bims-mecmid 2022-01-30 papers

bims-mecmid

Biomed News

on Membrane communication in mitochondrial dynamics

Issue of 2022–01–30
eleven papers selected by
Mauricio Cardenas Rodriguez, University of Padova

Mechanistic and therapeutic role of Drp1 in the pathogenesis of Alzheimer's Disease.
Coordinated Translocation of Presequence-Containing Precursor Proteins Across Two Mitochondrial Membranes: Knowns and Unknowns of How TOM and TIM23 Complexes Cooperate With Each Other.
Drp1/Fis1-Dependent Pathologic Fission and Associated Damaged Extracellular Mitochondria Contribute to Macrophage Dysfunction in Endotoxin Tolerance.
Dual role of Mic10 in mitochondrial cristae organization and ATP synthase-linked metabolic adaptation and respiratory growth.
Mitochondrial fragmentation is crucial for c-Myc-driven hepatoblastoma-like liver tumor.
Schizosaccharomyces pombe Fzo1 is subjected to the ubiquitin-proteasome-mediated degradation during the stationary phase.
Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria.
Propofol via Antioxidant Property Attenuated Hypoxia-Mediated Mitochondrial Dynamic Imbalance and Malfunction in Primary Rat Hippocampal Neurons.
N-acetyl L-cysteine ameliorates mitochondrial dysfunction in ischemia/reperfusion injury via attenuating Drp-1 mediated mitochondrial autophagy.
Mitofusin-2 Restrains Hepatic Stellate Cells' Proliferation via PI3K/Akt Signaling Pathway and Inhibits Liver Fibrosis in Rats.
Into the matrix: current methods for mitochondrial translation studies.

Eur J Neurosci. 2022 Jan 25.

Mechanistic and therapeutic role of Drp1 in the pathogenesis of Alzheimer's Disease.

Arpita Bera, Gantyada Lavanya, Ravada Reshmi, Kapil Dev, Rahul Kumar.

  Alzheimer's disease (AD), a progressive neurodegenerative disorder, has emerged as the most common form of dementia in the elderly. Two major pathological hallmarks have been identified for AD; extracellular amyloid plaques and intracellular neurofibrillary tangles (NFT). Recently, dynamin-related protein 1 (Drp1) was recognized to contribute significantly towards the pathogenesis of AD. Drp1 is primarily located in the cytosol, from where it translocates to the mitochondrial outer membrane and drives the mitochondrial fission via GTP hydrolysis. Drp1 interacts with Aβ and phosphorylated tau, leading to excessive mitochondrial fragmentation, which in turn results in synaptic dysfunction, neuronal damage, and cognitive decline. Several studies suggest an increase in the level of Drp1 in the post-mortem brain specimen collected from the AD patients and murine models of AD. Interestingly, heterozygous deletion of Drp1 in the transgenic murine model of AD ameliorates the mitochondrial dysfunction, improves learning and memory. The current review article discusses the possible mechanistic pathways by which Drp1 can influence the pathogenesis of AD. Besides, it will describe various inhibitors for Drp1 and their potential role as therapeutics for AD in the future.

Keywords:  Drp1; Mitophagy; Neurodegeneration; Neurofibrillary tangles; Tau phosphorylation; amyloid plaques

DOI:  https://doi.org/10.1111/ejn.15611
Front Physiol. 2021 ;12 806426

Coordinated Translocation of Presequence-Containing Precursor Proteins Across Two Mitochondrial Membranes: Knowns and Unknowns of How TOM and TIM23 Complexes Cooperate With Each Other.

Marcel G Genge, Dejana Mokranjac.

  The vast majority of mitochondrial proteins are encoded in the nuclear genome and synthesized on cytosolic ribosomes as precursor proteins with specific mitochondrial targeting signals. Mitochondrial targeting signals are very diverse, however, about 70% of mitochondrial proteins carry cleavable, N-terminal extensions called presequences. These amphipathic helices with one positively charged and one hydrophobic surface target proteins to the mitochondrial matrix with the help of the TOM and TIM23 complexes in the outer and inner membranes, respectively. Translocation of proteins across the two mitochondrial membranes does not take place independently of each other. Rather, in the intermembrane space, where the two complexes meet, components of the TOM and TIM23 complexes form an intricate network of protein-protein interactions that mediates initially transfer of presequences and then of the entire precursor proteins from the outer to the inner mitochondrial membrane. In this Mini Review, we summarize our current understanding of how the TOM and TIM23 complexes cooperate with each other and highlight some of the future challenges and unresolved questions in the field.

Keywords:  TIM23 complex; TOM complex; TOM-TIM23 contacts; intermembrane space; mitochondria; precursor transfer; presequence pathway; protein translocation

DOI:  https://doi.org/10.3389/fphys.2021.806426
Crit Care Med. 2022 Jan 24.

Drp1/Fis1-Dependent Pathologic Fission and Associated Damaged Extracellular Mitochondria Contribute to Macrophage Dysfunction in Endotoxin Tolerance.

Riddhita Mukherjee, Carly A Tompkins, Nicolai P Ostberg, Amit U Joshi, Liliana M Massis, Vijith Vijayan, Kanika Gera, Denise Monack, Timothy T Cornell, Mark W Hall, Daria Mochly-Rosen, Bereketeab Haileselassie.

OBJECTIVES: Recent publications have shown that mitochondrial dynamics can govern the quality and quantity of extracellular mitochondria subsequently impacting immune phenotypes. This study aims to determine if pathologic mitochondrial fission mediated by Drp1/Fis1 interaction impacts extracellular mitochondrial content and macrophage function in sepsis-induced immunoparalysis.
DESIGN: Laboratory investigation.
SETTING: University laboratory.
SUBJECTS: C57BL/6 and BALB/C mice.
INTERVENTIONS: Using in vitro and murine models of endotoxin tolerance (ET), we evaluated changes in Drp1/Fis1-dependent pathologic fission and simultaneously measured the quantity and quality of extracellular mitochondria. Next, by priming mouse macrophages with isolated healthy mitochondria (MC) and damaged mitochondria, we determined if damaged extracellular mitochondria are capable of inducing tolerance to subsequent endotoxin challenge. Finally, we determined if inhibition of Drp1/Fis1-mediated pathologic fission abrogates release of damaged extracellular mitochondria and improves macrophage response to subsequent endotoxin challenge.
MEASUREMENTS AND MAIN RESULTS: When compared with naïve macrophages (NMs), endotoxin-tolerant macrophages (ETM) demonstrated Drp1/Fis1-dependent mitochondrial dysfunction and higher levels of damaged extracellular mitochondria (Mitotracker-Green + events/50 μL: ETM = 2.42 × 106 ± 4,391 vs NM = 5.69 × 105 ± 2,478; p < 0.001). Exposure of NMs to damaged extracellular mitochondria (MH) induced cross-tolerance to subsequent endotoxin challenge, whereas MC had minimal effect (tumor necrosis factor [TNF]-α [pg/mL]: NM = 668 ± 3, NM + MH = 221 ± 15, and NM + Mc = 881 ± 15; p < 0.0001). Inhibiting Drp1/Fis1-dependent mitochondrial fission using heptapeptide (P110), a selective inhibitor of Drp1/Fis1 interaction, improved extracellular mitochondrial function (extracellular mitochondrial membrane potential, JC-1 [R/G] ETM = 7 ± 0.5 vs ETM + P110 = 19 ± 2.0; p < 0.001) and subsequently improved immune response in ETMs (TNF-α [pg/mL]; ETM = 149 ± 1 vs ETM + P110 = 1,150 ± 4; p < 0.0001). Similarly, P110-treated endotoxin tolerant mice had lower amounts of damaged extracellular mitochondria in plasma (represented by higher extracellular mitochondrial membrane potential, TMRM/MT-G: endotoxin tolerant [ET] = 0.04 ± 0.02 vs ET + P110 = 0.21 ± 0.02; p = 0.03) and improved immune response to subsequent endotoxin treatment as well as cecal ligation and puncture.
CONCLUSIONS: Inhibition of Drp1/Fis1-dependent mitochondrial fragmentation improved macrophage function and immune response in both in vitro and in vivo models of ET. This benefit is mediated, at least in part, by decreasing the release of damaged extracellular mitochondria, which contributes to endotoxin cross-tolerance. Altogether, these data suggest that alterations in mitochondrial dynamics may play an important role in sepsis-induced immunoparalysis.

DOI: https://doi.org/10.1097/CCM.0000000000005437
Cell Rep. 2022 Jan 25. pii: S2211-1247(21)01805-2. [Epub ahead of print]38(4): 110290

Dual role of Mic10 in mitochondrial cristae organization and ATP synthase-linked metabolic adaptation and respiratory growth.

Heike Rampelt, Florian Wollweber, Mariya Licheva, Rinse de Boer, Inge Perschil, Liesa Steidle, Thomas Becker, Maria Bohnert, Ida van der Klei, Claudine Kraft, Martin van der Laan, Nikolaus Pfanner.

  Invaginations of the mitochondrial inner membrane, termed cristae, are hubs for oxidative phosphorylation. The mitochondrial contact site and cristae organizing system (MICOS) and the dimeric F1Fo-ATP synthase play important roles in controlling cristae architecture. A fraction of the MICOS core subunit Mic10 is found in association with the ATP synthase, yet it is unknown whether this interaction is of relevance for mitochondrial or cellular functions. Here, we established conditions to selectively study the role of Mic10 at the ATP synthase. Mic10 variants impaired in MICOS functions stimulate ATP synthase oligomerization like wild-type Mic10 and promote efficient inner membrane energization, adaptation to non-fermentable carbon sources, and respiratory growth. Mic10's functions in respiratory growth largely depend on Mic10ATPsynthase, not on Mic10MICOS. We conclude that Mic10 plays a dual role as core subunit of MICOS and as partner of the F1Fo-ATP synthase, serving distinct functions in cristae shaping and respiratory adaptation and growth.

Keywords:  ATP synthase; MICOS; Mic10; cristae organization; inner membrane; membrane architecture; membrane potential; metabolic adaptation; mitochondria; respiration

DOI:  https://doi.org/10.1016/j.celrep.2021.110290
Mol Ther. 2022 Jan 24. pii: S1525-0016(22)00032-6. [Epub ahead of print]

Mitochondrial fragmentation is crucial for c-Myc-driven hepatoblastoma-like liver tumor.

Dalin Wang, Jiming Tian, Zeyu Yan, Qing Yuan, Dan Wu, Xiaoli Liu, Shirong Yang, Shanshan Guo, Jianxun Wang, Yongxiu Yang, Jinliang Xing, Jiaze An, Qichao Huang.

Hepatoblastoma is the most common liver cancer in children, and the aggressive subtype often has a poor prognosis and lacks effective targeted therapy. Although aggressive HB is often accompanied by abnormally high expression of the transcription factor c-Myc, the underlying mechanism remains unclear. In this study, we found that mitochondrial fragmentation was enhanced by c-Myc overexpression in human aggressive HB tissues and was associated with poor prognosis. Then, a mouse model resembling human HB was established via hydrodynamic injection of c-Myc plasmids. We observed that liver-specific knockout of mitochondrial fusion molecule MFN1 or overexpression of mitochondrial fission molecule DRP1 promoted the occurrence of c-Myc-driven liver cancer. In contrast, when MFN1 was overexpressed in the liver, tumor formation was delayed. In vitro experiments showed that c-Myc transcriptionally upregulated the expression of DRP1 and decreased MFN1 expression through upregulation of miR-373-3p. Moreover, enhanced mitochondrial fragmentation significantly promoted aerobic glycolysis and the proliferation of HB cells by significantly increasing ROS production and activating the AKT/mTOR and NF-κB pathways. Taken together, our results indicate that c-Myc-mediated mitochondrial fragmentation promotes malignant transformation and progression of HB by activating ROS-mediated multi-oncogenic signaling.

DOI: https://doi.org/10.1016/j.ymthe.2022.01.032
Int Microbiol. 2022 Jan 25.

Schizosaccharomyces pombe Fzo1 is subjected to the ubiquitin-proteasome-mediated degradation during the stationary phase.

Fawad Ahmad, Yun Zhang, Helong Yin, Ying Luo, Ying Huang.

  Mitochondria are highly dynamic organelles that undergo fission and fusion to adapt to the metabolic needs of the cell. Mitofusins are dynamin-like GTPases that play a key role in the regulation of mitochondrial fusion and metabolism. In Saccharomyces cerevisiae, mitofusin Fzo1 levels are controlled by post-translational ubiquitination and degradation. However, it is not clear whether the levels of the Schizosaccharomyces pombe mitofusin Fzo1 are similarly regulated. In this study, we examined the expression S. pombe Fzo1 during normal growth. We showed that Fzo1 protein levels but not mRNA expression levels were reduced during the stationary phase. The protein was stabilized by the proteasome inhibitor bortezomib. Disruption of ubc8 encoding a ubiquitin-conjugating enzyme and rsv2 encoding an S. pombe homolog of S. cerevisiae RPN4 known for activating the expression of genes required for proteasomal biogenesis suppresses the proteasomal degradation of Fzo1 during the stationary phase. Overexpression of fzo1 prevents its degradation. Our results suggest that like S. pombe Fzo1 expression is not regulated by transcription but rather by proteolytic degradation during the stationary phase. Our findings also suggest that although S. cerevisiae and S. pombe Fzo1 proteins are regulated by ubiquitin-proteasomal degradation, different ubiquitin-conjugating enzymes (E2) and ubiquitin ligases (E3) are involved in their degradation.

Keywords:  Fzo1 protein; Mitochondrial function; Schizosaccharomyces pombe; Ubc8 protein; Ubiquitin–proteasome pathway

DOI:  https://doi.org/10.1007/s10123-022-00231-2
J Vis Exp. 2022 Jan 07.

Measurement of Protein Import Capacity of Skeletal Muscle Mitochondria.

Ashley N Oliveira, Brandon J Richards, David A Hood.

Mitochondria are key metabolic and regulatory organelles that determine the energy supply as well as the overall health of the cell. In skeletal muscle, mitochondria exist in a series of complex morphologies, ranging from small oval organelles to a broad, reticulum-like network. Understanding how the mitochondrial reticulum expands and develops in response to diverse stimuli such as alterations in energy demand has long been a topic of research. A key aspect of this growth, or biogenesis, is the import of precursor proteins, originally encoded by the nuclear genome, synthesized in the cytosol, and translocated into various mitochondrial sub-compartments. Mitochondria have developed a sophisticated mechanism for this import process, involving many selective inner and outer membrane channels, known as the protein import machinery (PIM). Import into the mitochondrion is dependent on viable membrane potential and the availability of organelle-derived ATP through oxidative phosphorylation. Therefore its measurement can serve as a measure of organelle health. The PIM also exhibits a high level of adaptive plasticity in skeletal muscle that is tightly coupled to the energy status of the cell. For example, exercise training has been shown to increase import capacity, while muscle disuse reduces it, coincident with changes in markers of mitochondrial content. Although protein import is a critical step in the biogenesis and expansion of mitochondria, the process is not widely studied in skeletal muscle. Thus, this paper outlines how to use isolated and fully functional mitochondria from skeletal muscle to measure protein import capacity in order to promote a greater understanding of the methods involved and an appreciation of the importance of the pathway for organelle turnover in exercise, health, and disease.

DOI: https://doi.org/10.3791/63055
Oxid Med Cell Longev. 2022 ;2022 6298786

Propofol via Antioxidant Property Attenuated Hypoxia-Mediated Mitochondrial Dynamic Imbalance and Malfunction in Primary Rat Hippocampal Neurons.

Jingfeng Han, Weiping Tao, Wei Cui, Jiawei Chen.

Background: Hypoxia may induce mitochondrial abnormality, which is associated with a variety of clinical phenotypes in the central nervous system. Propofol is an anesthetic agent with neuroprotective property. We examined whether and how propofol protected hypoxia-induced mitochondrial abnormality in neurons.
Methods: Primary rat hippocampal neurons were exposed to propofol followed by hypoxia treatment. Neuron viability, mitochondrial morphology, mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential (MMP), and adenosine triphosphate (ATP) production were measured. Mechanisms including reactive oxygen species (ROS), extracellular regulated protein kinase (ERK), protein kinase A (PKA), HIF-1α, Drp1, Fis1, Mfn1, Mfn2, and Opa1 were investigated.
Results: Hypoxia increased intracellular ROS production and induced mPTP opening, while reducing ATP production, MMP values, and neuron viability. Hypoxia impaired mitochondrial dynamic balance by increasing mitochondrial fragmentation. Further, hypoxia induced the translocation of HIF-1α and increased the expression of Drp1, while having no effect on Fis1 expression. In addition, hypoxia induced the phosphorylation of ERK and Drp1ser616, while reducing the phosphorylation of PKA and Drp1ser637. Importantly, we demonstrated all these effects were attenuated by pretreatment of neurons with 50 μM propofol, antioxidant α-tocopherol, and ROS scavenger ebselen. Besides, hypoxia, propofol, α-tocopherol, or ebselen had no effect on the expression of Mfn1, Mfn2, and Opa1.
Conclusions: In rat hippocampal neurons, hypoxia induced oxidative stress, caused mitochondrial dynamic imbalance and malfunction, and reduced neuron viability. Propofol protected mitochondrial abnormality and neuron viability via antioxidant property, and the molecular mechanisms involved HIF-1α-mediated Drp1 expression and ERK/PKA-mediated Drp1 phosphorylation.

DOI: https://doi.org/10.1155/2022/6298786
Life Sci. 2022 Jan 19. pii: S0024-3205(22)00038-8. [Epub ahead of print] 120338

N-acetyl L-cysteine ameliorates mitochondrial dysfunction in ischemia/reperfusion injury via attenuating Drp-1 mediated mitochondrial autophagy.

Mubashshir Ali, Heena Tabassum, Mohd Mumtaz Alam, Suhel Parvez.

   BACKGROUND AND PURPOSE: Ischemic reperfusion (I/R) injury causes a wide array of functional and structure alternations of mitochondria, associated with oxidative stress and increased the severity of injury. Despite the previous evidence for N-acetyl L-cysteine (NAC) provide neuroprotection after I/R injury, it is unknown to evaluate the effect of NAC on altered mitochondrial autophagy forms an essential axis to impaired mitochondrial quality control in cerebral I/R injury.
METHODS: Male wistar rats subjected to I/R injury were used as transient Middle Cerebral Artery Occlusion (tMCAO) model. After I/R injury, the degree of cerebral tissue injury was detected by infarct volume, H&E staining and behavioral assessment. We also performed mitochondrial reactive oxygen species and mitochondrial membrane potential by flow cytometry and mitochondrial respiratory complexes to evaluate the mitochondrial dysfunction. Finally, we performed the western blotting analysis to measure the apoptotic and autophagic marker.
RESULTS: We found that NAC administration significantly ameliorates brain injury, improves neurobehavioral outcome, decreases neuroinflammation and mitochondrial mediated oxidative stress. We evaluated the neuroprotective effect of NAC against neuronal apoptosis by assessing its ability to sustained mitochondrial integrity and function. Further studies revealed that beneficial effects of NAC is through targeting the mitochondrial autophagy via regulating the GSK-3β/Drp1mediated mitochondrial fission and inhibiting the expression of beclin-1 and conversion of LC3, as well as activating the p-Akt pro-survival pathway.
CONCLUSION: Our results suggest that NAC exerts neuroprotective effects to inhibit the altered mitochondrial changes and cell death in I/R injury via regulation of p-GSK-3β mediated Drp-1 translocation to the mitochondria.

Keywords:  Apoptosis; Autophagy; Drp-1; Ischemic-stroke; Mitochondria

DOI:  https://doi.org/10.1016/j.lfs.2022.120338
J Healthc Eng. 2022 ;2022 6731335

Mitofusin-2 Restrains Hepatic Stellate Cells' Proliferation via PI3K/Akt Signaling Pathway and Inhibits Liver Fibrosis in Rats.

Zhiping Chen, Zeyu Lin, Jiandong Yu, Haifeng Zhong, Xianhua Zhuo, Changku Jia, Yunle Wan.

The mitochondrial GTPase mitofusin-2 (MFN2) gene can suppress the cell cycle and regulate cell proliferation in a number of cell types. However, its function in hepatic fibrosis remains largely unexplored. We attempted to understand the mechanism of MFN2 in hepatic stellate cell (HSC) proliferation and the development of hepatic fibrosis. Rat HSC-T6 HSC were cultured and transfected by adenovirus- (Ad-) Mfn2 or its negative control (NC) vector (Ad-green fluorescent protein (GFP)); a rat liver cirrhosis model was established via subcutaneous injection with carbon tetrachloride (CCl4). Seventy-two rats were randomly divided into four groups: CCl4, Mfn2, GFP, and NC. Ad-Mfn2 or Ad-GFP was transfected into the circulation via intravenous injection at day 1, 14, 28, 42, or 56 after the first injection of CCl4 in the Mfn2/GFP groups. Biomarkers related to HSC proliferation and the development of hepatic fibrosis were detected using western blotting, hematoxylin-eosin and Masson staining, and immunohistochemistry. In vitro, Mfn2 interfered specifically with platelet-derived growth factor- (PDGF-) induced signaling pathway (phosphatidylinositol 3-kinase- (PI3K-) AKT), inhibiting HSC-T6 cell activation and proliferation. During the process of hepatic fibrosis in vivo, extracellular collagen deposition and the expression of fibrosis-related proteins increased progressively, while Mfn2 expression decreased gradually. Upregulating Mfn2 expression at the early stage of fibrosis impeded the process, triggered the downregulation of type I collagen, and antagonized the formation of factors associated with liver fibrosis. Mfn2 suppresses HSC proliferation and activation and exhibits antifibrotic potential in early-stage hepatic fibrosis. Therefore, it may represent a significant therapeutic target for eradicating hepatic fibrosis.

DOI: https://doi.org/10.1155/2022/6731335
J Biochem. 2022 Jan 26. pii: mvac005. [Epub ahead of print]

Into the matrix: current methods for mitochondrial translation studies.

Antonios Apostolopoulos, Shintaro Iwasaki.

  In addition to the cytoplasmic translation system, eukaryotic cells house additional protein synthesis machinery in mitochondria. The importance of this in organello translation is exemplified by clinical pathologies associated with mutations in mitochondrial translation factors. Although a detailed understanding of mitochondrial translation has long been awaited, quantitative, comprehensive, and spatiotemporal measurements have posed analytic challenges. The recent development of novel approaches for studying mitochondrial protein synthesis has overcome these issues and expands our understanding of the unique translation system. Here, we review the current technologies for the investigation of mitochondrial translation and the insights provided by their application.

Keywords:  FUNCAT; Mitochondria; Mitoribosome; Ribosome profiling; Translation

DOI:  https://doi.org/10.1093/jb/mvac005