bims-mikwok 2023-11-05 papers

bims-mikwok

Biomed News

on Mitochondrial quality control

Issue of 2023–11–05
sixteen papers selected by
Gavin McStay, Liverpool John Moores University

TBK1 is ubiquitinated by TRIM5α to assemble mitophagy machinery.
Mitochondria makeover: unlocking the path to healthy longevity.
Mitochondrial complexome and import network.
A human mitofusin 2 mutation can cause mitophagic cardiomyopathy.
The Role of Mitokines in Diabetic Nephropathy.
Autoregulatory control of mitochondrial glutathione homeostasis.
UNC-49 is a redox-sensitive GABAA receptor that regulates the mitochondrial unfolded protein response cell nonautonomously.
Germacrone protects renal tubular cells against ferroptotic death and ROS release by re-activating mitophagy in diabetic nephropathy.
ROCK1 activates mitochondrial fission leading to oxidative stress and muscle atrophy.
Fibrinogen in mice cerebral microvessels induces blood-brain barrier dysregulation with aging via a dynamin-related protein 1-dependent pathway.
Mitophagy and mitochondrion-related expression profiles in response to physiological and pathological hypoxia in the corneal epithelium.
Activated Drp1 Initiates the Formation of Endoplasmic Reticulum-Mitochondrial Contacts via Shrm4-Mediated Actin Bundling.
RCCD1 promotes breast carcinogenesis through regulating hypoxia-associated mitochondrial homeostasis.
The iron chelator and OXPHOS inhibitor VLX600 induces mitophagy and an autophagy-dependent type of cell death in glioblastoma cells.
CKLF induces microglial activation via triggering defective mitophagy and mitochondrial dysfunction.
Mitochondrial regulation in stem cells.

bioRxiv. 2023 Oct 20. pii: 2023.10.19.563195. [Epub ahead of print]

TBK1 is ubiquitinated by TRIM5α to assemble mitophagy machinery.

Bhaskar Saha, Hallvard Olsvik, Geneva L Williams, Seeun Oh, Gry Evjen, Eva Sjøttem, Michael A Mandell.

Ubiquitination of mitochondrial proteins provides a basis for the downstream recruitment of mitophagy machinery, yet whether ubiquitination of the machinery itself contributes to mitophagy is unknown. Here, we show that K63-linked polyubiquitination of the key mitophagy regulator TBK1 is essential for its mitophagy functions. This modification is catalyzed by the ubiquitin ligase TRIM5α. Mitochondrial damage triggers TRIM5α's auto-ubiquitination and its interaction with ubiquitin-binding autophagy adaptors including NDP52, optineurin, and NBR1. Autophagy adaptors, along with TRIM27, enable TRIM5α to engage with TBK1. TRIM5α with intact ubiquitination function is required for the proper accumulation of active TBK1 on damaged mitochondria in Parkin-dependent and Parkin-independent mitophagy pathways. Additionally, we show that TRIM5α can directly recruit autophagy initiation machinery to damaged mitochondria. Our data support a model in which TRIM5α provides a self-amplifying, mitochondria-localized, ubiquitin-based, assembly platform for TBK1 and mitophagy adaptors that is ultimately required to recruit the core autophagy machinery.

DOI: https://doi.org/10.1101/2023.10.19.563195
Expert Opin Ther Targets. 2023 Oct 30. 1-4

Mitochondria makeover: unlocking the path to healthy longevity.

Andrés Caicedo, Keshav K Singh.



Keywords:  Aging; Extracellular Mitochondria; Hallmarks of Aging; Health; Healthy Longevity; Induced Pluripotent Stem Cells (iPSCs); Longevity; Mitochondria; Mitochondrial DNA (mtDNA); Mitochondrial Transfer; Mitochondrial Transplant; Rejuvenation; Senescent Cells; Telomeres

DOI:  https://doi.org/10.1080/14728222.2023.2277240
Trends Cell Biol. 2023 Oct 30. pii: S0962-8924(23)00208-8. [Epub ahead of print]

Mitochondrial complexome and import network.

Fabian den Brave, Uwe Schulte, Bernd Fakler, Nikolaus Pfanner, Thomas Becker.

  Mitochondria perform crucial functions in cellular metabolism, protein and lipid biogenesis, quality control, and signaling. The systematic analysis of protein complexes and interaction networks provided exciting insights into the structural and functional organization of mitochondria. Most mitochondrial proteins do not act as independent units, but are interconnected by stable or dynamic protein-protein interactions. Protein translocases are responsible for importing precursor proteins into mitochondria and form central elements of several protein interaction networks. These networks include molecular chaperones and quality control factors, metabolite channels and respiratory chain complexes, and membrane and organellar contact sites. Protein translocases link the distinct networks into an overarching network, the mitochondrial import network (MitimNet), to coordinate biogenesis, membrane organization and function of mitochondria.

Keywords:  cell organelles; energetics; metabolism; mitochondria; morphology; protein assembly; protein networks; protein sorting

DOI:  https://doi.org/10.1016/j.tcb.2023.10.004
Elife. 2023 Nov 01. pii: e84235. [Epub ahead of print]12

A human mitofusin 2 mutation can cause mitophagic cardiomyopathy.

Antonietta Franco, Jiajia Li, Daniel P Kelly, Ray E Hershberger, Ali J Marian, Renate M Lewis, Moshi Song, Xiawei Dang, Alina D Schmidt, Mary E Mathyer, John R Edwards, Cristina de Guzman Strong, Gerald W Dorn.

  Cardiac muscle has the highest mitochondrial density of any human tissue, but mitochondrial dysfunction is not a recognized cause of isolated cardiomyopathy. Here, we determined that the rare mitofusin (MFN) 2 R400Q mutation is 15-20× over-represented in clinical cardiomyopathy, whereas this specific mutation is not reported as a cause of MFN2 mutant-induced peripheral neuropathy, Charcot-Marie-Tooth disease type 2A (CMT2A). Accordingly, we interrogated the enzymatic, biophysical, and functional characteristics of MFN2 Q400 versus wild-type and CMT2A-causing MFN2 mutants. All MFN2 mutants had impaired mitochondrial fusion, the canonical MFN2 function. Compared to MFN2 T105M that lacked catalytic GTPase activity and exhibited normal activation-induced changes in conformation, MFN2 R400Q and M376A had normal GTPase activity with impaired conformational shifting. MFN2 R400Q did not suppress mitochondrial motility, provoke mitochondrial depolarization, or dominantly suppress mitochondrial respiration like MFN2 T105M. By contrast to MFN2 T105M and M376A, MFN2 R400Q was uniquely defective in recruiting Parkin to mitochondria. CRISPR editing of the R400Q mutation into the mouse Mfn2 gene induced perinatal cardiomyopathy with no other organ involvement; knock-in of Mfn2 T105M or M376V did not affect the heart. RNA sequencing and metabolomics of cardiomyopathic Mfn2 Q/Q400 hearts revealed signature abnormalities recapitulating experimental mitophagic cardiomyopathy. Indeed, cultured cardiomyoblasts and in vivo cardiomyocytes expressing MFN2 Q400 had mitophagy defects with increased sensitivity to doxorubicin. MFN2 R400Q is the first known natural mitophagy-defective MFN2 mutant. Its unique profile of dysfunction evokes mitophagic cardiomyopathy, suggesting a mechanism for enrichment in clinical cardiomyopathy.

Keywords:  cardiomyopathy; developmental biology; heart; mitochondria; mitofusins; mouse

DOI:  https://doi.org/10.7554/eLife.84235
Curr Med Chem. 2023 Oct 26.

The Role of Mitokines in Diabetic Nephropathy.

Ming Yang, Wei Chen, Liyu He, Xi Wang, Di Liu, Li Xiao, Lin Sun.

  Diabetic nephropathy (DN) has gradually become one of the main causes of end-stage renal disease (ESRD). However, there is still a lack of effective preventive measures to delay its progression. As the energy factory in the cell, mitochondria play an irreplaceable role in maintaining cell homeostasis. Interestingly, recent studies have shown that in addition to maintaining homeostasis in cells in which mitochondria reside, when mitochondrial perturbations occur in one tissue, distal tissues can also sense and act through mitochondrial stress response pathways through a group of proteins or peptides called "mitokines". Here, we reviewed the mitokines that have been found thus far and summarized their research progress in DN. Finally, we explored the possibility of mitokines as potential therapeutic targets for DN.

Keywords:  Diabetic nephropathy (DN); FGF21; Humanin; MOTS-c; Mitokines; mitochondrial stress ?

DOI:  https://doi.org/10.2174/0109298673255403230919061828
Science. 2023 Nov 02. eadf4154

Autoregulatory control of mitochondrial glutathione homeostasis.

Yuyang Liu, Shanshan Liu, Anju Tomar, Frederick S Yen, Gokhan Unlu, Nathalie Ropek, Ross A Weber, Ying Wang, Artem Khan, Mark Gad, Junhui Peng, Erdem Terzi, Hanan Alwaseem, Alexandra E Pagano, Søren Heissel, Henrik Molina, Benjamin Allwein, Timothy C Kenny, Richard L Possemato, Li Zhao, Richard K Hite, Ekaterina V Vinogradova, Sheref S Mansy, Kıvanç Birsoy.

Mitochondria must maintain adequate amounts of metabolites for protective and biosynthetic functions. However, how mitochondria sense the abundance of metabolites and regulate metabolic homeostasis is not well understood. We focused on glutathione (GSH), a critical redox metabolite in mitochondria and identified a feedback mechanism that controls its abundance through the mitochondrial GSH transporter, SLC25A39. Under physiological conditions, SLC25A39 is rapidly degraded by a mitochondrial protease, AFG3L2. Depletion of GSH dissociates AFG3L2 from SLC25A39, causing a compensatory increase in mitochondrial GSH uptake. Genetic and proteomic analysis identified a putative iron-sulfur cluster in the matrix-facing loop of SLC25A39 to be essential for this regulation, coupling mitochondrial iron homeostasis to GSH import. Altogether, our work revealed a paradigm for the autoregulatory control of metabolic homeostasis in organelles.

DOI: https://doi.org/10.1126/science.adf4154
Sci Adv. 2023 11 03. 9(44): eadh2584

UNC-49 is a redox-sensitive GABAA receptor that regulates the mitochondrial unfolded protein response cell nonautonomously.

Franziska Pohl, Allison L Germann, Jack Mao, Sydney Hou, Bayode Bakare, Paul Kong Thoo Lin, Kyari Yates, Michael L Nonet, Gustav Akk, Kerry Kornfeld, Jason M Held.

The γ-aminobutyric acid-mediated (GABAergic) system participates in many aspects of organismal physiology and disease, including proteostasis, neuronal dysfunction, and life-span extension. Many of these phenotypes are also regulated by reactive oxygen species (ROS), but the redox mechanisms linking the GABAergic system to these phenotypes are not well defined. Here, we report that GABAergic redox signaling cell nonautonomously activates many stress response pathways in Caenorhabditis elegans and enhances vulnerability to proteostasis disease in the absence of oxidative stress. Cell nonautonomous redox activation of the mitochondrial unfolded protein response (mitoUPR) proteostasis network requires UNC-49, a GABAA receptor that we show is activated by hydrogen peroxide. MitoUPR induction by a spinocerebellar ataxia type 3 (SCA3) C. elegans neurodegenerative disease model was similarly dependent on UNC-49 in C. elegans. These results demonstrate a multi-tissue paradigm for redox signaling in the GABAergic system that is transduced via a GABAA receptor to function in cell nonautonomous regulation of health, proteostasis, and disease.

DOI: https://doi.org/10.1126/sciadv.adh2584
Free Radic Res. 2023 Oct 28. 1-17

Germacrone protects renal tubular cells against ferroptotic death and ROS release by re-activating mitophagy in diabetic nephropathy.

Yunguang Wang, Xinxin He, Mengjiao Xue, Wenbo Sun, Qiang He, Juan Jin.

  Mitophagy is a critical intracellular event during the progression of diabetic nephropathy (DN). Our previous study demonstrated that germacrone has anti-ferroptotic properties and is a potential therapeutic agent for DN. However, the relationship among germacrone, mitophagy, and ferroptosis in DN remains unclear. In this study, the data confirmed that germacrone ameliorates high glucose (HG)-induced ferroptosis through limiting Fe (2+) content and lipid reactive oxygen species (ROS) accumulation in human kidney 2 (HK-2) cells. Germacrone reversed HG-mediated inhibition of mitophagy. Mitophagy inhibition and anabatic mitochondrial ROS abrogate germacrone-mediated protective effects against ferroptotic death, resulting in the subsequent activation of mitochondrial DNA (mtDNA) cytosolic leakage-induced stimulator of interferon response CGAMP interactor 1 (STING) signaling. The combination of a mitochondrial ROS antagonist and germacrone acts synergistically to alleviate the ferroptotic death of tubular cells and DN symptoms. In summary, germacrone ameliorated ferroptotic death in tubular cells by reactivating mitophagy and inhibiting mtDNA-STING signaling in DN. This study provides a novel insight into germacrone-mediated protection against DN progression and further confirms that antioxidant pharmacological strategies facilitate the treatment of DN.

Keywords:  Germacrone; STING; diabetic nephropathy; ferroptosis; mitophagy

DOI:  https://doi.org/10.1080/10715762.2023.2277143
bioRxiv. 2023 Oct 22. pii: 2023.10.22.563469. [Epub ahead of print]

ROCK1 activates mitochondrial fission leading to oxidative stress and muscle atrophy.

Meijun Si, Rizhen Yu, Hongchun Lin, Feng Li, Sungyun Jung, Sandhya S Thomas, Farhard S Danesh, Yanlin Wang, Hui Peng, Zhaoyong Hu.

Chronic kidney disease (CKD) is often associated with protein-energy wasting (PEW), which is characterized by a reduction in muscle mass and strength. Although mitochondrial dysfunction and oxidative stress have been implicated to play a role in the pathogenesis of muscle wasting, the underlying mechanisms remain unclear. In this study, we used transcriptomics, metabolomics analyses and mouse gene manipulating approaches to investigate the effects of mitochondrial plasticity and oxidative stress on muscle wasting in mouse CKD models. Our results showed that the expression of oxidative stress response genes was increased, and that of oxidative phosphorylation genes was decreased in the muscles of mice with CKD. This was accompanied by reduced oxygen consumption rates, decreased levels of mitochondrial electron transport chain proteins, and increased cellular oxidative damage. Excessive mitochondrial fission was also observed, and we found that the activation of ROCK1 was responsible for this process. Inducible expression of muscle-specific constitutively active ROCK1 (mROCK1 ca ) exacerbated mitochondrial fragmentation and muscle wasting in CKD mice. Conversely, ROCK1 depletion (ROCK1-/-) alleviated these phenomena. Mechanistically, ROCK1 activation promoted the recruitment of Drp1 to mitochondria, thereby facilitating fragmentation. Notably, the pharmacological inhibition of ROCK1 mitigated muscle wasting by suppressing mitochondrial fission and oxidative stress. Our findings demonstrate that ROCK1 participates in CKD-induced muscle wasting by promoting mitochondrial fission and oxidative stress, and pharmacological suppression of ROCK1 could be a therapeutic strategy for combating muscle wasting in CKD conditions.
Translational Statement: Protein-energy wasting (PEW) is a prevalent issue among patients with chronic kidney disease (CKD) and is characterized by the loss of muscle mass. Our research uncovers a critical role that ROCK1 activation plays in muscle wasting induced by CKD. We found that ROCK1 is instrumental in causing mitochondrial fission, which leads to increased oxidative stress in muscle cells. By employing a pharmacological inhibitor, hydroxyfasudil, we were able to effectively curb ROCK1 activity, which in turn mitigated muscle wasting by reducing both mitochondrial fission and oxidative stress. These findings suggest that pharmacological inhibition of ROCK1 presents a promising therapeutic strategy for combating the muscle wasting associated with CKD.

DOI: https://doi.org/10.1101/2023.10.22.563469
Geroscience. 2023 Oct 28.

Fibrinogen in mice cerebral microvessels induces blood-brain barrier dysregulation with aging via a dynamin-related protein 1-dependent pathway.

Partha K Chandra, Manesh Kumar Panner Selvam, Jorge A Castorena-Gonzalez, Ibolya Rutkai, Suresh C Sikka, Ricardo Mostany, David W Busija.

  We previously reported evidence that oxidative stress during aging leads to adverse protein profile changes of brain cortical microvessels (MVs: end arterioles, capillaries, and venules) that affect mRNA/protein stability, basement membrane integrity, and ATP synthesis capacity in mice. As an extension of our previous study, we also found that proteins which comprise the blood-brain barrier (BBB) and regulate mitochondrial quality control were also significantly decreased in the mice's cortical MVs with aging. Interestingly, the neuroinflammatory protein fibrinogen (Fgn) was increased in mice brain MVs, which corresponds with clinical reports indicating that the plasma Fgn concentration increased progressively with aging. In this study, protein-protein interaction network analysis indicated that high expression of Fgn is linked with downregulated expression of both BBB- and mitochondrial fission/fusion-related proteins in mice cortical MVs with aging. To investigate the mechanism of Fgn action, we observed that 2 mg/mL or higher concentration of human plasma Fgn changed cell morphology, induced cytotoxicity, and increased BBB permeability in primary human brain microvascular endothelial cells (HBMECs). The BBB tight junction proteins were significantly decreased with increasing concentration of human plasma Fgn in primary HBMECs. Similarly, the expression of phosphorylated dynamin-related protein 1 (pDRP1) and other mitochondrial fission/fusion-related proteins were also significantly reduced in Fgn-treated HBMECs. Interestingly, DRP1 knockdown by shRNA(h) resulted in the reduction of both BBB- and mitochondrial fission/fusion-related proteins in HBMECs. Our results suggest that elevated Fgn downregulates DRP1, leading to mitochondrial-dependent endothelial and BBB dysfunction in the brain microvasculature.

Keywords:  Brain aging; Cortical microvessels; Endothelial/blood–brain barrier dysfunction; Mitochondrial fission/fusion; Protein–protein interaction network; Proteomics

DOI:  https://doi.org/10.1007/s11357-023-00988-y
Genomics. 2023 Oct 31. pii: S0888-7543(23)00183-0. [Epub ahead of print] 110739

Mitophagy and mitochondrion-related expression profiles in response to physiological and pathological hypoxia in the corneal epithelium.

Ming-Feng Wu, Xi Peng, Jiang-Lan Zhao, Ming-Chang Zhang, Hua-Tao Xie.

  To study the mitochondrial and cellular responses to physiological and pathological hypoxia, corneal epithelial cells were preconditioned under 21% O2, 8% O2 or 1% O2. The cell survival rate, mitochondrial fluorescence and mitophagy flux were quantified using flow cytometry. After RNA sequencing, gene set enrichment analysis (GSEA) was performed. When the oxygen level decreased from 21% to 8%, mitochondrial fluorescence decreased by 45% (p < 0.001), accompanied by an 80% increase in mitophagy flux (p < 0.001). When the oxygen level dropped to 1%, the cell survival rate and mitochondrial fluorescence decreased, while mitophagy flux further increased (each p < 0.001). Comparison of 1% O2 vs. 21% O2 revealed enrichment of the HYPOXIA hallmark. Most of the significantly enriched mitochondrion-related gene sets were involved in apoptosis. The corresponding foremost leading edge genes belonged to the BCL-2 family. Corneal epithelial cell fate decisions under hypoxia may involve noncanonical pathways of mitophagy.

Keywords:  Corneal epithelial cells; Gene set enrichment analysis; Hypoxia; Mitochondria; Mitophagy

DOI:  https://doi.org/10.1016/j.ygeno.2023.110739
Adv Sci (Weinh). 2023 Nov 01. e2304885

Activated Drp1 Initiates the Formation of Endoplasmic Reticulum-Mitochondrial Contacts via Shrm4-Mediated Actin Bundling.

Chenyang Duan, Ruixue Liu, Lei Kuang, Zisen Zhang, Dongyao Hou, Danyang Zheng, Xinming Xiang, He Huang, Liangming Liu, Tao Li.

  Excessive mitochondrial fission following ischemia and hypoxia relies on the formation of contacts between the endoplasmic reticulum and mitochondria (ER-Mito); however, the specific mechanisms behind this process remain unclear. Confocal microscopy and time course recording are used to investigate how ischemia and hypoxia affect the activation of dynamin-related protein 1 (Drp1), a protein central to mitochondrial dynamics, ER-Mito interactions, and the consequences of modifying the expression of Drp1, shroom (Shrm) 4, and inverted formin (INF) 2 on ER-Mito contact establishment. Both Drp1 activation and ER-Mito contact initiation cause excessive mitochondrial fission and dysfunction under ischemic-hypoxic conditions. The activated form of Drp1 aids in ER-Mito contact initiation by recruiting Shrm4 and promoting actin bundling between the ER and mitochondria. This process relies on the structural interplay between INF2 and scattered F-actin on the ER. This study uncovers new roles of cytoplasmic Drp1, providing valuable insights for devising strategies to manage mitochondrial imbalances in the context of ischemic-hypoxic injury.

Keywords:  Drp1; ER-Mito contact; actin bundling; mitochondrial fission; shrm4

DOI:  https://doi.org/10.1002/advs.202304885
Oncogene. 2023 Oct 31.

RCCD1 promotes breast carcinogenesis through regulating hypoxia-associated mitochondrial homeostasis.

Yani Peng, Xiaoping Liu, Xinhua Liu, Xiao Cheng, Lu Xia, Leyi Qin, Sudun Guan, Yue Wang, Xiaodi Wu, Jiajing Wu, Dong Yan, Jianying Liu, Yu Zhang, Luyang Sun, Jing Liang, Yongfeng Shang.

Regulator of chromosome condensation domain-containing protein 1 (RCCD1), previously reported as a partner of histone H3K36 demethylase KDM8 involved in chromosome segregation, has been identified as a potential driver for breast cancer in a recent transcriptome-wide association study. We report here that, unexpectedly, RCCD1 is also localized in mitochondria. We show that RCCD1 resides in the mitochondrial matrix, where it interacts with the mitochondrial contact site/cristae organizing system (MICOS) and mitochondrial DNA (mtDNA) to regulate mtDNA transcription, oxidative phosphorylation, and the production of reactive oxygen species. Interestingly, RCCD1 is upregulated under hypoxic conditions, leading to decreased generation of reactive oxygen species and alleviated apoptosis favoring cancer cell survival. We show that RCCD1 promotes breast cancer cell proliferation in vitro and accelerates breast tumor growth in vivo. Indeed, RCCD1 is overexpressed in breast carcinomas, and its level of expression is associated with aggressive breast cancer phenotypes and poor patient survival. Our study reveals an additional dimension of RCCD1 functionality in regulating mitochondrial homeostasis, whose dysregulation inflicts pathologic states such as breast cancer.

DOI: https://doi.org/10.1038/s41388-023-02877-2
Am J Physiol Cell Physiol. 2023 Oct 30.

The iron chelator and OXPHOS inhibitor VLX600 induces mitophagy and an autophagy-dependent type of cell death in glioblastoma cells.

Lisa Reisbeck, Benedikt Linder, Georg Tascher, Süleyman Bozkurt, Katharina J Weber, Christel Herold-Mende, Sjoerd van Wijk, Rolf Marschalek, Liliana Schaefer, Christian Münch, Donat Kögel.

  Induction of alternative, non-apoptotic cell death programs such as cell-lethal autophagy and mitophagy represent possible strategies to combat glioblastoma (GBM). Here we report that VLX600, a novel iron chelator and oxidative phosphorylation (OXPHOS) inhibitor, induces a caspase-independent type of cell death that is partially rescued in adherent U251 ATG5/7 (autophagy related 5/7) knockout (KO) GBM cells and NCH644 ATG5/7 knockdown (KD) glioma stem-like cells (GSCs), suggesting that VLX600 induces an autophagy-dependent cell death (ADCD) in GBM. This ADCD is accompanied by decreased oxygen consumption, increased expression/mitochondrial localization of BNIP3 (BCL2 interacting protein 3) and BNIP3L (BCL2 interacting protein 3 like), the induction of mitophagy as demonstrated by diminished levels of mitochondrial marker proteins (e.g. COX4I1 (cytochrome c oxidase subunit 4I1)) and the mitoKeima assay as well as increased histone H3 and H4 lysine tri-methylation. Further, the extracellular addition of iron is able to significantly rescue VLX600-induced cell death and mitophagy, pointing out an important role of iron metabolism for GBM cell homeostasis. Interestingly, VLX600 is also able to completely eliminate NCH644 GSC tumors in an organotypic brain slice transplantation model. Our data support the therapeutic concept of ADCD induction in GBM and suggest that VLX600 may be an interesting novel drug candidate for the treatment of this tumor.

Keywords:  autophagy; brain tumor; iron metabolism; mitochondrial respiration; non-apoptotic cell death

DOI:  https://doi.org/10.1152/ajpcell.00293.2023
Autophagy. 2023 Oct 31.

CKLF induces microglial activation via triggering defective mitophagy and mitochondrial dysfunction.

Hongyun Wang, Junrui Ye, Ye Peng, Wenyu Ma, Haodong Chen, Hongshuo Sun, Zhongping Feng, Wenbin He, Gang Li, Shifeng Chu, Zhao Zhang, Naihong Chen.

  Although microglial activation is induced by an increase in chemokines, the role of mitophagy in this process remains unclear. This study aimed to elucidate the role of microglial mitophagy in CKLF/CKLF1 (chemokine-like factor 1)-induced microglial activation and neuroinflammation, as well as the underlying molecular mechanisms following CKLF treatment. This study determined that CKLF, an inducible chemokine in the brain, leads to an increase in mitophagy markers, such as DNM1L, PINK1 (PTEN induced putative kinase 1), PRKN, and OPTN, along with a simultaneous increase in autophagosome formation, as evidenced by elevated levels of BECN1 and MAP1LC3B (microtubule-associated protein 1 light chain 3 beta)-II. However, SQSTM1, a substrate of autophagy, was also accumulated by CKLF treatment, suggesting that mitophagy flux was reduced and mitophagosomes accumulated. These findings were confirmed by transmission electron microscopy and confocal microscopy. The defective mitophagy observed in our study was caused by impaired lysosomal function, including mitophagosome-lysosome fusion, lysosome generation, and acidification, resulting in the accumulation of damaged mitochondria in microglial cells. Further analysis revealed that pharmacological blocking or gene-silencing of mitophagy inhibited CKLF-mediated microglial activation, as evidenced by the expression of the microglial marker AIF1 (allograft inflammatory factor 1) and the mRNA of proinflammatory cytokines (Tnf and Il6). Ultimately, defective mitophagy induced by CKLF results in microglial activation, as observed in the brains of adult mice. In summary, CKLF induces defective mitophagy, microglial activation, and inflammation, providing a potential approach for treating neuroinflammatory diseases.

Keywords:  Chemokine-like factor 1; inflammation; lysosomal function; microglia; mitophagosome formation; neuroinflammatory diseases

DOI:  https://doi.org/10.1080/15548627.2023.2276639
Trends Cell Biol. 2023 Oct 31. pii: S0962-8924(23)00207-6. [Epub ahead of print]

Mitochondrial regulation in stem cells.

Yifei Wang, Marine Barthez, Danica Chen.

  Stem cells persist throughout the lifespan to repair and regenerate tissues due to their unique ability to self-renew and differentiate. Here we reflect on the recent discoveries in stem cells that highlight a mitochondrial metabolic checkpoint at the restriction point of the stem cell cycle. Mitochondrial activation supports stem cell proliferation and differentiation by providing energy supply and metabolites as signaling molecules. Concomitant mitochondrial stress can lead to loss of stem cell self-renewal and requires the surveillance of various mitochondrial quality control mechanisms. During aging, a mitochondrial protective program mediated by several sirtuins becomes dysregulated and can be targeted to reverse stem cell aging and tissue degeneration, giving hope for targeting the mitochondrial metabolic checkpoint for treating tissue degenerative diseases.

Keywords:  NAD; NLRP3; SIRT2; SIRT3; SIRT7; aging

DOI:  https://doi.org/10.1016/j.tcb.2023.10.003