bims-mitmed 2023-11-19 papers

bims-mitmed

Biomed News

on Mitochondrial medicine

Issue of 2023‒11‒19
twenty-two papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico

Genetic analysis and multimodal imaging identify novel mtDNA 12148T>C leading to multisystem dysfunction with tissue-specific heteroplasmy.
Mitochondrial entry gate as regulatory hub.
Teamwork makes the dream work: functional collaborations between families, scientists, and healthcare providers to drive progress in the treatment of Leigh Syndrome.
Dystonia in ATP Synthase Defects: Reconnecting Mitochondria and Dopamine.
Mitochondrial aminoacyl-tRNA synthetases trigger unique compensatory mechanisms in neurons.
Mitochondrial Complex I and β-Amyloid Peptide Interplay in Alzheimer's Disease: A Critical Review of New and Old Little Regarded Findings.
Interactions of mitochondrial and skeletal muscle biology in mitochondrial myopathy.
Nicotinamide Riboside, an NAD + Precursor, Protects Against Cardiac Mitochondrial Dysfunction in Fetal Guinea Pigs Exposed to Gestational Hypoxia.
Mitochondrial dysfunction in Parkinson's disease - a key disease hallmark with therapeutic potential.
Astrocyte and L-lactate in the anterior cingulate cortex modulate schema memory and neuronal mitochondrial biogenesis.
Knockout or inhibition of USP30 protects dopaminergic neurons in a Parkinson's disease mouse model.
MCUb is an inducible regulator of calcium-dependent mitochondrial metabolism and substrate utilization in muscle.
Mitochondria-associated membrane collapse impairs TBK1-mediated proteostatic stress response in ALS.
Quantitative analysis of mitochondrial DNA in porcine-mouse cloned embryos.
3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex.
A drug-like molecule engages nuclear hormone receptor DAF-12/FXR to regulate mitophagy and extend lifespan.
Integration of FUNDC1-associated mitochondrial protein import and mitochondrial quality control contributes to TDP-43 degradation.
Decreased Pyruvate but Not Fatty Acid Driven Mitochondrial Respiration in Skeletal Muscle of Growth Restricted Fetal Sheep.
Mitigating aberrant Cdk5 activation alleviates mitochondrial defects and motor neuron disease symptoms in spinal muscular atrophy.
Single-cell, whole-embryo phenotyping of mammalian developmental disorders.
Protocol to study human mitochondrial ribosome using quantitative density gradient analysis by mass spectrometry and complexome profiling analysis.
Skeletal muscle TFEB signaling promotes central nervous system function and reduces neuroinflammation during aging and neurodegenerative disease.

medRxiv. 2023 Nov 05. pii: 2023.11.03.23297854. [Epub ahead of print]

Genetic analysis and multimodal imaging identify novel mtDNA 12148T>C leading to multisystem dysfunction with tissue-specific heteroplasmy.

Kinsley Belle, Alexander Kreymerman, Nirmal Vadgama, Marco H Ji, Sandeep Randhawa, Juan Caicedo, Megan Wong, Stephanie P Muscat, Casey A Gifford, Richard T Lee, Jamal Nasir, Jill L Young, Gregory Enns, Ioannis Karakikes, Mark Mercola, Edward H Wood.

Patients with mitochondrial disorders present with clinically diverse symptoms, largely driven by heterogeneous mutations in mitochondrial-encoded and nuclear-encoded mitochondrial genes. These mutations ultimately lead to complex biochemical disorders with a myriad of clinical manifestations, often accumulating during childhood on into adulthood, contributing to life-altering and sometimes fatal events. It is therefore important to diagnose and characterize the associated disorders for each mitochondrial mutation as early as possible since medical management might be able to improve the quality and longevity of life in mitochondrial disease patients. Here we identify a novel mitochondrial variant in a mitochondrial transfer RNA for histidine (mt-tRNA-his) [m.12148T>C], that is associated with the development of ocular, aural, neurological, renal, and muscular dysfunctions. We provide a detailed account of a family harboring this mutation, as well as the molecular underpinnings contributing to cellular and mitochondrial dysfunction. In conclusion, this investigation provides clinical, biochemical, and morphological evidence of the pathogenicity of m.12148T>C. We highlight the importance of multiple tissue testing and in vitro disease modeling in diagnosing mitochondrial disease.

DOI: https://doi.org/10.1101/2023.11.03.23297854
Biochim Biophys Acta Mol Cell Res. 2023 Jul 04. pii: S0167-4889(23)00101-5. [Epub ahead of print] 119529

Mitochondrial entry gate as regulatory hub.

Fabian den Brave, Nikolaus Pfanner, Thomas Becker.

  Mitochondria import 1000-1300 different precursor proteins from the cytosol. The main mitochondrial entry gate is formed by the translocase of the outer membrane (TOM complex). Molecular coupling and modification of TOM subunits control and modulate protein import in response to cellular signaling. The TOM complex functions as regulatory hub to integrate mitochondrial protein biogenesis and quality control into the cellular proteostasis network.

Keywords:  Mitochondria; Protein sorting; Proteostasis; Quality control; Stress response; TOM complex

DOI:  https://doi.org/10.1016/j.bbamcr.2023.119529
Orphanet J Rare Dis. 2023 Nov 16. 18(1): 355

Teamwork makes the dream work: functional collaborations between families, scientists, and healthcare providers to drive progress in the treatment of Leigh Syndrome.

Jesse D Moreira, Karan K Smith, Sophia Zilber, Kasey Woleben, Jessica L Fetterman.

  BACKGROUND: Leigh syndrome, an inherited neurometabolic disorder, is estimated to be the most common pediatric manifestation of mitochondrial disease. No treatments are currently available for Leigh syndrome due to many hurdles in drug discovery efforts. Leigh syndrome causal variants span over 110 different genes and likely lead to both unique and shared biochemical alterations, often resulting in overlapping phenotypic features. The mechanisms by which pathogenic variants in mitochondrial genes alter cellular phenotype to promote disease remain poorly understood. The rarity of cases of specific causal variants creates barriers to drug discovery and adequately sized clinical trials. BODY: To address the current challenges in drug discovery and facilitate communication between researchers, healthcare providers, patients, and families, the Boston University integrative Cardiovascular Metabolism and Pathophysiology (iCAMP) Lab and Cure Mito Foundation hosted a Leigh Syndrome Symposium. This symposium brought together expert scientists and providers to highlight the current successes in drug discovery and novel models of mitochondrial disease, and to connect patients to providers and scientists to foster community and communication.CONCLUSION: In this symposium review, we describe the research presented, the hurdles ahead, and strategies to better connect the Leigh syndrome community members to advance treatments for Leigh syndrome.

Keywords:  Community; Leigh syndrome; Mitochondria; Mitochondrial disease; Mitochondrial genetics; Patient registries; Symposium

DOI:  https://doi.org/10.1186/s13023-023-02871-7
Mov Disord. 2023 Nov 14.

Dystonia in ATP Synthase Defects: Reconnecting Mitochondria and Dopamine.

Elisabetta Indelicato, Sylvia Boesch, Niccolo' E Mencacci, Daniele Ghezzi, Holger Prokisch, Juliane Winkelmann, Michael Zech.



Keywords:  ATP synthase; dystonia; mitochondrial diseases; movement disorder

DOI:  https://doi.org/10.1002/mds.29657
Hum Mol Genet. 2023 Nov 17. pii: ddad196. [Epub ahead of print]

Mitochondrial aminoacyl-tRNA synthetases trigger unique compensatory mechanisms in neurons.

Oliver Podmanicky, Fei Gao, Benjamin Munro, Matthew J Jennings, Veronika Boczonadi, Denisa Hathazi, Juliane S Mueller, Rita Horvath.

  Mitochondrial aminoacyl-tRNA synthetase (mt-ARS) mutations cause severe, progressive, and often lethal diseases with highly heterogeneous and tissue-specific clinical manifestations. This study investigates the molecular mechanisms triggered by three different mt-ARS defects caused by biallelic mutations in AARS2, EARS2, and RARS2, using an in vitro model of human neuronal cells. We report distinct molecular mechanisms of mitochondrial dysfunction among the mt-ARS defects studied. Our findings highlight the ability of proliferating neuronal progenitor cells (iNPCs) to compensate for mitochondrial translation defects and maintain balanced levels of oxidative phosphorylation (OXPHOS) components, which becomes more challenging in mature neurons. Mutant iNPCs exhibit unique compensatory mechanisms, involving specific branches of the integrated stress response, which may be gene-specific or related to the severity of the mitochondrial translation defect. RNA sequencing revealed distinct transcriptomic profiles showing dysregulation of neuronal differentiation and protein translation. This study provides valuable insights into the tissue-specific compensatory mechanisms potentially underlying the phenotypes of patients with mt-ARS defects. Our novel in vitro model may more accurately represent the neurological presentation of patients and offer an improved platform for future investigations and therapeutic development.

Keywords:  aminoacyl-tRNA synthetase; mitochondrial biology; neurological disease; protein synthesis

DOI:  https://doi.org/10.1093/hmg/ddad196
Int J Mol Sci. 2023 Nov 03. pii: 15951. [Epub ahead of print]24(21):

Mitochondrial Complex I and β-Amyloid Peptide Interplay in Alzheimer's Disease: A Critical Review of New and Old Little Regarded Findings.

Anna Atlante, Daniela Valenti.

  Alzheimer's disease (AD) is the most common neurodegenerative disorder and the main cause of dementia which is characterized by a progressive cognitive decline that severely interferes with daily activities of personal life. At a pathological level, it is characterized by the accumulation of abnormal protein structures in the brain-β-amyloid (Aβ) plaques and Tau tangles-which interfere with communication between neurons and lead to their dysfunction and death. In recent years, research on AD has highlighted the critical involvement of mitochondria-the primary energy suppliers for our cells-in the onset and progression of the disease, since mitochondrial bioenergetic deficits precede the beginning of the disease and mitochondria are very sensitive to Aβ toxicity. On the other hand, if it is true that the accumulation of Aβ in the mitochondria leads to mitochondrial malfunctions, it is otherwise proven that mitochondrial dysfunction, through the generation of reactive oxygen species, causes an increase in Aβ production, by initiating a vicious cycle: there is therefore a bidirectional relationship between Aβ aggregation and mitochondrial dysfunction. Here, we focus on the latest news-but also on neglected evidence from the past-concerning the interplay between dysfunctional mitochondrial complex I, oxidative stress, and Aβ, in order to understand how their interplay is implicated in the pathogenesis of the disease.

Keywords:  Alzheimer’s disease; amyloid-β peptide; mitochondrial complex I; mitochondrial dysfunction; reactive oxygen species

DOI:  https://doi.org/10.3390/ijms242115951
Biochem J. 2023 Nov 15. 480(21): 1767-1789

Interactions of mitochondrial and skeletal muscle biology in mitochondrial myopathy.

Valeria Di Leo, Tiago M Bernardino Gomes, Amy E Vincent.

  Mitochondrial dysfunction in skeletal muscle fibres occurs with both healthy aging and a range of neuromuscular diseases. The impact of mitochondrial dysfunction in skeletal muscle and the way muscle fibres adapt to this dysfunction is important to understand disease mechanisms and to develop therapeutic interventions. Furthermore, interactions between mitochondrial dysfunction and skeletal muscle biology, in mitochondrial myopathy, likely have important implications for normal muscle function and physiology. In this review, we will try to give an overview of what is known to date about these interactions including metabolic remodelling, mitochondrial morphology, mitochondrial turnover, cellular processes and muscle cell structure and function. Each of these topics is at a different stage of understanding, with some being well researched and understood, and others in their infancy. Furthermore, some of what we know comes from disease models. Whilst some findings are confirmed in humans, where this is not yet the case, we must be cautious in interpreting findings in the context of human muscle and disease. Here, our goal is to discuss what is known, highlight what is unknown and give a perspective on the future direction of research in this area.

Keywords:  function; metabolism; mitochondria; mitochondrial dysfunction; structure

DOI:  https://doi.org/10.1042/BCJ20220233
Reprod Sci. 2023 Nov 13.

Nicotinamide Riboside, an NAD + Precursor, Protects Against Cardiac Mitochondrial Dysfunction in Fetal Guinea Pigs Exposed to Gestational Hypoxia.

Loren P Thompson, Hong Song, Jamie Hartnett.

  Gestational hypoxia inhibits mitochondrial function in the fetal heart and placenta contributing to fetal growth restriction and organ dysfunction. NAD + deficiency may contribute to a metabolic deficit by inhibiting oxidative phosphorylation and ATP synthesis. We tested the effects of nicotinamide riboside (NR), an NAD + precursor, as a treatment for reversing known mitochondrial dysfunction in hypoxic fetal hearts. Pregnant guinea pigs were housed in room air (normoxia) or placed in a hypoxic chamber (10.5%O2) for the last 14 days of gestation (term = 65 days) and administered either water or NR (1.6 mg/ml) in the drinking bottle. Fetuses were excised at term, and NAD + levels of maternal liver, placenta, and fetal heart ventricles were measured. Indices of mitochondrial function (complex IV activity, sirtuin 3 activity, protein acetylation) and ATP synthesis were measured in fetal heart ventricles of NR-treated/untreated normoxic and hypoxic animals. Hypoxia reduced fetal body weight in both sexes (p = 0.01), which was prevented by NR. Hypoxia had no effect on maternal liver NAD + levels but decreased (p = 0.04) placenta NAD + levels, the latter normalized with NR treatment. Hypoxia had no effect on fetal heart NAD + but decreased (p < 0.05) mitochondrial complex IV and sirtuin 3 activities, ATP content, and increased mitochondrial acetylation, which were all normalized with maternal NR. Hypoxia increased (p < 0.05) mitochondrial acetylation in female fetal hearts but had no effect on other mitochondrial indices. We conclude that maternal NR is an effective treatment for normalizing mitochondrial dysfunction and ATP synthesis in the hypoxic fetal heart.

Keywords:  Acetylation; Fetus; Heart; Hypoxia; Mitochondria; NAD; Nicotinamide; Placenta; Sirtuin

DOI:  https://doi.org/10.1007/s43032-023-01387-6
Mol Neurodegener. 2023 Nov 11. 18(1): 83

Mitochondrial dysfunction in Parkinson's disease - a key disease hallmark with therapeutic potential.

Martin T Henrich, Wolfgang H Oertel, D James Surmeier, Fanni F Geibl.

  Mitochondrial dysfunction is strongly implicated in the etiology of idiopathic and genetic Parkinson's disease (PD). However, strategies aimed at ameliorating mitochondrial dysfunction, including antioxidants, antidiabetic drugs, and iron chelators, have failed in disease-modification clinical trials. In this review, we summarize the cellular determinants of mitochondrial dysfunction, including impairment of electron transport chain complex 1, increased oxidative stress, disturbed mitochondrial quality control mechanisms, and cellular bioenergetic deficiency. In addition, we outline mitochondrial pathways to neurodegeneration in the current context of PD pathogenesis, and review past and current treatment strategies in an attempt to better understand why translational efforts thus far have been unsuccessful.

Keywords:  Antioxidants; Electron transport chain; MPTP; Mitochondria; Mitochondrial dysfunction; Neuroprotective therapies; Parkinson’s disease; Synuclein

DOI:  https://doi.org/10.1186/s13024-023-00676-7
Elife. 2023 11 14. pii: e85751. [Epub ahead of print]12

Astrocyte and L-lactate in the anterior cingulate cortex modulate schema memory and neuronal mitochondrial biogenesis.

Mastura Akter, Mahadi Hasan, Aruna Surendran Ramkrishnan, Zafar Iqbal, Xianlin Zheng, Zhongqi Fu, Zhuogui Lei, Anwarul Karim, Ying Li.

  Astrocyte-derived L-lactate was shown to confer beneficial effects on synaptic plasticity and cognitive functions. However, how astrocytic Gi signaling in the anterior cingulate cortex (ACC) modulates L-lactate levels and schema memory is not clear. Here, using chemogenetic approach and well-established behavioral paradigm, we demonstrate that astrocytic Gi pathway activation in the ACC causes significant impairments in flavor-place paired associates (PAs) learning, schema formation, and PA memory retrieval in rats. It also impairs new PA learning even if a prior associative schema exists. These impairments are mediated by decreased L-lactate in the ACC due to astrocytic Gi activation. Concurrent exogenous L-lactate administration bilaterally into the ACC rescues these impairments. Furthermore, we show that the impaired schema memory formation is associated with a decreased neuronal mitochondrial biogenesis caused by decreased L-lactate level in the ACC upon astrocytic Gi activation. Our study also reveals that L-lactate-mediated mitochondrial biogenesis is dependent on monocarboxylate transporter 2 (MCT2) and NMDA receptor activity - discovering a previously unrecognized signaling role of L-lactate. These findings expand our understanding of the role of astrocytes and L-lactate in the brain functions.

Keywords:  DREADD; anterior cingulate cortex; astrocyte; lactate; mitochondrial biogenesis; neuroscience; rat; schema

DOI:  https://doi.org/10.7554/eLife.85751
Nat Commun. 2023 Nov 13. 14(1): 7295

Knockout or inhibition of USP30 protects dopaminergic neurons in a Parkinson's disease mouse model.

Tracy-Shi Zhang Fang, Yu Sun, Andrew C Pearce, Simona Eleuteri, Mark Kemp, Christopher A Luckhurst, Rachel Williams, Ross Mills, Sarah Almond, Laura Burzynski, Nóra M Márkus, Christopher J Lelliott, Natasha A Karp, David J Adams, Stephen P Jackson, Jin-Feng Zhao, Ian G Ganley, Paul W Thompson, Gabriel Balmus, David K Simon.

Mutations in SNCA, the gene encoding α-synuclein (αSyn), cause familial Parkinson's disease (PD) and aberrant αSyn is a key pathological hallmark of idiopathic PD. This α-synucleinopathy leads to mitochondrial dysfunction, which may drive dopaminergic neurodegeneration. PARKIN and PINK1, mutated in autosomal recessive PD, regulate the preferential autophagic clearance of dysfunctional mitochondria ("mitophagy") by inducing ubiquitylation of mitochondrial proteins, a process counteracted by deubiquitylation via USP30. Here we show that loss of USP30 in Usp30 knockout mice protects against behavioral deficits and leads to increased mitophagy, decreased phospho-S129 αSyn, and attenuation of SN dopaminergic neuronal loss induced by αSyn. These observations were recapitulated with a potent, selective, brain-penetrant USP30 inhibitor, MTX115325, with good drug-like properties. These data strongly support further study of USP30 inhibition as a potential disease-modifying therapy for PD.

DOI: https://doi.org/10.1038/s41467-023-42876-1
Cell Rep. 2023 Nov 16. pii: S2211-1247(23)01477-8. [Epub ahead of print]42(11): 113465

MCUb is an inducible regulator of calcium-dependent mitochondrial metabolism and substrate utilization in muscle.

Jiuzhou Huo, Vikram Prasad, Kelly M Grimes, Davy Vanhoutte, N Scott Blair, Suh-Chin Lin, Michael J Bround, Donald M Bers, Jeffery D Molkentin.

  Mitochondria use the electron transport chain to generate high-energy phosphate from oxidative phosphorylation, a process also regulated by the mitochondrial Ca2+ uniporter (MCU) and Ca2+ levels. Here, we show that MCUb, an inhibitor of MCU-mediated Ca2+ influx, is induced by caloric restriction, where it increases mitochondrial fatty acid utilization. To mimic the fasted state with reduced mitochondrial Ca2+ influx, we generated genetically altered mice with skeletal muscle-specific MCUb expression that showed greater fatty acid usage, less fat accumulation, and lower body weight. In contrast, mice lacking Mcub in skeletal muscle showed increased pyruvate dehydrogenase activity, increased muscle malonyl coenzyme A (CoA), reduced fatty acid utilization, glucose intolerance, and increased adiposity. Mechanistically, pyruvate dehydrogenase kinase 4 (PDK4) overexpression in muscle of Mcub-deleted mice abolished altered substrate preference. Thus, MCUb is an inducible control point in regulating skeletal muscle mitochondrial Ca2+ levels and substrate utilization that impacts total metabolic balance.

Keywords:  CP: Metabolism; metabolism; mitochondria; obesity; skeletal muscle; substrate utilization

DOI:  https://doi.org/10.1016/j.celrep.2023.113465
Proc Natl Acad Sci U S A. 2023 Nov 21. 120(47): e2315347120

Mitochondria-associated membrane collapse impairs TBK1-mediated proteostatic stress response in ALS.

Seiji Watanabe, Yuri Murata, Yasuyoshi Oka, Kotaro Oiwa, Mai Horiuchi, Yohei Iguchi, Okiru Komine, Akira Sobue, Masahisa Katsuno, Tomoo Ogi, Koji Yamanaka.

  The organelle contact site of the endoplasmic reticulum and mitochondria, known as the mitochondria-associated membrane (MAM), is a multifunctional microdomain in cellular homeostasis. We previously reported that MAM disruption is a common pathological feature in amyotrophic lateral sclerosis (ALS); however, the precise role of MAM in ALS was uncovered. Here, we show that the MAM is essential for TANK-binding kinase 1 (TBK1) activation under proteostatic stress conditions. A MAM-specific E3 ubiquitin ligase, autocrine motility factor receptor, ubiquitinated nascent proteins to activate TBK1 at the MAM, which results in ribosomal protein degradation. MAM or TBK1 deficiency under proteostatic stress conditions resulted in increased cellular vulnerability in vitro and motor impairment in vivo. Thus, MAM disruption exacerbates proteostatic stress via TBK1 inactivation in ALS. Our study has revealed a proteostatic mechanism mediated by the MAM-TBK1 axis, highlighting the physiological importance of the organelle contact sites.

Keywords:  TANK-binding kinase 1; amyotrophic lateral sclerosis; mitochondria-associated membrane; sigma-1 receptor; stress granules

DOI:  https://doi.org/10.1073/pnas.2315347120
J Anim Sci Technol. 2023 Jul;65(4): 767-778

Quantitative analysis of mitochondrial DNA in porcine-mouse cloned embryos.

Hyeonyeong Shin, Soyeon Kim, Myungyoun Kim, Jaeeun Lee, Dongil Jin.

  The aim of the research is to identify that porcine oocytes can function as recipients for interspecies cloning and have the ability to develop to blastocysts. Furthermore each mitochondrial DNA (mtDNA) in interspecises cloned embryos was analyzed. For the study, mouse-porcine and porcine-porcine cloned embryos were produced with mouse fetal fibroblasts (MFF) and porcine fetal fibroblasts (PFF), respectively, introduced as donor cells into enucleated porcine oocytes. The developmental rate and cell numbers of blastocysts between intraspecies porcine-porcine and interspecies mouse-porcine cloned embryos were compared and real-time polymerase chain reaction (PCR) was performed for the estimate of mouse and porcine mtDNA copy number in mouse-porcine cloned embryos at different stages.There was no significant difference in the developmental rate or total blastocyst number between mouse-porcine cloned embryos and porcine-porcine cloned embryos (11.1 ± 0.9%, 25 ± 3.5 vs. 10.1 ± 1.2%, 24 ± 6.3). In mouse-porcine reconstructed embryos, the copy numbers of mouse somatic cell-derived mtDNA decreased between the 1-cell and blastocyst stages, whereas the copy number of porcine oocyte-derived mtDNA significantly increased during this period, as assessed by real-time PCR analysis. In our real-time PCR analysis, we improved the standard curve construction-based method to analyze the level of mtDNA between mouse donor cells and porcine oocytes using the copy number of mouse beta-actin DNA as a standard. Our findings suggest that mouse-porcine cloned embryos have the ability to develop to blastocysts in vitro and exhibit mitochondrial heteroplasmy from the 1-cell to blastocyst stages and the mouse-derived mitochondria can be gradually replaced with those of the porcine oocyte in the early developmental stages of mouse-porcine cloned embryos.

Keywords:  Interspecies somatic cell nuclear transfer; Mitochondria; Porcine-mouse cloned embryo

DOI:  https://doi.org/10.5187/jast.2023.e2
Aging Cell. 2023 Nov 13. e14009

3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex.

Zer Vue, Edgar Garza-Lopez, Kit Neikirk, Prasanna Katti, Larry Vang, Heather Beasley, Jianqiang Shao, Andrea G Marshall, Amber Crabtree, Alexandria C Murphy, Brenita C Jenkins, Praveena Prasad, Chantell Evans, Brittany Taylor, Margaret Mungai, Mason Killion, Dominique Stephens, Trace A Christensen, Jacob Lam, Benjamin Rodriguez, Mark A Phillips, Nastaran Daneshgar, Ho-Jin Koh, Alice Koh, Jamaine Davis, Nina Devine, Saleem Muhammod, Estevão Scudese, Kenneth Ryan Arnold, Valeria Vanessa Chavarin, Ryan Daniel Robinson, Moumita Chakraborty, Jennifer A Gaddy, Mariya T Sweetwyne, Genesis Wilson, Elma Zaganjor, James Kezos, Cristiana Dondi, Anilkumar K Reddy, Brian Glancy, Annet Kirabo, Anita M Quintana, Dao-Fu Dai, Karen Ocorr, Sandra A Murray, Steven M Damo, Vernat Exil, Blake Riggs, Bret C Mobley, Jose A Gomez, Melanie R McReynolds, Antentor Hinton.

  During aging, muscle gradually undergoes sarcopenia, the loss of function associated with loss of mass, strength, endurance, and oxidative capacity. However, the 3D structural alterations of mitochondria associated with aging in skeletal muscle and cardiac tissues are not well described. Although mitochondrial aging is associated with decreased mitochondrial capacity, the genes responsible for the morphological changes in mitochondria during aging are poorly characterized. We measured changes in mitochondrial morphology in aged murine gastrocnemius, soleus, and cardiac tissues using serial block-face scanning electron microscopy and 3D reconstructions. We also used reverse transcriptase-quantitative PCR, transmission electron microscopy quantification, Seahorse analysis, and metabolomics and lipidomics to measure changes in mitochondrial morphology and function after loss of mitochondria contact site and cristae organizing system (MICOS) complex genes, Chchd3, Chchd6, and Mitofilin. We identified significant changes in mitochondrial size in aged murine gastrocnemius, soleus, and cardiac tissues. We found that both age-related loss of the MICOS complex and knockouts of MICOS genes in mice altered mitochondrial morphology. Given the critical role of mitochondria in maintaining cellular metabolism, we characterized the metabolomes and lipidomes of young and aged mouse tissues, which showed profound alterations consistent with changes in membrane integrity, supporting our observations of age-related changes in muscle tissues. We found a relationship between changes in the MICOS complex and aging. Thus, it is important to understand the mechanisms that underlie the tissue-dependent 3D mitochondrial phenotypic changes that occur in aging and the evolutionary conservation of these mechanisms between Drosophila and mammals.

Keywords:   Drosophila ; 3D morphometry; MICOS; aging; mitochondria; mitochondrial disease; mitochondrion; reconstruction; reticulum; serial block-face SEM; skeletal muscle

DOI:  https://doi.org/10.1111/acel.14009
Nat Aging. 2023 Nov 13.

A drug-like molecule engages nuclear hormone receptor DAF-12/FXR to regulate mitophagy and extend lifespan.

Manish Chamoli, Anand Rane, Anna Foulger, Shankar J Chinta, Azar Asadi Shahmirzadi, Caroline Kumsta, Dhanya K Nambiar, David Hall, Angelina Holcom, Suzanne Angeli, Minna Schmidt, Sharon Pitteri, Malene Hansen, Gordon J Lithgow, Julie K Andersen.

Autophagy-lysosomal function is crucial for maintaining healthy lifespan and preventing age-related diseases. The transcription factor TFEB plays a key role in regulating this pathway. Decreased TFEB expression is associated with various age-related disorders, making it a promising therapeutic target. In this study, we screened a natural product library and discovered mitophagy-inducing coumarin (MIC), a benzocoumarin compound that enhances TFEB expression and lysosomal function. MIC robustly increases the lifespan of Caenorhabditis elegans in an HLH-30/TFEB-dependent and mitophagy-dependent manner involving DCT-1/BNIP3 while also preventing mitochondrial dysfunction in mammalian cells. Mechanistically, MIC acts by inhibiting ligand-induced activation of the nuclear hormone receptor DAF-12/FXR, which, in turn, induces mitophagy and extends lifespan. In conclusion, our study uncovers MIC as a promising drug-like molecule that enhances mitochondrial function and extends lifespan by targeting DAF-12/FXR. Furthermore, we discovered DAF-12/FXR as a previously unknown upstream regulator of HLH-30/TFEB and mitophagy.

DOI: https://doi.org/10.1038/s43587-023-00524-9
Cell Death Dis. 2023 11 11. 14(11): 735

Integration of FUNDC1-associated mitochondrial protein import and mitochondrial quality control contributes to TDP-43 degradation.

Jinfa Ma, Lei Liu, Lu Song, Jianghong Liu, Lingyao Yang, Quan Chen, Jane Y Wu, Li Zhu.

Though TDP-43 protein can be translocated into mitochondria and causes mitochondrial damage in TDP-43 proteinopathy, little is known about how TDP-43 is imported into mitochondria. In addition, whether mitochondrial damage is caused by mitochondrial mislocalization of TDP-43 or a side effect of mitochondria-mediated TDP-43 degradation remains to be investigated. Here, our bioinformatical analyses reveal that mitophagy receptor gene FUNDC1 is co-expressed with TDP-43, and both TDP-43 and FUNDC1 expression is correlated with genes associated with mitochondrial protein import pathway in brain samples of patients diagnosed with TDP-43 proteinopathy. FUNDC1 promotes mitochondrial translocation of TDP-43 possibly by promoting TDP-43-TOM70 and DNAJA2-TOM70 interactions, which is independent of the LC3 interacting region of FUNDC1 in cellular experiments. In the transgenic fly model of TDP-43 proteinopathy, overexpressing FUNDC1 enhances TDP-43 induced mitochondrial damage, whereas down-regulating FUNDC1 reverses TDP-43 induced mitochondrial damage. FUNDC1 regulates mitochondria-mediated TDP-43 degradation not only by regulating mitochondrial TDP-43 import, but also by increasing LONP1 level and by activating mitophagy, which plays important roles in cytosolic TDP-43 clearance. Together, this study not only uncovers the mechanism of mitochondrial TDP-43 import, but also unravels the active role played by mitochondria in regulating TDP-43 homeostasis.

DOI: https://doi.org/10.1038/s41419-023-06261-6
Int J Mol Sci. 2023 Oct 30. pii: 15760. [Epub ahead of print]24(21):

Decreased Pyruvate but Not Fatty Acid Driven Mitochondrial Respiration in Skeletal Muscle of Growth Restricted Fetal Sheep.

Weicheng Zhao, Amy C Kelly, Rosa I Luna-Ramirez, Christopher A Bidwell, Miranda J Anderson, Sean W Limesand.

  Fetuses with intrauterine growth restriction (FGR) have impaired oxidative and energy metabolism, with persistent consequences on their postnatal development. In this study, we test the hypothesis that FGR skeletal muscle has lower mitochondrial respiration rate and alters the transcriptomic profiles associated with energy metabolism in an ovine model. At late gestation, mitochondrial oxygen consumption rates (OCRs) and transcriptome profiles were evaluated in the skeletal muscle collected from FGR and control fetuses. The ex vivo mitochondrial OCRs were reduced (p < 0.01) in permeabilized FGR soleus muscle compared to the control muscle but only with pyruvate as the metabolic substrate. Mitochondrial OCRs were similar between the FGR and control groups for palmitoyl-carnitine (fatty acid-driven) or pyruvate plus palmitoyl-carnitine metabolic substrates. A total of 2284 genes were differentially expressed in the semitendinosus muscle from growth restricted fetuses (false discovery rate (FDR) ≤ 0.05). A pathway analysis showed that the upregulated genes (FGR compared to control) were overrepresented for autophagy, HIF-1, AMPK, and FOXO signaling pathways (all with an FDR < 0.05). In addition, the expression of genes modulating pyruvate's entry into the TCA cycle was downregulated, whereas the genes encoding key fatty acid oxidation enzymes were upregulated in the FGR muscle. These findings show that FGR skeletal muscle had attenuated mitochondrial pyruvate oxidation, possibly associated with the inability of pyruvate to enter into the TCA cycle, and that fatty acid oxidation might compensate for the attenuated energy metabolism. The current study provided phenotypic and molecular evidence for adaptive deficiencies in FGR skeletal muscle.

Keywords:  developmental programming; fetus; intrauterine growth restriction; mitochondria; skeletal muscle

DOI:  https://doi.org/10.3390/ijms242115760
Proc Natl Acad Sci U S A. 2023 Nov 21. 120(47): e2300308120

Mitigating aberrant Cdk5 activation alleviates mitochondrial defects and motor neuron disease symptoms in spinal muscular atrophy.

Nimrod Miller, Zhaofa Xu, Katharina A Quinlan, Amy Ji, Jered V McGivern, Zhihua Feng, Han Shi, Chien-Ping Ko, Li-Huei Tsai, Charles J Heckman, Allison D Ebert, Yongchao C Ma.

  Spinal muscular atrophy (SMA), the top genetic cause of infant mortality, is characterized by motor neuron degeneration. Mechanisms underlying SMA pathogenesis remain largely unknown. Here, we report that the activity of cyclin-dependent kinase 5 (Cdk5) and the conversion of its activating subunit p35 to the more potent activator p25 are significantly up-regulated in mouse models and human induced pluripotent stem cell (iPSC) models of SMA. The increase of Cdk5 activity occurs before the onset of SMA phenotypes, suggesting that it may be an initiator of the disease. Importantly, aberrant Cdk5 activation causes mitochondrial defects and motor neuron degeneration, as the genetic knockout of p35 in an SMA mouse model rescues mitochondrial transport and fragmentation defects, and alleviates SMA phenotypes including motor neuron hyperexcitability, loss of excitatory synapses, neuromuscular junction denervation, and motor neuron degeneration. Inhibition of the Cdk5 signaling pathway reduces the degeneration of motor neurons derived from SMA mice and human SMA iPSCs. Altogether, our studies reveal a critical role for the aberrant activation of Cdk5 in SMA pathogenesis and suggest a potential target for therapeutic intervention.

Keywords:  Cdk5; mitochondria; motor neuron; neurodegeneration; spinal muscular atrophy

DOI:  https://doi.org/10.1073/pnas.2300308120
Nature. 2023 Nov 15.

Single-cell, whole-embryo phenotyping of mammalian developmental disorders.

Xingfan Huang, Jana Henck, Chengxiang Qiu, Varun K A Sreenivasan, Saranya Balachandran, Oana V Amarie, Martin Hrabě de Angelis, Rose Yinghan Behncke, Wing-Lee Chan, Alexandra Despang, Diane E Dickel, Madeleine Duran, Annette Feuchtinger, Helmut Fuchs, Valerie Gailus-Durner, Natja Haag, Rene Hägerling, Nils Hansmeier, Friederike Hennig, Cooper Marshall, Sudha Rajderkar, Alessa Ringel, Michael Robson, Lauren M Saunders, Patricia da Silva-Buttkus, Nadine Spielmann, Sanjay R Srivatsan, Sascha Ulferts, Lars Wittler, Yiwen Zhu, Vera M Kalscheuer, Daniel M Ibrahim, Ingo Kurth, Uwe Kornak, Axel Visel, Len A Pennacchio, David R Beier, Cole Trapnell, Junyue Cao, Jay Shendure, Malte Spielmann.

Mouse models are a critical tool for studying human diseases, particularly developmental disorders1. However, conventional approaches for phenotyping may fail to detect subtle defects throughout the developing mouse2. Here we set out to establish single-cell RNA sequencing of the whole embryo as a scalable platform for the systematic phenotyping of mouse genetic models. We applied combinatorial indexing-based single-cell RNA sequencing3 to profile 101 embryos of 22 mutant and 4 wild-type genotypes at embryonic day 13.5, altogether profiling more than 1.6 million nuclei. The 22 mutants represent a range of anticipated phenotypic severities, from established multisystem disorders to deletions of individual regulatory regions4,5. We developed and applied several analytical frameworks for detecting differences in composition and/or gene expression across 52 cell types or trajectories. Some mutants exhibit changes in dozens of trajectories whereas others exhibit changes in only a few cell types. We also identify differences between widely used wild-type strains, compare phenotyping of gain- versus loss-of-function mutants and characterize deletions of topological associating domain boundaries. Notably, some changes are shared among mutants, suggesting that developmental pleiotropy might be 'decomposable' through further scaling of this approach. Overall, our findings show how single-cell profiling of whole embryos can enable the systematic molecular and cellular phenotypic characterization of mouse mutants with unprecedented breadth and resolution.

DOI: https://doi.org/10.1038/s41586-023-06548-w
STAR Protoc. 2023 Nov 15. pii: S2666-1667(23)00572-5. [Epub ahead of print]4(4): 102605

Protocol to study human mitochondrial ribosome using quantitative density gradient analysis by mass spectrometry and complexome profiling analysis.

Petra Páleníková, Michal Minczuk, Pedro Rebelo-Guiomar.

  Dynamic macromolecular complexes containing a large number of components are often difficult to study using conventional approaches, such as immunoblotting. Here, we present a protocol for the analysis of macromolecular complexes in near-native conditions using a flexible setup to suit different cellular targets. We describe analysis of human mitochondrial ribosome, composed of 82 proteins, in a standardized way using density gradient ultracentrifugation coupled to quantitative mass spectrometry and subsequent analysis of the generated data (ComPrAn). For complete details on the use and execution of this protocol, please refer to Páleníková et al.1 and Rebelo-Guiomar et al.2.

Keywords:  Bioinformatics; Protein Expression and Purification; Proteomics

DOI:  https://doi.org/10.1016/j.xpro.2023.102605
Cell Rep. 2023 Nov 10. pii: S2211-1247(23)01448-1. [Epub ahead of print]42(11): 113436

Skeletal muscle TFEB signaling promotes central nervous system function and reduces neuroinflammation during aging and neurodegenerative disease.

Ian Matthews, Allison Birnbaum, Anastasia Gromova, Amy W Huang, Kailin Liu, Eleanor A Liu, Kristen Coutinho, Megan McGraw, Dalton C Patterson, Macy T Banks, Amber C Nobles, Nhat Nguyen, Gennifer E Merrihew, Lu Wang, Eric Baeuerle, Elizabeth Fernandez, Nicolas Musi, Michael J MacCoss, Helen C Miranda, Albert R La Spada, Constanza J Cortes.

  Skeletal muscle has recently arisen as a regulator of central nervous system (CNS) function and aging, secreting bioactive molecules known as myokines with metabolism-modifying functions in targeted tissues, including the CNS. Here, we report the generation of a transgenic mouse with enhanced skeletal muscle lysosomal and mitochondrial function via targeted overexpression of transcription factor E-B (TFEB). We discovered that the resulting geroprotective effects in skeletal muscle reduce neuroinflammation and the accumulation of tau-associated pathological hallmarks in a mouse model of tauopathy. Muscle-specific TFEB overexpression significantly ameliorates proteotoxicity, reduces neuroinflammation, and promotes transcriptional remodeling of the aged CNS, preserving cognition and memory in aged mice. Our results implicate the maintenance of skeletal muscle function throughout aging in direct regulation of CNS health and disease and suggest that skeletal muscle originating factors may act as therapeutic targets against age-associated neurodegenerative disorders.

Keywords:  CP: Neuroscience; TFEB; aging; brain; exercise; muscle; neurodegeneration; tau

DOI:  https://doi.org/10.1016/j.celrep.2023.113436