bims-mitmed 2024-10-13 papers

bims-mitmed

Biomed News

on Mitochondrial medicine

Issue of 2024‒10‒13
nineteen papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico

DELE1 maintains muscle proteostasis to promote growth and survival in mitochondrial myopathy.
A platform to map the mind-mitochondria connection and the hallmarks of psychobiology: the MiSBIE study.
Disease models of Leigh syndrome: From yeast to organoids.
Mitochondrial Extracellular Vesicles (mitoEVs): Emerging mediators of cell-to-cell communication in health, aging and age-related diseases.
Compensatory activity of the PC-ME1 metabolic axis underlies differential sensitivity to mitochondrial complex I inhibition.
Loss of mitochondrial Ca2+ response and CaMKII/ERK activation by LRRK2R1441G mutation correlate with impaired depolarization-induced mitophagy.
Coordinating BNIP3/NIX-mediated mitophagy in space and time.
A germline-to-soma signal triggers an age-related decline of mitochondrial stress response.
Drp1 acetylation mediated by CDK5-AMPK-GCN5L1 axis promotes cerebral ischemic injury via facilitating mitochondrial fission.
Nuclear compensatory evolution driven by mito-nuclear incompatibilities.
NAD+-boosting agent nicotinamide mononucleotide potently improves mitochondria stress response in Alzheimer's disease via ATF4-dependent mitochondrial UPR.
Inhibition of the FOXO1-ROCK1 axis mitigates cardiomyocyte injury under chronic hypoxia in Tetralogy of Fallot by maintaining mitochondrial quality control.
The brain-body energy conservation model of aging.
NAD+ depletion is central to placental dysfunction in an inflammatory subclass of preeclampsia.
Spatial and functional separation of mTORC1 signalling in response to different amino acid sources.
Hyperactive mTORC1/4EBP1 signaling dysregulates proteostasis and accelerates cardiac aging.
Ribosomes hibernate on mitochondria during cellular stress.
Idiopathic Pulmonary Fibrosis Caused by Damaged Mitochondria and Imbalanced Protein Homeostasis in Alveolar Epithelial Type II Cell.
Neuronal exosomes transport an miRISC cargo to preserve stem cell integrity during energy stress.

EMBO J. 2024 Oct 08.

DELE1 maintains muscle proteostasis to promote growth and survival in mitochondrial myopathy.

Hsin-Pin Lin, Jennifer D Petersen, Alexandra J Gilsrud, Angelo Madruga, Theresa M D'Silva, Xiaoping Huang, Mario K Shammas, Nicholas P Randolph, Kory R Johnson, Yan Li, Drew R Jones, Michael E Pacold, Derek P Narendra.

  Mitochondrial dysfunction causes devastating disorders, including mitochondrial myopathy, but how muscle senses and adapts to mitochondrial dysfunction is not well understood. Here, we used diverse mouse models of mitochondrial myopathy to show that the signal for mitochondrial dysfunction originates within mitochondria. The mitochondrial proteins OMA1 and DELE1 sensed disruption of the inner mitochondrial membrane and, in response, activated the mitochondrial integrated stress response (mt-ISR) to increase the building blocks for protein synthesis. In the absence of the mt-ISR, protein synthesis in muscle was dysregulated causing protein misfolding, and mice with early-onset mitochondrial myopathy failed to grow and survive. The mt-ISR was similar following disruptions in mtDNA maintenance (Tfam knockout) and mitochondrial protein misfolding (CHCHD10 G58R and S59L knockin) but heterogenous among mitochondria-rich tissues, with broad gene expression changes observed in heart and skeletal muscle and limited changes observed in liver and brown adipose tissue. Taken together, our findings identify that the DELE1 mt-ISR mediates a similar response to diverse forms of mitochondrial stress and is critical for maintaining growth and survival in early-onset mitochondrial myopathy.

Keywords:  Mitochondria Unfolded Protein Response (mt-UPR); Mitochondrial Disorders; Mitohormesis; Mitonuclear Communication; Mitophagy

DOI:  https://doi.org/10.1038/s44318-024-00242-x
Trends Endocrinol Metab. 2024 Oct 09. pii: S1043-2760(24)00225-X. [Epub ahead of print]

A platform to map the mind-mitochondria connection and the hallmarks of psychobiology: the MiSBIE study.

MiSBIE Study Group

  Health emerges from coordinated psychobiological processes powered by mitochondrial energy transformation. But how do mitochondria regulate the multisystem responses that shape resilience and disease risk across the lifespan? The Mitochondrial Stress, Brain Imaging, and Epigenetics (MiSBIE) study was established to address this question and determine how mitochondria influence the interconnected neuroendocrine, immune, metabolic, cardiovascular, cognitive, and emotional systems among individuals spanning the spectrum of mitochondrial energy transformation capacity, including participants with rare mitochondrial DNA (mtDNA) lesions causing mitochondrial diseases (MitoDs). This interdisciplinary effort is expected to generate new insights into the pathophysiology of MitoDs, provide a foundation to develop novel biomarkers of human health, and integrate our fragmented knowledge of bioenergetic, brain-body, and mind-mitochondria processes relevant to medicine and public health.

Keywords:  allostasis; metabolism; mitochondrial disorders; mtDNA; psychobiology; stress

DOI:  https://doi.org/10.1016/j.tem.2024.08.006
J Inherit Metab Dis. 2024 Oct 09.

Disease models of Leigh syndrome: From yeast to organoids.

Marie-Thérèse Henke, Alessandro Prigione, Markus Schuelke.

  Leigh syndrome (LS) is a severe mitochondrial disease that results from mutations in the nuclear or mitochondrial DNA that impairs cellular respiration and ATP production. Mutations in more than 100 genes have been demonstrated to cause LS. The disease most commonly affects brain development and function, resulting in cognitive and motor impairment. The underlying pathogenesis is challenging to ascertain due to the diverse range of symptoms exhibited by affected individuals and the variability in prognosis. To understand the disease mechanisms of different LS-causing mutations and to find a suitable treatment, several different model systems have been developed over the last 30 years. This review summarizes the established disease models of LS and their key findings. Smaller organisms such as yeast have been used to study the biochemical properties of causative mutations. Drosophila melanogaster, Danio rerio, and Caenorhabditis elegans have been used to dissect the pathophysiology of the neurological and motor symptoms of LS. Mammalian models, including the widely used Ndufs4 knockout mouse model of complex I deficiency, have been used to study the developmental, cognitive, and motor functions associated with the disease. Finally, cellular models of LS range from immortalized cell lines and trans-mitochondrial cybrids to more recent model systems such as patient-derived induced pluripotent stem cells (iPSCs). In particular, iPSCs now allow studying the effects of LS mutations in specialized human cells, including neurons, cardiomyocytes, and even three-dimensional organoids. These latter models open the possibility of developing high-throughput drug screens and personalized treatments based on defined disease characteristics captured in the context of a defined cell type. By analyzing all these different model systems, this review aims to provide an overview of past and present means to elucidate the complex pathology of LS. We conclude that each approach is valid for answering specific research questions regarding LS, and that their complementary use could be instrumental in finding treatment solutions for this severe and currently untreatable disease.

Keywords:  Leigh syndrome; animal models; disease modeling; mitochondrial diseases; organoids; phenotyping; pluripotent stem cells

DOI:  https://doi.org/10.1002/jimd.12804
Ageing Res Rev. 2024 Oct 05. pii: S1568-1637(24)00340-4. [Epub ahead of print]101 102522

Mitochondrial Extracellular Vesicles (mitoEVs): Emerging mediators of cell-to-cell communication in health, aging and age-related diseases.

Roberto Iorio, Sabrina Petricca, Giovanna Di Emidio, Stefano Falone, Carla Tatone.

  Mitochondria are metabolic and signalling hubs that integrate a plethora of interconnected processes to maintain cell homeostasis. They are also dormant mediators of inflammation and cell death, and with aging damages affecting mitochondria gradually accumulate, resulting in the manifestation of age-associated disorders. In addition to coordinate multiple intracellular functions, mitochondria mediate intercellular and inter-organ cross talk in different physiological and stress conditions. To fulfil this task, mitochondrial signalling has evolved distinct and complex conventional and unconventional routes of horizontal/vertical mitochondrial transfer. In this regard, great interest has been focused on the ability of extracellular vesicles (EVs), such as exosomes and microvesicles, to carry selected mitochondrial cargoes to target cells, in response to internal and external cues. Over the past years, the field of mitochondrial EVs (mitoEVs) has grown exponentially, revealing unexpected heterogeneity of these structures associated with an ever-expanding mitochondrial function, though the full extent of the underlying mechanisms is far from being elucidated. Therefore, emerging subsets of EVs encompass exophers, migrasomes, mitophers, mitovesicles, and mitolysosomes that can act locally or over long-distances to restore mitochondrial homeostasis and cell functionality, or to amplify disease. This review provides a comprehensive overview of our current understanding of the biology and trafficking of MitoEVs in different physiological and pathological conditions. Additionally, a specific focus on the role of mitoEVs in aging and the onset and progression of different age-related diseases is discussed.

Keywords:  Age-related diseases; Bioenergetic remodelling; Cancer; Intercellular communication; Mitochondria-specific ectocytosis; Mitochondrial derived vesicles (MDVs); Mitochondrial extracellular vesicles (mitoEVs); Mitochondrial quality control (MQC)

DOI:  https://doi.org/10.1016/j.arr.2024.102522
Nat Commun. 2024 Oct 07. 15(1): 8682

Compensatory activity of the PC-ME1 metabolic axis underlies differential sensitivity to mitochondrial complex I inhibition.

Lucia Del Prado, Myriam Jaraíz-Rodríguez, Mauro Agro, Marcos Zamora-Dorta, Natalia Azpiazu, Manuel Calleja, Mario Lopez-Manzaneda, Jaime de Juan-Sanz, Alba Fernández-Rodrigo, José A Esteban, Mònica Girona, Albert Quintana, Eduardo Balsa.

Deficiencies in the electron transport chain (ETC) lead to mitochondrial diseases. While mutations are distributed across the organism, cell and tissue sensitivity to ETC disruption varies, and the molecular mechanisms underlying this variability remain poorly understood. Here we show that, upon ETC inhibition, a non-canonical tricarboxylic acid (TCA) cycle upregulates to maintain malate levels and concomitant production of NADPH. Our findings indicate that the adverse effects observed upon CI inhibition primarily stem from reduced NADPH levels, rather than ATP depletion. Furthermore, we find that Pyruvate carboxylase (PC) and ME1, the key mediators orchestrating this metabolic reprogramming, are selectively expressed in astrocytes compared to neurons and underlie their differential sensitivity to ETC inhibition. Augmenting ME1 levels in the brain alleviates neuroinflammation and corrects motor function and coordination in a preclinical mouse model of CI deficiency. These studies may explain why different brain cells vary in their sensitivity to ETC inhibition, which could impact mitochondrial disease management.

DOI: https://doi.org/10.1038/s41467-024-52968-1
Cell Commun Signal. 2024 Oct 10. 22(1): 485

Loss of mitochondrial Ca2+ response and CaMKII/ERK activation by LRRK2R1441G mutation correlate with impaired depolarization-induced mitophagy.

Eunice Eun-Seo Chang, Huifang Liu, Zoe Yuen-Kiu Choi, Yasine Malki, Steffi Xi-Yue Zhang, Shirley Yin-Yu Pang, Michelle Hiu-Wai Kung, David B Ramsden, Shu-Leong Ho, Philip Wing-Lok Ho.

  BACKGROUND: Stress-induced activation of ERK/Drp1 serves as a checkpoint in the segregation of damaged mitochondria for autophagic clearance (mitophagy). Elevated cytosolic calcium (Ca2+) activates ERK, which is pivotal to mitophagy initiation. This process is altered in Parkinson's disease (PD) with mutations in leucine-rich repeat kinase 2 (LRRK2), potentially contributing to mitochondrial dysfunction. Pathogenic LRRK2 mutation is linked to dysregulated cellular Ca2+ signaling but the mechanism involved remains unclear.METHODS: Mitochondrial damages lead to membrane depolarization. To investigate how LRRK2 mutation impairs cellular response to mitochondrial damages, mitochondrial depolarization was induced by artificial uncoupler (FCCP) in wild-type (WT) and LRRK2R1441G mutant knockin (KI) mouse embryonic fibroblasts (MEFs). The resultant cytosolic Ca2+ flux was assessed using live-cell Ca2+ imaging. The role of mitochondria in FCCP-induced cytosolic Ca2+ surge was confirmed by co-treatment with the mitochondrial sodium-calcium exchanger (NCLX) inhibitor. Cellular mitochondrial quality and function were evaluated by Seahorse™ real-time cell metabolic analysis, flow cytometry, and confocal imaging. Mitochondrial morphology was visualized using transmission electron microscopy (TEM). Activation (phosphorylation) of stress response pathways were assessed by immunoblotting.
RESULTS: Acute mitochondrial depolarization induced by FCCP resulted in an immediate cytosolic Ca2+ surge in WT MEFs, mediated predominantly via mitochondrial NCLX. However, such cytosolic Ca2+ response was abolished in LRRK2 KI MEFs. This loss of response in KI was associated with impaired activation of Ca2+/calmodulin-dependent kinase II (CaMKII) and MEK, the two upstream kinases of ERK. Treatment of LRRK2 inhibitor did not rescue this phenotype indicating that it was not caused by mutant LRRK2 kinase hyperactivity. KI MEFs exhibited swollen mitochondria with distorted cristae, depolarized mitochondrial membrane potential, and reduced mitochondrial Ca2+ store and mitochondrial calcium uniporter (MCU) expression. These mutant cells also exhibited lower cellular ATP: ADP ratio albeit higher basal respiration than WT, indicating compensation for mitochondrial dysfunction. These defects may hinder cellular stress response and signals to Drp1-mediated mitophagy, as evident by impaired mitochondrial clearance in the mutant.
CONCLUSIONS: Pathogenic LRRK2R1441G mutation abolished mitochondrial depolarization-induced Ca2+ response and impaired the basal mitochondrial clearance. Inherent defects from LRRK2 mutation have weakened the cellular ability to scavenge damaged mitochondria, which may further aggravate mitochondrial dysfunction and neurodegeneration in PD.

Keywords:  Calcium-dependent pathways; Cellular stress response; LRRK2 mutation; Mitochondrial dysfunction; Mitophagy; NCLX; Parkinson disease

DOI:  https://doi.org/10.1186/s12964-024-01844-y
Biochem Soc Trans. 2024 Oct 08. pii: BST20221364. [Epub ahead of print]

Coordinating BNIP3/NIX-mediated mitophagy in space and time.

Natalie M Niemi, Jonathan R Friedman.

  Mitochondria maintain organellar homeostasis through multiple quality control pathways, including the clearance of defective or unwanted mitochondria by selective autophagy. This removal of mitochondria, mitophagy, is controlled in large part by the outer mitochondrial membrane mitophagy receptors BNIP3 and NIX. While it has long been appreciated that BNIP3 and NIX mediate mitophagy by controlling the recruitment of autophagic machinery to the mitochondrial surface, the requirement for the carefully controlled spatiotemporal regulation of receptor-mediated mitophagy has only recently come to light. Several new factors that regulate the BNIP3/NIX-mediated mitophagy pathway have emerged, and various loss-of-function cell and animal models have revealed the dire consequences of their dysregulation. In this mini-review, we discuss new insights into the mechanisms and roles of the regulation of BNIP3 and NIX and highlight questions that have emerged from the identification of these new regulators.

Keywords:  autophagy; mitochondria; mitophagy

DOI:  https://doi.org/10.1042/BST20221364
Nat Commun. 2024 Oct 08. 15(1): 8723

A germline-to-soma signal triggers an age-related decline of mitochondrial stress response.

Liankui Zhou, Liu Jiang, Lan Li, Chengchuan Ma, Peixue Xia, Wanqiu Ding, Ying Liu.

The abilities of an organism to cope with extrinsic stresses and activate cellular stress responses decline during aging. The signals that modulate stress responses in aged animals remain to be elucidated. Here, we discover that feeding Caenorhabditis elegans (C. elegans) embryo lysates to adult worms enabled the animals to activate the mitochondrial unfolded protein response (UPRmt) upon mitochondrial perturbations. This discovery led to subsequent investigations that unveil a hedgehog-like signal that is transmitted from the germline to the soma in adults to inhibit UPRmt in somatic tissues. Additionally, we find that the levels of germline-expressed piRNAs in adult animals markedly decreased. This reduction in piRNA levels coincides with the production and secretion of a hedgehog-like signal and suppression of the UPRmt in somatic cells. Building upon existing research, our study further elucidates the intricate mechanisms of germline-to-soma signaling and its role in modulating the trade-offs between reproduction and somatic maintenance within the context of organismal aging.

DOI: https://doi.org/10.1038/s41467-024-53064-0
Mol Med. 2024 Oct 10. 30(1): 173

Drp1 acetylation mediated by CDK5-AMPK-GCN5L1 axis promotes cerebral ischemic injury via facilitating mitochondrial fission.

Jiejie Zhang, Shan Wang, Haitao Zhang, Xiaotong Yang, Xin Ren, Lei Wang, Yihan Yang, Yi Yang, Ya Wen.

  The aberrant acetylation of mitochondrial proteins is involved in the pathogenesis of multiple diseases including neurodegenerative diseases and cerebral ischemic injury. Previous studies have shown that depletion of mitochondrial NAD+, which is necessary for mitochondrial deacetylase activity, leads to decreased activity of mitochondrial deacetylase and thus causes hyperacetylation of mitochondrial proteins in ischemic brain tissues, which results in altered mitochondrial dynamics. However, it remains largely unknown about how mitochondrial dynamics-related protein Drp1 is acetylated in ischemic neuronal cells and brain tissues. Here, we showed that Drp1 and GCN5L1 expression was up-regulated in OGD-treated neuronal cells and ischemic brain tissues induced by dMCAO, accompanied by the increased mitochondrial fission, mtROS accumulation, and cell apoptosis. Further, we confirmed that ischemia/hypoxia promoted Drp1 interaction with GCN5L1 in neuronal cells and brain tissues. GCN5L1 knockdown attenuated, while its overexpression enhanced Drp1 acetylation and mitochondrial fission, indicating that GCN5L1 plays a crucial role in ischemia/hypoxia-induced mitochondrial fission by acetylating Drp1. Mechanistically, ischemia/hypoxia induced Drp1 phosphorylation by CDK5 upregulation-mediated activation of AMPK in neuronal cells, which in turn facilitated the interaction of GCN5L1 with Drp1, thus enhancing Drp1 acetylation and mitochondrial fission. Accordingly, inhibition of AMPK alleviated ischemia/hypoxia- induced Drp1 acetylation and mitochondrial fission and protected brain tissues from ischemic damage. These findings provide a novel insight into the functional roles of GCN5L1 in regulating Drp1 acetylation and identify a previously unrecognized CDK5-AMPK-GCN5L1 pathway that mediates the acetylation of Drp1 in ischemic brain tissues.

Keywords:  AMPK; Acetylation; CDK5; Drp1; GCN5L1; Ischemic stroke; Mitochondrial fission; Neuronal cells

DOI:  https://doi.org/10.1186/s10020-024-00948-y
Proc Natl Acad Sci U S A. 2024 Oct 15. 121(42): e2411672121

Nuclear compensatory evolution driven by mito-nuclear incompatibilities.

Debora Princepe, Marcus A M de Aguiar.

  Mitochondrial function relies on the coordinated expression of mitochondrial and nuclear genes, exhibiting remarkable resilience despite high mitochondrial mutation rates. The nuclear compensation mechanism suggests deleterious mitochondrial alleles drive compensatory nuclear mutations to preserve mito-nuclear compatibility. However, prevalence and factors conditioning this phenomenon remain debated due to its conflicting evidence. Here, we investigate how mito-nuclear incompatibilities impact substitutions in a model for species radiation. Mating success depends on genetic compatibility (nuclear DNA) and spatial proximity. Populations evolve from partially compatible mito-nuclear states, simulating mitochondrial DNA (mtDNA) introgression. Mutations do not confer advantages nor disadvantages, but individual fecundity declines with increasing incompatibilities, selecting for mito-nuclear coordination. We find that selection for mito-nuclear compatibility affects each genome differently based on their initial state. In compatible gene pairs, selection reduces substitutions in both genomes, while in incompatible nuclear genes, it consistently promotes compensation, facilitated by more mismatches. Interestingly, high mitochondrial mutation rates can reduce nuclear compensation by increasing mtDNA rectification, while substitutions in initially compatible nuclear gene are boosted. Finally, the presence of incompatibilities accelerates species radiation, but equilibrium richness is not directly correlated to substitution rates, revealing the complex dynamics triggered by mitochondrial introgression and mito-nuclear coevolution. Our study provides a perspective on nuclear compensation and the role of mito-nuclear incompatibilities in speciation by exploring extreme scenarios and identifying trends that empirical data alone cannot reveal. We emphasize the challenges in detecting these dynamics and propose analyzing specific genomic signatures could shed light on this evolutionary process.

Keywords:  mito-nuclear coevolution; mitochondrial mutation rate; mtDNA introgression; nuclear compensation

DOI:  https://doi.org/10.1073/pnas.2411672121
Cell Death Dis. 2024 Oct 11. 15(10): 744

NAD+-boosting agent nicotinamide mononucleotide potently improves mitochondria stress response in Alzheimer's disease via ATF4-dependent mitochondrial UPR.

Xi Xiong, Jialong Hou, Yi Zheng, Tao Jiang, Xuemiao Zhao, Jinlai Cai, Jiani Huang, Haijun He, Jiaxue Xu, Shuangjie Qian, Yao Lu, XinShi Wang, Wenwen Wang, Qianqian Ye, Shuoting Zhou, Mengjia Lian, Jian Xiao, Weihong Song, Chenglong Xie.

Extensive studies indicate that mitochondria dysfunction is pivotal for Alzheimer's disease (AD) pathogenesis; while cumulative evidence suggests that increased mitochondrial stress response (MSR) may mitigate neurodegeneration in AD, explorations to develop a MSR-targeted therapeutic strategy against AD are scarce. We combined cell biology, molecular biology, and pharmacological approaches to unravel a novel molecular pathway by which NAD+-boosting agent nicotinamide mononucleotide (NMN) regulates MSR in AD models. Here, we report dyshomeostasis plasma UPRmt-mitophagy-mediated MSR profiles in AD patient samples. NMN restores NAD+ metabolic profiles and improves MSR through the ATF4-dependent UPRmt pathway in AD-related cross-species models. At the organismal level, NAD+ repletion with NMN supplementation ameliorates mitochondrial proteotoxicity, decreases hippocampal synaptic disruption, decreases neuronal loss, and brain atrophy in mice model of AD. Remarkably, omics features of the hippocampus with NMN show that NMN leads to transcriptional changes of genes and proteins involved in MSR characteristics, principally within the astrocyte unit rather than microglia and oligodendrocytes. In brief, our work provides evidence that MSR has an active role in the pathogenesis of AD, as reducing mitochondrial homeostasis via atf4 depletion in AD mice aggravates the hallmarks of the disease; conversely, bolstering mitochondrial proteostasis by NMN decreases protein aggregation, restores memory performance, and delays disease progression, ultimately translating to increased healthspan.

DOI: https://doi.org/10.1038/s41419-024-07062-1
Life Sci. 2024 Oct 05. pii: S0024-3205(24)00674-X. [Epub ahead of print]357 123084

Inhibition of the FOXO1-ROCK1 axis mitigates cardiomyocyte injury under chronic hypoxia in Tetralogy of Fallot by maintaining mitochondrial quality control.

Chunnian Ren, Linyun Xi, Hongbo Li, Zhengxia Pan, Yonggang Li, Gang Wang, Jiangtao Dai, Dawei He, Shulei Fan, Quan Wang.

  INTRODUCTION: Persistent chronic myocardial hypoxia causes disturbances in mitochondrial quality control (MQC), ultimately leading to increased cardiomyocyte injury in patients with Tetralogy of Fallot (TOF). The present study aimed to identify the key effector molecules of cardiomyocyte injury under chronic hypoxia in TOF.METHODS: Clinical data from TOF patients were collected and whole transcriptome sequencing was performed on myocardial samples. Chronic hypoxia models were established in cardiac-specific knockout mice and cardiomyocytes, and a series of molecular experiments were used to determine the specific mechanisms involved.
RESULTS: Clinical cohort data and whole-transcriptome sequencing analysis of myocardial samples from TOF patients revealed that forkhead box O1 (FOXO1) plays an important role in chronic hypoxic cardiomyocyte injury. In a model of chronic hypoxia established in FOXO1 cardiac-specific knockout mice and FOXO1 gene-deficient cardiomyocytes, the AMPK signaling pathway regulates the expression of FOXO1, which in turn disrupts MQC by regulating the transcriptional activation of Rho-associated protein kinase 1 (ROCK1), and increasing the production of mitochondrial ROS, thereby exacerbating damage to cardiomyocytes. Excessive reactive oxygen species (ROS) production during MQC dysfunction further activates Cox7a2L to increase the assembly of the respiratory chain supercomplex. In addition, we found that miR-27b-3p partially binds to the 3' untranslated region of FOXO1 to exert a protective effect.
CONCLUSIONS: Maintenance of MQC under chronic hypoxia is achieved through a series of injury-protection mechanisms, suggesting that FOXO1 inhibition may be crucial for future mitigation of chronic hypoxic cardiomyocyte injury in TOF.

Keywords:  Chronic hypoxia; Cox7a2L; Forkhead box O1; Mitochondrial quality control; Tetralogy of Fallot

DOI:  https://doi.org/10.1016/j.lfs.2024.123084
Nat Aging. 2024 Oct 08.

The brain-body energy conservation model of aging.

Evan D Shaulson, Alan A Cohen, Martin Picard.

Aging involves seemingly paradoxical changes in energy metabolism. Molecular damage accumulation increases cellular energy expenditure, yet whole-body energy expenditure remains stable or decreases with age. We resolve this apparent contradiction by positioning the brain as the mediator and broker in the organismal energy economy. As somatic tissues accumulate damage over time, costly intracellular stress responses are activated, causing aging or senescent cells to secrete cytokines that convey increased cellular energy demand (hypermetabolism) to the brain. To conserve energy in the face of a shrinking energy budget, the brain deploys energy conservation responses, which suppress low-priority processes, producing fatigue, physical inactivity, blunted sensory capacities, immune alterations and endocrine 'deficits'. We term this cascade the brain-body energy conservation (BEC) model of aging. The BEC outlines (1) the energetic cost of cellular aging, (2) how brain perception of senescence-associated hypermetabolism may drive the phenotypic manifestations of aging and (3) energetic principles underlying the modifiability of aging trajectories by stressors and geroscience interventions.

DOI: https://doi.org/10.1038/s43587-024-00716-x
Life Sci Alliance. 2024 Dec;pii: e202302505. [Epub ahead of print]7(12):

NAD+ depletion is central to placental dysfunction in an inflammatory subclass of preeclampsia.

Fahmida Jahan, Goutham Vasam, Yusmaris Cariaco, Abolfazl Nik-Akhtar, Alex Green, Keir J Menzies, Shannon A Bainbridge.

Preeclampsia (PE) is a hypertensive disorder of pregnancy and a major cause of maternal/perinatal adverse health outcomes with no effective therapeutic strategies. Our group previously identified distinct subclasses of PE, one of which exhibits heightened placental inflammation (inflammation-driven PE). In non-pregnant populations, chronic inflammation is associated with decreased levels of cellular NAD+, a vitamin B3 derivative involved in energy metabolism and mitochondrial function. Interestingly, specifically in placentas from women with inflammation-driven PE, we observed the increased activity of NAD+-consuming enzymes, decreased NAD+ content, decreased expression of mitochondrial proteins, and increased oxidative damage. HTR8 human trophoblasts likewise demonstrated increased NAD+-dependent ADP-ribosyltransferase (ART) activity, coupled with decreased mitochondrial respiration rates and invasive function under inflammatory conditions. Such adverse effects were attenuated by boosting cellular NAD+ levels with nicotinamide riboside (NR). Finally, in an LPS-induced rat model of inflammation-driven PE, NR administration (200 mg/kg/day) from gestational days 1-19 prevented maternal hypertension and fetal/placental growth restriction, improved placental mitochondrial function, and reduced inflammation and oxidative stress. This study demonstrates the critical role of NAD+ in maintaining placental function and identifies NAD+ boosting as a promising preventative strategy for PE.

DOI: https://doi.org/10.26508/lsa.202302505
Nat Cell Biol. 2024 Oct 09.

Spatial and functional separation of mTORC1 signalling in response to different amino acid sources.

Stephanie A Fernandes, Danai-Dimitra Angelidaki, Julian Nüchel, Jiyoung Pan, Peter Gollwitzer, Yoav Elkis, Filippo Artoni, Sabine Wilhelm, Marija Kovacevic-Sarmiento, Constantinos Demetriades.

Amino acid (AA) availability is a robust determinant of cell growth through controlling mechanistic/mammalian target of rapamycin complex 1 (mTORC1) activity. According to the predominant model in the field, AA sufficiency drives the recruitment and activation of mTORC1 on the lysosomal surface by the heterodimeric Rag GTPases, from where it coordinates the majority of cellular processes. Importantly, however, the teleonomy of the proposed lysosomal regulation of mTORC1 and where mTORC1 acts on its effector proteins remain enigmatic. Here, by using multiple pharmacological and genetic means to perturb the lysosomal AA-sensing and protein recycling machineries, we describe the spatial separation of mTORC1 regulation and downstream functions in mammalian cells, with lysosomal and non-lysosomal mTORC1 phosphorylating distinct substrates in response to different AA sources. Moreover, we reveal that a fraction of mTOR localizes at lysosomes owing to basal lysosomal proteolysis that locally supplies new AAs, even in cells grown in the presence of extracellular nutrients, whereas cytoplasmic mTORC1 is regulated by exogenous AAs. Overall, our study substantially expands our knowledge about the topology of mTORC1 regulation by AAs and hints at the existence of distinct, Rag- and lysosome-independent mechanisms that control its activity at other subcellular locations. Given the importance of mTORC1 signalling and AA sensing for human ageing and disease, our findings will probably pave the way towards the identification of function-specific mTORC1 regulators and thus highlight more effective targets for drug discovery against conditions with dysregulated mTORC1 activity in the future.

DOI: https://doi.org/10.1038/s41556-024-01523-7
Geroscience. 2024 Oct 09.

Hyperactive mTORC1/4EBP1 signaling dysregulates proteostasis and accelerates cardiac aging.

Weronika Zarzycka, Kamil A Kobak, Catherine J King, Frederick F Peelor, Benjamin F Miller, Ying Ann Chiao.

  The mechanistic target of rapamycin complex 1 (mTORC1) has a major impact on aging by regulation of proteostasis. It is well established that mTORC1 signaling is hyperactivated with aging and age-related diseases. Previous studies have shown that partial inhibition of mTOR signaling by rapamycin reverses age-related deteriorations in cardiac function and structure in old mice. However, the downstream signaling pathways involved in this protection against cardiac aging have not been established. mTORC1 phosphorylates 4E-binding protein 1 (4EBP1) to promote the initiation of cap-dependent translation. The objective of this project is to examine the role of the mTORC1/4EBP1 axis in age-related cardiac dysfunction. We used a whole-body 4EBP1 KO mouse model, which mimics a hyperactive mTORC1/4EBP1/eIF4E axis, to investigate the effects of hyperactive mTORC1/4EBP1 axis in cardiac aging. Echocardiographic measurements of middle-aged 4EBP1 KO mice show impaired diastolic function and myocardial performance compared to age-matched WT mice and these parameters are at similar levels as old WT mice, suggesting that 4EBP1 KO mice experience accelerated cardiac aging. Old 4EBP1 KO mice show further decline in systolic and diastolic function compared to middle-aged counterparts and have worse systolic and diastolic function than age-matched WT mice. Gene expression levels of heart failure markers are not different between 4EBP1 KO and WT hearts. However, ribosomal biogenesis and protein ubiquitination are significantly increased in 4EBP1 KO hearts when compared to WT controls, suggesting dysregulated proteostasis in 4EBP1 KO hearts. Together, these results show that a hyperactive mTORC1/4EBP1 axis accelerates cardiac aging, potentially by dysregulating proteostasis.

Keywords:  4EBP1; Cardiac aging; Proteostasis; mTOR

DOI:  https://doi.org/10.1007/s11357-024-01368-w
Nat Commun. 2024 Oct 08. 15(1): 8666

Ribosomes hibernate on mitochondria during cellular stress.

Olivier Gemin, Maciej Gluc, Higor Rosa, Michael Purdy, Moritz Niemann, Yelena Peskova, Simone Mattei, Ahmad Jomaa.

Cell survival under nutrient-deprived conditions relies on cells' ability to adapt their organelles and rewire their metabolic pathways. In yeast, glucose depletion induces a stress response mediated by mitochondrial fragmentation and sequestration of cytosolic ribosomes on mitochondria. This cellular adaptation promotes survival under harsh environmental conditions; however, the underlying mechanism of this response remains unknown. Here, we demonstrate that upon glucose depletion protein synthesis is halted. Cryo-electron microscopy structure of the ribosomes show that they are devoid of both tRNA and mRNA, and a subset of the particles depicted a conformational change in rRNA H69 that could prevent tRNA binding. Our in situ structural analyses reveal that the hibernating ribosomes tether to fragmented mitochondria and establish eukaryotic-specific, higher-order storage structures by assembling into oligomeric arrays on the mitochondrial surface. Notably, we show that hibernating ribosomes exclusively bind to the outer mitochondrial membrane via the small ribosomal subunit during cellular stress. We identify the ribosomal protein Cpc2/RACK1 as the molecule mediating ribosomal tethering to mitochondria. This study unveils the molecular mechanism connecting mitochondrial stress with the shutdown of protein synthesis and broadens our understanding of cellular responses to nutrient scarcity and cell quiescence.

DOI: https://doi.org/10.1038/s41467-024-52911-4
Adv Biol (Weinh). 2024 Oct 10. e2400297

Idiopathic Pulmonary Fibrosis Caused by Damaged Mitochondria and Imbalanced Protein Homeostasis in Alveolar Epithelial Type II Cell.

Zhaoxiong Dong, Xiaolong Wang, Peiwen Wang, Mingjian Bai, Tianyu Wang, Yanhui Chu, Yan Qin.

  Alveolar epithelial Type II (ATII) cells are closely associated with early events of Idiopathic pulmonary fibrosis (IPF). Proteostasis dysfunction, endoplasmic reticulum (ER) stress, and mitochondrial dysfunction are known causes of decreased proliferation of alveolar epithelial cells and the secretion of pro-fibrotic mediators. Here, a large body of evidence is systematized and a cascade relationship between protein homeostasis, endoplasmic reticulum stress, mitochondrial dysfunction, and fibrotropic cytokines is proposed, providing a theoretical basis for ATII cells dysfunction as a possible pathophysiological initiating event for idiopathic pulmonary fibrosis.

Keywords:  ATII cell; IPF; Mitochondria; Proteostasis; mtDAMP

DOI:  https://doi.org/10.1002/adbi.202400297
Cell Rep. 2024 Oct 10. pii: S2211-1247(24)01202-6. [Epub ahead of print]43(10): 114851

Neuronal exosomes transport an miRISC cargo to preserve stem cell integrity during energy stress.

Christopher Wong, Elena M Jurczak, Richard Roy.

  During periods of nutrient scarcity, many animals undergo germline quiescence to preserve reproductive capacity, and neurons are often necessary for this adaptation. We show here that starvation causes the release of neuronal microRNA (miRNA)/Argonaute-loaded exosomes following AMP kinase-regulated trafficking changes within serotonergic neurons. This neuron-to-germline communication is independent of classical neurotransmission but instead relies on endosome-derived vesicles that carry a pro-quiescent small RNA cargo to modify germline gene expression. Using an miRNA activity sensor, we show that neuronally expressed miRNAs can extinguish the expression of germline mRNA targets in an exosome-dependent manner. Our findings demonstrate how an adaptive neuronal response can change gene expression at a distance by redirecting intracellular trafficking to release neuronal exosomes with specific miRNA cargoes capable of tracking to their appropriate destinations.

Keywords:  Argonautes; C. elegans; CP: Developmental biology; CP: Stem cell research; dauer stage; developmental biology; energetic stress; exosomes; miRNA sensor; miRNAs; serotonergic neurons

DOI:  https://doi.org/10.1016/j.celrep.2024.114851