bims-minimp 2021-11-07 papers

on Mitochondria, innate immunity, proteostasis

Issue of 2021–11–07
27 papers selected by
Hanna Salmonowicz, International Institute of Molecular Mechanisms and Machines of the Polish Academy of Sciences

The mitospecific domain of Mrp7 (bL27) supports mitochondrial translation during fermentation and is required for effective adaptation to respiration.
ND3 Cys39 in complex I is exposed during mitochondrial respiration.
Mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force.
Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis.
SARS-CoV-2 and EBV; the cost of a second mitochondrial "whammy"?
Mitochondrial respiration contributes to the interferon gamma response in antigen presenting cells.
Microbiota-derived acetate enables the metabolic fitness of the brain innate immune system during health and disease.
The integrity and assay performance of tissue mitochondrial DNA is considerably affected by choice of isolation method.
Mitochondrial-nuclear cross-talk in the human brain is modulated by cell type and perturbed in neurodegenerative disease.
The crosstalk between the caspase family and the cGAS‒STING signaling pathway.
Blood biomarkers for assessment of mitochondrial dysfunction: An expert review.
BAX inhibitor-1 regulates autophagy by controlling the IRE1α branch of the unfolded protein response.
Subcellular Specialization of Mitochondrial Form and Function in Skeletal Muscle Cells.
Mice with disrupted mitochondria used to model Parkinson's disease.
Mitochondrial Drp1 recognizes and induces excessive mPTP opening after hypoxia through BAX-PiC and LRRK2-HK2.
Intranasal administration of mitochondria improves spatial memory in olfactory bulbectomized mice.
Human IFIT3 Protein Induces Interferon Signaling and Inhibits Adenovirus Immediate Early Gene Expression.
Ubiquitination is essential for recovery of cellular activities after heat shock.
β2-adrenergic receptor regulates ER-mitochondria contacts.
NAD+, Senolytics, or Pyruvate for Healthy Aging?
Disruption of mitochondrial complex I induces progressive parkinsonism.
Paradoxical implication of BAX/BAK in the persistence of tetraploid cells.
Cytosolic detection of phagosomal bacteria - mechanisms underlying PAMP exodus from the phagosome into the cytosol.
Novel small molecule inhibition of IKK/NF-κB activation reduces markers of senescence and improves healthspan in mouse models of aging.
Caseinolytic protease P (CLPP) activated by ONC201 inhibits proliferation and promotes apoptosis in human epithelial ovarian cancer cells by inducing mitochondrial dysfunction.
Linking immune-mediated damage to neurodegeneration in multiple sclerosis: could network-based MRI help?
First mitochondrial genome wide association study with metabolomics.

Mol Biol Cell. 2021 Nov 03. mbcE21070370

The mitospecific domain of Mrp7 (bL27) supports mitochondrial translation during fermentation and is required for effective adaptation to respiration.

Jessica M Anderson, Jodie M Box, Rosemary A Stuart.

We demonstrate here that mitoribosomal protein synthesis, responsible for the synthesis of oxidative phosphorylation (OXPHOS) subunits encoded by mitochondrial genome, occurs at high levels during glycolysis fermentation and in a manner uncoupled from OXPHOS complex assembly regulation. Furthermore, we provide evidence that the mitospecific domain of Mrp7 (bL27), a mitoribosomal component, is required to maintain mitochondrial protein synthesis during fermentation, but is not required under respiration growth conditions. Maintaining mitotranslation under high glucose fermentation conditions also involves Mam33 (p32/gC1qR homolog), a binding partner of Mrp7's mitospecific domain, and together they confer a competitive advantage for a cell's ability to adapt to respiration-based metabolism when glucose becomes limiting. Furthermore, our findings support that the mitoribosome, and specifically the central protuberance (CP) region, may be differentially regulated and/or assembled, under the different metabolic conditions of fermentation and respiration. Based on our findings, we propose the purpose of mitotranslation is not limited to the assembly of OXPHOS complexes, but also plays a role in mitochondrial signaling critical for switching cellular metabolism from a glycolysis- to a respiratory-based state.

DOI: https://doi.org/10.1091/mbc.E21-07-0370
Cell Chem Biol. 2021 Nov 02. pii: S2451-9456(21)00444-X. [Epub ahead of print]

ND3 Cys39 in complex I is exposed during mitochondrial respiration.

Nils Burger, Andrew M James, John F Mulvey, Kurt Hoogewijs, Shujing Ding, Ian M Fearnley, Marta Loureiro-López, Abigail A I Norman, Sabine Arndt, Amin Mottahedin, Olga Sauchanka, Richard C Hartley, Thomas Krieg, Michael P Murphy.

  Mammalian complex I can adopt catalytically active (A-) or deactive (D-) states. A defining feature of the reversible transition between these two defined states is thought to be exposure of the ND3 subunit Cys39 residue in the D-state and its occlusion in the A-state. As the catalytic A/D transition is important in health and disease, we set out to quantify it by measuring Cys39 exposure using isotopic labeling and mass spectrometry, in parallel with complex I NADH/CoQ oxidoreductase activity. To our surprise, we found significant Cys39 exposure during NADH/CoQ oxidoreductase activity. Furthermore, this activity was unaffected if Cys39 alkylation occurred during complex I-linked respiration. In contrast, alkylation of catalytically inactive complex I irreversibly blocked the reactivation of NADH/CoQ oxidoreductase activity by NADH. Thus, Cys39 of ND3 is exposed in complex I during mitochondrial respiration, with significant implications for our understanding of the A/D transition and the mechanism of complex I.

Keywords:  Cys39; NADH:ubiquinone oxidoreductase; active/deactive transition; complex I; ischemia-reperfusion (IR) injury; mitochondria; redox regulation; reverse electron transport (RET)

DOI:  https://doi.org/10.1016/j.chembiol.2021.10.010
FASEB J. 2021 Dec;35(12): e22010

Mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force.

Zhengye Liu, Thomas Chaillou, Estela Santos Alves, Theresa Mader, Baptiste Jude, Duarte M S Ferreira, Heidi Hynynen, Arthur J Cheng, William O Jonsson, Gianluigi Pironti, Daniel C Andersson, Ellinor Kenne, Jorge L Ruas, Pasi Tavi, Johanna T Lanner.

  The hypoxia-inducible nuclear-encoded mitochondrial protein NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 4-like 2 (NDUFA4L2) has been demonstrated to decrease oxidative phosphorylation and production of reactive oxygen species in neonatal cardiomyocytes, brain tissue and hypoxic domains of cancer cells. Prolonged local hypoxia can negatively affect skeletal muscle size and tissue oxidative capacity. Although skeletal muscle is a mitochondrial rich, oxygen sensitive tissue, the role of NDUFA4L2 in skeletal muscle has not previously been investigated. Here we ectopically expressed NDUFA4L2 in mouse skeletal muscles using adenovirus-mediated expression and in vivo electroporation. Moreover, femoral artery ligation (FAL) was used as a model of peripheral vascular disease to induce hind limb ischemia and muscle damage. Ectopic NDUFA4L2 expression resulted in reduced mitochondrial respiration and reactive oxygen species followed by lowered AMP, ADP, ATP, and NAD+ levels without affecting the overall protein content of the mitochondrial electron transport chain. Furthermore, ectopically expressed NDUFA4L2 caused a ~20% reduction in muscle mass that resulted in weaker muscles. The loss of muscle mass was associated with increased gene expression of atrogenes MurF1 and Mul1, and apoptotic genes caspase 3 and Bax. Finally, we showed that NDUFA4L2 was induced by FAL and that the Ndufa4l2 mRNA expression correlated with the reduced capacity of the muscle to generate force after the ischemic insult. These results show, for the first time, that mitochondrial NDUFA4L2 is a novel regulator of skeletal muscle mass and force. Specifically, induced NDUFA4L2 reduces mitochondrial activity leading to lower levels of important intramuscular metabolites, including adenine nucleotides and NAD+ , which are hallmarks of mitochondrial dysfunction and hence shows that dysfunctional mitochondrial activity may drive muscle wasting.

Keywords:  NDUFA4L2; mitochondria; muscle mass; skeletal muscle

DOI:  https://doi.org/10.1096/fj.202100066R
Hum Mol Genet. 2021 Oct 28. pii: ddab314. [Epub ahead of print]

Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis.

Kah Ying Ng, Uwe Richter, Christopher B Jackson, Sara Seneca, Brendan J Battersby.

Pathogenic variants that disrupt human mitochondrial protein synthesis are associated with a clinically heterogenous group of diseases. Despite an impairment in oxidative phosphorylation being a common phenotype, the underlying molecular pathogenesis is more complex than simply a bioenergetic deficiency. Currently, we have limited mechanistic understanding on the scope by which a primary defect in mitochondrial protein synthesis contributes to organelle dysfunction. Since the proteins encoded in the mitochondrial genome are hydrophobic and need co-translational insertion into a lipid bilayer, responsive quality control mechanisms are required to resolve aberrations that arise with the synthesis of truncated and misfolded proteins. Here, we show that defects in the OXA1L-mediated insertion of MT-ATP6 nascent chains into the mitochondrial inner membrane are rapidly resolved by the AFG3L2 protease complex. Using pathogenic MT-ATP6 variants, we then reveal discrete steps in this quality control mechanism and the differential functional consequences to mitochondrial gene expression. The inherent ability of a given cell type to recognize and resolve impairments in mitochondrial protein synthesis may in part contribute at the molecular level to the wide clinical spectrum of these disorders.

DOI: https://doi.org/10.1093/hmg/ddab314
Immun Ageing. 2021 Oct 30. 18(1): 40

SARS-CoV-2 and EBV; the cost of a second mitochondrial "whammy"?

Alistair V W Nunn, Geoffrey W Guy, Stanley W Botchway, Jimmy D Bell.

  We, and others, have suggested that as the SARS-CoV-2 virus may modulate mitochondrial function, good mitochondrial reserve and health could be key in determining disease severity when exposed to this virus, as the immune system itself is dependent on this organelle's function. With the recent publication of a paper showing that long COVID could be associated with the reactivation of the Epstein Barr Virus, which is well known to manipulate mitochondria, we suggest that this could represent a second mitochondrial "whammy" that might support the mitochondrial hypothesis underlying COVID-19 severity and potentially, the occurrence of longer-term symptoms. As mitochondrial function declines with age, this could be an important factor in why older populations are more susceptible. Key factors which ensure optimal mitochondrial health are generally those that ensure healthy ageing, such as a good lifestyle with plenty of physical activity. The ability of viruses to manipulate mitochondrial function is well described, and it is now also thought that for evolutionary reasons, they also manipulate the ageing process. Given that slowing the ageing process could well be linked to better economic outcomes, the link between mitochondrial health, economics, COVID-19 and other viruses, as well as lifestyle, needs to be considered.

Keywords:  Ageing; Cost; Epstein Barr Virus; Immunosenescence; Inflammaging; Long COVID; Mitochondria; SARS-CoV-2

DOI:  https://doi.org/10.1186/s12979-021-00252-x
Elife. 2021 Nov 02. pii: e65109. [Epub ahead of print]10

Mitochondrial respiration contributes to the interferon gamma response in antigen presenting cells.

Michael C Kiritsy, Katelyn McCann, Daniel Mott, Stephen M Holland, Samuel M Behar, Christopher M Sassetti, Andrew J Olive.

  The immunological synapse allows antigen presenting cells (APC) to convey a wide array of functionally distinct signals to T cells, which ultimately shape the immune response. The relative effect of stimulatory and inhibitory signals is influenced by the activation state of the APC, which is determined by an interplay between signal transduction and metabolic pathways. While pathways downstream of toll-like receptors rely on glycolytic metabolism for the proper expression of inflammatory mediators, little is known about the metabolic dependencies of other critical signals such as interferon gamma (IFNg). Using CRISPR-Cas9, we performed a series of genome-wide knockout screens in murine macrophages to identify the regulators of IFNg-inducible T cell stimulatory or inhibitory proteins MHCII, CD40, and PD-L1. Our multi-screen approach enabled us to identify novel pathways that control these functionally distinct markers. Further integration of these screening data implicated complex I of the mitochondrial respiratory chain in the expression of all three markers, and by extension the IFNg signaling pathway. We report that the IFNg response requires mitochondrial respiration, and APCs are unable to activate T cells upon genetic or chemical inhibition of complex I. These findings suggest a dichotomous metabolic dependency between IFNg and toll-like receptor signaling, implicating mitochondrial function as a fulcrum of innate immunity.

Keywords:  human; immunology; inflammation; mouse

DOI:  https://doi.org/10.7554/eLife.65109
Cell Metab. 2021 Nov 02. pii: S1550-4131(21)00488-5. [Epub ahead of print]33(11): 2260-2276.e7

Microbiota-derived acetate enables the metabolic fitness of the brain innate immune system during health and disease.

Daniel Erny, Nikolaos Dokalis, Charlotte Mezö, Angela Castoldi, Omar Mossad, Ori Staszewski, Maximilian Frosch, Matteo Villa, Vidmante Fuchs, Arun Mayer, Jana Neuber, Janika Sosat, Stefan Tholen, Oliver Schilling, Andreas Vlachos, Thomas Blank, Mercedes Gomez de Agüero, Andrew J Macpherson, Edward J Pearce, Marco Prinz.

  As tissue macrophages of the central nervous system (CNS), microglia constitute the pivotal immune cells of this organ. Microglial features are strongly dependent on environmental cues such as commensal microbiota. Gut bacteria are known to continuously modulate microglia maturation and function by the production of short-chain fatty acids (SCFAs). However, the precise mechanism of this crosstalk is unknown. Here we determined that the immature phenotype of microglia from germ-free (GF) mice is epigenetically imprinted by H3K4me3 and H3K9ac on metabolic genes associated with substantial functional alterations including increased mitochondrial mass and specific respiratory chain dysfunctions. We identified acetate as the essential microbiome-derived SCFA driving microglia maturation and regulating the homeostatic metabolic state, and further showed that it is able to modulate microglial phagocytosis and disease progression during neurodegeneration. These findings indicate that acetate is an essential bacteria-derived molecule driving metabolic pathways and functions of microglia during health and perturbation.

Keywords:  Alzheimer’s disease; SCFA; acetate; germ-free; metabolism; microbiota; microglia; mitochondria; respiratory chain

DOI:  https://doi.org/10.1016/j.cmet.2021.10.010
Mitochondrion. 2021 Oct 30. pii: S1567-7249(21)00145-8. [Epub ahead of print]

The integrity and assay performance of tissue mitochondrial DNA is considerably affected by choice of isolation method.

Bruno Marçal Repolês, Choco Michael Gorospe, Phong Tran, Anna Karin Nilsson, Paulina H Wanrooij.

  The integrity of mitochondrial DNA (mtDNA) isolated from solid tissues is critical for analyses such as long-range PCR, but is typically assessed under conditions that fail to provide information on the individual mtDNA strands. Using denaturing gel electrophoresis, we show that commonly-used isolation procedures generate mtDNA containing several single-strand breaks per strand. Through systematic comparison of DNA isolation methods, we identify a procedure yielding the highest integrity of mtDNA that we demonstrate displays improved performance in downstream assays. Our results highlight the importance of isolation method choice, and serve as a resource to researchers requiring high-quality mtDNA from solid tissues.

Keywords:  DNA integrity; long-range PCR; mitochondrial DNA; mtDNA; nuclease activity

DOI:  https://doi.org/10.1016/j.mito.2021.10.005
Commun Biol. 2021 Nov 04. 4(1): 1262

Mitochondrial-nuclear cross-talk in the human brain is modulated by cell type and perturbed in neurodegenerative disease.

Aine Fairbrother-Browne, Aminah T Ali, Regina H Reynolds, Sonia Garcia-Ruiz, David Zhang, Zhongbo Chen, Mina Ryten, Alan Hodgkinson.

Mitochondrial dysfunction contributes to the pathogenesis of many neurodegenerative diseases. The mitochondrial genome encodes core respiratory chain proteins, but the vast majority of mitochondrial proteins are nuclear-encoded, making interactions between the two genomes vital for cell function. Here, we examine these relationships by comparing mitochondrial and nuclear gene expression across different regions of the human brain in healthy and disease cohorts. We find strong regional patterns that are modulated by cell-type and reflect functional specialisation. Nuclear genes causally implicated in sporadic Parkinson's and Alzheimer's disease (AD) show much stronger relationships with the mitochondrial genome than expected by chance, and mitochondrial-nuclear relationships are highly perturbed in AD cases, particularly through synaptic and lysosomal pathways, potentially implicating the regulation of energy balance and removal of dysfunction mitochondria in the etiology or progression of the disease. Finally, we present MitoNuclearCOEXPlorer, a tool to interrogate key mitochondria-nuclear relationships in multi-dimensional brain data.

DOI: https://doi.org/10.1038/s42003-021-02792-w
J Mol Cell Biol. 2021 Oct 27. pii: mjab071. [Epub ahead of print]

The crosstalk between the caspase family and the cGAS‒STING signaling pathway.

Yongai Xiong, Yan-Dong Tang, Chunfu Zheng.

  Cytosolic nucleic acid sensors are critical for sensing nucleic acids and initiating innate immunity during microbial infections and/or cell death. Over the last decade, several key studies have characterized the conserved mechanism of cyclic GMP‒AMP synthase (cGAS) and the downstream signaling adaptor stimulator of interferon genes (STING) initiating the innate immune signaling pathways. Aside from its primary involvement in microbial infections and inflammatory diseases, there is growing interest in the alternate roles of cGAS‒STING-mediated signaling. Caspase family members are powerful functional proteins that respond to cellular stress, including cell death signals, inflammation, and innate immunity. Recent studies have uncovered how the caspase family cooperates with the cGAS‒STING signaling pathway. Most caspase family members negatively regulate the cGAS‒STING signaling pathway. In turn, some caspase family members can also be modulated by cGAS‒STING. This review gives a detailed account of the interplay between the caspase family and the cGAS‒STING signaling pathway, which will shed light on developing novel therapeutics targeting the caspase family and cGAS‒STING signaling in antiviral innate immunity, cancer, inflammatory, and autoimmunity.

Keywords:  cGAS‒STING; caspases; innate immunity; signaling pathway

DOI:  https://doi.org/10.1093/jmcb/mjab071
Mitochondrion. 2021 Nov 02. pii: S1567-7249(21)00148-3. [Epub ahead of print]

Blood biomarkers for assessment of mitochondrial dysfunction: An expert review.

W H G Hubens, A Vallbona-Garcia, I F M de Coo, F H J van Tienen, C A B Webers, H J M Smeets, T G M F Gorgels.

  Although mitochondrial dysfunction is the known cause of primary mitochondrial disease, mitochondrial dysfunction is often difficult to measure and prove, especially when biopsies of affected tissue are not available. In order to identify blood biomarkers of mitochondrial dysfunction, we reviewed studies that measured blood biomarkers in genetically, clinically or biochemically confirmed primary mitochondrial disease patients. In this way, we were certain that there was an underlying mitochondrial dysfunction which could validate the biomarker. We found biomarkers of three classes: 1) functional markers measured in blood cells, 2) biochemical markers of serum/plasma and 3) DNA markers. While none of the reviewed single biomarkers may perfectly reveal all underlying mitochondrial dysfunction, combining biomarkers that cover different aspects of mitochondrial impairment probably is a good strategy. This biomarker panel may assist in the diagnosis of primary mitochondrial disease patients. As mitochondrial dysfunction may also play a significant role in the pathophysiology of multifactorial disorders such as Alzheimer's disease and glaucoma, the panel may serve to assess mitochondrial dysfunction in complex multifactorial diseases as well and enable selection of patients who could benefit from therapies targeting mitochondria.

Keywords:  Mitochondrial disorder; biomarkers; blood; mitochondrial dysfunction; multifactorial diseases

DOI:  https://doi.org/10.1016/j.mito.2021.10.008
EMBO J. 2021 Nov 02. 40(21): e109149

BAX inhibitor-1 regulates autophagy by controlling the IRE1α branch of the unfolded protein response.

Karen Castillo, Diego Rojas-Rivera, Fernanda Lisbona, Benjamín Caballero, Melissa Nassif, Felipe A Court, Sebastian Schuck, Consuelo Ibar, Peter Walter, Jimena Sierralta, Alvaro Glavic, Claudio Hetz.

DOI: https://doi.org/10.15252/embj.2021109149
Front Cell Dev Biol. 2021 ;9 757305

Subcellular Specialization of Mitochondrial Form and Function in Skeletal Muscle Cells.

T Bradley Willingham, Peter T Ajayi, Brian Glancy.

  Across different cell types and within single cells, mitochondria are heterogeneous in form and function. In skeletal muscle cells, morphologically and functionally distinct subpopulations of mitochondria have been identified, but the mechanisms by which the subcellular specialization of mitochondria contributes to energy homeostasis in working muscles remains unclear. Here, we discuss the current data regarding mitochondrial heterogeneity in skeletal muscle cells and highlight potential new lines of inquiry that have emerged due to advancements in cellular imaging technologies.

Keywords:  bioenergetics; intermyofibrillar mitochondria; mitochondrial connectivity; mitochondrial respiration; organelle interactions; paranuclear mitochondria; paravascular mitochondria; subsarcolemmal mitochondria

DOI:  https://doi.org/10.3389/fcell.2021.757305
Nature. 2021 Nov 03.

Mice with disrupted mitochondria used to model Parkinson's disease.

Zak Doric, Ken Nakamura.



Keywords:  Neurodegeneration; Parkinson's disease

DOI:  https://doi.org/10.1038/d41586-021-02955-z
Cell Death Dis. 2021 Nov 05. 12(11): 1050

Mitochondrial Drp1 recognizes and induces excessive mPTP opening after hypoxia through BAX-PiC and LRRK2-HK2.

Chenyang Duan, Lei Kuang, Chen Hong, Xinming Xiang, Jiancang Liu, Qinghui Li, Xiaoyong Peng, Yuanqun Zhou, Hongchen Wang, Liangming Liu, Tao Li.

Mitochondrial mass imbalance is one of the key causes of cardiovascular dysfunction after hypoxia. The activation of dynamin-related protein 1 (Drp1), as well as its mitochondrial translocation, play important roles in the changes of both mitochondrial morphology and mitochondrial functions after hypoxia. However, in addition to mediating mitochondrial fission, whether Drp1 has other regulatory roles in mitochondrial homeostasis after mitochondrial translocation is unknown. In this study, we performed a series of interaction and colocalization assays and found that, after mitochondrial translocation, Drp1 may promote the excessive opening of the mitochondrial permeability transition pore (mPTP) after hypoxia. Firstly, mitochondrial Drp1 maximumly recognizes mPTP channels by binding Bcl-2-associated X protein (BAX) and a phosphate carrier protein (PiC) in the mPTP. Then, leucine-rich repeat serine/threonine-protein kinase 2 (LRRK2) is recruited, whose kinase activity is inhibited by direct binding with mitochondrial Drp1 after hypoxia. Subsequently, the mPTP-related protein hexokinase 2 (HK2) is inactivated at Thr-473 and dissociates from the mitochondrial membrane, ultimately causing structural disruption and overopening of mPTP, which aggravates mitochondrial and cellular dysfunction after hypoxia. Thus, our study interprets the dual direct regulation of mitochondrial Drp1 on mitochondrial morphology and functions after hypoxia and proposes a new mitochondrial fission-independent mechanism for the role of Drp1 after its translocation in hypoxic injury.

DOI: https://doi.org/10.1038/s41419-021-04343-x
Exp Biol Med (Maywood). 2021 Nov 02. 15353702211056866

Intranasal administration of mitochondria improves spatial memory in olfactory bulbectomized mice.

Natalia V Bobkova, Daria Y Zhdanova, Natalia V Belosludtseva, Nikita V Penkov, Galina D Mironova.

  Here, we found that functionally active mitochondria isolated from the brain of NMRI donor mice and administrated intranasally to recipient mice penetrated the brain structures in a dose-dependent manner. The injected mitochondria labeled with the MitoTracker Red localized in different brain regions, including the neocortex and hippocampus, which are responsible for memory and affected by degeneration in patients with Alzheimer's disease. In behavioral experiments, intranasal microinjections of brain mitochondria of native NMRI mice improved spatial memory in the olfactory bulbectomized (OBX) mice with Alzheimer's type degeneration. Control OBX mice demonstrated loss of spatial memory tested in the Morris water maze. Immunocytochemical analysis revealed that allogeneic mitochondria colocalized with the markers of astrocytes and neurons in hippocampal cell culture. The results suggest that a non-invasive route intranasal administration of mitochondria may be a promising approach to the treatment of neurodegenerative diseases characterized, like Alzheimer's disease, by mitochondrial dysfunction.

Keywords:  Mitochondrial therapy; intranasal microinjections; mitochondrial dysfunction; neurodegenerative diseases; olfactory bulbectomized mice; spatial memory

DOI:  https://doi.org/10.1177/15353702211056866
mBio. 2021 Nov 02. e0282921

Human IFIT3 Protein Induces Interferon Signaling and Inhibits Adenovirus Immediate Early Gene Expression.

Aniska Chikhalya, Meike Dittmann, Yueting Zheng, Sook-Young Sohn, Charles M Rice, Patrick Hearing.

  Interferons (IFNs) are one of the hallmarks of host antiviral immunity. IFNs exert their antiviral activities through the induction of IFN-stimulated genes (ISGs) and antiviral proteins; however, the mechanism by which ISGs inhibit adenovirus (Ad) replication is not clearly understood. IFNs repress Ad immediate early gene expression and, consequently, all subsequent aspects of the viral life cycle. In this study, we found that IFN-induced protein with tetratricopeptide repeats 3, IFIT3 (ISG60), restricts Ad replication. IFIT3 repressed Ad E1A immediate early gene expression but did not alter Ad genome entry into the nucleus. Expression of IFIT3 led to phosphorylation of TBK1, IRF3, and STAT1; increased expression of IFNβ and ISGs; and required IFIT1 and IFIT2 partner proteins. During RNA virus infections, it is known that IFIT3 stimulates IFN production through mitochondrial antiviral signaling (MAVS)-mediated activation of TBK1 which synergizes activation of IRF3 and NF-κB. MAVS or TBK1 depletion in cells expressing IFIT3 blocked IFN signaling and reversed the Ad replication restriction. In addition, STING depletion phenocopied the effect suggesting that IFIT3 activates the STING pathway with cross talk to the MAVS pathway. This occurs independently of viral pathogen-associated molecular patterns (PAMPs). These results demonstrate that the expression of a single ISG, IFIT3, activates IFN signaling and establishes a cellular antiviral state independent of viral PAMPs. IMPORTANCE IFITs belong to a family of IFN-induced proteins that have broad antiviral functions, primarily studied with RNA viruses leaving a gap of knowledge on the effects of these proteins on DNA viruses. In this study we show that IFIT3, with its partner proteins IFIT1 and IFIT2, specifically restricts replication of human Ad, a DNA virus, by stimulating IFNβ production via the STING and MAVS pathways. This effect enhanced the IFN response and is independent of viral PAMPs. These results reveal a novel mechanism of activation of IFN signaling to enhance cellular antiviral responses.

Keywords:  Adenovirus; IFIT; IFIT3; IFN; MAVS; STING; adenovirus; interferon

DOI:  https://doi.org/10.1128/mBio.02829-21
Science. 2021 Jun 25. 372(6549): eabc3593

Ubiquitination is essential for recovery of cellular activities after heat shock.

Brian A Maxwell, Youngdae Gwon, Ashutosh Mishra, Junmin Peng, Haruko Nakamura, Ke Zhang, Hong Joo Kim, J Paul Taylor.

Tailoring stress responsesWhen faced with environmental stress, cells respond by shutting down cellular processes such as translation and nucleocytoplasmic transport. At the same time, cells preserve cytoplasmic messenger RNAs in structures known as stress granules, and many cellular proteins are modified by the covalent addition of ubiquitin, which has long been presumed to reflect degradation of stress-damaged proteins (see the Perspective by Dormann). Maxwell et al. show that cells generate distinct patterns of ubiquitination in response to different stressors. Rather than reflecting the degradation of stress-damaged proteins, this ubiquitination primes cells to dismantle stress granules and reinitiate normal cellular activities once the stress is removed. Gwon et al. show that persistent stress granules are degraded by autophagy, whereas short-lived granules undergo a process of disassembly that is autophagy independent. The mechanism of this disassembly depends on the initiating stress.Science, abc3593 and abf6548, this issue p. eabc3593 and p. eabf6548; see also abj2400, p. 1393.

DOI: https://doi.org/10.1126/science.abc3593
Sci Rep. 2021 Nov 02. 11(1): 21477

β2-adrenergic receptor regulates ER-mitochondria contacts.

Youngshin Lim, Il-Taeg Cho, Helmut G Rennke, Ginam Cho.

Interactions between the endoplasmic reticulum (ER) and mitochondria (Mito) are crucial for many cellular functions, and their interaction levels change dynamically depending on the cellular environment. Little is known about how the interactions between these organelles are regulated within the cell. Here we screened a compound library to identify chemical modulators for ER-Mito contacts in HEK293T cells. Multiple agonists of G-protein coupled receptors (GPCRs), beta-adrenergic receptors (β-ARs) in particular, scored in this screen. Analyses in multiple orthogonal assays validated that β2-AR activation promotes physical and functional interactions between the two organelles. Furthermore, we have elucidated potential downstream effectors mediating β2-AR-induced ER-Mito contacts. Together our study identifies β2-AR signaling as an important regulatory pathway for ER-Mito coupling and highlights the role of these contacts in responding to physiological demands or stresses.

DOI: https://doi.org/10.1038/s41598-021-00801-w
Nutr Metab Insights. 2021 ;14 11786388211053407

NAD+, Senolytics, or Pyruvate for Healthy Aging?

Fang-Qiang Zhou.

  In last decades, healthy aging has become one of research hotspots in life science. It is well known that the nicotinamide adenine dinucleotide oxidized form (NAD+) level in cells decreases with aging and aging-related diseases. Several years ago, one of NAD+ precursors was first demonstrated with its new role in DNA damage repairing in mice, restoring old mice to their physical state at young ones. The finding encourages extensive studies in animal models and patients. NAD+ and its precursors have been popular products in nutrition markets. Alternatively, it was also evidenced that clearance of cellular senescence by senolytics preserved multiorgan (kidney and heart) function and extended healthy lifespan in mice. Subsequent studies confirmed findings in elderly patients subjected with idiopathic pulmonary fibrosis. The senolytic therapy is now focused on various diseases in animal and clinical studies. However, pyruvate, as both a NAD+ substitute and a new senolytic, may be advantageous, on the equimolar basis, over current products above in preventing and treating diseases and aging. Pyruvate-enriched fluids, particularly pyruvate oral rehydration salt, may be a novel intervention for diseases and aging besides critical care. Albeit the direct evidence that benefits healthy aging is still limited to date, pyruvate, as both NAD+ provider and senolytic agent, warrants intensive research to compare NAD+ or senolytics for healthy aging, specifically on the equimolar basis, in effective blood levels. This review briefly discussed the recognition of healthy aging by comparing NAD+ and Senolytics with sodium pyruvate from the clinical point of view.

Keywords:  Healthy aging; NAD+; pyruvate; senescence; senolytics

DOI:  https://doi.org/10.1177/11786388211053407
Nature. 2021 Nov 03.

Disruption of mitochondrial complex I induces progressive parkinsonism.

Patricia González-Rodríguez, Enrico Zampese, Kristen A Stout, Jaime N Guzman, Ema Ilijic, Ben Yang, Tatiana Tkatch, Mihaela A Stavarache, David L Wokosin, Lin Gao, Michael G Kaplitt, José López-Barneo, Paul T Schumacker, D James Surmeier.

Loss of functional mitochondrial complex I (MCI) in the dopaminergic neurons of the substantia nigra is a hallmark of Parkinson's disease1. Yet, whether this change contributes to Parkinson's disease pathogenesis is unclear2. Here we used intersectional genetics to disrupt the function of MCI in mouse dopaminergic neurons. Disruption of MCI induced a Warburg-like shift in metabolism that enabled neuronal survival, but triggered a progressive loss of the dopaminergic phenotype that was first evident in nigrostriatal axons. This axonal deficit was accompanied by motor learning and fine motor deficits, but not by clear levodopa-responsive parkinsonism-which emerged only after the later loss of dopamine release in the substantia nigra. Thus, MCI dysfunction alone is sufficient to cause progressive, human-like parkinsonism in which the loss of nigral dopamine release makes a critical contribution to motor dysfunction, contrary to the current Parkinson's disease paradigm3,4.

DOI: https://doi.org/10.1038/s41586-021-04059-0
Cell Death Dis. 2021 Nov 01. 12(11): 1039

Paradoxical implication of BAX/BAK in the persistence of tetraploid cells.

Jiayin Deng, Lucía G Gutiérrez, Gautier Stoll, Omar Motiño, Isabelle Martins, Lucía Núñez, José Manuel Bravo-San Pedro, Juliette Humeau, Chloé Bordenave, Juncheng Pan, Hélène Fohrer-Ting, Sylvie Souquere, Gerard Pierron, Claudio Hetz, Carlos Villalobos, Guido Kroemer, Laura Senovilla.

Pro-apoptotic multi-domain proteins of the BCL2 family such as BAX and BAK are well known for their important role in the induction of mitochondrial outer membrane permeabilization (MOMP), which is the rate-limiting step of the intrinsic pathway of apoptosis. Human or mouse cells lacking both BAX and BAK (due to a double knockout, DKO) are notoriously resistant to MOMP and cell death induction. Here we report the surprising finding that BAX/BAK DKO cells proliferate less than control cells expressing both BAX and BAK (or either BAX or BAK) when they are driven into tetraploidy by transient exposure to the microtubule inhibitor nocodazole. Mechanistically, in contrast to their BAX/BAK-sufficient controls, tetraploid DKO cells activate a senescent program, as indicated by the overexpression of several cyclin-dependent kinase inhibitors and the activation of β-galactosidase. Moreover, DKO cells manifest alterations in ionomycin-mobilizable endoplasmic reticulum (ER) Ca2+ stores and store-operated Ca2+ entry that are affected by tetraploidization. DKO cells manifested reduced expression of endogenous sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (Serca2a) and transfection-enforced reintroduction of Serca2a, or reintroduction of an ER-targeted variant of BAK into DKO cells reestablished the same pattern of Ca2+ fluxes as observed in BAX/BAK-sufficient control cells. Serca2a reexpression and ER-targeted BAK also abolished the tetraploidy-induced senescence of DKO cells, placing ER Ca2+ fluxes downstream of the regulation of senescence by BAX/BAK. In conclusion, it appears that BAX/BAK prevent the induction of a tetraploidization-associated senescence program. Speculatively, this may contribute to the low incidence of cancers in BAX/BAK DKO mice and explain why human cancers rarely lose the expression of both BAX and BAK.

DOI: https://doi.org/10.1038/s41419-021-04321-3
Mol Microbiol. 2021 Nov 04.

Cytosolic detection of phagosomal bacteria - mechanisms underlying PAMP exodus from the phagosome into the cytosol.

Stephanie A Ragland, Jonathan C Kagan.

  The metazoan innate immune system senses bacterial infections by detecting highly conserved bacterial molecules, termed pathogen-associated molecular patterns (PAMPs). PAMPs are detected by a variety of host pattern recognition receptors (PRRs), whose function is to coordinate downstream immune responses. PRR activities are, in part, regulated by their subcellular localizations. Accordingly, professional phagocytes can detect extracellular bacteria and their PAMPs via plasma membrane-oriented PRRs. Conversely, phagocytosed bacteria and their PAMPs are detected by transmembrane PRRs oriented towards the phagosomal lumen. Even though PAMPs are unable to passively diffuse across membranes, phagocytosed bacteria are also detected by PRRs localized within the host cell cytosol. This phenomenon is explained upon phagocytosis of bacteria that specialize in phagosomal escape and cytosolic residence. Contrary to this cytosolic lifestyle, most bacteria studied to date spend their entire intracellular lifestyle contained within phagosomes, yet they also stimulate cytosolic PRRs. Herein, we will review our current understanding for how phagosomal PAMPs become accessible to cytosolic PRRs, as well as highlight knowledge gaps that should inspire future investigations.

Keywords:  STING; cGAS; caspase-11; caspase-4; caspase-5; cyclic dinucleotides; guanylate binding proteins; lipopolysaccharide; macrophage; pathogen-associated molecular pattern; pattern recognition receptor; phagosome

DOI:  https://doi.org/10.1111/mmi.14841
Aging Cell. 2021 Nov 03. e13486

Novel small molecule inhibition of IKK/NF-κB activation reduces markers of senescence and improves healthspan in mouse models of aging.

Lei Zhang, Jing Zhao, Xiaodong Mu, Sara J McGowan, Luise Angelini, Ryan D O'Kelly, Matthew J Yousefzadeh, Ayumi Sakamoto, Zaira Aversa, Nathan K LeBrasseur, Yousin Suh, Johnny Huard, Theodore M Kamenecka, Laura J Niedernhofer, Paul D Robbins.

  Constitutive NF-κB activation is associated with cellular senescence and stem cell dysfunction and rare variants in NF-κB family members are enriched in centenarians. We recently identified a novel small molecule (SR12343) that inhibits IKK/NF-κB activation by disrupting the association between IKKβ and NEMO. Here we investigated the therapeutic effects of SR12343 on senescence and aging in three different mouse models. SR12343 reduced senescence-associated beta-galactosidase (SA-β-gal) activity in oxidative stress-induced senescent mouse embryonic fibroblasts as well as in etoposide-induced senescent human IMR90 cells. Chronic administration of SR12343 to the Ercc1-/ ∆ and Zmpste24-/- mouse models of accelerated aging reduced markers of cellular senescence and SASP and improved multiple parameters of aging. SR12343 also reduced markers of senescence and increased muscle fiber size in 2-year-old WT mice. Taken together, these results demonstrate that IKK/NF-κB signaling pathway represents a promising target for reducing markers of cellular senescence, extending healthspan and treating age-related diseases.

Keywords:  NEMO; NF-κB; SR12343; aging; senescence

DOI:  https://doi.org/10.1111/acel.13486
Ann Transl Med. 2021 Sep;9(18): 1463

Caseinolytic protease P (CLPP) activated by ONC201 inhibits proliferation and promotes apoptosis in human epithelial ovarian cancer cells by inducing mitochondrial dysfunction.

Xinxin Kou, Hui Ding, Lei Li, Hongtu Chao.

   Background: Caseinolytic protease P (CLPP) is a mitochondrial specific protein which has been reported to be related to tumor cell apoptosis. This study aims to explore the roles of CLPP in human epithelial ovarian cancer (EOC).
Methods: We determined CLPP expression in paracancerous tissues and cancer tissues obtained from 20 EOC patients, and also in 4 EOC cell lines, and one normal ovarian cell line (IOSE-80). We knocked CLPP expression down in SK-OV-3 and A2780 cells and overexpressed it in SW626 and OVcar3 cells. The effect of CLPP expression on cell proliferation, mitochondrial membrane potential, and apoptosis was then assessed by flow cytometry assay. Furthermore, the effect of ONC201 (agonist of CLPP) on the EOC cell lines was also investigated.
Results: The CLPP expression was markedly down-regulated in EOC cancer tissues, and the Kaplan-Meier Plotter database revealed its low expression was linked to poor prognosis in EOC patients. Low expression of CLPP up-regulated the expression of NADH: ubiquinone oxidoreductase subunit A12 (NDUFA12), succinate dehydrogenase complex flavoprotein subunit A (SDHA), and succinate dehydrogenase complex iron sulfur subunit B (SDHB), which are key members of the mitochondrial respiratory chain, and these up-regulated proteins further led to the increase of mitochondrial membrane potential, cell proliferation promotion and neoplasm metastasis. Conversely, while overexpression of CLPP led to the opposite results, including inducing the decrease of mitochondrial membrane potential and apoptosis. In addition, stimulation with ONC201 enhanced the function of CLPP in SW626 and OVcar3 cells, and silencing of CLPP could neutralize the effect of ONC201.
Conclusions: Our findings suggest that CLPP mediated mitochondrial dysfunction inhibits the proliferation and migration of EOC cells.

Keywords:  Epithelial ovarian cancer (EOC); caseinolytic protease P (CLPP); cell apoptosis; mitochondria

DOI:  https://doi.org/10.21037/atm-21-4321
Brain Commun. 2021 ;3(4): fcab237

Linking immune-mediated damage to neurodegeneration in multiple sclerosis: could network-based MRI help?

Sergiu Groppa, Gabriel Gonzalez-Escamilla, Arman Eshaghi, Sven G Meuth, Olga Ciccarelli.

  Inflammatory demyelination characterizes the initial stages of multiple sclerosis, while progressive axonal and neuronal loss are coexisting and significantly contribute to the long-term physical and cognitive impairment. There is an unmet need for a conceptual shift from a dualistic view of multiple sclerosis pathology, involving either inflammatory demyelination or neurodegeneration, to integrative dynamic models of brain reorganization, where, glia-neuron interactions, synaptic alterations and grey matter pathology are longitudinally envisaged at the whole-brain level. Functional and structural MRI can delineate network hallmarks for relapses, remissions or disease progression, which can be linked to the pathophysiology behind inflammatory attacks, repair and neurodegeneration. Here, we aim to unify recent findings of grey matter circuits dynamics in multiple sclerosis within the framework of molecular and pathophysiological hallmarks combined with disease-related network reorganization, while highlighting advances from animal models (in vivo and ex vivo) and human clinical data (imaging and histological). We propose that MRI-based brain networks characterization is essential for better delineating ongoing pathology and elaboration of particular mechanisms that may serve for accurate modelling and prediction of disease courses throughout disease stages.

Keywords:  brain networks; demyelination; multiple sclerosis; neurodegeneration; neuroinflammation

DOI:  https://doi.org/10.1093/braincomms/fcab237
Hum Mol Genet. 2021 Oct 27. pii: ddab312. [Epub ahead of print]

First mitochondrial genome wide association study with metabolomics.

Brahim Aboulmaouahib, Gabi Kastenmüller, Karsten Suhre, Sebastian Zöllner, Hansi Weissensteiner, Christian Gieger, Rui Wang-Sattler, Peter Lichtner, Konstantin Strauch, Antònia Flaquer.

INTRODUCTION: In the era of personalized medicine with more and more patient specific targeted therapies being used, we need reliable, dynamic, faster, and sensitive biomarkers both to track the causes of disease and to develop and evolve therapies during the course of treatment. Metabolomics recently has shown substantial evidence to support its emerging role in disease diagnosis and prognosis. Aside from biomarkers and development of therapies, it is also an important goal to understand the involvement of mitochondrial DNA mtDNA in metabolic regulation, aging, and disease development. Somatic mutations of the mitochondrial genome are also heavily implicated in age-related disease and aging. The general hypothesis is that an alteration in the concentration of metabolite profiles (possibly conveyed by lifestyle and environmental factors) influences the increase of mutation rate in the mtDNA, and thereby contributes to a range of pathophysiological alterations observed in complex diseases.
METHODS: We performed an inverted mitochondrial genome wide association analysis between mitochondrial nucleotide variants (mtSNVs) and concentration of metabolites. We used 151 metabolites and the whole sequenced mitochondrial genome from 2718 individuals to identify genetic variants associated with metabolite profiles. Because of the high coverage, next generation sequencing-based analysis of the mitochondrial genome allows for an accurate detection of mitochondrial heteroplasmy and for identification of variants associated with the metabolome.
RESULTS: The strongest association was found for mt715G > A located in the MT-12SrRNA with the metabolite ratio C2/C10:1 (p-value = 6.82*10-09, β = 0.909). The second most significant mtSNV was found for mt3714A > G located in the MT-ND1 with the metabolite ratio PC ae C42:5/PC ae C44:5 (p-value = 1.02*10-08, β = 3.631). A large number of significant metabolite ratios were observed involving PC aa C36:6 and the variant mt10689G > A, located in the MT-ND4L gene.
CONCLUSION: These results show an important interconnection between mitochondria and metabolite concentrations. Considering that some of the significant metabolites found in this study have been previously related to complex diseases such as neurological disorders and metabolic conditions, these associations found here might play a crucial role for further investigations of such complex diseases. Understanding the mechanisms that control human health and disease, in particular the role of genetic predispositions and their interaction with environmental factors is a prerequisite for the development of safe and efficient therapies for complex disorders.

DOI: https://doi.org/10.1093/hmg/ddab312