RARE DISEASE
NARP syndrome
NARP syndrome
NARP syndrome
Synonyms: Neurogenic muscle weakness-ataxia-retinitis pigmentosa syndrome, Neuropathy-ataxia-retinitis pigmentosa syndrome
Synonyms: Neurogenic muscle weakness-ataxia-retinitis pigmentosa syndrome, Neuropathy-ataxia-retinitis pigmentosa syndrome
Synonyms: Neurogenic muscle weakness-ataxia-retinitis pigmentosa syndrome, Neuropathy-ataxia-retinitis pigmentosa syndrome
Drug discovery
0
drugs
With orphan designations
Overview
Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) Syndrome is a rare, progressive mitochondrial disorder caused by heteroplasmic mutations in the MT-ATP6 gene, disrupting ATP synthase function [1][6][10]. It presents with proximal neurogenic muscle weakness, sensory neuropathy, cerebellar ataxia, and retinitis pigmentosa, alongside variable neurological features like seizures, cognitive decline, and hearing loss [1][6][10]. Diagnosis relies on clinical evaluation, genetic testing, and imaging (MRI/CT showing cerebral/cerebellar atrophy) [1][3][10]. Management is symptomatic, with multidisciplinary supportive care [7][15][18].
Categories: rare genetic diseases, rare inborn errors of metabolism, rare neurological diseases, rare ophthalmic disorders
Research Papers
60 drug discovery papers about NARP syndrome, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
60 drug discovery papers about NARP syndrome, with 1 first-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
small molecules
2026-01-26 | Targeting mitochondrial deubiquitinase USP30 to induce mitophagy in heteroplasmic mitochondrial diseases.
BACKGROUND: Mitochondrial DNA (mtDNA) diseases are heterogeneous and lack effective treatments. Their severity correlates with mutant mtDNA load. Mitophagy degrades dysfunctional mitochondria, contributing to a healthy mitochondrial pool. USP30, a mitochondrial deubiquitinase, limits mitophagy by removing the ubiquitin tagging mitochondria for degradation. We investigated whether inhibiting USP30 could enhance mitophagy and reduce mutant mtDNA load in a heteroplasmic mitochondrial disease. METHODS: Cybrids cells harboring mutant m.8993T > G mtDNA - common cause of NARP syndrome and maternally inherited Leigh syndrome (MILS) - were treated with USP30 inhibitor MF-094 under glycolytic and oxidative phosphorylation conditions. On-target activity of MF-094 was assessed by mitochondrial ubiquitination (western-blot) and mitolysosome formation (microscopy). The mutation’s effects were investigated on cell proliferation and metabolism (respirometry and ATP levels). The impact of MF-094 on mutant mtDNA load and mtDNA copy number was quantified by PCR. RESULTS: Comparing with control cells (0% mutant mtDNA), cells with mutant mtDNA exhibited reduced proliferation and ATP levels under oxidative phosphorylation conditions; and reduced oxygen consumption, increased extracellular acidification, and sustained resazurin metabolism after mitochondrial inhibition under glycolytic conditions. MF-094 induced mitophagy via increased mitolysosome formation. Mechanistically, MF-094 showed on-target effects, increasing mitochondrial ubiquitination. However, chronic treatment (3–6 weeks) evoked only a small (5%) non-significant reduction in mutant mtDNA load. CONCLUSIONS: Despite inducing mitophagy, the USP30 inhibitor MF-094 showed little potential to manage m.8993T > G related diseases, as it did not significantly reduce the load of this NARP/MILS causing mtDNA mutation. These results highlight the complexity of mutant mtDNA management and the need for innovative strategies for these disorders.
2024-08-28 | Pathological Role of High Sugar in Mitochondrial Respiratory Chain Defect-Augmented Mitochondrial Stress.
According to many research groups, high glucose induces the overproduction of superoxide anions, with reactive oxygen species (ROS) generally being considered the link between high glucose levels and the toxicity seen at cellular levels. Respiratory complex anomalies can lead to the production of ROS. Calcium [Ca2+] at physiological levels serves as a second messenger in many physiological functions. Accordingly, mitochondrial calcium [Ca2+]m overload leads to ROS production, which can be lethal to the mitochondria through various mechanisms. F1F0-ATPase (ATP synthase or complex V) is the enzyme responsible for catalyzing the final step of oxidative phosphorylation. This is achieved by F1F0-ATPase coupling the translocation of protons in the mitochondrial intermembrane space and shuttling them to the mitochondrial matrix for ATP synthesis to take place. Mitochondrial complex V T8993G mutation specifically blocks the translocation of protons across the intermembrane space, thereby blocking ATP synthesis and, in turn, leading to Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome. This study seeks to explore the possibility of [Ca2+]m overload mediating the pathological roles of high glucose in defective respiratory chain-mediated mitochondrial stress. NARP cybrids are the in vitro experimental models of cells with F1FO-ATPase defects, with these cells harboring 98% of mtDNA T8993G mutations. Their counterparts, 143B osteosarcoma cell lines, are the parental cell lines used for comparison. We observed that NARP cells mediated and enhanced the death of cells (apoptosis) when incubated with hydrogen peroxide (H2O2) and high glucose, as depicted using the MTT assay of cell viability. Furthermore, using fluorescence probe-coupled laser scanning confocal imaging microscopy, NARP cells were found to significantly enable mitochondrial reactive oxygen species (mROS) formation and enhance the depolarization of the mitochondrial membrane potential (ΔΨm). Elucidating the mechanisms of sugar-enhanced toxicity on the mitochondria may, in the future, help to alleviate the symptoms of patients with NARP syndromes and other neurodegenerative diseases.
2024-02-26 | Variants in Human ATP Synthase Mitochondrial Genes: Biochemical Dysfunctions, Associated Diseases, and Therapies.
Mitochondrial ATP synthase (Complex V) catalyzes the last step of oxidative phosphorylation and provides most of the energy (ATP) required by human cells. The mitochondrial genes MT-ATP6 and MT-ATP8 encode two subunits of the multi-subunit Complex V. Since the discovery of the first MT-ATP6 variant in the year 1990 as the cause of Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome, a large and continuously increasing number of inborn variants in the MT-ATP6 and MT-ATP8 genes have been identified as pathogenic. Variants in these genes correlate with various clinical phenotypes, which include several neurodegenerative and multisystemic disorders. In the present review, we report the pathogenic variants in mitochondrial ATP synthase genes and highlight the molecular mechanisms underlying ATP synthase deficiency that promote biochemical dysfunctions. We discuss the possible structural changes induced by the most common variants found in patients by considering the recent cryo-electron microscopy structure of human ATP synthase. Finally, we provide the state-of-the-art of all therapeutic proposals reported in the literature, including drug interventions targeting mitochondrial dysfunctions, allotopic gene expression- and nuclease-based strategies, and discuss their potential translation into clinical trials.
2019-10-01 | A Therapeutic Role for the F1FO-ATP Synthase
Recently, the F1FO-ATP synthase, due to its dual role of life enzyme as main adenosine triphosphate (ATP) maker and of death enzyme, as ATP dissipator and putative structural component of the mitochondrial permeability transition pore (mPTP), which triggers cell death, has been increasingly considered as a drug target. Accordingly, the enzyme offers new strategies to counteract the increased antibiotic resistance. The challenge is to find or synthesize compounds able to discriminate between prokaryotic and mitochondrial F1FO-ATP synthase, exploiting subtle structural differences to kill pathogens without affecting the host. From this perspective, the eukaryotic enzyme could also be made refractory to macrolide antibiotics by chemically produced posttranslational modifications. Moreover, because the mitochondrial F1FO-ATPase activity stimulated by Ca2+ instead of by the natural modulator Mg2+ is most likely involved in mPTP formation, effectors preferentially targeting the Ca2+-activated enzyme may modulate the mPTP. If the enzyme involvement in the mPTP is confirmed, Ca2+-ATPase inhibitors may counteract conditions featured by an increased mPTP activity, such as neurodegenerative and cardiovascular diseases and physiological aging. Conversely, mPTP opening could be pharmacologically stimulated to selectively kill unwanted cells. On the basis of recent literature and promising lab findings, the action mechanism of F1 and FO inhibitors is considered. These molecules may act as enzyme modifiers and constitute new drugs to kill pathogens, improve compromised enzyme functions, and limit the deathly enzyme role in pathologies. The enzyme offers a wide spectrum of therapeutic strategies to fight at the molecular level diseases whose treatment is still insufficient or merely symptomatic.
2018-08-01 | Molecular basis of diseases caused by the mtDNA mutation m.8969G>A in the subunit a of ATP synthase
The ATP synthase which provides aerobic eukaryotes with ATP, organizes into a membrane-extrinsic catalytic domain, where ATP is generated, and a membrane-embedded FO domain that shuttles protons across the membrane. We previously identified a mutation in the mitochondrial MT-ATP6 gene (m.8969G>A) in a 14-year-old Chinese female who developed an isolated nephropathy followed by brain and muscle problems. This mutation replaces a highly conserved serine residue into asparagine at amino acid position 148 of the membrane-embedded subunit a of ATP synthase. We showed that an equivalent of this mutation in yeast (aS175N) prevents FO-mediated proton translocation. Herein we identified four first-site intragenic suppressors (aN175D, aN175K, aN175I, and aN175T), which, in light of a recently published atomic structure of yeast FO indicates that the detrimental consequences of the original mutation result from the establishment of hydrogen bonds between aN175 and a nearby glutamate residue (aE172) that was proposed to be critical for the exit of protons from the ATP synthase towards the mitochondrial matrix. Interestingly also, we found that the aS175N mutation can be suppressed by second-site suppressors (aP12S, aI171F, aI171N, aI239F, and aI200M), of which some are very distantly located (by 20-30 Å) from the original mutation. The possibility to compensate through long-range effects the aS175N mutation is an interesting observation that holds promise for the development of therapeutic molecules.
gene therapies
2026-04-29 | Specific elimination of m.8993T>G mitochondrial haplotype in NARP cybrid cells by CRISPR-Cas9 system.
Mutations in mitochondrial DNA can cause a wide range of neuromuscular and neurodegenerative diseases in humans. The heteroplasmy level, coexistence of both wild-type and mutant mtDNA within a cell, determines the manifestation and severity of disease symptoms. Therefore, the development of strategies to shift heteroplasmy toward wild-type mtDNA is critical for advancing therapies for mitochondrial disorders. Mitochondrial localization of the modified CRISPR-Cas9 system components was analyzed using western blotting, immunocytochemical staining, confocal microscopy, and immunoelectron microscopy. To assess the heteroplasmy shift, cybrid cell lines carrying the clinically relevant m.8993T>G variant associated with Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome were used. The heteroplasmy level was evaluated by RFLP analysis of PCR-amplified mtDNA fragments encompassing the mutation site. We adapted the widely used CRISPR-Cas9 system, originally designed for editing nuclear DNA, to induce a heteroplasmy shift of the pathogenic m.8993T>G point mutation in human cybrid cells. We demonstrated that the modified components of the CRISPR-Cas9 system – the mitoCas9 nuclease fused to the mitochondrial targeting sequence from COX8A, and a single guide RNA containing a mitochondrial import determinant within the tetraloop – are effectively imported into the mitochondrial matrix. Transient transfection of the modified sgRNA into cybrid cells stably expressing mitoCas9 resulted in a detectable shift in heteroplasmy. Mitochondria-targeted CRISPR-SpCas9 system can selectively reduce the mutant m.8993T>G mtDNA load in human cybrid cells, achieving a reproducible shift in heteroplasmy. The online version contains supplementary material available at 10.1038/s41598-026-49007-y.
2025-05-01 | Mitochondrial DNA point mutations and large-scale deletions in maternally inherited metabolic disorders: Genotype-phenotype correlations
Mitochondrial diseases are not rare. They affect roughly 1 in 5,000 individuals, yet their genetic heterogeneity continues to challenge clinical diagnosis and prognosis. This research analyzed genotype-phenotype correlations in 128 patients diagnosed with maternally inherited metabolic disorders carrying mitochondrial DNA (mtDNA) point mutations or large-scale deletions. The patient cohort presented with six primary clinical phenotypes: MELAS, MERRF, NARP/Leigh syndrome, chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, and maternally inherited diabetes with deafness. Heteroplasmy levels ranged from 18% to 97% across different tissues, with blood showing consistently lower values than muscle. A positive correlation (r² = 0.73) was identified between heteroplasmy level and clinical severity score. Patients harboring the m.8993T>G mutation displayed the highest median severity, while those with single large-scale deletions showed the most variable clinical presentations. These findings reinforce that heteroplasmy thresholds differ substantially among mutation types and affected tissues.
2021-10-21 | Amelioration of Leigh syndrome induced by mouse blastocyst complementation with a mutant human mitochondrial ATP synthase 6
Abstract Mutations in mitochondrial genes are primary causes of multiple inherited disorders, especially affecting tissues with high aerobic energy demands such as the eye, brain, heart, and skeletal muscles. Such mitochondrial diseases are untreatable, have poor prognoses, and relevant animal models are few. Here we microinjected into the mouse blastocyst an adeno-associated virus (AAV) that we redirected to mitochondria to deliver the mutant human adenosine triphosphate (ATP) synthase subunit 6 gene (m.8993T>G) responsible for Maternally Inherited Leigh Syndrome, a neurologic disease renowned for causing rapidly fatal encephalomyelopathy in childhood or Neuropathy, Ataxia and Retinitis Pigmentosa in adults. Mice bred over six generations exhibited hallmarks of the human disease with one or multiple systemic symptoms including early death, paralysis, hunching, vision loss and seizures. Necropsy revealed spongiform encephalopathy, retinal degeneration, and cardiomegaly. Intravenous injection of a mitochondrially directed AAV serotype 9 vector containing wild-type ATP6 after disease onset, conferred prolonged survival and reduced paralysis. When administered prior to disease onset, all treated mice survived, and visual and motor function improved. These results support further development of gene therapy strategies involving intravenous delivery of mito-targeted AAV9.
2020-03-18 | Inheritance of mitochondrial DNA in humans: implications for rare and common diseases
Abstract The first draft human mitochondrial DNA (mtDNA) sequence was published in 1981, paving the way for two decades of discovery linking mtDNA variation with human disease. Severe pathogenic mutations cause sporadic and inherited rare disorders that often involve the nervous system. However, some mutations cause mild organ‐specific phenotypes that have a reduced clinical penetrance, and polymorphic variation of mtDNA is associated with an altered risk of developing several late‐onset common human diseases including Parkinson’s disease. mtDNA mutations also accumulate during human life and are enriched in affected organs in a number of age‐related diseases. Thus, mtDNA contributes to a wide range of human pathologies. For many decades, it has generally been accepted that mtDNA is inherited exclusively down the maternal line in humans. Although recent evidence has challenged this dogma, whole‐genome sequencing has identified nuclear‐encoded mitochondrial sequences (NUMTs) that can give the false impression of paternally inherited mtDNA. This provides a more likely explanation for recent reports of ‘bi‐parental inheritance’, where the paternal alleles are actually transmitted through the nuclear genome. The presence of both mutated and wild‐type variant alleles within the same individual (heteroplasmy) and rapid shifts in allele frequency can lead to offspring with variable severity of disease. In addition, there is emerging evidence that selection can act for and against specific mtDNA variants within the developing germ line, and possibly within developing tissues. Thus, understanding how mtDNA is inherited has far‐reaching implications across medicine. There is emerging evidence that this highly dynamic system is amenable to therapeutic manipulation, raising the possibility that we can harness new understanding to prevent and treat rare and common human diseases where mtDNA mutations play a key role.
2018-11-07 | Functional investigation of an universally conserved leucine residue in subunit a of ATP synthase targeted by the pathogenic m.9176 T>G mutation
Protons are transported from the mitochondrial matrix to the intermembrane space of mitochondria during the transfer of electrons to oxygen and shuttled back to the matrix by the a subunit and a ring of identical c subunits across the membrane domain (FO) of ATP synthase, which is coupled to ATP synthesis. A mutation (m.9176 T > G) of the mitochondrial ATP6 gene that replaces an universally conserved leucine residue into arginine at amino acid position 217 of human subunit a (aL217R) has been associated to NARP (Neuropathy, Ataxia and Retinitis Pigmentosa) and MILS (Maternally Inherited Leigh's Syndrome) diseases. We previously showed that an equivalent thereof in Saccharomyces cerevisiae (aL237R) severely impairs subunit a assembly/stability and decreases by >90% the rate of mitochondrial ATP synthesis. Herein we identified three spontaneous first-site intragenic suppressors (aR237M, aR237T and aR237S) that fully restore ATP synthase assembly. However, mitochondrial ATP synthesis rate was only partially recovered (40–50% vs wild type yeast). In light of recently described high-resolution yeast ATP synthase structures, the detrimental consequences of the aL237R change can be explained by steric and electrostatic hindrance with the universally conserved subunit a arginine residue (aR176) that is essential to FO activity. aL237 together with three other nearby hydrophobic residues have been proposed to prevent ion shortage between two physically separated hydrophilic pockets within the FO. Our results suggest that aL237 favors subunit c-ring rotation by optimizing electrostatic interaction between aR176 and an acidic residue in subunit c (cE59) known to be essential also to the activity of FO.
oligonucleotides
2023-08-01 | Mitochondrial transport of catalytic RNAs and targeting of the organellar transcriptome in human cells
Abstract Mutations in the small genome present in mitochondria often result in severe pathologies. Different genetic strategies have been explored, aiming to rescue such mutations. A number of these strategies were based on the capacity of human mitochondria to import RNAs from the cytosol and designed to repress the replication of the mutated genomes or to provide the organelles with wild-type versions of mutant transcripts. However, the mutant RNAs present in mitochondria turned out to be an obstacle to therapy and little attention has been devoted so far to their elimination. Here, we present the development of a strategy to knockdown mitochondrial RNAs in human cells using the transfer RNA-like structure of Brome mosaic virus or Tobacco mosaic virus as a shuttle to drive trans-cleaving ribozymes into the organelles in human cell lines. We obtained a specific knockdown of the targeted mitochondrial ATP6 mRNA, followed by a deep drop in ATP6 protein and a functional impairment of the oxidative phosphorylation chain. Our strategy provides a powerful approach to eliminate mutant organellar transcripts and to analyse the control and communication of the human organellar genetic system.
2016-09-04 | Stable nuclear expression of ATP8 and ATP6 genes rescues a mtDNA Complex V null mutant.
We explore the possibility of re-engineering mitochondrial genes and expressing them from the nucleus as an approach to rescue defects arising from mitochondrial DNA mutations. We have used a patient cybrid cell line with a single point mutation in the overlap region of the ATP8 and ATP6 genes of the human mitochondrial genome. These cells are null for the ATP8 protein, have significantly lowered ATP6 protein levels and no Complex V function. Nuclear expression of only the ATP8 gene with the ATP5G1 mitochondrial targeting sequence appended restored viability on Krebs cycle substrates and ATP synthesis capabilities but, failed to restore ATP hydrolysis and was insensitive to various inhibitors of oxidative phosphorylation. Co-expressing both ATP8 and ATP6 genes under similar conditions resulted in stable protein expression leading to successful integration into Complex V of the oxidative phosphorylation machinery. Tests for ATP hydrolysis / synthesis, oxygen consumption, glycolytic metabolism and viability all indicate a significant functional rescue of the mutant phenotype (including re-assembly of Complex V) following stable co-expression of ATP8 and ATP6. Thus, we report the stable allotopic expression, import and function of two mitochondria encoded genes, ATP8 and ATP6, resulting in simultaneous rescue of the loss of both mitochondrial proteins.
2007-05-23 | Allotopic mRNA Localization to the Mitochondrial Surface Rescues Respiratory Chain Defects in Fibroblasts Harboring Mitochondrial DNA Mutations Affecting Complex I or V Subunits
The possibility of synthesizing mitochondrial DNA (mtDNA)-coded proteins in the cytosolic compartment, called allotopic expression, provides an attractive option for genetic treatment of human diseases caused by mutations of the corresponding genes. However, it is now appreciated that the high hydrophobicity of proteins encoded by the mitochondrial genome represents a strong limitation on their mitochondrial import when translated in the cytosol. Recently, we optimized the allotopic expression of a recoded ATP6 gene in human cells, by forcing its mRNA to localize to the mitochondrial surface. In this study, we show that this approach leads to a long-lasting and complete rescue of mitochondrial dysfunction of fibroblasts harboring the neurogenic muscle weakness, ataxia and retinitis Pigmentosa T8993G ATP6 mutation or the Leber hereditary optic neuropathy G11778A ND4 mutation. The recoded ATP6 gene was associated with the cis-acting elements of SOD2, while the ND4 gene was associated with the cis-acting elements of COX10. Both ATP6 and ND4 gene products were efficiently translocated into the mitochondria and functional within their respective respiratory chain complexes. Indeed, the abilities to grow in galactose and to produce adenosine triphosphate (ATP) in vitro were both completely restored in fibroblasts allotopically expressing either ATP6 or ND4. Notably, in fibroblasts harboring the ATP6 mutation, allotopic expression of ATP6 led to the recovery of complex V enzymatic activity. Therefore, mRNA sorting to the mitochondrial surface represents a powerful strategy that could ultimately be applied in human therapy and become available for an array of devastating disorders caused by mtDNA mutations.
proteins
2024-12-02 | Expanded-Access Use of Elamipretide Improves Quality of Life in Patients With Rare Mitochondrial Disorders Characterized by Ophthalmic Symptoms: A Case Series.
This case series presents the use of elamipretide in two patients with different progressive mitochondrial disorders (chronic progressive external ophthalmoplegia [CPEO] plus and neuropathy, ataxia, and retinitis pigmentosa [NARP] syndrome) characterized by ophthalmic traits. Elamipretide was well tolerated and both patients demonstrated improvement in symptoms while on therapy.
2022-11-26 | Molecular basis of diseases induced by the mitochondrial DNA mutation m.9032T>C
The mitochondrial DNA mutation m.9032T>C was previously identified in patients presenting with NARP (Neuropathy Ataxia Retinitis Pigmentosa). Their clinical features had a maternal transmission and patient's cells showed a reduced oxidative phosphorylation capacity, elevated reactive oxygen species (ROS) production and hyperpolarization of the mitochondrial inner membrane, providing evidence that m.9032T>C is truly pathogenic. This mutation leads to replacement of a highly conserved leucine residue with proline at position 169 of ATP synthase subunit a (L169P). This protein and a ring of identical c-subunits (c-ring) move protons through the mitochondrial inner membrane coupled to ATP synthesis. We herein investigated the consequences of m.9032T>C on ATP synthase in a strain of Saccharomyces cerevisiae with an equivalent mutation (L186P). The mutant enzyme assembled correctly but was mostly inactive as evidenced by a > 95% drop in the rate of mitochondrial ATP synthesis and absence of significant ATP-driven proton pumping across the mitochondrial membrane. Intragenic suppressors selected from L186P yeast restoring ATP synthase function to varying degrees (30-70%) were identified at the original mutation site (L186S) or in another position of the subunit a (H114Q, I118T). In light of atomic structures of yeast ATP synthase recently described, we conclude from these results that m.9032T>C disrupts proton conduction between the external side of the membrane and the c-ring, and that H114Q and I118T enable protons to access the c-ring through a modified pathway.
2019-07-04 | Deregulating mitochondrial metabolite and ion transport has beneficial effects in yeast and human cellular models for NARP syndrome
Abstract The m.8993T>G mutation of the mitochondrial MT-ATP6 gene has been associated with numerous cases of neuropathy, ataxia and retinitis pigmentosa and maternally inherited Leigh syndrome, which are diseases known to result from abnormalities affecting mitochondrial energy transduction. We previously reported that an equivalent point mutation severely compromised proton transport through the ATP synthase membrane domain (FO) in Saccharomyces cerevisiae and reduced the content of cytochrome c oxidase (Complex IV or COX) by 80%. Herein, we report that overexpression of the mitochondrial oxodicarboxylate carrier (Odc1p) considerably increases Complex IV abundance and tricarboxylic acid-mediated substrate-level phosphorylation of ADP coupled to conversion of α-ketoglutarate into succinate in m.8993T>G yeast. Consistently in m.8993T>G yeast cells, the retrograde signaling pathway was found to be strongly induced in order to preserve α-ketoglutarate production; when Odc1p was overexpressed, this stress pathway returned to an almost basal activity. Similar beneficial effects were induced by a partial uncoupling of the mitochondrial membrane with the proton ionophore, cyanide m-chlorophenyl hydrazone. This chemical considerably improved the glutamine-based, respiration-dependent growth of human cytoplasmic hybrid cells that are homoplasmic for the m.8993T>G mutation. These findings shed light on the interdependence between ATP synthase and Complex IV biogenesis, which could lay the groundwork for the creation of nutritional or metabolic interventions for attenuating the effects of mtDNA mutations.
2018-02-28 | Peptide Derivatives of Erythropoietin in the Treatment of Neuroinflammation and Neurodegeneration
During the past 35 years, recombinant DNA technology has allowed the production of a wide range of hematopoietic and neurotrophic growth factors including erythropoietin (EPO). These have emerged as promising protein drugs in various human diseases. Accumulated evidences have recently demonstrated the neuroprotective effect of EPO in preclinical models of acute and chronic degenerative disorders. Nevertheless, tissue protective effect of EPO could not be translated to the clinical trials because of common lethal thromboembolic events, erythropoiesis and hypertension. Although chemically modified nonerythropoietic analogs of EPO bypass these side effects, high expense, development of antidrug antibodies, and promotion of tumorigenicity are still concern especially in long-term use. As an alternative, nonerythropoietic EPO mimetic peptides can be used as candidate drugs with their high potency and selectivity, easy production, low cost, and immunogenicity properties. Recent experimental studies suggest that these peptides prevent ischemic brain injury and neuroinflammation. The results of clinical trial in patients with neuropathic pain are also promising. Herein, we summarize these studies and review advanced experimental and in silico methods in peptide drug discovery.
2010-06-14 | Parkin overexpression selects against a deleterious mtDNA mutation in heteroplasmic cybrid cells
Mitochondrial genomes with deleterious mutations can replicate in cells along with wild-type genomes in a state of heteroplasmy, and are a cause of severe inherited syndromes, such as mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke (MELAS), neuropathy, ataxia, retinitis pigmentosa-maternally inherited Leigh syndrome (NARP-MILS), and Leber's hereditary optic neuropathy (LHON). The cytosolic E3 ligase, Parkin, commonly mutated in recessive familial parkinsonism, translocates to depolarized mitochondria and induces their autophagic elimination, suggesting that Parkin may signal the selective removal of defective mitochondria within the cell. We report that long-term overexpression of Parkin can eliminate mitochondria with deleterious COXI mutations in heteroplasmic cybrid cells, thereby enriching cells for wild-type mtDNA and restoring cytochrome c oxidase activity. After relieving cybrid cells of Parkin overexpression, a more favorable wild-type to mutant mitochondrial genome ratio is stably maintained. These data support the model that Parkin functions in a mitochondrial quality control pathway. Additionally, they suggest that transiently increasing levels of Parkin expression might ameliorate certain mitochondrial diseases.
small molecules
2026-01-26 | Targeting mitochondrial deubiquitinase USP30 to induce mitophagy in heteroplasmic mitochondrial diseases.
BACKGROUND: Mitochondrial DNA (mtDNA) diseases are heterogeneous and lack effective treatments. Their severity correlates with mutant mtDNA load. Mitophagy degrades dysfunctional mitochondria, contributing to a healthy mitochondrial pool. USP30, a mitochondrial deubiquitinase, limits mitophagy by removing the ubiquitin tagging mitochondria for degradation. We investigated whether inhibiting USP30 could enhance mitophagy and reduce mutant mtDNA load in a heteroplasmic mitochondrial disease. METHODS: Cybrids cells harboring mutant m.8993T > G mtDNA - common cause of NARP syndrome and maternally inherited Leigh syndrome (MILS) - were treated with USP30 inhibitor MF-094 under glycolytic and oxidative phosphorylation conditions. On-target activity of MF-094 was assessed by mitochondrial ubiquitination (western-blot) and mitolysosome formation (microscopy). The mutation’s effects were investigated on cell proliferation and metabolism (respirometry and ATP levels). The impact of MF-094 on mutant mtDNA load and mtDNA copy number was quantified by PCR. RESULTS: Comparing with control cells (0% mutant mtDNA), cells with mutant mtDNA exhibited reduced proliferation and ATP levels under oxidative phosphorylation conditions; and reduced oxygen consumption, increased extracellular acidification, and sustained resazurin metabolism after mitochondrial inhibition under glycolytic conditions. MF-094 induced mitophagy via increased mitolysosome formation. Mechanistically, MF-094 showed on-target effects, increasing mitochondrial ubiquitination. However, chronic treatment (3–6 weeks) evoked only a small (5%) non-significant reduction in mutant mtDNA load. CONCLUSIONS: Despite inducing mitophagy, the USP30 inhibitor MF-094 showed little potential to manage m.8993T > G related diseases, as it did not significantly reduce the load of this NARP/MILS causing mtDNA mutation. These results highlight the complexity of mutant mtDNA management and the need for innovative strategies for these disorders.
2024-08-28 | Pathological Role of High Sugar in Mitochondrial Respiratory Chain Defect-Augmented Mitochondrial Stress.
According to many research groups, high glucose induces the overproduction of superoxide anions, with reactive oxygen species (ROS) generally being considered the link between high glucose levels and the toxicity seen at cellular levels. Respiratory complex anomalies can lead to the production of ROS. Calcium [Ca2+] at physiological levels serves as a second messenger in many physiological functions. Accordingly, mitochondrial calcium [Ca2+]m overload leads to ROS production, which can be lethal to the mitochondria through various mechanisms. F1F0-ATPase (ATP synthase or complex V) is the enzyme responsible for catalyzing the final step of oxidative phosphorylation. This is achieved by F1F0-ATPase coupling the translocation of protons in the mitochondrial intermembrane space and shuttling them to the mitochondrial matrix for ATP synthesis to take place. Mitochondrial complex V T8993G mutation specifically blocks the translocation of protons across the intermembrane space, thereby blocking ATP synthesis and, in turn, leading to Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome. This study seeks to explore the possibility of [Ca2+]m overload mediating the pathological roles of high glucose in defective respiratory chain-mediated mitochondrial stress. NARP cybrids are the in vitro experimental models of cells with F1FO-ATPase defects, with these cells harboring 98% of mtDNA T8993G mutations. Their counterparts, 143B osteosarcoma cell lines, are the parental cell lines used for comparison. We observed that NARP cells mediated and enhanced the death of cells (apoptosis) when incubated with hydrogen peroxide (H2O2) and high glucose, as depicted using the MTT assay of cell viability. Furthermore, using fluorescence probe-coupled laser scanning confocal imaging microscopy, NARP cells were found to significantly enable mitochondrial reactive oxygen species (mROS) formation and enhance the depolarization of the mitochondrial membrane potential (ΔΨm). Elucidating the mechanisms of sugar-enhanced toxicity on the mitochondria may, in the future, help to alleviate the symptoms of patients with NARP syndromes and other neurodegenerative diseases.
2024-02-26 | Variants in Human ATP Synthase Mitochondrial Genes: Biochemical Dysfunctions, Associated Diseases, and Therapies.
Mitochondrial ATP synthase (Complex V) catalyzes the last step of oxidative phosphorylation and provides most of the energy (ATP) required by human cells. The mitochondrial genes MT-ATP6 and MT-ATP8 encode two subunits of the multi-subunit Complex V. Since the discovery of the first MT-ATP6 variant in the year 1990 as the cause of Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome, a large and continuously increasing number of inborn variants in the MT-ATP6 and MT-ATP8 genes have been identified as pathogenic. Variants in these genes correlate with various clinical phenotypes, which include several neurodegenerative and multisystemic disorders. In the present review, we report the pathogenic variants in mitochondrial ATP synthase genes and highlight the molecular mechanisms underlying ATP synthase deficiency that promote biochemical dysfunctions. We discuss the possible structural changes induced by the most common variants found in patients by considering the recent cryo-electron microscopy structure of human ATP synthase. Finally, we provide the state-of-the-art of all therapeutic proposals reported in the literature, including drug interventions targeting mitochondrial dysfunctions, allotopic gene expression- and nuclease-based strategies, and discuss their potential translation into clinical trials.
2019-10-01 | A Therapeutic Role for the F1FO-ATP Synthase
Recently, the F1FO-ATP synthase, due to its dual role of life enzyme as main adenosine triphosphate (ATP) maker and of death enzyme, as ATP dissipator and putative structural component of the mitochondrial permeability transition pore (mPTP), which triggers cell death, has been increasingly considered as a drug target. Accordingly, the enzyme offers new strategies to counteract the increased antibiotic resistance. The challenge is to find or synthesize compounds able to discriminate between prokaryotic and mitochondrial F1FO-ATP synthase, exploiting subtle structural differences to kill pathogens without affecting the host. From this perspective, the eukaryotic enzyme could also be made refractory to macrolide antibiotics by chemically produced posttranslational modifications. Moreover, because the mitochondrial F1FO-ATPase activity stimulated by Ca2+ instead of by the natural modulator Mg2+ is most likely involved in mPTP formation, effectors preferentially targeting the Ca2+-activated enzyme may modulate the mPTP. If the enzyme involvement in the mPTP is confirmed, Ca2+-ATPase inhibitors may counteract conditions featured by an increased mPTP activity, such as neurodegenerative and cardiovascular diseases and physiological aging. Conversely, mPTP opening could be pharmacologically stimulated to selectively kill unwanted cells. On the basis of recent literature and promising lab findings, the action mechanism of F1 and FO inhibitors is considered. These molecules may act as enzyme modifiers and constitute new drugs to kill pathogens, improve compromised enzyme functions, and limit the deathly enzyme role in pathologies. The enzyme offers a wide spectrum of therapeutic strategies to fight at the molecular level diseases whose treatment is still insufficient or merely symptomatic.
2018-08-01 | Molecular basis of diseases caused by the mtDNA mutation m.8969G>A in the subunit a of ATP synthase
The ATP synthase which provides aerobic eukaryotes with ATP, organizes into a membrane-extrinsic catalytic domain, where ATP is generated, and a membrane-embedded FO domain that shuttles protons across the membrane. We previously identified a mutation in the mitochondrial MT-ATP6 gene (m.8969G>A) in a 14-year-old Chinese female who developed an isolated nephropathy followed by brain and muscle problems. This mutation replaces a highly conserved serine residue into asparagine at amino acid position 148 of the membrane-embedded subunit a of ATP synthase. We showed that an equivalent of this mutation in yeast (aS175N) prevents FO-mediated proton translocation. Herein we identified four first-site intragenic suppressors (aN175D, aN175K, aN175I, and aN175T), which, in light of a recently published atomic structure of yeast FO indicates that the detrimental consequences of the original mutation result from the establishment of hydrogen bonds between aN175 and a nearby glutamate residue (aE172) that was proposed to be critical for the exit of protons from the ATP synthase towards the mitochondrial matrix. Interestingly also, we found that the aS175N mutation can be suppressed by second-site suppressors (aP12S, aI171F, aI171N, aI239F, and aI200M), of which some are very distantly located (by 20-30 Å) from the original mutation. The possibility to compensate through long-range effects the aS175N mutation is an interesting observation that holds promise for the development of therapeutic molecules.
gene therapies
2026-04-29 | Specific elimination of m.8993T>G mitochondrial haplotype in NARP cybrid cells by CRISPR-Cas9 system.
Mutations in mitochondrial DNA can cause a wide range of neuromuscular and neurodegenerative diseases in humans. The heteroplasmy level, coexistence of both wild-type and mutant mtDNA within a cell, determines the manifestation and severity of disease symptoms. Therefore, the development of strategies to shift heteroplasmy toward wild-type mtDNA is critical for advancing therapies for mitochondrial disorders. Mitochondrial localization of the modified CRISPR-Cas9 system components was analyzed using western blotting, immunocytochemical staining, confocal microscopy, and immunoelectron microscopy. To assess the heteroplasmy shift, cybrid cell lines carrying the clinically relevant m.8993T>G variant associated with Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome were used. The heteroplasmy level was evaluated by RFLP analysis of PCR-amplified mtDNA fragments encompassing the mutation site. We adapted the widely used CRISPR-Cas9 system, originally designed for editing nuclear DNA, to induce a heteroplasmy shift of the pathogenic m.8993T>G point mutation in human cybrid cells. We demonstrated that the modified components of the CRISPR-Cas9 system – the mitoCas9 nuclease fused to the mitochondrial targeting sequence from COX8A, and a single guide RNA containing a mitochondrial import determinant within the tetraloop – are effectively imported into the mitochondrial matrix. Transient transfection of the modified sgRNA into cybrid cells stably expressing mitoCas9 resulted in a detectable shift in heteroplasmy. Mitochondria-targeted CRISPR-SpCas9 system can selectively reduce the mutant m.8993T>G mtDNA load in human cybrid cells, achieving a reproducible shift in heteroplasmy. The online version contains supplementary material available at 10.1038/s41598-026-49007-y.
2025-05-01 | Mitochondrial DNA point mutations and large-scale deletions in maternally inherited metabolic disorders: Genotype-phenotype correlations
Mitochondrial diseases are not rare. They affect roughly 1 in 5,000 individuals, yet their genetic heterogeneity continues to challenge clinical diagnosis and prognosis. This research analyzed genotype-phenotype correlations in 128 patients diagnosed with maternally inherited metabolic disorders carrying mitochondrial DNA (mtDNA) point mutations or large-scale deletions. The patient cohort presented with six primary clinical phenotypes: MELAS, MERRF, NARP/Leigh syndrome, chronic progressive external ophthalmoplegia, Kearns-Sayre syndrome, and maternally inherited diabetes with deafness. Heteroplasmy levels ranged from 18% to 97% across different tissues, with blood showing consistently lower values than muscle. A positive correlation (r² = 0.73) was identified between heteroplasmy level and clinical severity score. Patients harboring the m.8993T>G mutation displayed the highest median severity, while those with single large-scale deletions showed the most variable clinical presentations. These findings reinforce that heteroplasmy thresholds differ substantially among mutation types and affected tissues.
2021-10-21 | Amelioration of Leigh syndrome induced by mouse blastocyst complementation with a mutant human mitochondrial ATP synthase 6
Abstract Mutations in mitochondrial genes are primary causes of multiple inherited disorders, especially affecting tissues with high aerobic energy demands such as the eye, brain, heart, and skeletal muscles. Such mitochondrial diseases are untreatable, have poor prognoses, and relevant animal models are few. Here we microinjected into the mouse blastocyst an adeno-associated virus (AAV) that we redirected to mitochondria to deliver the mutant human adenosine triphosphate (ATP) synthase subunit 6 gene (m.8993T>G) responsible for Maternally Inherited Leigh Syndrome, a neurologic disease renowned for causing rapidly fatal encephalomyelopathy in childhood or Neuropathy, Ataxia and Retinitis Pigmentosa in adults. Mice bred over six generations exhibited hallmarks of the human disease with one or multiple systemic symptoms including early death, paralysis, hunching, vision loss and seizures. Necropsy revealed spongiform encephalopathy, retinal degeneration, and cardiomegaly. Intravenous injection of a mitochondrially directed AAV serotype 9 vector containing wild-type ATP6 after disease onset, conferred prolonged survival and reduced paralysis. When administered prior to disease onset, all treated mice survived, and visual and motor function improved. These results support further development of gene therapy strategies involving intravenous delivery of mito-targeted AAV9.
2020-03-18 | Inheritance of mitochondrial DNA in humans: implications for rare and common diseases
Abstract The first draft human mitochondrial DNA (mtDNA) sequence was published in 1981, paving the way for two decades of discovery linking mtDNA variation with human disease. Severe pathogenic mutations cause sporadic and inherited rare disorders that often involve the nervous system. However, some mutations cause mild organ‐specific phenotypes that have a reduced clinical penetrance, and polymorphic variation of mtDNA is associated with an altered risk of developing several late‐onset common human diseases including Parkinson’s disease. mtDNA mutations also accumulate during human life and are enriched in affected organs in a number of age‐related diseases. Thus, mtDNA contributes to a wide range of human pathologies. For many decades, it has generally been accepted that mtDNA is inherited exclusively down the maternal line in humans. Although recent evidence has challenged this dogma, whole‐genome sequencing has identified nuclear‐encoded mitochondrial sequences (NUMTs) that can give the false impression of paternally inherited mtDNA. This provides a more likely explanation for recent reports of ‘bi‐parental inheritance’, where the paternal alleles are actually transmitted through the nuclear genome. The presence of both mutated and wild‐type variant alleles within the same individual (heteroplasmy) and rapid shifts in allele frequency can lead to offspring with variable severity of disease. In addition, there is emerging evidence that selection can act for and against specific mtDNA variants within the developing germ line, and possibly within developing tissues. Thus, understanding how mtDNA is inherited has far‐reaching implications across medicine. There is emerging evidence that this highly dynamic system is amenable to therapeutic manipulation, raising the possibility that we can harness new understanding to prevent and treat rare and common human diseases where mtDNA mutations play a key role.
2018-11-07 | Functional investigation of an universally conserved leucine residue in subunit a of ATP synthase targeted by the pathogenic m.9176 T>G mutation
Protons are transported from the mitochondrial matrix to the intermembrane space of mitochondria during the transfer of electrons to oxygen and shuttled back to the matrix by the a subunit and a ring of identical c subunits across the membrane domain (FO) of ATP synthase, which is coupled to ATP synthesis. A mutation (m.9176 T > G) of the mitochondrial ATP6 gene that replaces an universally conserved leucine residue into arginine at amino acid position 217 of human subunit a (aL217R) has been associated to NARP (Neuropathy, Ataxia and Retinitis Pigmentosa) and MILS (Maternally Inherited Leigh's Syndrome) diseases. We previously showed that an equivalent thereof in Saccharomyces cerevisiae (aL237R) severely impairs subunit a assembly/stability and decreases by >90% the rate of mitochondrial ATP synthesis. Herein we identified three spontaneous first-site intragenic suppressors (aR237M, aR237T and aR237S) that fully restore ATP synthase assembly. However, mitochondrial ATP synthesis rate was only partially recovered (40–50% vs wild type yeast). In light of recently described high-resolution yeast ATP synthase structures, the detrimental consequences of the aL237R change can be explained by steric and electrostatic hindrance with the universally conserved subunit a arginine residue (aR176) that is essential to FO activity. aL237 together with three other nearby hydrophobic residues have been proposed to prevent ion shortage between two physically separated hydrophilic pockets within the FO. Our results suggest that aL237 favors subunit c-ring rotation by optimizing electrostatic interaction between aR176 and an acidic residue in subunit c (cE59) known to be essential also to the activity of FO.
oligonucleotides
2023-08-01 | Mitochondrial transport of catalytic RNAs and targeting of the organellar transcriptome in human cells
Abstract Mutations in the small genome present in mitochondria often result in severe pathologies. Different genetic strategies have been explored, aiming to rescue such mutations. A number of these strategies were based on the capacity of human mitochondria to import RNAs from the cytosol and designed to repress the replication of the mutated genomes or to provide the organelles with wild-type versions of mutant transcripts. However, the mutant RNAs present in mitochondria turned out to be an obstacle to therapy and little attention has been devoted so far to their elimination. Here, we present the development of a strategy to knockdown mitochondrial RNAs in human cells using the transfer RNA-like structure of Brome mosaic virus or Tobacco mosaic virus as a shuttle to drive trans-cleaving ribozymes into the organelles in human cell lines. We obtained a specific knockdown of the targeted mitochondrial ATP6 mRNA, followed by a deep drop in ATP6 protein and a functional impairment of the oxidative phosphorylation chain. Our strategy provides a powerful approach to eliminate mutant organellar transcripts and to analyse the control and communication of the human organellar genetic system.
2016-09-04 | Stable nuclear expression of ATP8 and ATP6 genes rescues a mtDNA Complex V null mutant.
We explore the possibility of re-engineering mitochondrial genes and expressing them from the nucleus as an approach to rescue defects arising from mitochondrial DNA mutations. We have used a patient cybrid cell line with a single point mutation in the overlap region of the ATP8 and ATP6 genes of the human mitochondrial genome. These cells are null for the ATP8 protein, have significantly lowered ATP6 protein levels and no Complex V function. Nuclear expression of only the ATP8 gene with the ATP5G1 mitochondrial targeting sequence appended restored viability on Krebs cycle substrates and ATP synthesis capabilities but, failed to restore ATP hydrolysis and was insensitive to various inhibitors of oxidative phosphorylation. Co-expressing both ATP8 and ATP6 genes under similar conditions resulted in stable protein expression leading to successful integration into Complex V of the oxidative phosphorylation machinery. Tests for ATP hydrolysis / synthesis, oxygen consumption, glycolytic metabolism and viability all indicate a significant functional rescue of the mutant phenotype (including re-assembly of Complex V) following stable co-expression of ATP8 and ATP6. Thus, we report the stable allotopic expression, import and function of two mitochondria encoded genes, ATP8 and ATP6, resulting in simultaneous rescue of the loss of both mitochondrial proteins.
2007-05-23 | Allotopic mRNA Localization to the Mitochondrial Surface Rescues Respiratory Chain Defects in Fibroblasts Harboring Mitochondrial DNA Mutations Affecting Complex I or V Subunits
The possibility of synthesizing mitochondrial DNA (mtDNA)-coded proteins in the cytosolic compartment, called allotopic expression, provides an attractive option for genetic treatment of human diseases caused by mutations of the corresponding genes. However, it is now appreciated that the high hydrophobicity of proteins encoded by the mitochondrial genome represents a strong limitation on their mitochondrial import when translated in the cytosol. Recently, we optimized the allotopic expression of a recoded ATP6 gene in human cells, by forcing its mRNA to localize to the mitochondrial surface. In this study, we show that this approach leads to a long-lasting and complete rescue of mitochondrial dysfunction of fibroblasts harboring the neurogenic muscle weakness, ataxia and retinitis Pigmentosa T8993G ATP6 mutation or the Leber hereditary optic neuropathy G11778A ND4 mutation. The recoded ATP6 gene was associated with the cis-acting elements of SOD2, while the ND4 gene was associated with the cis-acting elements of COX10. Both ATP6 and ND4 gene products were efficiently translocated into the mitochondria and functional within their respective respiratory chain complexes. Indeed, the abilities to grow in galactose and to produce adenosine triphosphate (ATP) in vitro were both completely restored in fibroblasts allotopically expressing either ATP6 or ND4. Notably, in fibroblasts harboring the ATP6 mutation, allotopic expression of ATP6 led to the recovery of complex V enzymatic activity. Therefore, mRNA sorting to the mitochondrial surface represents a powerful strategy that could ultimately be applied in human therapy and become available for an array of devastating disorders caused by mtDNA mutations.
proteins
2024-12-02 | Expanded-Access Use of Elamipretide Improves Quality of Life in Patients With Rare Mitochondrial Disorders Characterized by Ophthalmic Symptoms: A Case Series.
This case series presents the use of elamipretide in two patients with different progressive mitochondrial disorders (chronic progressive external ophthalmoplegia [CPEO] plus and neuropathy, ataxia, and retinitis pigmentosa [NARP] syndrome) characterized by ophthalmic traits. Elamipretide was well tolerated and both patients demonstrated improvement in symptoms while on therapy.
2022-11-26 | Molecular basis of diseases induced by the mitochondrial DNA mutation m.9032T>C
The mitochondrial DNA mutation m.9032T>C was previously identified in patients presenting with NARP (Neuropathy Ataxia Retinitis Pigmentosa). Their clinical features had a maternal transmission and patient's cells showed a reduced oxidative phosphorylation capacity, elevated reactive oxygen species (ROS) production and hyperpolarization of the mitochondrial inner membrane, providing evidence that m.9032T>C is truly pathogenic. This mutation leads to replacement of a highly conserved leucine residue with proline at position 169 of ATP synthase subunit a (L169P). This protein and a ring of identical c-subunits (c-ring) move protons through the mitochondrial inner membrane coupled to ATP synthesis. We herein investigated the consequences of m.9032T>C on ATP synthase in a strain of Saccharomyces cerevisiae with an equivalent mutation (L186P). The mutant enzyme assembled correctly but was mostly inactive as evidenced by a > 95% drop in the rate of mitochondrial ATP synthesis and absence of significant ATP-driven proton pumping across the mitochondrial membrane. Intragenic suppressors selected from L186P yeast restoring ATP synthase function to varying degrees (30-70%) were identified at the original mutation site (L186S) or in another position of the subunit a (H114Q, I118T). In light of atomic structures of yeast ATP synthase recently described, we conclude from these results that m.9032T>C disrupts proton conduction between the external side of the membrane and the c-ring, and that H114Q and I118T enable protons to access the c-ring through a modified pathway.
2019-07-04 | Deregulating mitochondrial metabolite and ion transport has beneficial effects in yeast and human cellular models for NARP syndrome
Abstract The m.8993T>G mutation of the mitochondrial MT-ATP6 gene has been associated with numerous cases of neuropathy, ataxia and retinitis pigmentosa and maternally inherited Leigh syndrome, which are diseases known to result from abnormalities affecting mitochondrial energy transduction. We previously reported that an equivalent point mutation severely compromised proton transport through the ATP synthase membrane domain (FO) in Saccharomyces cerevisiae and reduced the content of cytochrome c oxidase (Complex IV or COX) by 80%. Herein, we report that overexpression of the mitochondrial oxodicarboxylate carrier (Odc1p) considerably increases Complex IV abundance and tricarboxylic acid-mediated substrate-level phosphorylation of ADP coupled to conversion of α-ketoglutarate into succinate in m.8993T>G yeast. Consistently in m.8993T>G yeast cells, the retrograde signaling pathway was found to be strongly induced in order to preserve α-ketoglutarate production; when Odc1p was overexpressed, this stress pathway returned to an almost basal activity. Similar beneficial effects were induced by a partial uncoupling of the mitochondrial membrane with the proton ionophore, cyanide m-chlorophenyl hydrazone. This chemical considerably improved the glutamine-based, respiration-dependent growth of human cytoplasmic hybrid cells that are homoplasmic for the m.8993T>G mutation. These findings shed light on the interdependence between ATP synthase and Complex IV biogenesis, which could lay the groundwork for the creation of nutritional or metabolic interventions for attenuating the effects of mtDNA mutations.
2018-02-28 | Peptide Derivatives of Erythropoietin in the Treatment of Neuroinflammation and Neurodegeneration
During the past 35 years, recombinant DNA technology has allowed the production of a wide range of hematopoietic and neurotrophic growth factors including erythropoietin (EPO). These have emerged as promising protein drugs in various human diseases. Accumulated evidences have recently demonstrated the neuroprotective effect of EPO in preclinical models of acute and chronic degenerative disorders. Nevertheless, tissue protective effect of EPO could not be translated to the clinical trials because of common lethal thromboembolic events, erythropoiesis and hypertension. Although chemically modified nonerythropoietic analogs of EPO bypass these side effects, high expense, development of antidrug antibodies, and promotion of tumorigenicity are still concern especially in long-term use. As an alternative, nonerythropoietic EPO mimetic peptides can be used as candidate drugs with their high potency and selectivity, easy production, low cost, and immunogenicity properties. Recent experimental studies suggest that these peptides prevent ischemic brain injury and neuroinflammation. The results of clinical trial in patients with neuropathic pain are also promising. Herein, we summarize these studies and review advanced experimental and in silico methods in peptide drug discovery.
2010-06-14 | Parkin overexpression selects against a deleterious mtDNA mutation in heteroplasmic cybrid cells
Mitochondrial genomes with deleterious mutations can replicate in cells along with wild-type genomes in a state of heteroplasmy, and are a cause of severe inherited syndromes, such as mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke (MELAS), neuropathy, ataxia, retinitis pigmentosa-maternally inherited Leigh syndrome (NARP-MILS), and Leber's hereditary optic neuropathy (LHON). The cytosolic E3 ligase, Parkin, commonly mutated in recessive familial parkinsonism, translocates to depolarized mitochondria and induces their autophagic elimination, suggesting that Parkin may signal the selective removal of defective mitochondria within the cell. We report that long-term overexpression of Parkin can eliminate mitochondria with deleterious COXI mutations in heteroplasmic cybrid cells, thereby enriching cells for wild-type mtDNA and restoring cytochrome c oxidase activity. After relieving cybrid cells of Parkin overexpression, a more favorable wild-type to mutant mitochondrial genome ratio is stably maintained. These data support the model that Parkin functions in a mitochondrial quality control pathway. Additionally, they suggest that transiently increasing levels of Parkin expression might ameliorate certain mitochondrial diseases.
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