Therapeutic role of PTEN in tissue regeneration for management of neurological disorders: stem cell behaviors to an in-depth review

Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) represents the initial tumor suppressor gene identified to possess phosphatase activity, governing various cellular processes including cell cycle regulation, migration, metabolic pathways, autophagy, oxidative stress response, and cellular senescence. Current evidence suggests that PTEN is critical for stem cell maintenance, self-renewal, migration, lineage commitment, and differentiation. Based on the latest available evidence, we provide a comprehensive overview of the mechanisms by which PTEN regulates activities of different stem cell populations and influences neurological disorders, encompassing autism, stroke, spinal cord injury, traumatic brain injury, Alzheimer's disease and Parkinson's disease. This review aims to elucidate the therapeutic impacts and mechanisms of PTEN in relation to neurogenesis or the stem cell niche across a range of neurological disorders, offering a foundation for innovative therapeutic approaches aimed at tissue repair and regeneration in neurological disorders. This review unravels novel therapeutic strategies for tissue restoration and regeneration in neurological disorders based on the regulatory mechanisms of PTEN on neurogenesis and the stem cell niche.

NAK-associated protein 1/NAP1 activates TBK1 to ensure accurate mitosis and cytokinesis

Subcellular location and activation of Tank Binding Kinase 1 (TBK1) govern precise progression through mitosis. Either loss of activated TBK1 or its sequestration from the centrosomes causes errors in mitosis and growth defects. Yet, what regulates its recruitment and activation on the centrosomes is unknown. We identified that NAK-associated protein 1 (NAP1) is essential for mitosis, binding to and activating TBK1, which both localize to centrosomes. Loss of NAP1 causes several mitotic and cytokinetic defects due to inactivation of TBK1. Our quantitative phosphoproteomics identified numerous TBK1 substrates that are not only confined to the centrosomes but are also associated with microtubules. Substrate motifs analysis indicates that TBK1 acts upstream of other essential cell cycle kinases like Aurora and PAK kinases. We also identified NAP1 as a TBK1 substrate phosphorylating NAP1 at S318 to promote its degradation by the ubiquitin proteasomal system. These data uncover an important distinct function for the NAP1-TBK1 complex during cell division.

Comprehensive analysis of mitophagy-related genes in NSCLC diagnosis and immune scenery: based on bulk and single-cell RNA sequencing data

Lung cancer is the main cause of cancer-related deaths, and non-small cell lung cancer (NSCLC) is the most common type. Understanding the potential mechanisms, prognosis, and treatment aspects of NSCLC is essential. This study systematically analyzed the correlation between mitophagy and NSCLC. Six mitophagy-related feature genes (SRC, UBB, PINK1, FUNDC1, MAP1LC3B, and CSNK2A1) were selected through machine learning and used to construct a diagnostic model for NSCLC. These feature genes are closely associated with the occurrence and development of NSCLC. Additionally, NSCLC was divided into two subtypes using unsupervised consensus clustering, and their differences in clinical characteristics, immune infiltration, and immunotherapy were systematically analyzed. Furthermore, the interaction between mitophagy-related genes (MRGs) and immune cells was analyzed using single-cell sequencing data. The findings of this study will contribute to the development of potential diagnostic biomarkers for NSCLC and the advancement of personalized treatment strategies.

The mystery of phospho-Drp1 with four adaptors in cell cycle: when mitochondrial fission couples to cell fate decisions

Recent study had deepened our knowledge of the mitochondrial dynamics to classify mitochondrial fission into two types. To further clarify the relationship between the two distinct fission machinery and the four major adaptors of Drp1, we propose a model of mechanism elucidating the multiple functions of phospho-Drp1 with its adaptors during cell cycle and providing in-depth insights into the molecular basis and evolutionary implications in depth. The model highlights not only the clustering characteristics of different phospho-Drp1 with respective subsets of mitochondrial pro-fission adaptors but also the correlation, crosstalk and shifting between different clustering of phosphorylated Drp1-adaptors during different key fission situations. Particularly, phospho-Drp1 (Ser616) couples with Mff/MiD51 to exert mitochondrial division and phospho-Drp1 (Ser637) couples with MiD49/Fis1 to execute mitophagy in M-phase. We then apply the model to address the relationship of mitochondrial dynamics to Parkinson's disease (PD) and carcinogenesis. Our proposed model is indeed compatible with current research results and pathological observations, providing promising directions for future treatment design.

Loss of STING in parkin mutant flies suppresses muscle defects and mitochondria damage

The early pathogenesis and underlying molecular causes of motor neuron degeneration in Parkinson's Disease (PD) remains unresolved. In the model organism Drosophila melanogaster, loss of the early-onset PD gene parkin (the ortholog of human PRKN) results in impaired climbing ability, damage to the indirect flight muscles, and mitochondrial fragmentation with swelling. These stressed mitochondria have been proposed to activate innate immune pathways through release of damage associated molecular patterns (DAMPs). Parkin-mediated mitophagy is hypothesized to suppress mitochondrial damage and subsequent activation of the cGAS/STING innate immunity pathway, but the relevance of this interaction in the fly remains unresolved. Using a combination of genetics, immunoassays, and RNA sequencing, we investigated a potential role for STING in the onset of parkin-null phenotypes. Our findings demonstrate that loss of Drosophila STING in flies rescues the thorax muscle defects and the climbing ability of parkin-/- mutants. Loss of STING also suppresses the disrupted mitochondrial morphology in parkin-/- flight muscles, suggesting unexpected feedback of STING on mitochondria integrity or activation of a compensatory mitochondrial pathway. In the animals lacking both parkin and sting, PINK1 is activated and cell death pathways are suppressed. These findings support a unique, non-canonical role for Drosophila STING in the cellular and organismal response to mitochondria stress.

Effect of Exercise and Oral Niacinamide Mononucleotide on Improving Mitochondrial Autophagy in Alzheimer's Disease

Oral niacinamide mononucleotide (NMN) and aerobic exercise have been shown to enhance niacinamide adenine dinucleotide (NAD⁺) in the body. NAD⁺ plays a critical role in the body and can directly and indirectly affect many key cellular functions, including metabolic pathways, DNA repair, chromatin remodeling, cell aging, and immune cell function. It is noteworthy that the level of NAD⁺ decreases gradually with increasing age. Decreased levels of NAD⁺ have been causally associated with a number of diseases associated with aging, including cognitive decline, cancer, metabolic diseases, sarcopenia, and frailty. Many diseases related to aging can be slowed down or even reversed by restoring NAD⁺ levels. For example, oral NMN or exercise to increase NAD⁺ levels in APP/PS1 mice have been proven to improve mitochondrial autophagy, but currently, there is no regimen combining oral NMN with exercise. This review summarizes recent studies on the effect of oral NMN on the enhancement of NAD⁺ in vivo and the improvements in mitochondrial autophagy abnormalities in AD through aerobic exercise, focusing on (1) how oral NMN improves the internal NAD⁺ level; (2) how exercise regulates the content of NAD⁺ in the body; (3) the relationship between exercise activation of NAD⁺ and AMPK; (4) how SIRT1 is regulated by NAD⁺ and AMPK and activates PGC-1α to mediate mitochondrial autophagy through changes in mitochondrial dynamics. By summarizing the results of the above four aspects, and combined with the synthesis of NAD⁺ in vivo, we can infer how exercise elevates the level of NAD⁺ in vivo to mediate mitochondrial autophagy, so as to propose a new hypothesis that exercise interferes with Alzheimer's disease (AD).

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.

CRISPR-activation screen identified potassium channels for protection against mycotoxins through cell cycle progression and mitochondrial function

Zearalenone (ZEA) exposure has carcinogenic effects on human and animal health by exhibiting intestinal, hepatic, and renal toxicity. At present, the underlying mechanisms on how ZEA induces apoptosis and damage to tissues still remain unclear. In this study, we aimed to identify genes that modulate the cellular response to ZEA using clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 screening, and further validate novel gene functions to elucidate molecular mechanisms underlying particular biological processes in vivo and in vitro. Two ZEA-resistant cell lines, designated Ov-KCNJ4 and Ov-KCNJ12, were yielded by CRISPR activation screening which had significant changes in ZEA resistance and growth rates. Results showed that ZEA could interact with the cell membrane proteins KCNJ4 and KCNJ12, inducing cell cycle arrest, disruption of DNA replication and base excision repair. Overexpression of KCNJ4 and KCNJ12 was involved in ZEA resistance by regulating cell cycle to neutralize toxicity, sustaining mitochondrial morphology and function via attenuating the damage from oxidative stress in the KCNJ4-mitoK_ATP pathway. In vivo experiments showed that AAV-KCNJ4 delivery significantly improved ZEA-induced renal impairment and increased antioxidative enzyme activity by improving mitochondrial function. Our findings suggest that increasing potassium channel levels may be a putative therapeutic target for mycotoxin-induced damage.

Berberine Rescues D-Ribose-Induced Alzheimer's Pathology via Promoting Mitophagy

Mitochondrial dysfunction is considered an early event of Alzheimer disease (AD). D-ribose is a natural monosaccharide that exists in cells, especially in mitochondria, and can lead to cognitive dysfunction. However, the reason for this is unclear. Berberine (BBR) is an isoquinoline alkaloid that can target mitochondria and has great prospect in the treatment of AD. The methylation of PINK1 reinforces the burden of Alzheimer's pathology. This study explores the role of BBR and D-ribose in the mitophagy and cognitive function of AD related to DNA methylation. APP/PS1 mice and N2a cells were treated with D-ribose, BBR, and mitophagy inhibitor Mdivi-1 to observe their effects on mitochondrial morphology, mitophagy, neuron histology, AD pathology, animal behavior, and PINK1 methylation. The results showed that D-ribose induced mitochondrial dysfunction, mitophagy damage, and cognitive impairment. However, BBR inhibition of PINK1 promoter methylation can reverse the above effects caused by D-ribose, improve mitochondrial function, and restore mitophagy through the PINK1-Parkin pathway, thus reducing cognitive deficits and the burden of AD pathology. This experiment puts a new light on the mechanism of action of D-ribose in cognitive impairment and reveals new insights in the use of BBR for AD treatment.

Dysfunction in parkin aggravates inflammatory bone erosion by reinforcing osteoclast activity

BACKGROUND

Parkin dysfunction associated with the progression of parkinsonism contributes to a progressive systemic skeletal disease characterized by low bone mineral density. However, the role of parkin in bone remodeling has not yet been elucidated in detail.

RESULT

We observed that decreased parkin in monocytes is linked to osteoclastic bone-resorbing activity. siRNA-mediated knockdown of parkin significantly enhanced the bone-resorbing activity of osteoclasts (OCs) on dentin without any changes in osteoblast differentiation. Moreover, Parkin-deficient mice exhibited an osteoporotic phenotype with a lower bone volume accompanied by increased OC-mediated bone-resorbing capacity displaying increased acetylation of α-tubulin compared to wild-type (WT) mice. Notably, compared to WT mice, the Parkin-deficient mice displayed increased susceptibility to inflammatory arthritis, reflected by a higher arthritis score and a marked bone loss after arthritis induction using K/BxN serum transfer, but not ovariectomy-induced bone loss. Intriguingly, parkin colocalized with microtubules and parkin-depleted-osteoclast precursor cells (Parkin^-/- OCPs) displayed augmented ERK-dependent acetylation of α-tubulin due to failure of interaction with histone deacetylase 6 (HDAC6), which was promoted by IL-1β signaling. The ectopic expression of parkin in Parkin^-/- OCPs limited the increase in dentin resorption induced by IL-1β, accompanied by the reduced acetylation of α-tubulin and diminished cathepsin K activity.

CONCLUSION

These results indicate that a deficiency in the function of parkin caused by a decrease in parkin expression in OCPs under the inflammatory condition may enhance inflammatory bone erosion by altering microtubule dynamics to maintain OC activity.

Mitophagy: A promising therapeutic target for neuroprotection during ageing and age-related diseases

Mitochondria and mitochondria-mediated signalling pathways are known to control synaptic signalling, as well as long-lasting changes in neuronal structure and function. Mitochondrial impairment is linked to synaptic dysfunction in normal ageing and age-associated neurodegenerative ailments, including Parkinson's disease (PD) and Alzheimer's disease (AD). Both proteolysis and mitophagy perform a major role in neuroprotection, by maintaining a healthy mitochondrial population during ageing. Mitophagy, a highly evolutionarily conserved cellular process, helps in the clearance of damaged mitochondria and thereby maintains the mitochondrial and metabolic balance, energy supply, neuronal survival and neuronal health. Besides the maintenance of brain homeostasis, hippocampal mitophagy also helps in synapse formation, axonal development, dopamine release and long-term depression. In contrast, defective mitophagy contributes to ageing and age-related neurodegeneration by promoting the accumulation of damaged mitochondria leading to cellular dysfunction. Exercise, stress management, maintaining healthy mitochondrial dynamics and administering natural or synthetic pharmacological compounds are some of the strategies used for neuroprotection during ageing and age-related neurological diseases. The current review discusses the impact of defective mitophagy in ageing and age-associated neurodegenerative conditions, the underlying molecular pathways and potential therapies based on recently elucidated mitophagy-inducing strategies.

Time-resolved RNA signatures of CD4+ T cells in Parkinson's disease

Parkinson's disease (PD) emerges as a complex, multifactorial disease. While there is increasing evidence that dysregulated T cells play a central role in PD pathogenesis, elucidation of the pathomechanical changes in related signaling is still in its beginnings. We employed time-resolved RNA expression upon the activation of peripheral CD4+ T cells to track and functionally relate changes on cellular signaling in representative cases of patients at different stages of PD. While only few miRNAs showed time-course related expression changes in PD, we identified groups of genes with significantly altered expression for each different time window. Towards a further understanding of the functional consequences, we highlighted pathways with decreased or increased activity in PD, including the most prominent altered IL-17 pathway. Flow cytometric analyses showed not only an increased prevalence of Th17 cells but also a specific subtype of IL-17 producing γδ-T cells, indicating a previously unknown role in PD pathogenesis.

TBK1 inhibitors enhance transfection efficiency by suppressing p62/SQSTM1 phosphorylation

DNA transfection is an essential technique in the life sciences. Non-viral transfection reagents are widely used for transfection in basic science. However, low transfection efficiency is a problem in some cell types. This low efficiency can be primarily attributed to the intracellular degradation of transfected DNA by p62-dependent selective autophagy, specifically by p62 phosphorylated at the S403 residue (p62-S403-P). To achieve efficient DNA transfection, we focused on a phosphorylation process that generates p62-S403-P and investigated whether inhibition of this process affects transfection efficiency. One of the kinases that phosphorylate p62 is TBK1. The TBK1 gene depletion in murine embryonic fibroblast cells by genome editing caused a significant reduction or loss of p62-S405-P (equivalent to human S403-P) and enhanced transfection efficiency, suggesting that TBK1 is a major kinase that phosphorylates p62 at S403. Therefore, TBK1 is a viable target for drug treatment to increase transfection efficiency. Transfection efficiency was enhanced when cells were treated with one of the following TBK1 inhibitors BX795, MRT67307, or amlexanox. This effect was synergistically improved when the two inhibitors were used in combination. Our results indicate that TBK1 inhibitors enhanced transfection efficiency by suppressing p62 phosphorylation.

A Comprehensive Analysis of the Effects of Key Mitophagy Genes on the Progression and Prognosis of Lung Adenocarcinoma

The aim of our study was to perform a comprehensive analysis of the gene expression, copy number variation (CNV) and mutation of key mitophagy genes in the progression and prognosis of lung adenocarcinoma (LUAD). We obtained the data from The Cancer Genome Atlas (TCGA). Clustering analysis was performed to stratify the mitophagy related groups. The least absolute shrinkage and selection operator (LASSO) based cox model was used to select hub survival genes. An independent validation cohort was retrieved from Gene Expression Omnibus database. We found 24 out of 27 mitophagy genes were aberrantly expressed between tumor and normal samples. CNV gains were associated with higher expression of mitophagy genes in 23 of 27 mitophagy genes. The clustering analysis identified high and low risk mitophagy groups with distinct survival differences. The high risk mitophagy groups had higher tumor mutation burden, stemness phenotype, total CNVs and lower CD4+ T cells infiltration. Drugs targeted to high risk mitophagy groups were identified including the PI3K/AKT/mTOR inhibitor, HDAC inhibitor and chemotherapy agents such as cisplatin and gemcitabine. In addition, the differentially expressed genes (DEGs) were identified between mitophagy groups. Further univariate Cox analysis of each DEG and subsequent LASSO-based Cox model revealed a mitophagy-related prognostic signature. The risk score model of this signature showed a strong ability to predict the overall survival of LUAD patients in training and validation datasets. In conclusion, the mitophagy genes played an important role in the progression and prognosis of LUAD, which might provide useful information for the treatment of LUAD.

Effective-component compatibility of Bufei Yishen formula III ameliorated COPD by improving airway epithelial cell senescence by promoting mitophagy via the NRF2/PINK1 pathway

Background

Effective-component compatibility of Bufei Yishen formula III (ECC-BYF III) demonstrates positive effects on stable chronic obstructive pulmonary disease (COPD).

Purpose

To investigate the mechanisms of ECC-BYF III on COPD rats from the aspect of airway epithelial cell senescence.

Methods

COPD model rats (Sprague-Dawley rat) were treated with ECC-BYF III for 8 weeks, and the efficacy was evaluated. Cigarette smoke extract (CSE)-induced senescence model of airway epithelial cells was treated with ECC-BYF III, and related enzymes and proteins involved in oxidative stress and mitophagy were detected.

Results

ECC-BYF III markedly rescued pulmonary function and histopathological changes, which might be associated with the amelioration of lung senescence, including the reduction of malondialdehyde (MDA) and tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and matrix metalloproteinase (MMP)-9 levels, increase of the level in total superoxide dismutase (T-SOD), and decease in the p21 level in the airways. Furthermore, ECC-BYF III suppressed p16 and p21 expressions and senescence-associated β-galactosidase (SA-β-Gal) in CSE-induced airway epithelial cells. Moreover, ECC-BYF III upregulated mitophagy-related proteins, including the co-localizations of TOM20 and LC3B, PINK1 and PARK2, and improved mitochondrial function by upregulating mitochondrial mitofusin (MFN)2 and reducing dynamin-related protein 1 (DRP1) expression. ECC-BYF III enhanced the activities of T-SOD and GSH-PX by up-regulating NRF2, thus inhibiting oxidative stress. After intervention with NRF2 inhibitor, the regulation effects of ECC-BYF III on oxidative stress, mitophagy and senescence in airway epithelial cells were significantly suppressed.

Conclusions

ECC-BYF III exerts beneficial effects on COPD rats by ameliorating airway epithelial cell senescence, which is mediated by inhibiting oxidative stress and subsequently enhancing mitophagy through the activation of NRF2 signaling.

NLRP3 inflammasomes: A potential target to improve mitochondrial biogenesis in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative condition for which no approved treatment exists to prevent collective neuronal death. There is ample evidence that mitochondrial dysfunction, reactive oxygen species (ROS), and associated caspase activity underlie the pathology observed. Neurons rely on mitochondrial activity since they have such high energy consumption. Therefore, it is not surprising that mitochondrial alterations favour neuronal degeneration. In particular, mitochondrial dysregulation contributes to PD, based on the observation that mitochondrial toxins can cause parkinsonism in humans and animal models. Also, it is known that inflammatory cytokine-mediated neuroinflammation is the key pathogenic mechanism in neuronal loss. In recent years, the research has focussed on mitochondria being the platform for nucleotide-binding oligomerization domain-like receptors 3 (NLRP3) inflammasome activation. Mitochondrial dysfunction and NLRP3 activation are emerging as critical players in inducing and sustaining neuroinflammation. Moreover, mitochondrial-derived ROS and mitochondrial DNA (mtDNA) could serve as the priming signal for forming inflammasome complexes responsible for the activation, maturation, and release of pro-inflammatory cytokines, including interleukin-1(IL-1) and interleukin-18 (IL-18). The current review takes a more comprehensive approach to elucidating the link between mitochondrial dysfunction and aberrant NLRP3 activation in PD. In addition, we focus on some inhibitors of NLRP3 inflammatory pathways to alleviate the progression of PD.

Antibody for Serine 65 Phosphorylated Ubiquitin Identifies PLK1-Mediated Phosphorylation of Mitotic Proteins and APC1

Deciphering the protein posttranslational modification (PTM) code is one of the greatest biochemical challenges of our time. Phosphorylation and ubiquitylation are key PTMs that dictate protein function, recognition, sub-cellular localization, stability, turnover and fate. Hence, failures in their regulation leads to various disease. Chemical protein synthesis allows preparation of ubiquitinated and phosphorylated proteins to study their biochemical properties in great detail. However, monitoring these modifications in intact cells or in cell extracts mostly depends on antibodies, which often have off-target binding. Here, we report that the most widely used antibody for ubiquitin (Ub) phosphorylated at serine 65 (pUb) has significant off-targets that appear during mitosis. These off-targets are connected to polo-like kinase 1 (PLK1) mediated phosphorylation of cell cycle-related proteins and the anaphase promoting complex subunit 1 (APC1).

Metformin Attenuates UVA-Induced Skin Photoaging by Suppressing Mitophagy and the PI3K/AKT/mTOR Pathway

Ultraviolet (UV) radiation is a major cause of photoaging that can induce DNA damage, oxidative stress, and cellular aging. Metformin (MF) can repair DNA damage, scavenge reactive oxygen species (ROS), and protect cells. However, the mechanism by which MF inhibits cell senescence in chronic skin damage induced by UVA is unclear. In this study, human foreskin fibroblasts (HFFs) treated with UVA were used as an in vitro model and UVA-induced skin photoaging in Kunming mice was used as an in vivo model to investigate the potential skin protective mechanism of MF. The results revealed that MF treatment attenuated UVA-induced cell viability, skin aging, and activation of the PI3K/AKT/mTOR signaling pathway. Furthermore, MF treatment alleviated the mitochondrial oxidative stress and decreased mitophagy. Knockdown of Parkin by siRNA increased the clearance of MF in senescent cells. The treatment of Kunming mice with MF at a dose of 10 mg/kg/day significantly reduced UVA-induced skin roughness, epidermal thinning, collagen degradation, and skin aging. In conclusion, our experimental results suggest that MF exerts anti-photoaging effects by inhibiting mitophagy and the PI3K/AKT/mTOR signaling pathway. Therefore, our study improves the current understanding of the protective mechanism of MF against photoaging.

NDP52 Protects Against Myocardial Infarction-Provoked Cardiac Anomalies Through Promoting Autophagosome-Lysosome Fusion via Recruiting TBK1 and RAB7

Aims: Acute myocardial infarction (MI), caused by acute coronary artery obstruction, is a common cardiovascular event leading to mortality. Nuclear dot protein 52 (NDP52) is an essential selective autophagy adaptor, although its function in MI is still obscure. This study was designed to examine the function of NDP52 in MI and the associated mechanisms. Results: Our results revealed that MI challenge overtly impaired myocardial geometry and systolic function, along with cardiomyocyte apoptosis, myocardial interstitial fibrosis, and mitochondrial damage, and NDP52 nullified such devastating responses. Further studies showed that the blockade of mitochondrial clearance is related to MI-induced buildup of damaged mitochondria. Mechanistic approaches depicted that 7-day MI induced abnormal mitophagy flux, resulting in poor lysosomal clearance of injured mitochondria. NDP52 promoted mitophagy flux through the recruitment of Ras-associated protein RAB7 (RAB7) and TANK-binding kinase 1 (TBK1). On protein co-localization, TBK1 phosphorylated RAB7, in line with the finding that chloroquine or a TBK1 inhibitor reversed NDP52-dependent beneficial responses. Innovation: This study denoted a novel mechanism that NDP52 promotes cardioprotection against ischemic heart diseases through interaction with TBK1 and RAB7, leading to RAB7 phosphorylation, induction of mitophagy to clear ischemia-induced impaired mitochondria, thus preventing cardiomyocyte apoptosis in MI. Conclusion: Our results indicate that NDP52 promotes autophagic flux and clears damaged mitochondria to diminish reactive oxygen species and cell death in a TBK1/RAB7-dependent manner and thus limits MI-induced injury. Antioxid. Redox Signal. 36, 1119-1135.

The multifaceted role of autophagy in cancer

Autophagy is a cellular degradative pathway that plays diverse roles in maintaining cellular homeostasis. Cellular stress caused by starvation, organelle damage, or proteotoxic aggregates can increase autophagy, which uses the degradative capacity of lysosomal enzymes to mitigate intracellular stresses. Early studies have shown a role for autophagy in the suppression of tumorigenesis. However, work in genetically engineered mouse models and in vitro cell studies have now shown that autophagy can be either cancer-promoting or inhibiting. Here, we summarize the effects of autophagy on cancer initiation, progression, immune infiltration, and metabolism. We also discuss the efforts to pharmacologically target autophagy in the clinic and highlight future areas for exploration.

The role of TBK1 in cancer pathogenesis and anticancer immunity

The TANK-binding kinase 1 (TBK1) is a serine/threonine kinase belonging to the non-canonical inhibitor of nuclear factor-κB (IκB) kinase (IKK) family. TBK1 can be activated by pathogen-associated molecular patterns (PAMPs), inflammatory cytokines, and oncogenic kinases, including activated K-RAS/N-RAS mutants. TBK1 primarily mediates IRF3/7 activation and NF-κB signaling to regulate inflammatory cytokine production and the activation of innate immunity. TBK1 is also involved in the regulation of several other cellular activities, including autophagy, mitochondrial metabolism, and cellular proliferation. Although TBK1 mutations have not been reported in human cancers, aberrant TBK1 activation has been implicated in the oncogenesis of several types of cancer, including leukemia and solid tumors with KRAS-activating mutations. As such, TBK1 has been proposed to be a feasible target for pharmacological treatment of these types of cancer. Studies suggest that TBK1 inhibition suppresses cancer development not only by directly suppressing the proliferation and survival of cancer cells but also by activating antitumor T-cell immunity. Several small molecule inhibitors of TBK1 have been identified and interrogated. However, to this point, only momelotinib (MMB)/CYT387 has been evaluated as a cancer therapy in clinical trials, while amlexanox (AMX) has been evaluated clinically for treatment of type II diabetes, nonalcoholic fatty liver disease, and obesity. In this review, we summarize advances in research into TBK1 signaling pathways and regulation, as well as recent studies on TBK1 in cancer pathogenesis. We also discuss the potential molecular mechanisms of targeting TBK1 for cancer treatment. We hope that our effort can help to stimulate the development of novel strategies for targeting TBK1 signaling in future approaches to cancer therapy.

Tight association of autophagy and cell cycle in leukemia cells

Background

Autophagy plays an essential role in maintaining cellular homeostasis and in the response to cellular stress. Autophagy is also involved in cell cycle progression, yet the relationship between these processes is not clearly defined.

Results

In exploring this relationship, we observed that the inhibition of autophagy impaired the G2/M phase-arresting activity of etoposide but enhanced the G1 phase-arresting activity of palbociclib. We further investigated the connection of basal autophagy and cell cycle by utilizing the autophagosome tracer dye Cyto-ID in two ways. First, we established a double-labeling flow-cytometric procedure with Cyto-ID and the DNA probe DRAQ5, permitting the cell cycle phase-specific determination of autophagy in live cells. This approach demonstrated that different cell cycle phases were associated with different autophagy levels: G1-phase cells had the lowest level, and G2/M-phase cells had the highest one. Second, we developed a flow-cytometric cell-sorting procedure based on Cyto-ID that separates cell populations into fractions with low, medium, and high autophagy. Cell cycle analysis of Cyto-ID-sorted cells confirmed that the high-autophagy fraction contained a much higher percentage of G2/M-phase cells than the low-autophagy fraction. In addition, Cyto-ID-based cell sorting also proved to be useful for assessing other autophagy-related processes: extracellular flux analysis revealed metabolic differences between the cell populations, with higher autophagy being associated with higher respiration, higher mitochondrial ATP production, and higher glycolysis.

Conclusion

This work provides clear evidence of high autophagy in G2/M-phase cells by establishing a novel cell sorting technique based on Cyto-ID.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-022-00334-8.

Role of the mtDNA Mutations and Mitophagy in Inflammaging

Ageing is an unavoidable multi-factorial process, characterised by a gradual decrease in physiological functionality and increasing vulnerability of the organism to environmental factors and pathogens, ending, eventually, in death. One of the most elaborated ageing theories implies a direct connection between ROS-mediated mtDNA damage and mutations. In this review, we focus on the role of mitochondrial metabolism, mitochondria generated ROS, mitochondrial dynamics and mitophagy in normal ageing and pathological conditions, such as inflammation. Also, a chronic form of inflammation, which could change the long-term status of the immune system in an age-dependent way, is discussed. Finally, the role of inflammaging in the most common neurodegenerative diseases, such as Alzheimer’s and Parkinson’s, is also discussed.

Mitochondrial transport, partitioning and quality control at the heart of cell proliferation and fate acquisition

Mitochondria are essential to cell homeostasis, and alterations in mitochondrial distribution, segregation or turnover have been linked to complex pathologies such as neurodegenerative diseases or cancer. Understanding how these functions are coordinated in specific cell types is a major challenge to discover how mitochondria globally shape cell functionality. In this review, we will first describe how mitochondrial transport and dynamics are regulated throughout the cell cycle in yeast and in mammals. Second, we will explore the functional consequences of mitochondrial transport and partitioning on cell proliferation, fate acquisition, stemness, and on the way cells adapt their metabolism. Last, we will focus on how mitochondrial clearance programs represent a further layer of complexity for cell differentiation, or in the maintenance of stemness. Defining how mitochondrial transport, dynamics and clearance are mutually orchestrated in specific cell types may help our understanding of how cells can transition from a physiological to a pathological state.

Single-cell transcriptomics of human iPSC differentiation dynamics reveal a core molecular network of Parkinson's disease

Parkinson's disease (PD) is the second-most prevalent neurodegenerative disorder, characterized by the loss of dopaminergic neurons (mDA) in the midbrain. The underlying mechanisms are only partly understood and there is no treatment to reverse PD progression. Here, we investigated the disease mechanism using mDA neurons differentiated from human induced pluripotent stem cells (hiPSCs) carrying the ILE368ASN mutation within the PINK1 gene, which is strongly associated with PD. Single-cell RNA sequencing (RNAseq) and gene expression analysis of a PINK1-ILE368ASN and a control cell line identified genes differentially expressed during mDA neuron differentiation. Network analysis revealed that these genes form a core network, members of which interact with all known 19 protein-coding Parkinson's disease-associated genes. This core network encompasses key PD-associated pathways, including ubiquitination, mitochondrial function, protein processing, RNA metabolism, and vesicular transport. Proteomics analysis showed a consistent alteration in proteins of dopamine metabolism, indicating a defect of dopaminergic metabolism in PINK1-ILE368ASN neurons. Our findings suggest the existence of a network onto which pathways associated with PD pathology converge, and offers an inclusive interpretation of the phenotypic heterogeneity of PD.

The Intricate Interplay between Cell Cycle Regulators and Autophagy in Cancer

Simple Summary

Autophagy is an intracellular catabolic program regulated by multiple external and internal cues. A large amount of evidence unraveled that cell-cycle regulators are crucial in its control. This review highlights the interplay between cell-cycle regulators, including cyclin-dependent kinase inhibitors, cyclin-dependent kinases, and E2F factors, in the control of autophagy all along the cell cycle. Beyond the intimate link between cell cycle and autophagy, this review opens therapeutic perspectives in modulating together these two aspects to block cancer progression.

Abstract

In the past decade, cell cycle regulators have extended their canonical role in cell cycle progression to the regulation of various cellular processes, including cellular metabolism. The regulation of metabolism is intimately connected with the function of autophagy, a catabolic process that promotes the efficient recycling of endogenous components from both extrinsic stress, e.g., nutrient deprivation, and intrinsic sub-lethal damage. Mediating cellular homeostasis and cytoprotection, autophagy is found to be dysregulated in numerous pathophysiological contexts, such as cancer. As an adaptative advantage, the upregulation of autophagy allows tumor cells to integrate stress signals, escaping multiple cell death mechanisms. Nevertheless, the precise role of autophagy during tumor development and progression remains highly context-dependent. Recently, multiple articles has suggested the importance of various cell cycle regulators in the modulation of autophagic processes. Here, we review the current clues indicating that cell-cycle regulators, including cyclin-dependent kinase inhibitors (CKIs), cyclin-dependent kinases (CDKs), and E2F transcription factors, are intrinsically linked to the regulation of autophagy. As an increasing number of studies highlight the importance of autophagy in cancer progression, we finally evoke new perspectives in therapeutic avenues that may include both cell cycle inhibitors and autophagy modulators to synergize antitumor efficacy.

Valsartan- and melatonin-supported adipose-derived mesenchymal stem cells preserve renal function in chronic kidney disease rat through upregulation of prion protein participated in promoting PI3K-Akt-mTOR signaling and cell proliferation

This study tested the hypothesis that valsartan (Val) and melatonin (Mel)-assisted adipose-derived mesenchymal stem cells (ADMSCs) preserved the residual renal function in chronic kidney disease (CKD) rat through promoting cellular-prior-protein (PrP^C) to upregulate PI3K/Akt/mTOR signaling and cell proliferation. In vitro study demonstrated that as compared with CKD-derived-ADMSCs, Val/Mel/overexpression of PrP^C-treated CKD derived-ADMSCs significantly upregulated cell proliferation and protein expressions of PrP^C and phosphorylated (p)-PI3K/p-Akt/p-mTOR, and downregulated oxidative stress (all p < 0.001). Rats (n = 42) were categorized into group 1 (sham-operated-control), group 2 (CKD), group 3 (CKD + ADMSCs/1.2 ×10⁶ cells) + Mel/20 mg/kg/day), group 4 (CKD + siRNA-PrP^C-ADMSCs/1.2 ×10⁶ cells), group 5 (CKD + ADMSCs/1.2 ×10⁶ cells + Val/20 mg/kg/day) and group 6 (CKD + Val + Mel). By day 35, the kidney specimens were harvested and the result showed that the protein expression of PrP^C was highest in group 1, lowest in groups 2/4 and significantly lower in group 6 than in groups 3/5, but it was similar in groups 3/5 (all p < 0.0001). The protein expressions of cell-stress-signaling (p-PI3K/p-Akt/p-mTOR) and cell-cycle activity (cyclin-D1/clyclin-E2/Cdk2/Cdk4) exhibited an identical pattern, whereas the protein expressions of oxidative-stress (NOX-1/NOX-2)/mitochondrial fission (PINK1/DRP1)/apoptosis (cleaved-capsase3/cleaved-PARP) and fibrosis (TFG-ß/Smad3) as well as creatinine/BUN levels, ratio of urine-protein to urine-creatine and kidney-injured score exhibited an opposite pattern of PrP^C among the groups (all p < 0.0001). In conclusion, Mel/Val facilitated-ADMSCs preserved renal architecture and function in CKD rat through promoting PrP^C to regulate the cell proliferation/oxidative-stress/cell-stress signalings.

Development and validation of a survival model for esophageal adenocarcinoma based on autophagy-associated genes

Autophagy is a highly conserved catabolic process which has been implicated in esophageal adenocarcinoma (EAC). We sought to investigate the biological functions and prognostic value of autophagy-related genes (ARGs) in EAC. A total of 21 differentially expressed ARGs were identified between EAC and normal samples. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were then applied for the differentially expressed ARGs in EAC, and the protein-protein interaction (PPI) network was established. Cox survival analysis and Lasso regression analysis were performed to establish a prognostic prediction model based on nine overall survival (OS)-related ARGs (CAPN1, GOPC, TBK1, SIRT1, ARSA, BNIP1, ERBB2, NRG2, PINK1). The 9-gene prognostic signature significantly stratified patient outcomes in The Cancer Genome of Atlas (TCGA)-EAC cohort and was considered as an independently prognostic predictor for EAC patients. Moreover, Gene set enrichment analysis (GSEA) analyses revealed several important cellular processes and signaling pathways correlated with the high-risk group in EAC. This prognostic prediction model was confirmed in an independent validation cohort (GSE13898) from The Gene Expression Omnibus (GEO) database. We also developed a nomogram with a concordance index of 0.78 to predict the survival possibility of EAC patients by integrating the risk signature and clinicopathological features. The calibration curves substantiated favorable concordance between actual observation and nomogram prediction. Last but not least, Erb-B2 Receptor Tyrosine Kinase 2 (ERBB2), a member of the prognostic gene signature, was identified as a potential therapeutic target for EAC patients. To sum up, we established and verified a novel prognostic prediction model based on ARGs which could optimize the individualized survival prediction in EAC.

The Combination of β-Asarone and Icariin Inhibits Amyloid-β and Reverses Cognitive Deficits by Promoting Mitophagy in Models of Alzheimer's Disease

β-Asarone is the main constituent of Acorus tatarinowii Schott and exhibits important effects in diseases such as neurodegenerative and neurovascular diseases. Icariin (ICA) is a major active ingredient of Epimedium that has attracted increasing attention because of its unique pharmacological effects in degenerative disease. In this paper, we primarily explored the effects of the combination of β-asarone and ICA in clearing noxious proteins and reversing cognitive deficits. The accumulation of damaged mitochondria and mitophagy are hallmarks of aging and age-related neurodegeneration, including Alzheimer's disease (AD). Here, we provide evidence that autophagy/mitophagy is impaired in the hippocampus of APP/PS1 mice and in Aβ1-42-induced PC12 cell models. Enhanced mitophagic activity has been reported to promote Aβ and tau clearance in in vitro and in vivo models. Meanwhile, there is growing evidence that treatment of AD should be preceded by intervention before the formation of pathological products. The efficacy of the combination therapy was better than that of the individual therapies applied separately. Then, we found that the combination therapy also inhibited cell and mitochondrial damage by inducing autophagy/mitophagy. These findings suggest that impaired removal of defective mitochondria is a pivotal event in AD pathogenesis, and that combination treatment with mitophagy inducers represents a potential strategy for therapeutic intervention.

The Multifaceted Regulation of Mitochondrial Dynamics During Mitosis

Mitosis ensures genome integrity by mediating precise segregation of the duplicated genetic material. Segregation of subcellular organelles during mitosis also needs to be tightly coordinated in order to warrant their proper inheritance and cellular homeostasis. The inheritance of mitochondria, a powerhouse of the cell, is tightly regulated in order to meet the high energy demand to fuel the mitotic machinery. Mitochondria are highly dynamic organelles, which undergo events of fission, fusion and transport during different cell cycle stages. Importantly, during mitosis several kinases phosphorylate the key mitochondrial factors and drive fragmentation of mitochondria to allow for their efficient distribution and inheritance to two daughter cells. Recent evidence suggests that mitochondrial fission can also actively contribute to the regulation of mitotic progression. This review aims at summarizing established and emerging concepts about the complex regulatory networks which couple crucial mitotic factors and events to mitochondrial dynamics and which could be implicated in human disease.

Transcriptomic Signatures Associated With Regional Cortical Thickness Changes in Parkinson's Disease

Cortical atrophy is a common manifestation in Parkinson's disease (PD), particularly in advanced stages of the disease. To elucidate the molecular underpinnings of cortical thickness changes in PD, we performed an integrated analysis of brain-wide healthy transcriptomic data from the Allen Human Brain Atlas and patterns of cortical thickness based on T1-weighted anatomical MRI data of 149 PD patients and 369 controls. For this purpose, we used partial least squares regression to identify gene expression patterns correlated with cortical thickness changes. In addition, we identified gene expression patterns underlying the relationship between cortical thickness and clinical domains of PD. Our results show that genes whose expression in the healthy brain is associated with cortical thickness changes in PD are enriched in biological pathways related to sumoylation, regulation of mitotic cell cycle, mitochondrial translation, DNA damage responses, and ER-Golgi traffic. The associated pathways were highly related to each other and all belong to cellular maintenance mechanisms. The expression of genes within most pathways was negatively correlated with cortical thickness changes, showing higher expression in regions associated with decreased cortical thickness (atrophy). On the other hand, sumoylation pathways were positively correlated with cortical thickness changes, showing higher expression in regions with increased cortical thickness (hypertrophy). Our findings suggest that alterations in the balanced interplay of these mechanisms play a role in changes of cortical thickness in PD and possibly influence motor and cognitive functions.

Molecular functions of autophagy adaptors upon ubiquitin-driven mitophagy

BACKGROUND

Perturbations in organellar health can lead to an accumulation of unwanted and/or damaged organelles that are toxic to the cell and which can contribute to the onset of neurodegenerative diseases such as Parkinson's disease. Mitochondrial health is particularly critical given the indispensable role the organelle has not only in adenosine triphosphate production but also other metabolic processes. Byproducts of oxidative respiration, such as reactive oxygen species, however, can negatively impact mitochondrial fitness. Consequently, selective degradation of damaged mitochondria, which occurs via a specific autophagic process termed mitophagy, is essential for normal cell maintenance.

SCOPE OF REVIEW

Recent accumulating evidence has shown that autophagy adaptors (also referred to as autophagy receptors) play critical roles in connecting ubiquitinated mitochondria with the autophagic machinery of the autophagy-lysosome pathway that is required for degradation. In this review, we focus on our current understanding of the autophagy adaptor mechanisms underlying PINK1/Parkin-driven mitophagy.

MAJOR CONCLUSIONS

Although autophagy adaptors are canonically defined as proteins that possess ubiquitin-binding domains and ATG8s-binding motifs, the recent identification of novel binding partners has contributed to the development of a more sophisticated model for how autophagy adaptors contribute to the molecular hub that organizes autophagic cargo-degradation.

GENERAL SIGNIFICANCE

Although mitophagy is recognized as one of the selective autophagy pathways that removes dysfunctional mitochondria, a more nuanced understanding of the interactions connecting autophagy adaptors and their associated proteins is needed to gain deeper insights into the fundamental biological processes underlying human diseases, including neurodegenerative disorders. This review is part of a Special Issue entitled Mitophagy.

ALS- and FTD-associated missense mutations in TBK1 differentially disrupt mitophagy

TANK-binding kinase 1 (TBK1) is a multifunctional kinase with an essential role in mitophagy, the selective clearance of damaged mitochondria. More than 90 distinct mutations in TBK1 are linked to amyotrophic lateral sclerosis (ALS) and fronto-temporal dementia, including missense mutations that disrupt the abilities of TBK1 to dimerize, associate with the mitophagy receptor optineurin (OPTN), autoactivate, or catalyze phosphorylation. We investigated how ALS-associated mutations in TBK1 affect Parkin-dependent mitophagy using imaging to dissect the molecular mechanisms involved in clearing damaged mitochondria. Some mutations cause severe dysregulation of the pathway, while others induce limited disruption. Mutations that abolish either TBK1 dimerization or kinase activity were insufficient to fully inhibit mitophagy, while mutations that reduced both dimerization and kinase activity were more disruptive. Ultimately, both TBK1 recruitment and OPTN phosphorylation at S177 are necessary for engulfment of damaged mitochondra by autophagosomal membranes. Surprisingly, we find that ULK1 activity contributes to the phosphorylation of OPTN in the presence of either wild-type or kinase-inactive TBK1. In primary neurons, TBK1 mutants induce mitochondrial stress under basal conditions; network stress is exacerbated with further mitochondrial insult. Our study further refines the model for TBK1 function in mitophagy, demonstrating that some ALS-linked mutations likely contribute to disease pathogenesis by inducing mitochondrial stress or inhibiting mitophagic flux. Other TBK1 mutations exhibited much less impact on mitophagy in our assays, suggesting that cell-type-specific effects, cumulative damage, or alternative TBK1-dependent pathways such as innate immunity and inflammation also factor into the development of ALS in affected individuals.

Mitochondrial Ca2+ and cell cycle regulation

It has been demonstrated for more than 40 years that intracellular calcium (Ca²⁺) controls a variety of cellular functions, including mitochondrial metabolism and cell proliferation. Cytosolic Ca²⁺ fluctuation during key stages of the cell cycle can lead to mitochondrial Ca²⁺ uptake and subsequent activation of mitochondrial oxidative phosphorylation and a range of signaling. However, the relationship between mitochondrial Ca²⁺ and cell cycle progression has long been neglected because the molecule responsible for Ca²⁺ uptake has been unknown. Recently, the identification of the mitochondrial Ca²⁺ uniporter (MCU) has led to key advances. With improved Ca²⁺ imaging and detection, effects of MCU-mediated mitochondrial Ca²⁺ have been observed at different stages of the cell cycle. Elevated Ca²⁺ signaling boosts ATP and ROS production, remodels cytosolic Ca²⁺ pathways and reprograms cell fate-determining networks. These findings suggest that manipulating mitochondrial Ca²⁺ signaling may serve as a potential strategy in the control of many crucial biological events, such as tumor development and cell division in hematopoietic stem cells (HSCs). In this review, we summarize the current understanding of the role of mitochondrial Ca²⁺ signaling during different stages of the cell cycle and highlight the potential physiological and pathological significance of mitochondrial Ca²⁺ signaling.

Deciphering the dual role and prognostic potential of PINK1 across cancer types

Metabolic rewiring and deregulation of the cell cycle are hallmarks shared by many cancers. Concerted mutations in key tumor suppressor genes, such as PTEN, and oncogenes predispose cancer cells for marked utilization of resources to fuel accelerated cell proliferation and chemotherapeutic resistance. Mounting research has demonstrated that PTEN-induced putative kinase 1 (PINK1) acts as a pivotal regulator of mitochondrial homeostasis in several cancer types, a function that also extends to the regulation of tumor cell proliferative capacity. In addition, involvement of PINK1 in modulating inflammatory responses has been highlighted by recent studies, further expounding PINK1's multifunctional nature. This review discusses the oncogenic roles of PINK1 in multiple tumor cell types, with an emphasis on maintenance of mitochondrial homeostasis, while also evaluating literature suggesting a dual oncolytic mechanism based on PINK1's modulation of the Warburg effect. From a clinical standpoint, its expression may also dictate the response to genotoxic stressors commonly used to treat multiple malignancies. By detailing the evidence suggesting that PINK1 possesses distinct prognostic value in the clinical setting and reviewing the duality of PINK1 function in a context-dependent manner, we present avenues for future studies of this dynamic protein.

Mitophagy in tumorigenesis and metastasis

Cells use mitophagy to remove dysfunctional or excess mitochondria, frequently in response to imposed stresses, such as hypoxia and nutrient deprivation. Mitochondrial cargo receptors (MCR) induced by these stresses target mitochondria to autophagosomes through interaction with members of the LC3/GABARAP family. There are a growing number of these MCRs, including BNIP3, BNIP3L, FUNDC1, Bcl2-L-13, FKBP8, Prohibitin-2, and others, in addition to mitochondrial protein targets of PINK1/Parkin phospho-ubiquitination. There is also an emerging link between mitochondrial lipid signaling and mitophagy where ceramide, sphingosine-1-phosphate, and cardiolipin have all been shown to promote mitophagy. Here, we review the upstream signaling mechanisms that regulate mitophagy, including components of the mitochondrial fission machinery, AMPK, ATF4, FoxOs, Sirtuins, and mtDNA release, and address the significance of these pathways for stress responses in tumorigenesis and metastasis. In particular, we focus on how mitophagy modulators intersect with cell cycle control and survival pathways in cancer, including following ECM detachment and during cell migration and metastasis. Finally, we interrogate how mitophagy affects tissue atrophy during cancer cachexia and therapy responses in the clinic.

Expanding the View of IKK: New Substrates and New Biology

The inhibitor of kappa B kinase (IKK) family consists of IKKα, IKKβ, and the IKK-related kinases TBK1 and IKKε. These kinases are considered master regulators of inflammation and innate immunity via their control of the transcription factors NF-κB, IRF3, and IRF7. Novel phosphorylated substrates have been attributed to these kinases, a subset of which is not directly related to either inflammation or innate immunity. These findings have greatly expanded the perspectives on the biological activities of these kinases. In this review we highlight some of the novel substrates for this kinase family and discuss the biological implications of these phosphorylation events.

Hidden phenotypes of PINK1/Parkin knockout mice

PINK1, a serine/threonine ubiquitin kinase, and Parkin, an E3 ubiquitin ligase, work in coordination to target damaged mitochondria to the lysosome in a process called mitophagy. This review will cover what we have learned from PINK1 and Parkin knockout (KO) mice. Systemic PINK1 and Parkin KO mouse models haven't faithfully recapitulated early onset forms of Parkinson's disease found in humans with recessive mutations in these genes. However, the utilization of these mouse models has given us insight into how PINK1 and Parkin contribute to mitochondrial quality control and function in different tissues beyond the brain such as in heart and adipose tissue. Although PINK1 and Parkin KO mice have been generated over a decade ago, these models are still being used today to creatively elucidate cell-type specific functions. Recently, these mouse models have uncovered that these proteins contribute to innate immunity and cancer phenotypes.

Mitochondria and Parkinson's Disease: Clinical, Molecular, and Translational Aspects

Mitochondrial dysfunction represents a well-established player in the pathogenesis of both monogenic and idiopathic Parkinson’s disease (PD). Initially originating from the observation that mitochondrial toxins cause PD, findings from genetic PD supported a contribution of mitochondrial dysfunction to the disease. Here, proteins encoded by the autosomal recessively inherited PD genes Parkin, PTEN-induced kinase 1 (PINK1), and DJ-1 are involved in mitochondrial pathways. Additional evidence for mitochondrial dysfunction stems from models of autosomal-dominant PD due to mutations in alpha-synuclein (SNCA) and leucine-rich repeat kinase 2 (LRRK2). Moreover, patients harboring alterations in mitochondrial polymerase gamma (POLG) often exhibit signs of parkinsonism. While some molecular studies suggest that mitochondrial dysfunction is a primary event in PD, others speculate that it is the result of impaired mitochondrial clearance. Most recent research even implicated damage-associated molecular patterns released from non-degraded mitochondria in neuroinflammatory processes in PD. Here, we summarize the manifold literature dealing with mitochondria in the context of PD. Moreover, in light of recent advances in the field of personalized medicine, patient stratification according to the degree of mitochondrial impairment followed by mitochondrial enhancement therapy may hold potential for at least a subset of genetic and idiopathic PD cases. Thus, in the second part of this review, we discuss therapeutic approaches targeting mitochondrial dysfunction with the aim to prevent or delay neurodegeneration in PD.

Molecular mechanisms and physiological functions of mitophagy

Degradation of mitochondria via a selective form of autophagy, named mitophagy, is a fundamental mechanism conserved from yeast to humans that regulates mitochondrial quality and quantity control. Mitophagy is promoted via specific mitochondrial outer membrane receptors, or ubiquitin molecules conjugated to proteins on the mitochondrial surface leading to the formation of autophagosomes surrounding mitochondria. Mitophagy-mediated elimination of mitochondria plays an important role in many processes including early embryonic development, cell differentiation, inflammation, and apoptosis. Recent advances in analyzing mitophagy in vivo also reveal high rates of steady-state mitochondrial turnover in diverse cell types, highlighting the intracellular housekeeping role of mitophagy. Defects in mitophagy are associated with various pathological conditions such as neurodegeneration, heart failure, cancer, and aging, further underscoring the biological relevance. Here, we review our current molecular understanding of mitophagy, and its physiological implications, and discuss how multiple mitophagy pathways coordinately modulate mitochondrial fitness and populations.

Multitasking guardian of mitochondrial quality: Parkin function and Parkinson's disease

The familial form of Parkinson’s disease (PD) is linked to mutations in specific genes. The mutations in parkin are one of the most common causes of early-onset PD. Mitochondrial dysfunction is an emerging active player in the pathology of neurodegenerative diseases, because mitochondria are highly dynamic structures integrated with many cellular functions. Herein, we overview and discuss the role of the parkin protein product, Parkin E3 ubiquitin ligase, in the cellular processes related to mitochondrial function, and how parkin mutations can result in pathology in vitro and in vivo.

Long-term T cell fitness and proliferation is driven by AMPK-dependent regulation of reactive oxygen species

The AMP-activated kinase (AMPK) is a major energy sensor metabolic enzyme that is activated early during T cell immune responses but its role in the generation of effector T cells is still controversial. Using both in vitro and in vivo models of T cell proliferation, we show herein that AMPK is dispensable for early TCR signaling and short-term proliferation but required for sustained long-term T cell proliferation and effector/memory T cell survival. In particular, AMPK promoted accumulation of effector/memory T cells in competitive homeostatic proliferation settings. Transplantation of AMPK-deficient hematopoïetic cells into allogeneic host recipients led to a reduced graft-versus-host disease, further bolstering a role for AMPK in the expansion and pathogenicity of effector T cells. Mechanistically, AMPK expression enhances the mitochondrial membrane potential of T cells, limits reactive oxygen species (ROS) production, and resolves ROS-mediated toxicity. Moreover, dampening ROS production alleviates the proliferative defect of AMPK-deficient T cells, therefore indicating a role for an AMPK-mediated ROS control of T cell fitness.

CDK1, the Other 'Master Regulator' of Autophagy

Autophagy and cap-dependent mRNA translation are tightly regulated by the mechanistic target of rapamycin complex 1 (mTORC1) signalling complex in response to nutrient availability. However, the regulation of these processes, and mTORC1 itself, is different during mitosis, and this has remained an area of significant controversy; for example, studies have argued that autophagy is either repressed or highly active during mitosis. Recent studies have shown that autophagy initiation is repressed, and cap-dependent mRNA translation is maintained during mitosis despite mTORC1 activity being repressed. This is achieved in large part by a switch from mTORC1- to cyclin-dependent kinase 1 (CDK1)-mediated regulation. Here, we review the history and recent advances and seek to present a unifying model to inform the future study of autophagy and mTORC1 during mitosis.

PINK1/PARKIN signalling in neurodegeneration and neuroinflammation

Mutations in the PTEN-induced kinase 1 (PINK1) and Parkin RBR E3 ubiquitin-protein ligase (PARKIN) genes are associated with familial forms of Parkinson’s disease (PD). PINK1, a protein kinase, and PARKIN, an E3 ubiquitin ligase, control the specific elimination of dysfunctional or superfluous mitochondria, thus fine-tuning mitochondrial network and preserving energy metabolism. PINK1 regulates PARKIN translocation in impaired mitochondria and drives their removal via selective autophagy, a process known as mitophagy. As knowledge obtained using different PINK1 and PARKIN transgenic animal models is being gathered, growing evidence supports the contribution of mitophagy impairment to several human pathologies, including PD and Alzheimer’s diseases (AD). Therefore, therapeutic interventions aiming to modulate PINK1/PARKIN signalling might have the potential to treat these diseases. In this review, we will start by discussing how the interplay of PINK1 and PARKIN signalling helps mediate mitochondrial physiology. We will continue by debating the role of mitochondrial dysfunction in disorders such as amyotrophic lateral sclerosis, Alzheimer’s, Huntington’s and Parkinson’s diseases, as well as eye diseases such as age-related macular degeneration and glaucoma, and the causative factors leading to PINK1/PARKIN-mediated neurodegeneration and neuroinflammation. Finally, we will discuss PINK1/PARKIN gene augmentation possibilities with a particular focus on AD, PD and glaucoma.

Targeting TANK-binding kinase 1 (TBK1) in cancer

INTRODUCTION

TANK-binding kinase 1 (TBK1) is a Ser/Thr kinase with a central role in coordinating the cellular response to invading pathogens and regulating key inflammatory signaling cascades. While intact TBK1 signaling is required for successful anti-viral signaling, dysregulated TBK1 signaling has been linked to a variety of pathophysiologic conditions, including cancer. Several lines of evidence support a role for TBK1 in cancer pathogenesis, but the specific roles and regulation of TBK1 remain incompletely understood. A key challenge is the diversity of cellular processes that are regulated by TBK1, including inflammation, cell cycle, autophagy, energy homeostasis, and cell death. Nevertheless, evidence from pre-clinical cancer models suggests that targeting TBK1 may be an effective strategy for anti-cancer therapy in specific settings.

AREAS COVERED

This review provides an overview of the roles and regulation of TBK1 with a focus on cancer pathogenesis and drug targeting of TBK1 as an anti-cancer strategy. Relevant literature was derived from a PubMed search encompassing studies from 1999 to 2020.

EXPERT OPINION

TBK1 is emerging as a potential target for anti-cancer therapy. Inhibition of TBK1 alone may be insufficient to restrain the growth of most cancers; hence, combination strategies will likely be necessary. Improved understanding of tumor-intrinsic and tumor-extrinsic TBK1 signaling will inform novel therapeutic strategies.

The Links between Parkinson's Disease and Cancer

Epidemiologic studies indicate a decreased incidence of most cancer types in Parkinson’s disease (PD) patients. However, some neoplasms are associated with a higher risk of occurrence in PD patients. Both pathologies share some common biological pathways. Although the etiologies of PD and cancer are multifactorial, some factors associated with PD, such as α-synuclein aggregation; mutations of PINK1, PARKIN, and DJ-1; mitochondrial dysfunction; and oxidative stress can also be involved in cancer proliferation or cancer suppression. The main protein associated with PD, i.e., α-synuclein, can be involved in some types of neoplastic formations. On the other hand, however, its downregulation has been found in the other cancers. PINK1 can act as oncogenic or a tumor suppressor. PARKIN dysfunction may lead to some cancers’ growth, and its expression may be associated with some tumors’ suppression. DJ-1 mutation is involved in PD pathogenesis, but its increased expression was found in some neoplasms, such as melanoma or breast, lung, colorectal, uterine, hepatocellular, and nasopharyngeal cancers. Both mitochondrial dysfunction and oxidative stress are involved in PD and cancer development. The aim of this review is to summarize the possible associations between PD and carcinogenesis.