bims-midneu 2021-05-16 papers

bims-midneu

Biomed News

on Mitochondrial dysfunction in neurodegeneration

Issue of 2021–05–16
twenty-two papers selected by
Radha Desai, Merck Sharp & Dohme Corp.

Imaging mass cytometry reveals generalised deficiency in OXPHOS complexes in Parkinson's disease.
Oxygen tension modulates the mitochondrial genetic bottleneck and influences the segregation of a heteroplasmic mtDNA variant in vitro.
TP53INP1 exerts neuroprotection under ageing and Parkinson's disease-related stress condition.
Mitochondrial fission and mitophagy are independent mechanisms regulating ischemia/reperfusion injury in primary neurons.
Phenotypic diversity of brain MRI patterns in mitochondrial aminoacyl-tRNA synthetase mutations.
VCP/p97 cofactor UBXN1/SAKS1 regulates mitophagy by modulating MFN2 removal from mitochondria.
Neuronal mitochondrial dynamics coordinate systemic mitochondrial morphology and stress response to confer pathogen resistance in C. elegans.
Mitochondrial matrix proteases - quality control and beyond.
TSG101 negatively regulates mitochondrial biogenesis in axons.
Nanoscopic quantification of sub-mitochondrial morphology, mitophagy and mitochondrial dynamics in living cells derived from patients with mitochondrial diseases.
Mild hypothermia facilitates mitochondrial transfer from astrocytes to injured neurons during oxygen-glucose deprivation/reoxygenation.
SREBP2 gene therapy targeting striatal astrocytes ameliorates Huntington's disease phenotypes.
USP19 promotes hypoxia-induced mitochondrial division via FUNDC1 at ER-mitochondria contact sites.
Resveratrol Improves Mitochondrial Biogenesis Function and Activates PGC-1α Pathway in a Preclinical Model of Early Brain Injury Following Subarachnoid Hemorrhage.
The role of sigma 1 receptor in organization of endoplasmic reticulum signaling microdomains.
Prodromal sensory neuropathy in Pink1-/- SNCAA53T double mutant Parkinson mice.
Intermittent hypoxia preconditioning protects WRL68 cells against oxidative injury: Involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1.
MicroRNA-338 inhibition protects against focal cerebral ischemia and preserves mitochondrial function in vitro in astrocytes and neurons via COX4I1.
FUNDC1-dependent mitochondria-associated endoplasmic reticulum membranes are involved in angiogenesis and neoangiogenesis.
Iron activates microglia and directly stimulates indoleamine-2,3-dioxygenase activity in the N171-82Q mouse model of Huntington's disease.
The Mitochondrial mitoNEET Ligand NL-1 Is Protective in a Murine Model of Transient Cerebral Ischemic Stroke.
Generation of mitochondrial reactive oxygen species is controlled by ATPase inhibitory factor 1 and regulates cognition.

NPJ Parkinsons Dis. 2021 May 12. 7(1): 39

Imaging mass cytometry reveals generalised deficiency in OXPHOS complexes in Parkinson's disease.

Chun Chen, David McDonald, Alasdair Blain, Ashwin Sachdeva, Laura Bone, Anna L M Smith, Charlotte Warren, Sarah J Pickett, Gavin Hudson, Andrew Filby, Amy E Vincent, Doug M Turnbull, Amy K Reeve.

Here we report the application of a mass spectrometry-based technology, imaging mass cytometry, to perform in-depth proteomic profiling of mitochondrial complexes in single neurons, using metal-conjugated antibodies to label post-mortem human midbrain sections. Mitochondrial dysfunction, particularly deficiency in complex I has previously been associated with the degeneration of dopaminergic neurons in Parkinson's disease. To further our understanding of the nature of this dysfunction, and to identify Parkinson's disease specific changes, we validated a panel of antibodies targeting subunits of all five mitochondrial oxidative phosphorylation complexes in dopaminergic neurons from Parkinson's disease, mitochondrial disease, and control cases. Detailed analysis of the expression profile of these proteins, highlighted heterogeneity between individuals. There is a widespread decrease in expression of all complexes in Parkinson's neurons, although more severe in mitochondrial disease neurons, however, the combination of affected complexes varies between the two groups. We also provide evidence of a potential neuronal response to mitochondrial dysfunction through a compensatory increase in mitochondrial mass. This study highlights the use of imaging mass cytometry in the assessment and analysis of expression of oxidative phosphorylation proteins, revealing the complexity of deficiencies of these proteins within individual neurons which may contribute to and drive neurodegeneration in Parkinson's disease.

DOI: https://doi.org/10.1038/s41531-021-00182-x
Commun Biol. 2021 May 14. 4(1): 584

Oxygen tension modulates the mitochondrial genetic bottleneck and influences the segregation of a heteroplasmic mtDNA variant in vitro.

Mikael G Pezet, Aurora Gomez-Duran, Florian Klimm, Juvid Aryaman, Stephen Burr, Wei Wei, Mitinori Saitou, Julien Prudent, Patrick F Chinnery.

Most humans carry a mixed population of mitochondrial DNA (mtDNA heteroplasmy) affecting ~1-2% of molecules, but rapid percentage shifts occur over one generation leading to severe mitochondrial diseases. A decrease in the amount of mtDNA within the developing female germ line appears to play a role, but other sub-cellular mechanisms have been implicated. Establishing an in vitro model of early mammalian germ cell development from embryonic stem cells, here we show that the reduction of mtDNA content is modulated by oxygen and reaches a nadir immediately before germ cell specification. The observed genetic bottleneck was accompanied by a decrease in mtDNA replicating foci and the segregation of heteroplasmy, which were both abolished at higher oxygen levels. Thus, differences in oxygen tension occurring during early development likely modulate the amount of mtDNA, facilitating mtDNA segregation and contributing to tissue-specific mutation loads.

DOI: https://doi.org/10.1038/s42003-021-02069-2
Cell Death Dis. 2021 May 08. 12(5): 460

TP53INP1 exerts neuroprotection under ageing and Parkinson's disease-related stress condition.

Emilie Dinh, Thomas Rival, Alice Carrier, Noemi Asfogo, Olga Corti, Christophe Melon, Pascal Salin, Sylviane Lortet, Lydia Kerkerian-Le Goff.

TP53INP1 is a stress-induced protein, which acts as a dual positive regulator of transcription and of autophagy and whose deficiency has been linked with cancer and metabolic syndrome. Here, we addressed the unexplored role of TP53INP1 and of its Drosophila homolog dDOR in the maintenance of neuronal homeostasis under chronic stress, focusing on dopamine (DA) neurons under normal ageing- and Parkinson's disease (PD)-related context. Trp53inp1-/- mice displayed additional loss of DA neurons in the substantia nigra compared to wild-type (WT) mice, both with ageing and in a PD model based on targeted overexpression of α-synuclein. Nigral Trp53inp1 expression of WT mice was not significantly modified with ageing but was markedly increased in the PD model. Trp53inp2 expression showed similar evolution and did not differ between WT and Trp53inp1-/- mice. In Drosophila, pan-neuronal dDOR overexpression improved survival under paraquat exposure and mitigated the progressive locomotor decline and the loss of DA neurons caused by the human α-synuclein A30P variant. dDOR overexpression in DA neurons also rescued the locomotor deficit in flies with RNAi-induced downregulation of dPINK1 or dParkin. Live imaging, confocal and electron microscopy in fat bodies, neurons, and indirect flight muscles showed that dDOR acts as a positive regulator of basal autophagy and mitophagy independently of the PINK1-mediated pathway. Analyses in a mammalian cell model confirmed that modulating TP53INP1 levels does not impact mitochondrial stress-induced PINK1/Parkin-dependent mitophagy. These data provide the first evidence for a neuroprotective role of TP53INP1/dDOR and highlight its involvement in the regulation of autophagy and mitophagy in neurons.

DOI: https://doi.org/10.1038/s41419-021-03742-4
Cell Death Dis. 2021 May 12. 12(5): 475

Mitochondrial fission and mitophagy are independent mechanisms regulating ischemia/reperfusion injury in primary neurons.

Anthony R Anzell, Garrett M Fogo, Zoya Gurm, Sarita Raghunayakula, Joseph M Wider, Kathleen J Maheras, Katlynn J Emaus, Timothy D Bryson, Madison Wang, Robert W Neumar, Karin Przyklenk, Thomas H Sanderson.

Mitochondrial dynamics and mitophagy are constitutive and complex systems that ensure a healthy mitochondrial network through the segregation and subsequent degradation of damaged mitochondria. Disruption of these systems can lead to mitochondrial dysfunction and has been established as a central mechanism of ischemia/reperfusion (I/R) injury. Emerging evidence suggests that mitochondrial dynamics and mitophagy are integrated systems; however, the role of this relationship in the context of I/R injury remains unclear. To investigate this concept, we utilized primary cortical neurons isolated from the novel dual-reporter mitochondrial quality control knockin mice (C57BL/6-Gt(ROSA)26Sortm1(CAG-mCherry/GFP)Ganl/J) with conditional knockout (KO) of Drp1 to investigate changes in mitochondrial dynamics and mitophagic flux during in vitro I/R injury. Mitochondrial dynamics was quantitatively measured in an unbiased manner using a machine learning mitochondrial morphology classification system, which consisted of four different classifications: network, unbranched, swollen, and punctate. Evaluation of mitochondrial morphology and mitophagic flux in primary neurons exposed to oxygen-glucose deprivation (OGD) and reoxygenation (OGD/R) revealed extensive mitochondrial fragmentation and swelling, together with a significant upregulation in mitophagic flux. Furthermore, the primary morphology of mitochondria undergoing mitophagy was classified as punctate. Colocalization using immunofluorescence as well as western blot analysis revealed that the PINK1/Parkin pathway of mitophagy was activated following OGD/R. Conditional KO of Drp1 prevented mitochondrial fragmentation and swelling following OGD/R but did not alter mitophagic flux. These data provide novel evidence that Drp1 plays a causal role in the progression of I/R injury, but mitophagy does not require Drp1-mediated mitochondrial fission.

DOI: https://doi.org/10.1038/s41419-021-03752-2
Mol Genet Metab. 2021 Apr 21. pii: S1096-7192(21)00695-8. [Epub ahead of print]

Phenotypic diversity of brain MRI patterns in mitochondrial aminoacyl-tRNA synthetase mutations.

Charles-Joris Roux, Giulia Barcia, Manuel Schiff, Marie Sissler, Raphaël Levy, Volodia Dangouloff-Ros, Isabelle Desguerre, Shimon Edvardson, Orli Elpeleg, Agnès Rötig, Arnold Munnich, Nathalie Boddaert.

   BACKGROUND AND PURPOSE: Mitochondrial aminoacyl-tRNA synthetases-encoded by ARS2 genes-are evolutionarily conserved enzymes that catalyse the attachment of amino acids to their cognate tRNAs, ensuring the accuracy of the mitochondrial translation process. ARS2 gene mutations are associated with a wide range of clinical presentations affecting the CNS.
METHODS: Two senior neuroradiologists analysed brain MRI of 25 patients (age range: 3 d-25 yrs.; 11 males; 14 females) with biallelic pathogenic variants of 11 ARS2 genes in a retrospective study conducted between 2002 and 2019.
RESULTS: Though several combinations of brain MRI anomalies were highly suggestive of specific aetiologies (DARS2, EARS2, AARS2 and RARS2 mutations), our study detected no MRI pattern common to all patients. Stroke-like lesions were associated with pathogenic SARS2 and FARS2 variants. We also report early onset cerebellar atrophy and calcifications in AARS2 mutations, early white matter involvement in RARS2 mutations, and absent involvement of thalami in EARS2 mutations. Finally, our findings show that normal brain MRI results do not exclude the presence of ARS2 mutations: 5 patients with normal MRI images were carriers of pathogenic IARS2, YARS2, and FARS2 variants.
CONCLUSION: Our study extends the spectrum of brain MRI anomalies associated with pathogenic ARS2 variants and suggests ARS2 mutations are largely underdiagnosed.

Keywords:  ARS; Aminoacyl-tRNA synthetases; Brain MRI; Mitochondria; Stroke-like

DOI:  https://doi.org/10.1016/j.ymgme.2021.04.004
Autophagy. 2021 May 09. 1-20

VCP/p97 cofactor UBXN1/SAKS1 regulates mitophagy by modulating MFN2 removal from mitochondria.

Chantal Mengus, Melanie Neutzner, Ana Catarina Pinho Ferreira Bento, Claudia C Bippes, Corina Kohler, Sarah Decembrini, Jessica Häusel, Charles Hemion, Lara Sironi, Stephan Frank, Hendrik P N Scholl, Albert Neutzner.

  Initiation of PINK1- and PRKN-dependent mitophagy is a highly regulated process involving the activity of the AAA-ATPase VCP/p97, a cofactor-guided multifunctional protein central to handling ubiquitinated client proteins. Removal of ubiquitinated substrates such as the mitofusin MFN2 from the outer mitochondrial membrane by VCP is critical for PRKN accumulation on mitochondria, which drives mitophagy. Here we characterize the role of the UBA and UBX-domain containing VCP cofactor UBXN1/SAKS1 during mitophagy. Following mitochondrial depolarization and depending on PRKN, UBXN1 translocated alongside VCP to mitochondria. Prior to mitophagy, loss of UBXN1 led to mitochondrial fragmentation, diminished ATP production, and impaired ER-mitochondrial apposition. When mitophagy was induced in cells lacking UBXN1, mitochondrial translocation of VCP and PRKN was impaired, diminishing mitophagic flux. In addition, UBXN1 physically interacted with PRKN in a UBX-domain depending manner. Interestingly, ectopic expression of the pro-mitophagic VCP cofactor UBXN6/UBXD1 fully reversed impaired PRKN recruitment in UBXN1-/- cells. Mechanistically, UBXN1 acted downstream of PINK1 by facilitating MFN2 removal from mitochondria. In UBXN1-/- cells exposed to mitochondrial stress, MFN2 formed para-mitochondrial blobs likely representing blocked intermediates of the MFN2 removal process partly reversible by expression of UBXN6. Presence of these MFN2 blobs strongly correlated with impaired PRKN translocation to depolarized mitochondria. Our observations connect the VCP cofactor UBXN1 to the initiation and maintenance phase of PRKN-dependent mitophagy, and indicate that, upon mitochondrial stress induction, MFN2 removal from mitochondria occurs through a specialized process.

Keywords:  MFN2; PRKN; UBXN1; UBXN6; VCP; mitophagy

DOI:  https://doi.org/10.1080/15548627.2021.1922982
Dev Cell. 2021 May 07. pii: S1534-5807(21)00359-2. [Epub ahead of print]

Neuronal mitochondrial dynamics coordinate systemic mitochondrial morphology and stress response to confer pathogen resistance in C. elegans.

Li-Tzu Chen, Chih-Ta Lin, Liang-Yi Lin, Jiun-Min Hsu, Yu-Chun Wu, Chun-Liang Pan.

  Mitochondrial functions across different tissues are regulated in a coordinated fashion to optimize the fitness of an organism. Mitochondrial unfolded protein response (UPRmt) can be nonautonomously elicited by mitochondrial perturbation in neurons, but neuronal signals that propagate such response and its physiological significance remain incompletely understood. Here, we show that in C. elegans, loss of neuronal fzo-1/mitofusin induces nonautonomous UPRmt through multiple neurotransmitters and neurohormones, including acetylcholine, serotonin, glutamate, tyramine, and insulin-like peptides. Neuronal fzo-1 depletion also triggers nonautonomous mitochondrial fragmentation, which requires autophagy and mitophagy genes. Systemic activation of UPRmt and mitochondrial fragmentation in C. elegans via perturbing neuronal mitochondrial dynamics improves resistance to pathogenic Pseudomonas infection, which is supported by transcriptomic signatures of immunity and stress-response genes. We propose that C. elegans surveils neuronal mitochondrial dynamics to coordinate systemic UPRmt and mitochondrial connectivity for pathogen defense and optimized survival under bacterial infection.

Keywords:  C. elegans; autophagy; mitochondria; mitochondrial dynamics; mitophagy; neurons; neuropeptides; neurotransmitters; pathogen defense; stress response

DOI:  https://doi.org/10.1016/j.devcel.2021.04.021
FEBS J. 2021 May 10.

Mitochondrial matrix proteases - quality control and beyond.

Karolina Szczepanowska, Aleksandra Trifunovic.

  To ensure correct function, mitochondria have developed several mechanisms of protein quality control (QC). Protein homeostasis highly relies on chaperones and proteases to maintain proper folding and remove damaged proteins that might otherwise form cell-toxic aggregates. Besides quality control, mitochondrial proteases modulate and regulate many essential functions, such as trafficking, processing, and activation of mitochondrial proteins, mitochondrial dynamics, mitophagy, and apoptosis. Therefore, the impaired function of mitochondrial proteases is associated with various pathological conditions, including cancer, metabolic syndromes, and neurodegenerative disorders. This review recapitulates and discusses the emerging roles of two major proteases of the mitochondrial matrix, LON and ClpXP. Although commonly acknowledge for their protein quality control role, recent advances have uncovered several highly regulated processes controlled by the LON and ClpXP connected to mitochondrial gene expression and respiratory chain function maintenance. Furthermore, both proteases have been lately recognized as potent targets for anti-cancer therapies, and we summarize those findings.

Keywords:  ClpXP; LONP1; cancer; degradation; metabolism; mitochondria; mitochondrial matrix; mtDNA; proteases; protein quality control; proteolysis; respiratory complexes

DOI:  https://doi.org/10.1111/febs.15964
Proc Natl Acad Sci U S A. 2021 May 18. pii: e2018770118. [Epub ahead of print]118(20):

TSG101 negatively regulates mitochondrial biogenesis in axons.

Tzu-Huai Lin, Dana M Bis-Brewer, Amy E Sheehan, Louise N Townsend, Daniel C Maddison, Stephan Züchner, Gaynor A Smith, Marc R Freeman.

  There is a tight association between mitochondrial dysfunction and neurodegenerative diseases and axons that are particularly vulnerable to degeneration, but how mitochondria are maintained in axons to support their physiology remains poorly defined. In an in vivo forward genetic screen for mutants altering axonal mitochondria, we identified tsg101 Neurons mutant for tsg101 exhibited an increase in mitochondrial number and decrease in mitochondrial size. TSG101 is best known as a component of the endosomal sorting complexes required for transport (ESCRT) complexes; however, loss of most other ESCRT components did not affect mitochondrial numbers or size, suggesting TSG101 regulates mitochondrial biology in a noncanonical, ESCRT-independent manner. The TSG101-mutant phenotype was not caused by lack of mitophagy, and we found that autophagy blockade was detrimental only to the mitochondria in the cell bodies, arguing mitophagy and autophagy are dispensable for the regulation of mitochondria number in axons. Interestingly, TSG101 mitochondrial phenotypes were instead caused by activation of PGC-1ɑ/Nrf2-dependent mitochondrial biogenesis, which was mTOR independent and TFEB dependent and required the mitochondrial fission-fusion machinery. Our work identifies a role for TSG101 in inhibiting mitochondrial biogenesis, which is essential for the maintenance of mitochondrial numbers and sizes, in the axonal compartment.

Keywords:  ESCRT; TSG101; mitochondria; mitochondrial biogenesis; neurodegeneration

DOI:  https://doi.org/10.1073/pnas.2018770118
J Nanobiotechnology. 2021 May 13. 19(1): 136

Nanoscopic quantification of sub-mitochondrial morphology, mitophagy and mitochondrial dynamics in living cells derived from patients with mitochondrial diseases.

Weiwei Zou, Qixin Chen, Jesse Slone, Li Yang, Xiaoting Lou, Jiajie Diao, Taosheng Huang.

  SLC25A46 mutations have been found to lead to mitochondrial hyper-fusion and reduced mitochondrial respiratory function, which results in optic atrophy, cerebellar atrophy, and other clinical symptoms of mitochondrial disease. However, it is generally believed that mitochondrial fusion is attributable to increased mitochondrial oxidative phosphorylation (OXPHOS), which is inconsistent with the decreased OXPHOS of highly-fused mitochondria observed in previous studies. In this paper, we have used the live-cell nanoscope to observe and quantify the structure of mitochondrial cristae, and the behavior of mitochondria and lysosomes in patient-derived SLC25A46 mutant fibroblasts. The results show that the cristae have been markedly damaged in the mutant fibroblasts, but there is no corresponding increase in mitophagy. This study suggests that severely damaged mitochondrial cristae might be the predominant cause of reduced OXPHOS in SLC25A46 mutant fibroblasts. This study demonstrates the utility of nanoscope-based imaging for realizing the sub-mitochondrial morphology, mitophagy and mitochondrial dynamics in living cells, which may be particularly valuable for the quick evaluation of pathogenesis of mitochondrial morphological abnormalities.

Keywords:  Cristae; Mitochondrial disease; Mitophagy; Nanoscope; SLC25A46

DOI:  https://doi.org/10.1186/s12951-021-00882-9
Neurosci Lett. 2021 May 07. pii: S0304-3940(21)00318-9. [Epub ahead of print] 135940

Mild hypothermia facilitates mitochondrial transfer from astrocytes to injured neurons during oxygen-glucose deprivation/reoxygenation.

Xiaowei Li, Yanli Li, Zhiqiang Zhang, Qinghu Bian, Zan Gao, Shan Zhang.

  Mitochondrial dysfunction is now considered an important sign of neuronal death during cerebral ischemia/reperfusion (I/R) injury. Studies have shown that the transfer of mitochondria from astrocytes to injured neurons contributes to endogenous neuroprotection after stroke. Basic and clinical studies have shown that mild hypothermia exerts a clear protective effect on neurons after cerebral ischemic injury, but the role of mild hypothermia in this endogenous neuroprotective mechanism remains unclear. Here, we established a neuronal cell oxygen-glucose deprivation (OGD)/reoxygenation (OGD/R)-induced injury model and explored the effect of mild hypothermia on the transfer of mitochondria from astrocytes to injured neurons. Astrocytes in the hypothermia group (33 °C) released more functional mitochondria into the extracellular medium than those in the normal temperature group (37 °C). Compared with cells in the normal temperature group, OGD-injured neuronal cells in the mild hypothermia group exhibited an increased intracellular ATP content, mitochondrial membrane potential (MMP) and cellular viability and a decreased death rate after the addition of astrocyte-derived conditioned medium. Based on the results of this study, mild hypothermia promotes endogenous neuroprotective effects through a mechanism related to functional mitochondria released from astrocytes into the extracellular space and transferred into injured neurons.

Keywords:  Mild hypothermia; Mitochondrial transfer; Oxygen-glucose deprivation/reoxygenation

DOI:  https://doi.org/10.1016/j.neulet.2021.135940
Brain. 2021 May 11. pii: awab186. [Epub ahead of print]

SREBP2 gene therapy targeting striatal astrocytes ameliorates Huntington's disease phenotypes.

Giulia Birolini, Gianluca Verlengia, Francesca Talpo, Claudia Maniezzi, Lorena Zentilin, Mauro Giacca, Paola Conforti, Chiara Cordiglieri, Claudio Caccia, Valerio Leoni, Franco Taroni, Gerardo Biella, Michele Simonato, Elena Cattaneo, Marta Valenza.

  Brain cholesterol is produced mainly by astrocytes and is important for neuronal function. Its biosynthesis is severely reduced in mouse models of Huntington's disease. One possible mechanism is a diminished nuclear translocation of the transcription factor sterol regulatory element binding protein 2 (SREBP2) and, consequently, reduced activation of SREBP-controlled genes in the cholesterol biosynthesis pathway. Here we evaluated the efficacy of a gene therapy based on the unilateral intra-striatal injection of a recombinant adeno-associated virus 2/5 (AAV2/5) targeting astrocytes specifically and carrying the transcriptionally active N-terminal fragment of human SREBP2. Robust hSREBP2 expression in striatal glial cells in R6/2 Huntington's disease mice activated the transcription of cholesterol biosynthesis pathway genes, restored synaptic transmission, reversed Drd2 transcript levels decline, cleared mutant Huntingtin aggregates and attenuated behavioral deficits. We conclude that glial SREBP2 participates in Huntington's disease brain pathogenesis in vivo and that AAV-based delivery of SREBP2 to astrocytes counteracts key features of the disease.

Keywords:  Huntington’s disease; SREBP2; astrocytes; cholesterol

DOI:  https://doi.org/10.1093/brain/awab186
J Cell Biol. 2021 Jul 05. pii: e202010006. [Epub ahead of print]220(7):

USP19 promotes hypoxia-induced mitochondrial division via FUNDC1 at ER-mitochondria contact sites.

Peiyuan Chai, Yiru Cheng, Chuyi Hou, Lei Yin, Donghui Zhang, Yingchun Hu, Qingzhou Chen, Pengli Zheng, Junlin Teng, Jianguo Chen.

The ER tethers tightly to mitochondria and the mitochondrial protein FUNDC1 recruits Drp1 to ER-mitochondria contact sites, subsequently facilitating mitochondrial fission and preventing mitochondria from undergoing hypoxic stress. However, the mechanisms by which the ER modulates hypoxia-induced mitochondrial fission are poorly understood. Here, we show that USP19, an ER-resident deubiquitinase, accumulates at ER-mitochondria contact sites under hypoxia and promotes hypoxia-induced mitochondrial division. In response to hypoxia, USP19 binds to and deubiquitinates FUNDC1 at ER-mitochondria contact sites, which facilitates Drp1 oligomerization and Drp1 GTP-binding and hydrolysis activities, thereby promoting mitochondrial division. Our findings reveal a unique hypoxia response pathway mediated by an ER protein that regulates mitochondrial dynamics.

DOI: https://doi.org/10.1083/jcb.202010006
Front Mol Biosci. 2021 ;8 620683

Resveratrol Improves Mitochondrial Biogenesis Function and Activates PGC-1α Pathway in a Preclinical Model of Early Brain Injury Following Subarachnoid Hemorrhage.

Jian Zhou, Zaijia Yang, Ruiming Shen, Wangwang Zhong, Huiduan Zheng, Zhenggang Chen, Jianjian Tang, Juan Zhu.

  Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) has been shown to play a pivotal role in the regulation of mitochondrial biogenesis in diseases. Resveratrol (RSV), a natural polyphenolic reagent, has powerful antioxidant properties and the ability to scavenge mitochondrial reactive oxygen species (ROS) in a variety of central nervous system diseases. However, the underlying molecular mechanisms of RSV on mitochondrial biogenesis in early brain injury (EBI) following subarachnoid hemorrhage (SAH) remain poorly understood. This study aimed to explore the potential neuroprotective effects of RSV on mitochondrial biogenesis and function by activation of the PGC-1α signaling pathway in a prechiasmatic cistern SAH model. PGC-1α expression and related mitochondrial biogenesis were detected. Amounts of nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM) were determined to evaluate the extent of mitochondrial biogenesis. Increased PGC-1α and mitochondrial biogenesis after SAH were observed in the temporal cortex. Resveratrol increased the expression of PGC-1α, NRF1, and TFAM, and promoted PGC-1α nuclear translocation. Moreover, RSV could scavenge excess ROS, increase the activity of superoxide dismutase (SOD), enhance the potential of mitochondrial membrane and ATP levels, reduce the number of mitochondrial DNA copy, and decrease the level of malondialdehyde (MDA). RSV significantly ameliorated the release of apoptosis-related cytokines, namely P53, cleaved caspase-3, cytochrome c, and BAX, leading to the amelioration of neuronal apoptosis, brain edema, and neurological impairment 24 h after SAH. These results indicate that resveratrol promotes mitochondrial biogenesis and function by activation of the PGC-1α signaling pathway in EBI following SAH.

Keywords:  PGC-1α; early brain injury; mitochondrial biogenesis-function; resveratrol; subarachnoid hemorrhage

DOI:  https://doi.org/10.3389/fmolb.2021.620683
Elife. 2021 May 11. pii: e65192. [Epub ahead of print]10

The role of sigma 1 receptor in organization of endoplasmic reticulum signaling microdomains.

Vladimir Zhemkov, Jonathon A Ditlev, Wan-Ru Lee, Mikaela Wilson, Jen Liou, Michael K Rosen, Ilya Bezprozvanny.

  Sigma 1 receptor (S1R) is a 223-amino-acid-long transmembrane endoplasmic reticulum (ER) protein. S1R modulates activity of multiple effector proteins and is a well-established drug target. However, signaling functions of S1R in cells are poorly understood. Here, we test the hypothesis that biological activity of S1R in cells can be explained by its ability to interact with cholesterol and to form cholesterol-enriched microdomains in the ER membrane. By performing experiments in reduced reconstitution systems, we demonstrate direct effects of cholesterol on S1R clustering. We identify a novel cholesterol-binding motif in the transmembrane region of human S1R. Mutations of this motif impair association of recombinant S1R with cholesterol beads, affect S1R clustering in vitro and disrupt S1R subcellular localization. We demonstrate that S1R-induced membrane microdomains have increased local membrane thickness and that increased local cholesterol concentration and/or membrane thickness in these microdomains can modulate signaling of inositol-requiring enzyme 1α in the ER. Further, S1R agonists cause disruption of S1R clusters, suggesting that biological activity of S1R agonists is linked to remodeling of ER membrane microdomains. Our results provide novel insights into S1R-mediated signaling mechanisms in cells.

Keywords:  cell biology; cholesterol; endoplasmic reticulum; human; lipid microdomains; mitochondria-associated membranes; neurodegeneration; neuroscience; sigma-1 receptor

DOI:  https://doi.org/10.7554/eLife.65192
Neuropathol Appl Neurobiol. 2021 May 11.

Prodromal sensory neuropathy in Pink1-/- SNCAA53T double mutant Parkinson mice.

Lucie Valek, Bao Tran, Annett Wilken-Schmitz, Sandra Trautmann, Juliana Heidler, Tobias Schmid, Bernhard Brüne, Dominique Thomas, Thomas Deller, Gerd Geisslinger, Georg Auburger, Irmgard Tegeder.

   AIMS: Parkinson's Disease (PD) is frequently associated with a prodromal sensory neuropathy manifesting with sensory loss and chronic pain. We have recently shown that PD-associated sensory neuropathy in patients is associated with high levels of glucosylceramides. Here, we assessed the underlying pathology and mechanisms in Pink1-/- SNCAA53T double mutant mice.
METHODS: We studied nociceptive and olfactory behaviour and the neuropathology of dorsal root ganglia (DRGs), including ultrastructure, mitochondrial respiration, transcriptomes, outgrowth and calcium currents of primary neurons, and tissue ceramides and sphingolipids before the onset of a PD-like disease that spontaneously develops in Pink1-/- SNCAA53T double mutant mice after 15 months of age.
RESULTS: Similar to PD patients, Pink1-/- SNCAA53T mice developed a progressive prodromal sensory neuropathy with a loss of thermal sensitivity starting as early as four months of age. In analogy to human plasma, lipid analyses revealed an accumulation of glucosylceramides (GlcCer) in the DRGs and sciatic nerves, which was associated with pathologic mitochondria, impairment of mitochondrial respiration, and deregulation of transient receptor potential and TRPV and TRPA channels at mRNA, protein and functional levels in DRGs. Direct exposure of DRG neurons to GlcCer caused transient hyperexcitability, followed by a premature decline of the viability of sensory neurons cultures upon repeated GlcCer application.
CONCLUSIONS: The results suggest that pathological GlcCer contribute to prodromal sensory disease in PD mice via mitochondrial damage and calcium channel hyperexcitability. GlcCer-associated sensory neuron pathology might be amenable to GlcCer lowering therapeutic strategies.

Keywords:  PTEN inducible kinase 1; Parkinson's Disease; alpha-synuclein; glucosylceramides; innate immunity; mitochondrial respiration; pain; sensory loss

DOI:  https://doi.org/10.1111/nan.12734
Mitochondrion. 2021 Apr 30. pii: S1567-7249(21)00058-1. [Epub ahead of print]59 113-122

Intermittent hypoxia preconditioning protects WRL68 cells against oxidative injury: Involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1.

Yapeng Lu, Jiangpei Bian, Huiwen Kan, Wangwang Ding, Dan Wang, Xueting Wang, Qianqian Luo, Xiaomei Wu, Li Zhu.

  The protective effect of intermittent hypoxia (IH) preconditioning against oxidative injury in hepatic cells was investigated and the involvement of the PINK1/Parkin-mediated mitophagy regulated by nuclear respiratory factor 1 (NRF-1) was evaluated. The results showed that IH preconditioning protected HepG2 cells against oxygen and glucose deprivation/reperfusion (OGD/Rep)-induced injury and protected WRL68 cells against H2O2 or AMA-induced oxidative injury. IH preconditioning up-regulated the protein level of NRF-1, PINK1, Parkin, and LC3 II, promoted the recruitment of the cytosolic Parkin, indicating the initiation of the PINK1/Parkin-mediated mitophagy in WRL68 cells. When NRF-1 was down-regulated by NRF-1 specific shRNA, the protein level of PINK1 and Parkin as well as the mitophagy level were significantly decreased. After IH preconditioning, the protein level of PINK1 and the recruitment of Parkin in CCCP-treated group were significantly higher than that of the control group, indicating the increased mitophagy capacity. And the increased mitophagy capacity induced by IH preconditioning was also reduced by down-regulation of NRF-1. Furthermore, the protective effect of IH preconditioning against H2O2-induced oxidative injury in WRL68 cells was inhibited when NRF-1 or PINK1 was down-regulated by specific shRNA. Mitochondrial ROS generation may be responsible for the increased expression of NRF-1 induced by IH preconditioning. In conclusion, the PINK1/Parkin-mediated mitophagy regulated by NRF-1 was involved in IH preconditioning-induced protective effect against oxidative cellular injury in hepatic cells.

Keywords:  Intermittent hypoxia; Mitophagy; Nuclear respiratory factor 1; PINK1; Parkin

DOI:  https://doi.org/10.1016/j.mito.2021.04.012
Mitochondrion. 2021 Apr 30. pii: S1567-7249(21)00059-3. [Epub ahead of print]59 105-112

MicroRNA-338 inhibition protects against focal cerebral ischemia and preserves mitochondrial function in vitro in astrocytes and neurons via COX4I1.

Le Li, Ludmila Voloboueva, Brian B Griffiths, Lijun Xu, Rona G Giffard, Creed M Stary.

  Brain-enriched microRNA-338 (miR-338) is known to play a central role in brain mitochondrial function, however the role of miR-338 in stroke injury remains unknown. This study investigated the role of miR-338 in injury from transient focal cerebral ischemia in mice, and in cell survival and mitochondrial function after in vitro ischemia in astrocyte and neuronal cultures. Pre-treatment of mice with intracerebroventricular injection of miR-338 antagomir 24 h prior to 1 h of middle cerebral artery occlusion (MCAO) significantly reduced infarct size and improved neurological score at both 24 h and 7d after injury. Levels of the miR-338 target cytochrome-c oxidase subunit 4I1 (COX4I1), which plays an essential role in maintaining brain mitochondrial ATP production, were increased in miR-338 antagomir-treated mice. Mouse primary astrocyte cell cultures subjected to glucose deprivation exhibited increased cell survival when pre-treated with miR-338 inhibitor, and greater cell death with miR-338 mimic. Decreased miR-338 levels were associated with increased ATP production, augmented cytochrome c oxidative (CcO) activity and preservation of COX4I1. In vitro protection with miR-338 inhibitor was blocked by concurrent knockdown of COX4I1 with small interfering RNA. Parallel studies in mouse neuronal N2a cultures resulted in preserved ATP content and CcO activity with miR-338 inhibition, indicating a shared miR-338-dependent response to ischemic stress between brain cell types. These results suggest that miR-338 inhibition and/or COX4I1-targeted therapies may be novel clinical strategies to protect against stroke injury via preservation of mitochondrial function in multiple cell types.

Keywords:  ATP; Glia; Oxidative phosphorylation; ROS; Stroke; TMRE; miRNA

DOI:  https://doi.org/10.1016/j.mito.2021.04.013
Nat Commun. 2021 May 10. 12(1): 2616

FUNDC1-dependent mitochondria-associated endoplasmic reticulum membranes are involved in angiogenesis and neoangiogenesis.

Cheng Wang, Xiaoyan Dai, Shengnan Wu, Wenjing Xu, Ping Song, Kai Huang.

FUN14 domain-containing protein 1 (FUNDC1) is an integral mitochondrial outer-membrane protein, and mediates the formation of mitochondria-associated endoplasmic reticulum membranes (MAMs). This study aims to determine the contributions of FUNDC1-mediated MAMs to angiogenesis in vitro and in vivo. In cultured endothelial cells, VEGF significantly increases the formation of MAMs and MAM-related proteins, including FUNDC1. Endothelial cell-specific deletion of FUNDC1, which disrupts MAM formation in endothelial cells, lowers VEGFR2 expression and reduces tube formation, spheroid-sprouting, and functional blood vessel formation in vitro and in vivo. Conversely, increased MAM formation using MAM linkers mimics the effects of VEGF and promotes endothelial angiogenesis. Mechanistically, increased MAMs formation led to increased levels of Ca2+ in cytosol, promoted the phosphorylation of serum response factor (SRF) and enhanced the binding of SRF to VEGFR2 promoter, resulting in increased VEGFR2 production, with consequent angiogenesis. Moreover, blocking FUNDC1-related MAM formation with a cell-penetrating inhibitory peptide significantly suppresses the expressions of downstream angiogenic genes and inhibits tumor angiogenesis. We conclude that decreased MAMs formation by silencing FUNDC1 can inhibit angiogenesis by decreasing VEGFR2 expression, and targeting FUNDC1-dependent MAMs might be a promising approach for treating human disorders characterized by defective angiogenesis.

DOI: https://doi.org/10.1038/s41467-021-22771-3
PLoS One. 2021 ;16(5): e0250606

Iron activates microglia and directly stimulates indoleamine-2,3-dioxygenase activity in the N171-82Q mouse model of Huntington's disease.

David W Donley, Marley Realing, Jason P Gigley, Jonathan H Fox.

Huntington's disease (HD) is a neurodegenerative disorder caused by a dominant CAG-repeat expansion in the huntingtin gene. Microglial activation is a key feature of HD pathology, and is present before clinical disease onset. The kynurenine pathway (KP) of tryptophan degradation is activated in HD, and is thought to contribute to disease progression. Indoleamine-2,3-dioxygenase (IDO) catalyzes the first step in this pathway; this and other pathway enzymes reside with microglia. While HD brain microglia accumulate iron, the role of iron in promoting microglial activation and KP activity is unclear. Here we utilized the neonatal iron supplementation model to investigate the relationship between iron, microglial activation and neurodegeneration in adult HD mice. We show in the N171-82Q mouse model of HD microglial morphologic changes consistent with immune activation. Neonatal iron supplementation in these mice promoted neurodegeneration and resulted in additional microglial activation in adults as determined by increased soma volume and decreased process length. We further demonstrate that iron activates IDO, both in brain lysates and purified recombinant protein (EC50 = 1.24 nM). Brain IDO activity is increased by HD. Neonatal iron supplementation further promoted IDO activity in cerebral cortex, altered KP metabolite profiles, and promoted HD neurodegeneration as measured by brain weights and striatal volumes. Our results demonstrate that dietary iron is an important activator of microglia and the KP pathway in this HD model, and that this occurs in part through a direct effect on IDO. The findings are relevant to understanding how iron promotes neurodegeneration in HD.

DOI: https://doi.org/10.1371/journal.pone.0250606
Pharm Res. 2021 May 12.

The Mitochondrial mitoNEET Ligand NL-1 Is Protective in a Murine Model of Transient Cerebral Ischemic Stroke.

Pushkar Saralkar, Alexander Mdzinarishvili, Tasneem A Arsiwala, Yoon-Kwang Lee, Patrick G Sullivan, Mark V Pinti, John M Hollander, Eric E Kelley, Xuefang Ren, Heng Hu, James Simpkins, Candice Brown, Lori E Hazlehurst, Jason D Huber, Werner J Geldenhuys.

   PURPOSE: Therapeutic strategies to treat ischemic stroke are limited due to the heterogeneity of cerebral ischemic injury and the mechanisms that contribute to the cell death. Since oxidative stress is one of the primary mechanisms that cause brain injury post-stroke, we hypothesized that therapeutic targets that modulate mitochondrial function could protect against reperfusion-injury after cerebral ischemia, with the focus here on a mitochondrial protein, mitoNEET, that modulates cellular bioenergetics.
METHOD: In this study, we evaluated the pharmacology of the mitoNEET ligand NL-1 in an in vivo therapeutic role for NL-1 in a C57Bl/6 murine model of ischemic stroke.
RESULTS: NL-1 decreased hydrogen peroxide production with an IC50 of 5.95 μM in neuronal cells (N2A). The in vivo activity of NL-1 was evaluated in a murine 1 h transient middle cerebral artery occlusion (t-MCAO) model of ischemic stroke. We found that mice treated with NL-1 (10 mg/kg, i.p.) at time of reperfusion and allowed to recover for 24 h showed a 43% reduction in infarct volume and 68% reduction in edema compared to sham-injured mice. Additionally, we found that when NL-1 was administered 15 min post-t-MCAO, the ischemia volume was reduced by 41%, and stroke-associated edema by 63%.
CONCLUSION: As support of our hypothesis, as expected, NL-1 failed to reduce stroke infarct in a permanent photothrombotic occlusion model of stroke. This report demonstrates the potential therapeutic benefits of using mitoNEET ligands like NL-1 as novel mitoceuticals for treating reperfusion-injury with cerebral stroke.

Keywords:  Bioenergetics; CDGSH; OXPHOS; PAMPA; iron-sulfur; t-MCAO

DOI:  https://doi.org/10.1007/s11095-021-03046-4
PLoS Biol. 2021 May 13. 19(5): e3001252

Generation of mitochondrial reactive oxygen species is controlled by ATPase inhibitory factor 1 and regulates cognition.

Pau B Esparza-Moltó, Inés Romero-Carramiñana, Cristina Núñez de Arenas, Marta P Pereira, Noelia Blanco, Beatriz Pardo, Georgina R Bates, Carla Sánchez-Castillo, Rafael Artuch, Michael P Murphy, José A Esteban, José M Cuezva.

The mitochondrial ATP synthase emerges as key hub of cellular functions controlling the production of ATP, cellular signaling, and fate. It is regulated by the ATPase inhibitory factor 1 (IF1), which is highly abundant in neurons. Herein, we ablated or overexpressed IF1 in mouse neurons to show that IF1 dose defines the fraction of active/inactive enzyme in vivo, thereby controlling mitochondrial function and the production of mitochondrial reactive oxygen species (mtROS). Transcriptomic, proteomic, and metabolomic analyses indicate that IF1 dose regulates mitochondrial metabolism, synaptic function, and cognition. Ablation of IF1 impairs memory, whereas synaptic transmission and learning are enhanced by IF1 overexpression. Mechanistically, quenching the IF1-mediated increase in mtROS production in mice overexpressing IF1 reduces the increased synaptic transmission and obliterates the learning advantage afforded by the higher IF1 content. Overall, IF1 plays a key role in neuronal function by regulating the fraction of ATP synthase responsible for mitohormetic mtROS signaling.

DOI: https://doi.org/10.1371/journal.pbio.3001252