bims-midneu 2021-05-30 papers

bims-midneu

Biomed News

on Mitochondrial dysfunction in neurodegeneration

Issue of 2021–05–30
twenty-two papers selected by
Radha Desai, Merck Sharp & Dohme Corp.

Transcription- and phosphorylation-dependent control of a functional interplay between XBP1s and PINK1 governs mitophagy and potentially impacts Parkinson disease pathophysiology.
Astrocyte-Neuron Metabolic Crosstalk in Neurodegeneration: A Mitochondrial Perspective.
Monitoring PINK1-Parkin Signaling Using Dopaminergic Neurons from iPS Cells.
Identification of bioactive metabolites in human iPSC-derived dopaminergic neurons with PARK2 mutation: Altered mitochondrial and energy metabolism.
miR-204 silencing reduces mitochondrial autophagy and ROS production in a murine AD model via the TRPML1-activated STAT3 pathway.
Ndufs4 ablation decreases synaptophysin expression in hippocampus.
Mitochondrial dysfunction and apoptosis are attenuated through activation of AMPK/GSK-3β/PP2A pathway in Parkinson's disease.
FUNDC1 inhibits NLRP3-mediated inflammation after intracerebral hemorrhage by promoting mitophagy in mice.
Structures of the human LONP1 protease reveal regulatory steps involved in protease activation.
Generation of somatic mitochondrial DNA-replaced cells for mitochondrial dysfunction treatment.
Aldehyde Dehydrogenase 2 Protects Against Lipopolysaccharide-Induced Myocardial Injury by Suppressing Mitophagy.
Machine learning algorithms reveal the secrets of mitochondrial dynamics.
Genome-wide CRISPRi screening identifies OCIAD1 as a prohibitin client and regulatory determinant of mitochondrial Complex III assembly in human cells.
Mitochondrial and metabolic dysfunction in Friedreich ataxia: update on pathophysiological relevance and clinical interventions.
Elevated type I interferon responses potentiate metabolic dysfunction, inflammation, and accelerated aging in mtDNA mutator mice.
SAMM50 acts with p62 in piecemeal basal- and OXPHOS-induced mitophagy of SAM and MICOS components.
Generation of Mitochondrial Toxin Rodent Models of Parkinson's Disease Using 6-OHDA , MPTP , and Rotenone.
Single channel properties of mitochondrial large conductance potassium channel formed by BK-VEDEC splice variant.
Amyotrophic lateral sclerosis alters the metabolic aging profile in patient derived fibroblasts.
The stimulator of interferon genes (STING) pathway is upregulated in striatal astrocytes of patients with multiple system atrophy.
Cytosolic and Mitochondrial Ca2+ Imaging in Drosophila Dopaminergic Neurons.
Mitochondrial dysfunction as a driver of NLRP3 inflammasome activation and its modulation through mitophagy for potential therapeutics.

Autophagy. 2021 May 24. 1-23

Transcription- and phosphorylation-dependent control of a functional interplay between XBP1s and PINK1 governs mitophagy and potentially impacts Parkinson disease pathophysiology.

Wejdane El Manaa, Eric Duplan, Thomas Goiran, Inger Lauritzen, Loan Vaillant Beuchot, Sandra Lacas-Gervais, Vanessa Alexandra Morais, Han You, Ling Qi, Mario Salazar, Umut Ozcan, Mounia Chami, Frédéric Checler, Cristine Alves da Costa.

  Parkinson disease (PD)-affected brains show consistent endoplasmic reticulum (ER) stress and mitophagic dysfunctions. The mechanisms underlying these perturbations and how they are directly linked remain a matter of questions. XBP1 is a transcription factor activated upon ER stress after unconventional splicing by the nuclease ERN1/IREα thereby yielding XBP1s, whereas PINK1 is a kinase considered as the sensor of mitochondrial physiology and a master gatekeeper of mitophagy process. We showed that XBP1s transactivates PINK1 in human cells, primary cultured neurons and mice brain, and triggered a pro-mitophagic phenotype that was fully dependent of endogenous PINK1. We also unraveled a PINK1-dependent phosphorylation of XBP1s that conditioned its nuclear localization and thereby, governed its transcriptional activity. PINK1-induced XBP1s phosphorylation occurred at residues reminiscent of, and correlated to, those phosphorylated in substantia nigra of sporadic PD-affected brains. Overall, our study delineated a functional loop between XBP1s and PINK1 governing mitophagy that was disrupted in PD condition.Abbreviations: 6OHDA: 6-hydroxydopamine; baf: bafilomycin A1; BECN1: beclin 1; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CASP3: caspase 3; CCCP: carbonyl cyanide chlorophenylhydrazone; COX8A: cytochrome c oxidase subunit 8A; DDIT3/CHOP: DNA damage inducible transcript 3; EGFP: enhanced green fluorescent protein; ER: endoplasmic reticulum; ERN1/IRE1α: endoplasmic reticulum to nucleus signaling 1; FACS: fluorescence-activated cell sorting; HSPD1/HSP60: heat shock protein family D (Hsp60) member 1; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MFN2: mitofusin 2; OPTN: optineurin; PD: Parkinson disease; PINK1: PTEN-induced kinase 1; PCR: polymerase chain reaction:; PRKN: parkin RBR E3 ubiquitin protein ligase; XBP1s [p-S61A]: XBP1s phosphorylated at serine 61; XBP1s [p-T48A]: XBP1s phosphorylated at threonine 48; shRNA: short hairpin RNA, SQSTM1/p62: sequestosome 1; TIMM23: translocase of inner mitochondrial membrane 23; TM: tunicamycin; TMRM: tetramethyl rhodamine methylester; TOMM20: translocase of outer mitochondrial membrane 20; Toy: toyocamycin; TP: thapsigargin; UB: ubiquitin; UB (S65): ubiquitin phosphorylated at serine 65; UPR: unfolded protein response, XBP1: X-box binding protein 1; XBP1s: spliced X-box binding protein 1.

Keywords:  Mitophagy; PINK1; Parkinson disease; XBP1; phosphorylation; transcription; unfolded protein response

DOI:  https://doi.org/10.1080/15548627.2021.1917129
Front Endocrinol (Lausanne). 2021 ;12 668517

Astrocyte-Neuron Metabolic Crosstalk in Neurodegeneration: A Mitochondrial Perspective.

Patrycja Mulica, Anne Grünewald, Sandro L Pereira.

  Converging evidence made clear that declining brain energetics contribute to aging and are implicated in the initiation and progression of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. Indeed, both pathologies involve instances of hypometabolism of glucose and oxygen in the brain causing mitochondrial dysfunction, energetic failure and oxidative stress. Importantly, recent evidence suggests that astrocytes, which play a key role in supporting neuronal function and metabolism, might contribute to the development of neurodegenerative diseases. Therefore, exploring how the neuro-supportive role of astrocytes may be impaired in the context of these disorders has great therapeutic potential. In the following, we will discuss some of the so far identified features underlining the astrocyte-neuron metabolic crosstalk. Thereby, special focus will be given to the role of mitochondria. Furthermore, we will report on recent advancements concerning iPSC-derived models used to unravel the metabolic contribution of astrocytes to neuronal demise. Finally, we discuss how mitochondrial dysfunction in astrocytes could contribute to inflammatory signaling in neurodegenerative diseases.

Keywords:  Alzheimer’s disease; Parkinson’s disease; astrocytes; metabolism; neurodegeneration; neurons

DOI:  https://doi.org/10.3389/fendo.2021.668517
Methods Mol Biol. 2021 ;2322 81-92

Monitoring PINK1-Parkin Signaling Using Dopaminergic Neurons from iPS Cells.

Kahori Shiba-Fukushima, Yuzuru Imai.

  The physiological importance of mitochondrial quality control has been uncovered by the finding that genes for early onset Parkinson's disease (PD), PINK1 and Parkin, regulate mitochondrial autophagy, called mitophagy, and motility. Dopaminergic neurons derived from human-induced pluripotent stem (iPS) cells are a useful tool for analyzing the pathogenesis caused by defects in mitochondrial quality control and for screening candidate drugs for PD. Moreover, dopaminergic neurons could provide new findings not obtained in other cells. In this chapter, we will describe our method for monitoring PINK1-Parkin signaling using iPS cell-derived dopaminergic neurons.

Keywords:  Autophagy; Dopaminergic neuron; Immunocytochemistry; Mitochondria; PINK1; Parkin; Ubiquitin; Western blot; iPS cells

DOI:  https://doi.org/10.1007/978-1-0716-1495-2_9
Stem Cell Reports. 2021 May 18. pii: S2213-6711(21)00217-4. [Epub ahead of print]

Identification of bioactive metabolites in human iPSC-derived dopaminergic neurons with PARK2 mutation: Altered mitochondrial and energy metabolism.

Justyna Okarmus, Jesper F Havelund, Matias Ryding, Sissel I Schmidt, Helle Bogetofte, Rachel Heon-Roberts, Richard Wade-Martins, Sally A Cowley, Brent J Ryan, Nils J Færgeman, Poul Hyttel, Morten Meyer.

  PARK2 (parkin) mutations cause early-onset Parkinson's disease (PD). Parkin is an ubiquitin E3 ligase that participates in several cellular functions, including mitochondrial homeostasis. However, the specific metabolomic changes caused by parkin depletion remain unknown. Here, we used isogenic human induced pluripotent stem cells (iPSCs) with and without PARK2 knockout (KO) to investigate the effect of parkin loss of function by comparative metabolomics supplemented with ultrastructural and functional analyses. PARK2 KO neurons displayed increased tricarboxylic acid (TCA) cycle activity, perturbed mitochondrial ultrastructure, ATP depletion, and dysregulation of glycolysis and carnitine metabolism. These perturbations were combined with increased oxidative stress and a decreased anti-oxidative response. Key findings for PARK2 KO cells were confirmed using patient-specific iPSC-derived neurons. Overall, our data describe a unique metabolomic profile associated with parkin dysfunction and show that combining metabolomics with an iPSC-derived dopaminergic neuronal model of PD is a valuable approach to obtain novel insight into the disease pathogenesis.

Keywords:  Parkinson's disease; induced pluripotent stem cells; metabolomics; mitochondria; oxidative stress; parkin

DOI:  https://doi.org/10.1016/j.stemcr.2021.04.022
Mol Ther Nucleic Acids. 2021 Jun 04. 24 822-831

miR-204 silencing reduces mitochondrial autophagy and ROS production in a murine AD model via the TRPML1-activated STAT3 pathway.

Lu Zhang, Yu Fang, Xinyu Zhao, Yake Zheng, Yunqing Ma, Shuang Li, Zhi Huang, Lihao Li.

  Mitochondrial dysfunction is an early feature of Alzheimer's disease (AD), whereby accumulation of damaged mitochondria in conjunction with impaired mitophagy contributes to neurodegeneration. Various non-transcribed microRNAs (miRNAs) are involved in this process. In the present study, we aimed to decipher the participation of miR-204 in a murine AD model. Primary hippocampal neurons were isolated from mice and treated with β-amyloid 1-42 (Aβ1-42) to establish a cell model of AD. Dichloro-dihydro-fluorescein diacetate and dihydrorhodamine 123 staining assays were performed to measure total reactive oxygen species (ROS) and mitochondrial ROS production in neurons, and MitoSOX staining was done to analyze mitochondrial ROS production in hippocampus. Furthermore, mitochondrial autophagy was observed in hippocampus from amyloid precursor protein/pesenilin-1 AD modeled mice, and their cognitive function was assessed by Morris water maze. Mitochondrial damage, ROS production, and mitochondrial autophagy were observed in AD cell model induced by Aβ1-42. In AD, signal transducer and activator of transcription 3 (STAT3) and transient receptor potential mucolipin-1 (TRPML1) expression was downregulated, although miR-204 expression was upregulated. TRPML1 overexpression, downregulation of miR-204, or STAT3 pathway activation reduced the Aβ1-42-induced mitochondrial damage, along with ROS production and mitochondrial autophagy in vivo and in vitro. Silencing of miR-204 could upregulate TRPML1 expression, thus suppressing ROS production and mitochondrial autophagy in AD through STAT3 pathway.

Keywords:  Alzheimer’s disease; Aβ1-42; hippocampal neurons; microRNA-204; mitochondrial autophagy; reactive oxygen species; signal transducer and activator of transcription 3; transient receptor potential mucolipin-1

DOI:  https://doi.org/10.1016/j.omtn.2021.02.010
Sci Rep. 2021 May 26. 11(1): 10969

Ndufs4 ablation decreases synaptophysin expression in hippocampus.

Subrata Kumar Shil, Yoshiteru Kagawa, Banlanjo Abdulaziz Umaru, Fumika Nanto-Hara, Hirofumi Miyazaki, Yui Yamamoto, Shuhei Kobayashi, Chitose Suzuki, Takaaki Abe, Yuji Owada.

Altered function of mitochondrial respiratory chain in brain cells is related to many neurodegenerative diseases. NADH Dehydrogenase (Ubiquinone) Fe-S protein 4 (Ndufs4) is one of the subunits of mitochondrial complex I and its mutation in human is associated with Leigh syndrome. However, the molecular biological role of Ndufs4 in neuronal function is poorly understood. In this study, upon Ndufs4 expression confirmation in NeuN-positive neurons, and GFAP-positive astrocytes in WT mouse hippocampus, we found significant decrease of mitochondrial respiration in Ndufs4-KO mouse hippocampus. Although there was no change in the number of NeuN positive neurons in Ndufs4-KO hippocampus, the expression of synaptophysin, a presynaptic protein, was significantly decreased. To investigate the detailed mechanism, we silenced Ndufs4 in Neuro-2a cells and we observed shorter neurite lengths with decreased expression of synaptophysin. Furthermore, western blot analysis for phosphorylated extracellular regulated kinase (pERK) revealed that Ndufs4 silencing decreases the activity of ERK signalling. These results suggest that Ndufs4-modulated mitochondrial activity may be involved in neuroplasticity via regulating synaptophysin expression.

DOI: https://doi.org/10.1038/s41598-021-90127-4
Eur J Pharmacol. 2021 May 25. pii: S0014-2999(21)00355-1. [Epub ahead of print] 174202

Mitochondrial dysfunction and apoptosis are attenuated through activation of AMPK/GSK-3β/PP2A pathway in Parkinson's disease.

Jianhua Su, Junhua Zhang, Rui Bao, Changbo Xia, Yu Zhang, Zhujun Zhu, Qi Lv, Yingjie Qi, Jianqin Xue.

  Parkinson's disease (PD) is a common neurological disorder worldwide, characterized by loss of dopaminergic neurons and decrease of dopamine content. Mitochondria plays an important role in the development of PD. Adenosine 5'-monophosphate-activated protein kinase (AMPK), glycogen synthase kinase 3 (GSK-3β) and protein phosphatase 2A (PP2A) are all key proteins that regulate mitochondrial metabolism and apoptosis, and they are involved in a variety of neurodegenerative diseases. Here, we aimed to explore the involvement of mitochondrial dysfunction and apoptosis in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine hydrochloride (MPTP)-induced PD mice and MPP+ iodide-induced PC12 cells. MPTP-induced mice were subjected to behavioral testing to assess PD-like behaviors. Various molecular biological techniques including ELISA, Western blot, TUNEL assay, flow cytometry, and the important instruments Seahorse XF24 Extracellular and high performance liquid chromatography (HPLC), were used to identify the underlying molecular events of mitochondria. Treatment with the AMPK activator GSK621 dramatically ameliorated PD by increasing the levels of dopamine and rescuing the loss of dopaminergic neurons, which is dependent on the mitochondrial pathway. Moreover, regulation of AMPK/GSK-3β/PP2A pathway-related proteins by GSK621 was partially inhibited the development of PD, suggesting a negative feedback loop exists between AMPK action and mitochondrial dysfunction-mediated apoptosis. Our data preliminarily indicated that mitochondrial dysfunction and apoptosis in the pathogenesis of PD might be mediated by AMPK/GSK-3β/PP2A pathway action, which might be a promising new option for future therapy of PD.

Keywords:  AMPK/GSK-3β/PP2A pathway; Apoptosis; MPTP/MPP(+); Mitochondrial dysfunction; Parkinson’s disease

DOI:  https://doi.org/10.1016/j.ejphar.2021.174202
Neurosci Lett. 2021 May 19. pii: S0304-3940(21)00345-1. [Epub ahead of print]756 135967

FUNDC1 inhibits NLRP3-mediated inflammation after intracerebral hemorrhage by promoting mitophagy in mice.

Shuyue Zheng, Dan Jian, Hui Gan, Lu Wang, Jing Zhao, Xuan Zhai.

  Inflammation is a fundamental element in secondary brain injury (SBI) besides intracerebral hemorrhage (ICH). Pyrin domain that contains 3 inflammasome (NLRP3) was regarded as a key role of the nod-like receptor family and played an important part in the inflammatory response following ICH-induced injury. FUN14 domain containing 1 (FUNDC1) is a kind of mitophagy receptor, which can eliminate mitochondrial dysfunction after hypoxia and mitochondrial stress. Previous research showed that mitophagy prevents inflammation through inhibiting NLRP3 inflammasome pathway. However, the relationship between FUNDC1 and ICH-induced inflammatory response stays uncertain. In this study, we investigate that FUNDC1 inhibit NLRP3 inflammasome activation by promoting mitophagy, thereby alleviate ICH-induced injury. We established ICH model by injecting tail venous blood into the basal ganglia of C57 mice (healthy, male adult). We injected siRNA to knockdown FUNDC1. In order to deeply seek for the mechanisms of FUNDC1 in ICH-induced injury, FUNDC1 was overexpressed by adeno-associated virus (AAV) and mitophagy was suppressed by specific inhibitor (mdivi-1). The protein level of FUNDC1 was upregulated and got peak at 12h after ICH. We noticed that silencing FUNDC1 can suppress mitophagy, promote NLRP3-mediated inflammation and exacerbate ICH injury. Furthermore, the results indicated that mitophagy participated in the inhibitory effect of FUNDC1 on NLRP3-mediated inflammatory response after ICH. Our results showed that FUNDC1 alleviated ICH-induced inflammation in mice by promoting mitophagy. Those data suggested that FUNDC1 may be a potential target for the treatment of ICH.

Keywords:  FUNDC1; Inflammation; Intracerebral hemorrhage; Mitophagy; NLRP3

DOI:  https://doi.org/10.1016/j.neulet.2021.135967
Nat Commun. 2021 May 28. 12(1): 3239

Structures of the human LONP1 protease reveal regulatory steps involved in protease activation.

Mia Shin, Edmond R Watson, Albert S Song, Jeffrey T Mindrebo, Scott J Novick, Patrick R Griffin, R Luke Wiseman, Gabriel C Lander.

The human mitochondrial AAA+ protein LONP1 is a critical quality control protease involved in regulating diverse aspects of mitochondrial biology including proteostasis, electron transport chain activity, and mitochondrial transcription. As such, genetic or aging-associated imbalances in LONP1 activity are implicated in pathologic mitochondrial dysfunction associated with numerous human diseases. Despite this importance, the molecular basis for LONP1-dependent proteolytic activity remains poorly defined. Here, we solved cryo-electron microscopy structures of human LONP1 to reveal the underlying molecular mechanisms governing substrate proteolysis. We show that, like bacterial Lon, human LONP1 adopts both an open and closed spiral staircase orientation dictated by the presence of substrate and nucleotide. Unlike bacterial Lon, human LONP1 contains a second spiral staircase within its ATPase domain that engages substrate as it is translocated toward the proteolytic chamber. Intriguingly, and in contrast to its bacterial ortholog, substrate binding within the central ATPase channel of LONP1 alone is insufficient to induce the activated conformation of the protease domains. To successfully induce the active protease conformation in substrate-bound LONP1, substrate binding within the protease active site is necessary, which we demonstrate by adding bortezomib, a peptidomimetic active site inhibitor of LONP1. These results suggest LONP1 can decouple ATPase and protease activities depending on whether AAA+ or both AAA+ and protease domains bind substrate. Importantly, our structures provide a molecular framework to define the critical importance of LONP1 in regulating mitochondrial proteostasis in health and disease.

DOI: https://doi.org/10.1038/s41467-021-23495-0
Sci Rep. 2021 May 25. 11(1): 10897

Generation of somatic mitochondrial DNA-replaced cells for mitochondrial dysfunction treatment.

Hideki Maeda, Daisuke Kami, Ryotaro Maeda, Akira Shikuma, Satoshi Gojo.

Mitochondrial diseases currently have no cure regardless of whether the cause is a nuclear or mitochondrial genome mutation. Mitochondrial dysfunction notably affects a wide range of disorders in aged individuals, including neurodegenerative diseases, cancers, and even senescence. Here, we present a procedure to generate mitochondrial DNA-replaced somatic cells with a combination of a temporal reduction in endogenous mitochondrial DNA and coincubation with exogeneous isolated mitochondria. Heteroplasmy in mitochondrial disease patient-derived fibroblasts in which the mutant genotype was dominant over the wild-type genotype was reversed. Mitochondrial disease patient-derived fibroblasts regained respiratory function and showed lifespan extension. Mitochondrial membranous components were utilized as a vehicle to deliver the genetic materials into endogenous mitochondria-like horizontal genetic transfer in prokaryotes. Mitochondrial DNA-replaced cells could be a resource for transplantation to treat maternal inherited mitochondrial diseases.

DOI: https://doi.org/10.1038/s41598-021-90316-1
Front Pharmacol. 2021 ;12 641058

Aldehyde Dehydrogenase 2 Protects Against Lipopolysaccharide-Induced Myocardial Injury by Suppressing Mitophagy.

Wenqing Ji, Tiantian Wan, Fang Zhang, Xiaomei Zhu, Shubin Guo, Xue Mei.

  Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis-induced circulatory and cardiac dysfunction is associated with high mortality rates. Mitophagy, a specific form of autophagy, is excessively activated in lipopolysaccharide-induced myocardial injury. The present study investigated whether aldehyde dehydrogenase 2 (ALDH2) regulates mitophagy in sepsis-induced myocardial dysfunction. After lipopolysaccharide administration, cardiac dysfunction, inflammatory cell infiltration, biochemical indicators of myocardial cell injury, and cardiomyocyte apoptosis were ameliorated in mice by ALDH2 activation or overexpression. In contrast, cardiac dysfunction and cardiomyocyte apoptosis were exacerbated in mice followed ALDH2 inhibition. Moreover, ALDH2 activation or overexpression regulated mitophagy by suppressing the expression of phosphatase and tensin homolog-induced putative kinase 1 (PINK1)/Parkin, by preventing the accumulation of 4-hydroxy-trans-nonenal. Conversely, ALDH2 inhibition promoted the expression of LC3B by increasing 4-hydroxy-trans-2-nonenal accumulation. Consequently, ALDH2 may protect the heart from lipopolysaccharide-induced injury by suppressing PINK1/Parkin-dependent mitophagy.

Keywords:  ALDH2; PINK1/parkin; lipopolysaccharide; mitophagy; myocardium; oxidative stress

DOI:  https://doi.org/10.3389/fphar.2021.641058
EMBO Mol Med. 2021 May 27. e14316

Machine learning algorithms reveal the secrets of mitochondrial dynamics.

Jack J Collier, Robert W Taylor.

Mitochondria exist as dynamic networks whose morphology is driven by the complex interplay between fission and fusion events. Failure to modulate these processes can be detrimental to human health as evidenced by dominantly inherited, pathogenic variants in OPA1, an effector enzyme of mitochondrial fusion, that lead to network fragmentation, cristae dysmorphology and impaired oxidative respiration, manifesting typically as isolated optic atrophy. However, a significant number of patients develop more severe, systemic phenotypes, although no genetic modifiers of OPA1-related disease have been identified to date. In this issue of EMBO Molecular Medicine, supervised machine learning algorithms underlie a novel tool that enables automated, high throughput and unbiased screening of changes in mitochondrial morphology measured using confocal microscopy. By coupling this approach with a bespoke siRNA library targeting the entire mitochondrial proteome, the work described by Cretin and colleagues yielded significant insight into mitochondrial biology, discovering 91 candidate genes whose endogenous depletion can remedy impaired mitochondrial dynamics caused by OPA1 deficiency.

DOI: https://doi.org/10.15252/emmm.202114316
Elife. 2021 May 26. pii: e67624. [Epub ahead of print]10

Genome-wide CRISPRi screening identifies OCIAD1 as a prohibitin client and regulatory determinant of mitochondrial Complex III assembly in human cells.

Maxence Le Vasseur, Jonathan Friedman, Marco Jost, Jiawei Xu, Justin Yamada, Martin Kampmann, Max A Horlbeck, Michelle R Salemi, Brett S Phinney, Jonathan S Weissman, Jodi Nunnari.

  Dysfunction of the mitochondrial electron transport chain (mETC) is a major cause of human mitochondrial diseases. To identify determinants of mETC function, we screened a genome-wide human CRISPRi library under oxidative metabolic conditions with selective inhibition of mitochondrial Complex III and identified ovarian carcinoma immunoreactive antigen (OCIA) domain-containing protein 1 (OCIAD1) as a Complex III assembly factor. We find that OCIAD1 is an inner mitochondrial membrane protein that forms a complex with supramolecular prohibitin assemblies. Our data indicate that OCIAD1 is required for maintenance of normal steady-state levels of Complex III and the proteolytic processing of the catalytic subunit cytochrome c1 (CYC1). In OCIAD1 depleted mitochondria, unprocessed CYC1 is hemylated and incorporated into Complex III. We propose that OCIAD1 acts as an adaptor within prohibitin assemblies to stabilize and/or chaperone CYC1 and to facilitate its proteolytic processing by the IMMP2L protease.

Keywords:  Complex III; cell biology; cytochrome c1; electron transport chain; human; mitochondria; prohibitin; protease

DOI:  https://doi.org/10.7554/eLife.67624
Neuronal Signal. 2021 Jun;5(2): NS20200093

Mitochondrial and metabolic dysfunction in Friedreich ataxia: update on pathophysiological relevance and clinical interventions.

David R Lynch, Garrett Farmer.

  Friedreich ataxia (FRDA) is a recessive disorder resulting from relative deficiency of the mitochondrial protein frataxin. Frataxin functions in the process of iron-sulfur (Fe-S) cluster synthesis. In this review, we update some of the processes downstream of frataxin deficiency that may mediate the pathophysiology. Based on cellular models, in vivo models and observations of patients, ferroptosis may play a major role in the pathogenesis of FRDA along with depletion of antioxidant reserves and abnormalities of mitochondrial biogenesis. Ongoing clinical trials with ferroptosis inhibitors and nuclear factor erythroid 2-related factor 2 (Nrf2) activators are now targeting each of the processes. In addition, better understanding of the mitochondrial events in FRDA may allow the development of improved imaging methodology for assessing the disorder. Though not technologically feasible at present, metabolic imaging approaches may provide a direct methodology to understand the mitochondrial changes occurring in FRDA and provide a methodology to monitor upcoming trials of frataxin restoration.

Keywords:  biomarkers; clinical trial; mitochondrial biogenesis

DOI:  https://doi.org/10.1042/NS20200093
Sci Adv. 2021 May;pii: eabe7548. [Epub ahead of print]7(22):

Elevated type I interferon responses potentiate metabolic dysfunction, inflammation, and accelerated aging in mtDNA mutator mice.

Yuanjiu Lei, Camila Guerra Martinez, Sylvia Torres-Odio, Samantha L Bell, Christine E Birdwell, Joshua D Bryant, Carl W Tong, Robert O Watson, Laura Ciaccia West, A Phillip West.

Mitochondrial dysfunction is a key driver of inflammatory responses in human disease. However, it remains unclear whether alterations in mitochondria-innate immune cross-talk contribute to the pathobiology of mitochondrial disorders and aging. Using the polymerase gamma (POLG) mutator model of mitochondrial DNA instability, we report that aberrant activation of the type I interferon (IFN-I) innate immune axis potentiates immunometabolic dysfunction, reduces health span, and accelerates aging in mutator mice. Mechanistically, elevated IFN-I signaling suppresses activation of nuclear factor erythroid 2-related factor 2 (NRF2), which increases oxidative stress, enhances proinflammatory cytokine responses, and accelerates metabolic dysfunction. Ablation of IFN-I signaling attenuates hyperinflammatory phenotypes by restoring NRF2 activity and reducing aerobic glycolysis, which combine to lessen cardiovascular and myeloid dysfunction in aged mutator mice. These findings further advance our knowledge of how mitochondrial dysfunction shapes innate immune responses and provide a framework for understanding mitochondria-driven immunopathology in POLG-related disorders and aging.

DOI: https://doi.org/10.1126/sciadv.abe7548
J Cell Biol. 2021 Aug 02. pii: e202009092. [Epub ahead of print]220(8):

SAMM50 acts with p62 in piecemeal basal- and OXPHOS-induced mitophagy of SAM and MICOS components.

Yakubu Princely Abudu, Birendra Kumar Shrestha, Wenxin Zhang, Anthimi Palara, Hanne Britt Brenne, Kenneth Bowitz Larsen, Deanna Lynn Wolfson, Gianina Dumitriu, Cristina Ionica Øie, Balpreet Singh Ahluwalia, Gahl Levy, Christian Behrends, Sharon A Tooze, Stephane Mouilleron, Trond Lamark, Terje Johansen.

Mitophagy is the degradation of surplus or damaged mitochondria by autophagy. In addition to programmed and stress-induced mitophagy, basal mitophagy processes exert organelle quality control. Here, we show that the sorting and assembly machinery (SAM) complex protein SAMM50 interacts directly with ATG8 family proteins and p62/SQSTM1 to act as a receptor for a basal mitophagy of components of the SAM and mitochondrial contact site and cristae organizing system (MICOS) complexes. SAMM50 regulates mitochondrial architecture by controlling formation and assembly of the MICOS complex decisive for normal cristae morphology and exerts quality control of MICOS components. To this end, SAMM50 recruits ATG8 family proteins through a canonical LIR motif and interacts with p62/SQSTM1 to mediate basal mitophagy of SAM and MICOS components. Upon metabolic switch to oxidative phosphorylation, SAMM50 and p62 cooperate to mediate efficient mitophagy.

DOI: https://doi.org/10.1083/jcb.202009092
Methods Mol Biol. 2021 ;2322 95-110

Generation of Mitochondrial Toxin Rodent Models of Parkinson's Disease Using 6-OHDA , MPTP , and Rotenone.

Hiroharu Maegawa, Hitoshi Niwa.

  Several animal models are employed to discover novel treatments for the symptoms of Parkinson's disease (PD). PD models can be divided into two models: neurotoxin models and genetic models. Among neurotoxins to produce PD models, 6-hydroxydopamine (6-OHDA), 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and rotenone, which inhibit the mitochondrial complex I, are widely used. Animal models of PD using these neurotoxins are also known as mitochondrial toxin models. Here this chapter describes the preparation of these mitochondrial toxin models.

Keywords:  1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP); 6-Hydroxydoopamine (6-OHDA); Mitochondrial complex I; Mouse; Rat; Rotenone

DOI:  https://doi.org/10.1007/978-1-0716-1495-2_10
Sci Rep. 2021 May 25. 11(1): 10925

Single channel properties of mitochondrial large conductance potassium channel formed by BK-VEDEC splice variant.

Shur Gałecka, Bogusz Kulawiak, Piotr Bednarczyk, Harpreet Singh, Adam Szewczyk.

The activation of mitochondrial large conductance calcium-activated potassium (mitoBKCa) channels increases cell survival during ischemia/reperfusion injury of cardiac cells. The basic biophysical and pharmacological properties of mitoBKCa correspond to the properties of the BKCa channels from the plasma membrane. It has been suggested that the VEDEC splice variant of the KCNMA1 gene product encoding plasma membrane BKCa is targeted toward mitochondria. However there has been no direct evidence that this protein forms a functional channel in mitochondria. In our study, we used HEK293T cells to express the VEDEC splice variant and observed channel activity in mitochondria using the mitoplast patch-clamp technique. For the first time, we found that transient expression with the VEDEC isoform resulted in channel activity with the conductance of 290 ± 3 pS. The channel was voltage-dependent and activated by calcium ions. Moreover, the activity of the channel was stimulated by the potassium channel opener NS11021 and inhibited by hemin and paxilline, which are known BKCa channel blockers. Immunofluorescence experiments confirmed the partial colocalization of the channel within the mitochondria. From these results, we conclude that the VEDEC isoform of the BKCa channel forms a functional channel in the inner mitochondrial membrane. Additionally, our data show that HEK293T cells are a promising experimental model for expression and electrophysiological studies of mitochondrial potassium channels.

DOI: https://doi.org/10.1038/s41598-021-90465-3
Neurobiol Aging. 2021 Apr 27. pii: S0197-4580(21)00129-9. [Epub ahead of print]105 64-77

Amyotrophic lateral sclerosis alters the metabolic aging profile in patient derived fibroblasts.

Margarita Gerou, Benjamin Hall, Ryan Woof, Jessica Allsop, Stephen J Kolb, Kathrin Meyer, Pamela J Shaw, Scott P Allen.

  Aging is a major risk factor for neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). As metabolic alterations are a hallmark of aging and have previously been observed in ALS, it is important to examine the effect of aging in the context of ALS metabolic function. Here, using a newly established phenotypic metabolic approach, we examined the effect of aging on the metabolic profile of fibroblasts derived from ALS cases compared to controls. We found that ALS fibroblasts have an altered metabolic profile, which is influenced by age. In control cases, we found significant increases with age in NADH metabolism in the presence of several metabolites including lactic acid, trehalose, uridine and fructose, which was not recapitulated in ALS cases. Conversely, we found a reduction of NADH metabolism with age of biopsy, age of onset and age of death in the presence of glycogen in the ALS cohort. Furthermore, we found that NADH production correlated with disease progression rates in relation to a number of metabolites including inosine and α-ketoglutaric acid. Inosine or α-ketoglutaric acid supplementation in ALS fibroblasts was bioenergetically favourable. Overall, we found aging related defects in energy substrates that feed carbon into glycolysis at various points as well as the tricarboxylic acid (TCA) cycle in ALS fibroblasts, which was validated in induced neuronal progenitor cell derived iAstrocytes. Our results suggest that supplementing those pathways may protect against age related metabolic dysfunction in ALS.

Keywords:  Aging, ALS; Fibroblasts; Metabolism

DOI:  https://doi.org/10.1016/j.neurobiolaging.2021.04.013
Neurosci Lett. 2021 May 22. pii: S0304-3940(21)00350-5. [Epub ahead of print] 135972

The stimulator of interferon genes (STING) pathway is upregulated in striatal astrocytes of patients with multiple system atrophy.

Yutaka Inoue, Takashi Ayaki, Tomoyuki Ishimoto, Hodaka Yamakado, Takakuni Maki, Shuichi Matsuzawa, Nobukatsu Sawamoto, Ryosuke Takahashi.

  Multiple system atrophy (MSA) is a progressive neurodegenerative disorder characterized by the accumulation of pathogenic phosphorylated α-synuclein in oligodendrocytes. In brains affected by MSA, severe astrogliosis is also observed, but its precise role in MSA pathogenesis remains largely unknown. Recently, the stimulator of interferon genes (STING) pathway and type I interferons, its downstream molecules, have been reported to be involved in the neurodegenerative process and to be activated in astrocytes. This study aimed to investigate the role of the STING pathway in the pathogenesis of MSA using postmortem brains. Samples used for immunohistochemical analysis included 6 cases of MSA parkinsonism type (MSA-P), 6 cases of MSA cerebellar type (MSA-C), and 7 age-matched controls. In MSA-P cases, astrocytes immunopositive for STING and TANK-binding kinase 1 (TBK1), its downstream molecule, were abundantly observed in the putamen and the substantia nigra. Moreover, these molecules colocalized with glial fibrillary acidic protein (GFAP) in reactive astrocytes, and the density of STING-positive astrocytes correlated with that of GFAP-positive reactive astrocytes in the brains of patients with MSA-P. These results suggest that the upregulated expression of STING pathway-related proteins in astrocytes and the subsequent inflammation may contribute to the pathogenesis in MSA-P and could provide novel therapeutic targets for the treatment of MSA.

Keywords:  Astrocyte; Multiple system atrophy; Stimulator of interferon genes; TANK-binding kinase 1; Type I interferons

DOI:  https://doi.org/10.1016/j.neulet.2021.135972
Methods Mol Biol. 2021 ;2322 207-214

Cytosolic and Mitochondrial Ca2+ Imaging in Drosophila Dopaminergic Neurons.

Tsuyoshi Inoshita, Yuzuru Imai.

  The ATP-producing organelle mitochondrion controls cellular or synaptic Ca2+ concentrations through temporal uptake of Ca2+ outside of the mitochondria. Although intracellular Ca2+ influx occurs during neuronal activity, a persistently higher concentration of intracellular Ca2+ is neurotoxic. Healthy mitochondria ensure rapid Ca2+ uptake, which is necessary for proper neuronal activity. Mitochondrial Ca2+ buffering activity decreases in aged or sick neurons. In this chapter, we will introduce our protocol for evaluating Ca2+ buffering activity through the mitochondria during neuronal activity of dopaminergic neurons.

Keywords:  Ca2+ buffering; Dopaminergic neuron; Drosophila; GCaMP; Live imaging; Mitochondria; Synaptic activity

DOI:  https://doi.org/10.1007/978-1-0716-1495-2_20
Int J Biochem Cell Biol. 2021 May 19. pii: S1357-2725(21)00091-1. [Epub ahead of print] 106013

Mitochondrial dysfunction as a driver of NLRP3 inflammasome activation and its modulation through mitophagy for potential therapeutics.

Soumya R Mishra, Kewal K Mahapatra, Bishnu P Behera, Srimanta Patra, Chandra S Bhol, Debasna P Panigrahi, Prakash P Praharaj, Amruta Singh, Shankargouda Patil, Rohan Dhiman, Sujit K Bhutia.

  The NLR family pyrin domain containing 3 (NLRP3) inflammasome is responsible for the sensation of various pathogenic and non-pathogenic damage signals and has a vital role in neuroinflammation and neural diseases. Various stimuli, such as microbial infection, misfolded protein aggregates, and aberrant deposition of proteins including amyloid-β, α-synuclein can induce NLRP3 inflammasome in neural cells. Once triggered, the NLRP3 inflammasome leads to the activation of caspase-1, which in turn activates inflammatory cytokines, such as interleukin-1β and interleukin -18, and induces pyroptotic cell death. Mitochondria are critically involved in diverse cellular processes and are involved in regulating cellular redox status, calcium levels, inflammasome activation, and cell death. Mitochondrial dysfunction and subsequent accumulation of mitochondrial reactive oxygen species, mitochondrial deoxyribonucleic acid, and other mitochondria-associated proteins and lipids play vital roles in the instigation of the NLRP3 inflammasome. In addition, the processes of mitochondrial dynamics, such as fission and fusion, are essential in the maintenance of mitochondrial integrity and their imbalance also promotes NLRP3 inflammasome activation. In this connection, mitophagy-mediated maintenance of mitochondrial homeostasis restricts NLRP3 inflammasome hyperactivation and its consequences in various neurological disorders. Hence, mitophagy can be exploited as a potential strategy to target damaged mitochondria-derived NLRP3 inflammasome activation and its lethal consequences. Therefore, the identification of novel mitophagy modulators has promising therapeutic potential for NLRP3 inflammasome-associated neuronal diseases.

Keywords:  Inflammasome; NLRP3; mitochondria; mitochondrial dynamics; mitophagy

DOI:  https://doi.org/10.1016/j.biocel.2021.106013