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The Pathomechanism of Mitochondrial Diseases
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The Pathomechanism of Mitochondrial Diseases

A topical collection in Cells (ISSN 2073-4409). This collection belongs to the section "Mitochondria".

Viewed by 27109

Editor

Prof. Ann Saada

E-Mail Website
Collection Editor
Hadassah Medical Center; Department of Genetics and Hebrew University of Jerusalem; Faculty of Medicince, pob 12000, Jerusalem 9112001, Israel
Interests: pathomechanism of inborn errors of metabolism and mitochondrial diseases; mitochondrial respiratory chain function in health and disease

Topical Collection Information

Dear Colleagues,

Mitochondrial diseases are a heterogenous group of common inborn errors of metabolism, originating from pathogenic variants in the mitochondrial or nuclear genome, resulting in respiratory chain deficiency, mostly with devastating consequences. Moreover, mitochondrial dysfunction is associated with numerous other pathological conditions, including neurodegenerative diseases, diabetes, cancer, immune dysfunction, and heart and kidney diseases.

Although next-generation sequencing (NGS) techniques are a game changer in the diagnosis of mitochondrial diseases, they have not signtificantly resulted in providing better treatment options, which are presently very limited. Studying the patomechanistic aspects (cell biology and physiology, molecular biology, and biophysics) of the individual diseases in cellular and animal models is a vital step towards developing more effective treatments.

The aim of this Topical Collection is to broaden knowledge and understanding of the various pathomechanisms involving mitochondrial dysfuction in disease, including evaluating the effect of small molecules and other treatments in model systems.

Prof. Ann Saada
Collection Editor

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Keywords

  • mitochondrial diseases
  • mitochondrial dysfunction
  • mitochondrial respiratory chain
  • mitochondrial DNA
  • pathomechanism
  • treatment

Published Papers (8 papers)

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2023

Jump to: 2022, 2021

22 pages, 4227 KiB  
Article
Systematic Approaches to Study Eclipsed Targeting of Proteins Uncover a New Family of Mitochondrial Proteins
by Maayan Mark, Ofir Klein, Yu Zhang, Koyeli Das, Adi Elbaz, Reut Noa Hazan, Michal Lichtenstein, Norbert Lehming, Maya Schuldiner and Ophry Pines
Cells 2023, 12(11), 1550; https://doi.org/10.3390/cells12111550 - 05 Jun 2023
Cited by 1 | Viewed by 1279
Abstract
Dual localization or dual targeting refers to the phenomenon by which identical, or almost identical, proteins are localized to two (or more) separate compartments of the cell. From previous work in the field, we had estimated that a third of the mitochondrial proteome [...] Read more.
Dual localization or dual targeting refers to the phenomenon by which identical, or almost identical, proteins are localized to two (or more) separate compartments of the cell. From previous work in the field, we had estimated that a third of the mitochondrial proteome is dual-targeted to extra-mitochondrial locations and suggested that this abundant dual targeting presents an evolutionary advantage. Here, we set out to study how many additional proteins whose main activity is outside mitochondria are also localized, albeit at low levels, to mitochondria (eclipsed). To do this, we employed two complementary approaches utilizing the α-complementation assay in yeast to uncover the extent of such an eclipsed distribution: one systematic and unbiased and the other based on mitochondrial targeting signal (MTS) predictions. Using these approaches, we suggest 280 new eclipsed distributed protein candidates. Interestingly, these proteins are enriched for distinctive properties compared to their exclusively mitochondrial-targeted counterparts. We focus on one unexpected eclipsed protein family of the Triose-phosphate DeHydrogenases (TDH) and prove that, indeed, their eclipsed distribution in mitochondria is important for mitochondrial activity. Our work provides a paradigm of deliberate eclipsed mitochondrial localization, targeting and function, and should expand our understanding of mitochondrial function in health and disease. Full article
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2022

Jump to: 2023, 2021

26 pages, 3314 KiB  
Review
Mitochondrial VDAC1: A Potential Therapeutic Target of Inflammation-Related Diseases and Clinical Opportunities
by Hang Hu, Linlin Guo, Jay Overholser and Xing Wang
Cells 2022, 11(19), 3174; https://doi.org/10.3390/cells11193174 - 10 Oct 2022
Cited by 16 | Viewed by 5192
Abstract
The multifunctional protein, voltage-dependent anion channel 1 (VDAC1), is located on the mitochondrial outer membrane. It is a pivotal protein that maintains mitochondrial function to power cellular bioactivities via energy generation. VDAC1 is involved in regulating energy production, mitochondrial oxidase stress, Ca2+ [...] Read more.
The multifunctional protein, voltage-dependent anion channel 1 (VDAC1), is located on the mitochondrial outer membrane. It is a pivotal protein that maintains mitochondrial function to power cellular bioactivities via energy generation. VDAC1 is involved in regulating energy production, mitochondrial oxidase stress, Ca2+ transportation, substance metabolism, apoptosis, mitochondrial autophagy (mitophagy), and many other functions. VDAC1 malfunction is associated with mitochondrial disorders that affect inflammatory responses, resulting in an up-regulation of the body’s defensive response to stress stimulation. Overresponses to inflammation may cause chronic diseases. Mitochondrial DNA (mtDNA) acts as a danger signal that can further trigger native immune system activities after its secretion. VDAC1 mediates the release of mtDNA into the cytoplasm to enhance cytokine levels by activating immune responses. VDAC1 regulates mitochondrial Ca2+ transportation, lipid metabolism and mitophagy, which are involved in inflammation-related disease pathogenesis. Many scientists have suggested approaches to deal with inflammation overresponse issues via specific targeting therapies. Due to the broad functionality of VDAC1, it may become a useful target for therapy in inflammation-related diseases. The mechanisms of VDAC1 and its role in inflammation require further exploration. We comprehensively and systematically summarized the role of VDAC1 in the inflammatory response, and hope that our research will lead to novel therapeutic strategies that target VDAC1 in order to treat inflammation-related disorders. Full article
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15 pages, 7618 KiB  
Review
Is Type 2 Diabetes a Primary Mitochondrial Disorder?
by Sarah Weksler-Zangen
Cells 2022, 11(10), 1617; https://doi.org/10.3390/cells11101617 - 12 May 2022
Cited by 11 | Viewed by 3087
Abstract
Diabetes mellitus is the most common endocrine disturbance in inherited mitochondrial diseases. It is essential to increase awareness of the correct diagnosis and treatment of diabetes in these patients and screen for the condition in family members, as diabetes might appear with distinctive [...] Read more.
Diabetes mellitus is the most common endocrine disturbance in inherited mitochondrial diseases. It is essential to increase awareness of the correct diagnosis and treatment of diabetes in these patients and screen for the condition in family members, as diabetes might appear with distinctive clinical features, complications and at different ages of onset. The severity of mitochondrial-related diabetes is likely to manifest on a large scale of phenotypes depending on the location of the mutation and whether the number of affected mitochondria copies (heteroplasmy) reaches a critical threshold. Regarding diabetes treatment, the first-choice treatment for type 2 diabetes (T2D), metformin, is not recommended because of the risk of lactic acidosis. The preferred treatment for diabetes in patients with mitochondrial disorders is SGLT-2i and mitochondrial GLP-1-related substances. The tight relationship between mitochondrial dysfunction, reduced glucose-stimulated insulin secretion (GSIS), and diabetes development in human patients is acknowledged. However, despite the well-characterized role of mitochondria in GSIS, there is a relative lack of data in humans implicating mitochondrial dysfunction as a primary defect in T2D. Our recent studies have provided data supporting the significant role of the mitochondrial respiratory-chain enzyme, cytochrome c oxidase (COX), in regulating GSIS in a rodent model of T2D, the Cohen diabetic sensitive (CDs) rat. The nutritionally induced diabetic CDs rat demonstrates several features of mitochondrial diseases: markedly reduced COX activity in several tissues, increased reactive oxygen production, decreased ATP generation, and increased lactate dehydrogenase expression in islets. Moreover, our data demonstrate that reduced islet-COX activity precedes the onset of diabetes, suggesting that islet-COX deficiency is the primary defect causing diabetes in this model. This review examines the possibility of including T2D as a primary mitochondrial-related disease. Understanding the critical interdependence between diabetes and mitochondrial dysfunction, centering on the role of COX, may open novel avenues to diagnose and treat diabetes in patients with mitochondrial diseases and mitochondrial dysfunction in diabetic patients. Full article
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10 pages, 1700 KiB  
Article
Biallelic Variants in ENDOG Associated with Mitochondrial Myopathy and Multiple mtDNA Deletions
by Alessia Nasca, Andrea Legati, Megi Meneri, Melisa Emel Ermert, Chiara Frascarelli, Nadia Zanetti, Manuela Garbellini, Giacomo Pietro Comi, Alessia Catania, Costanza Lamperti, Dario Ronchi and Daniele Ghezzi
Cells 2022, 11(6), 974; https://doi.org/10.3390/cells11060974 - 12 Mar 2022
Cited by 5 | Viewed by 2568
Abstract
Endonuclease G (ENDOG) is a nuclear-encoded mitochondrial-localized nuclease. Although its precise biological function remains unclear, its proximity to mitochondrial DNA (mtDNA) makes it an excellent candidate to participate in mtDNA replication, metabolism and maintenance. Indeed, several roles for ENDOG have been hypothesized, including [...] Read more.
Endonuclease G (ENDOG) is a nuclear-encoded mitochondrial-localized nuclease. Although its precise biological function remains unclear, its proximity to mitochondrial DNA (mtDNA) makes it an excellent candidate to participate in mtDNA replication, metabolism and maintenance. Indeed, several roles for ENDOG have been hypothesized, including maturation of RNA primers during mtDNA replication, splicing of polycistronic transcripts and mtDNA repair. To date, ENDOG has been deemed as a determinant of cardiac hypertrophy, but no pathogenic variants or genetically defined patients linked to this gene have been described. Here, we report biallelic ENDOG variants identified by NGS in a patient with progressive external ophthalmoplegia, mitochondrial myopathy and multiple mtDNA deletions in muscle. The absence of the ENDOG protein in the patient’s muscle and fibroblasts indicates that the identified variants are pathogenic. The presence of multiple mtDNA deletions supports the role of ENDOG in mtDNA maintenance; moreover, the patient’s clinical presentation is very similar to mitochondrial diseases caused by mutations in other genes involved in mtDNA homeostasis. Although the patient’s fibroblasts did not present multiple mtDNA deletions or delay in the replication process, interestingly, we detected an accumulation of low-level heteroplasmy mtDNA point mutations compared with age-matched controls. This may indicate a possible role of ENDOG in mtDNA replication or repair. Our report provides evidence of the association of ENDOG variants with mitochondrial myopathy. Full article
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12 pages, 2698 KiB  
Article
Cytochrome c Oxidase Activity as a Metabolic Regulator in Pancreatic Beta-Cells
by Genya Aharon-Hananel, Leonor Romero-Afrima, Ann Saada, Carmit Mantzur, Itamar Raz and Sarah Weksler-Zangen
Cells 2022, 11(6), 929; https://doi.org/10.3390/cells11060929 - 08 Mar 2022
Cited by 8 | Viewed by 2323
Abstract
Pancreatic β-cells couple glucose-stimulated insulin secretion (GSIS) with oxidative phosphorylation via cytochrome c oxidase (COX), a mitochondrial respiratory-chain enzyme. The Cohen diabetic-sensitive (CDs) rats exhibit hyperglycemia when fed a diabetogenic diet but maintain normoglycemia on a regular diet. We have previously reported a [...] Read more.
Pancreatic β-cells couple glucose-stimulated insulin secretion (GSIS) with oxidative phosphorylation via cytochrome c oxidase (COX), a mitochondrial respiratory-chain enzyme. The Cohen diabetic-sensitive (CDs) rats exhibit hyperglycemia when fed a diabetogenic diet but maintain normoglycemia on a regular diet. We have previously reported a decreased COX activity in CDs rats and explored its relevance for type 2 diabetes (T2D). In this study, we investigated the relation between COX activity in islets, peripheral-blood mononuclear cells (PBMCs), and GSIS during diabetes development in CDs rats fed a diabetogenic diet for 4, 11, 20, and 30 days and during reversion to normoglycemia in hyperglycemic CDs rats fed a reversion diet for 7, 11, and 20 days. An oral glucose-tolerance test was performed at different periods of the diets measuring blood glucose and insulin concentrations. COX activity was determined in islets and PBMCs isolated from rats at the different periods of the diets. We demonstrated a progressive reduction in COX activity in CDs-islets that correlated positively with the decreasing GSIS (R2 = 0.9691, p < 0.001) and inversely with the elevation in blood glucose levels (R2 = 0.8396, p < 0.001). Hyperglycemia was initiated when islet COX activity decreased below 46%. The reversion diet restored >46% of the islet COX activity and GSIS while re-establishing normoglycemia. Interestingly, COX activity in PBMCs correlated significantly with islet COX activity (R2 = 0.8944, p < 0.001). Our data support islet COX activity as a major metabolic regulator of β-cells function. The correlation between COX activity in PBMCs and islets may serve as a noninvasive biomarker to monitor β-cell dysfunction in diabetes. Full article
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17 pages, 4397 KiB  
Article
Multifaceted Analyses of Isolated Mitochondria Establish the Anticancer Drug 2-Hydroxyoleic Acid as an Inhibitor of Substrate Oxidation and an Activator of Complex IV-Dependent State 3 Respiration
by Kumudesh Mishra, Mária Péter, Anna Maria Nardiello, Guy Keller, Victoria Llado, Paula Fernandez-Garcia, Ulf D. Kahlert, Dinorah Barasch, Ann Saada, Zsolt Török, Gábor Balogh, Pablo V. Escriba, Stefano Piotto and Or Kakhlon
Cells 2022, 11(3), 578; https://doi.org/10.3390/cells11030578 - 07 Feb 2022
Cited by 2 | Viewed by 2591
Abstract
The synthetic fatty acid 2-hydroxyoleic acid (2OHOA) has been extensively investigated as a cancer therapy mainly based on its regulation of membrane lipid composition and structure, activating various cell fate pathways. We discovered, additionally, that 2OHOA can uncouple oxidative phosphorylation, but this has [...] Read more.
The synthetic fatty acid 2-hydroxyoleic acid (2OHOA) has been extensively investigated as a cancer therapy mainly based on its regulation of membrane lipid composition and structure, activating various cell fate pathways. We discovered, additionally, that 2OHOA can uncouple oxidative phosphorylation, but this has never been demonstrated mechanistically. Here, we explored the effect of 2OHOA on mitochondria isolated by ultracentrifugation from U118MG glioblastoma cells. Mitochondria were analyzed by shotgun lipidomics, molecular dynamic simulations, spectrophotometric assays for determining respiratory complex activity, mass spectrometry for assessing beta oxidation and Seahorse technology for bioenergetic profiling. We showed that the main impact of 2OHOA on mitochondrial lipids is their hydroxylation, demonstrated by simulations to decrease co-enzyme Q diffusion in the liquid disordered membranes embedding respiratory complexes. This decreased co-enzyme Q diffusion can explain the inhibition of disjointly measured complexes I–III activity. However, it doesn’t explain how 2OHOA increases complex IV and state 3 respiration in intact mitochondria. This increased respiration probably allows mitochondrial oxidative phosphorylation to maintain ATP production against the 2OHOA-mediated inhibition of glycolytic ATP production. This work correlates 2OHOA function with its modulation of mitochondrial lipid composition, reflecting both 2OHOA anticancer activity and adaptation to it by enhancement of state 3 respiration. Full article
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2021

Jump to: 2023, 2022

23 pages, 5470 KiB  
Article
The Energy Status of Astrocytes Is the Achilles’ Heel of eIF2B-Leukodystrophy
by Melisa Herrero, Maron Daw, Andrea Atzmon and Orna Elroy-Stein
Cells 2021, 10(8), 1858; https://doi.org/10.3390/cells10081858 - 22 Jul 2021
Cited by 7 | Viewed by 5146
Abstract
Translation initiation factor 2B (eIF2B) is a master regulator of global protein synthesis in all cell types. The mild genetic Eif2b5(R132H) mutation causes a slight reduction in eIF2B enzymatic activity which leads to abnormal composition of mitochondrial electron transfer chain complexes and impaired [...] Read more.
Translation initiation factor 2B (eIF2B) is a master regulator of global protein synthesis in all cell types. The mild genetic Eif2b5(R132H) mutation causes a slight reduction in eIF2B enzymatic activity which leads to abnormal composition of mitochondrial electron transfer chain complexes and impaired oxidative phosphorylation. Previous work using primary fibroblasts isolated from Eif2b5(R132H/R132H) mice revealed that owing to increased mitochondrial biogenesis they exhibit normal cellular ATP level. In contrast to fibroblasts, here we show that primary astrocytes isolated from Eif2b5(R132H/R132H) mice are unable to compensate for their metabolic impairment and exhibit chronic state of low ATP level regardless of extensive adaptation efforts. Mutant astrocytes are hypersensitive to oxidative stress and to further energy stress. Moreover, they show migration deficit upon exposure to glucose starvation. The mutation in Eif2b5 prompts reactive oxygen species (ROS)-mediated inferior ability to stimulate the AMP-activated protein kinase (AMPK) axis, due to a requirement to increase the mammalian target of rapamycin complex-1 (mTORC1) signalling in order to enable oxidative glycolysis and generation of specific subclass of ROS-regulating proteins, similar to cancer cells. The data disclose the robust impact of eIF2B on metabolic and redox homeostasis programs in astrocytes and point at their hyper-sensitivity to mutated eIF2B. Thereby, it illuminates the central involvement of astrocytes in Vanishing White Matter Disease (VWMD), a genetic neurodegenerative leukodystrophy caused by homozygous hypomorphic mutations in genes encoding any of the 5 subunits of eIF2B. Full article
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15 pages, 4796 KiB  
Article
Upregulation of COX4-2 via HIF-1α in Mitochondrial COX4-1 Deficiency
by Liza Douiev, Chaya Miller, Shmuel Ruppo, Hadar Benyamini, Bassam Abu-Libdeh and Ann Saada
Cells 2021, 10(2), 452; https://doi.org/10.3390/cells10020452 - 20 Feb 2021
Cited by 8 | Viewed by 3362
Abstract
Cytochrome-c-oxidase (COX) subunit 4 (COX4) plays important roles in the function, assembly and regulation of COX (mitochondrial respiratory complex 4), the terminal electron acceptor of the oxidative phosphorylation (OXPHOS) system. The principal COX4 isoform, COX4-1, is expressed in all tissues, whereas [...] Read more.
Cytochrome-c-oxidase (COX) subunit 4 (COX4) plays important roles in the function, assembly and regulation of COX (mitochondrial respiratory complex 4), the terminal electron acceptor of the oxidative phosphorylation (OXPHOS) system. The principal COX4 isoform, COX4-1, is expressed in all tissues, whereas COX4-2 is mainly expressed in the lungs, or under hypoxia and other stress conditions. We have previously described a patient with a COX4-1 defect with a relatively mild presentation compared to other primary COX deficiencies, and hypothesized that this could be the result of a compensatory upregulation of COX4-2. To this end, COX4-1 was downregulated by shRNAs in human foreskin fibroblasts (HFF) and compared to the patient’s cells. COX4-1, COX4-2 and HIF-1α were detected by immunocytochemistry. The mRNA transcripts of both COX4 isoforms and HIF-1 target genes were quantified by RT-qPCR. COX activity and OXPHOS function were measured by enzymatic and oxygen consumption assays, respectively. Pathways were analyzed by CEL-Seq2 and by RT-qPCR. We demonstrated elevated COX4-2 levels in the COX4-1-deficient cells, with a concomitant HIF-1α stabilization, nuclear localization and upregulation of the hypoxia and glycolysis pathways. We suggest that COX4-2 and HIF-1α are upregulated also in normoxia as a compensatory mechanism in COX4-1 deficiency. Full article
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