bims-cytox1 Biomed News
on Cytochrome oxidase subunit 1
Issue of 2020‒01‒19
nine papers selected by
Gavin McStay
Staffordshire University

  1. Annu Rev Biochem. 2020 Jan 14.
    Lill R, Freibert SA.
      Mitochondria are essential in most eukaryotes and are involved in numerous biological functions including ATP production, cofactor biosyntheses, apoptosis, lipid synthesis, and steroid metabolism. Work over the past two decades has uncovered the biogenesis of cellular iron-sulfur (Fe/S) proteins as the essential and minimal function of mitochondria. This process is catalyzed by the bacteria-derived iron-sulfur cluster assembly (ISC) machinery and has been dissected into three major steps: de novo synthesis of a [2Fe-2S] cluster on a scaffold protein; Hsp70 chaperone-mediated trafficking of the cluster and insertion into [2Fe-2S] target apoproteins; and catalytic conversion of the [2Fe-2S] into a [4Fe-4S] cluster and subsequent insertion into recipient apoproteins. ISC components of the first two steps are also required for biogenesis of numerous essential cytosolic and nuclear Fe/S proteins, explaining the essentiality of mitochondria. This review summarizes the molecular mechanisms underlying the ISC protein-mediated maturation of mitochondrial Fe/S proteins and the importance for human disease. Expected final online publication date for the Annual Review of Biochemistry, Volume 89 is June 22, 2020. Please see for revised estimates.
  2. Annu Rev Biophys. 2020 Jan 13.
    Ruan L, Wang Y, Zhang X, Tomaszewski A, McNamara JT, Li R.
      Mitochondria are essential organelles in eukaryotes. Most mitochondrial proteins are encoded by the nuclear genome and translated in the cytosol. Nuclear-encoded mitochondrial proteins need to be imported, processed, folded, and assembled into their functional states. To maintain protein homeostasis (proteostasis), mitochondria are equipped with a distinct set of quality control machineries. Deficiencies in such systems lead to mitochondrial dysfunction, which is a hallmark of aging and many human diseases, such as neurodegenerative diseases, cardiovascular diseases, and cancer. In this review, we discuss the unique challenges and solutions of proteostasis in mitochondria. The import machinery coordinates with mitochondrial proteases and chaperones to maintain the mitochondrial proteome. Moreover, mitochondrial proteostasis depends on cytosolic protein quality control mechanisms during crises. In turn, mitochondria facilitate cytosolic proteostasis. Increasing evidence suggests that enhancing mitochondrial proteostasis may hold therapeutic potential to protect against protein aggregation-associated cellular defects. Expected final online publication date for the Annual Review of Biophysics, Volume 49 is May 6, 2020. Please see for revised estimates.
  3. PeerJ. 2020 ;8 e8362
    Yoo BC, Yadav NS, Orozco EM, Sakai H.
      We present a new approach to edit both mitochondrial and chloroplast genomes. Organelles have been considered off-limits to CRISPR due to their impermeability to most RNA and DNA. This has prevented applications of Cas9/gRNA-mediated genome editing in organelles while the tool has been widely used for engineering of nuclear DNA in a number of organisms in the last several years. To overcome the hurdle, we designed a new approach to enable organelle genome editing. The plasmids, designated "Edit Plasmids," were constructed with two expression cassettes, one for the expression of Cas9, codon-optimized for each organelle, under promoters specific to each organelle, and the other cassette for the expression of guide RNAs under another set of promoters specific to each organelle. In addition, Edit Plasmids were designed to carry the donor DNA for integration between two double-strand break sites induced by Cas9/gRNAs. Each donor DNA was flanked by the regions homologous to both ends of the integration site that were short enough to minimize spontaneous recombination events. Furthermore, the donor DNA was so modified that it did not carry functional gRNA target sites, allowing the stability of the integrated DNA without being excised by further Cas9/gRNAs activity. Edit Plasmids were introduced into organelles through microprojectile transformation. We confirmed donor DNA insertion at the target sites facilitated by homologous recombination only in the presence of Cas9/gRNA activity in yeast mitochondria and Chlamydomonas chloroplasts. We also showed that Edit Plasmids persist and replicate in mitochondria autonomously for several dozens of generations in the presence of the wild-type genomes. Finally, we did not find insertions and/or deletions at one of the Cas9 cleavage sites in Chloroplasts, which are otherwise hallmarks of Cas9/gRNA-mediated non-homologous end joining (NHEJ) repair events in nuclear DNA. This is consistent with previous reports of the lack of NHEJ repair system in most bacteria, which are believed to be ancestors of organelles. This is the first demonstration of CRISPR-mediated genome editing in both mitochondria and chloroplasts in two distantly related organisms. The Edit Plasmid approach is expected to open the door to engineer organelle genomes of a wide range of organisms in a precise fashion.
    Keywords:  CRISPR; Cas9/gRNA; Chlamydomonas; Chloroplast; DNA replacement; Edit Plasmid; Genome editing; Mitochondria; Organelle; Yeast
  4. Front Cell Dev Biol. 2019 ;7 305
    Vardi-Oknin D, Arava Y.
      Mitochondria exert their many functions through a repertoire of hundreds of proteins. The vast majority of these proteins are encoded in the nuclear genome, translated in the cytosol and imported into the mitochondria. Current models, derived mainly from work in yeast, suggest that the translation of many of these proteins can occur in close vicinity to the mitochondria outer membrane by localized ribosomes. Here, we applied ribosome-proximity biotin labeling to address this possibility. A clear biotinylation of ribosomes by mitochondrial Tom20-BirA fusion protein was observed in a human cell line. Isolation of these ribosomes revealed their preferred association with mRNAs encoding mitochondrial proteins. Furthermore, knock down of the mitochondrial protein receptor Tom70 resulted in a decrease in ribosomes translating mRNAs encoding proteins predicted to be recognized by Tom70. Intriguingly, levels of ribosomes translating mRNAs encoding targets of Tom20 were increased. We also knocked down the RNA binding protein CLUH that is implicated in regulation of mRNA encoding mitochondrial proteins, and found an increase in association of CLUH targets with mitochondria-proximal ribosomes. This is consistent with a role for CLUH in maintaining mRNAs encoding mitochondrial proteins in the cytosol. Overall, these data shed light on factors that contribute to association of translating ribosomes with human mitochondria and may suggest a co-translational mode of protein import into this organelle.
    Keywords:  CLUH; Tom20; Tom70; localized translation; mRNA localization; mitochondria; ribosome-proximity labeling; ribosomes
  5. Biochim Biophys Acta Bioenerg. 2020 Jan 11. pii: S0005-2728(20)30001-3. [Epub ahead of print] 148153
    Yoga EG, Angerer H, Parey K, Zickermann V.
      Complex I is the largest and most intricate redox-driven proton pump of the respiratory chain. The structure of bacterial and mitochondrial complex I has been determined by X-ray crystallography and cryo-EM at increasing resolution. The recent cryo-EM structures of the complex I-like NDH complex and membrane bound hydrogenase open a new and more comprehensive perspective on the complex I superfamily. Functional studies and molecular modeling approaches have greatly advanced our understanding of the catalytic cycle of complex I. However, the molecular mechanism by which energy is extracted from the redox reaction and utilized to drive proton translocation is unresolved and a matter of ongoing debate. Here, we review progress in structure determination and functional characterization of complex I and discuss current mechanistic models.
    Keywords:  Membrane bound hydrogenase; Mitochondria; NADH:Ubiquinone oxidoreductase; Oxidative phosphorylation; Redox-linked proton translocation; Respiratory chain
  6. Hum Mutat. 2020 Jan 16.
    Wei X, Du M, Li D, Wen S, Xie J, Li Y, Chen A, Zhang K, Xu P, Jia M, Wen C, Zhou H, Lyu J, Yang Y, Fang H.
      Mutations in FASTKD2, a mitochondrial RNA binding protein, have been associated with mitochondrial encephalomyopathy with isolated complex IV deficiency. However, deficiencies related to other oxidative phosphorylation system (OXPHOS) complexes have not been reported. Here, we identified three novel FASTKD2 mutations, c.808_809insTTTCAGTTTTG, homoplasmic mutation c.868C>T, and heteroplasmic mutation c.1859delT/c.868C>T, in patients with mitochondrial encephalomyopathy. Cell-based complementation assay revealed that these three FASTKD2 mutations were pathogenic. Mitochondrial functional analysis revealed that mutations in FASTKD2 impaired the mitochondrial function in patient-derived lymphocytes due to the deficiency in multi-OXPHOS complexes, whereas mitochondrial complex II remained unaffected. Consistent results were also found in human primary muscle cell and zebrafish with knockdown of FASTKD2. Furthermore, we discovered that FASTKD2 mutation is not inherently associated with epileptic seizures, optic atrophy, and loss of visual function. Alternatively, a patient with FASTKD2 mutation can show sinus tachycardia and hypertrophic cardiomyopathy, which was partially confirmed in zebrafish with knockdown of FASTKD2. In conclusion, both in vivo and in vitro studies suggest that loss of function mutation in FASTKD2 is responsible for multi-OXPHOS complexes deficiency, and FASTKD2-associated mitochondrial disease has a high degree of clinical heterogenicity. This article is protected by copyright. All rights reserved.
    Keywords:   FASTKD2 ; Metabolic genetic diseases; OXPHOS complex; mitochondrial disease
  7. Mol Med Rep. 2019 Nov 22.
    Ding Y, Ye YF, Li MY, Xia BH, Leng JH.
      Certain mutations in mitochondrial DNA (mtDNA) are associated with Leber's hereditary optic neuropathy (LHON). In particular, the well‑known NADH dehydrogenase 4 (ND4) m.11778G>A mutation is one of the most common LHON‑associated primary mutations worldwide. However, how specific mtDNA mutations, or variants, affect LHON penetrance is not fully understood. The aim of the current study was to explore the relationship between mtDNA mutations and LHON, and to provide useful information for early detection and prevention of this disease. Following the molecular characterization of a Han Chinese family with maternally inherited LHON, four out of eight matrilineal relatives demonstrated varying degrees of both visual impairment and age of onset. Through PCR amplification of mitochondrial genomes and direct Sanger sequencing analysis, a homoplasmic mitochondrial‑encoded ND4 m.11778G>A mutation, alongside a set of genetic variations belonging to human mtDNA haplogroup B5b1 were identified. Among these sequence variants, alanine transfer RNA (tRNA)Ala m.5601C>T was of particular interest. This variant occurred at position 59 in the TψC loop and altered the base pairing, which led to mitochondrial RNA (mt‑RNA) metabolism failure and defects in mitochondrial protein synthesis. Bioinformatics analysis suggested that the m.5601C>T variant altered tRNAAla structure. Therefore, impaired mitochondrial functions caused by the ND4 m.11778G>A mutation may be enhanced by the mt‑tRNAAla m.5601C>T variant. These findings suggested that the tRNAAla m.5601C>T variant might modulate the clinical manifestation of the LHON‑associated primary mutation.
  8. Int J Biochem Cell Biol. 2020 Jan 10. pii: S1357-2725(20)30011-X. [Epub ahead of print] 105694
    Busch KB.
      Mitochondria are known as dynamic organelles that fuse and divide under the control of certain proteins. These dynamics are important to shape mitochondria, maintain a healthy mitochondrial population, and enable physiological adaptations, to name just a few key processes. We are less aware that mitochondrial membrane lipids and proteins also exhibit dynamics in terms of lateral mobility and translocation. This single molecule dynamics is equally important for the above processes as it enables interaction with other proteins and complexes. Here we discuss some mitochondrial proteins and the role of their specific dynamic spatiotemporal organization for function and adaptation. For example, respiratory proteins are preferentially localized in cristae sheets, ATP synthase at the edges of cristae and compounds of the MICOS complex at cristae junctions. Trajectory patterns show how and whether molecules are restricted in their mobility and how this determines their distribution. The formation of supercomplexes has an influence on this. Recent studies have also shown that the distribution of proteins is not absolutely static. For example, the metabolic state of the cell obviously determines the activity of the mitochondria and finally the organization of the bioenergetic and structure-determining proteins inside. The ATP synthase has both classifications and additionally shows functional interactions with other cristae shaping proteins at cristae cunctions. To understand the dynamics of mitochondria we have to consider all scales: from the dynamics of the molecular structure of the proteins to the dynamics of the molecules with respect to their localization and lateral mobility to the dynamics of the organelle structure.
    Keywords:  ATP synthase; MICOS; OXPHOS supercomplexes; Single molecule tracking; membrane protein diffusion; spatio-temporal organization; superresolution
  9. DNA Cell Biol. 2020 Jan 16.
    Nguyen NNY, Kim SS, Jo YH.
      Mitochondria play various important roles in energy production, metabolism, and apoptosis. Mitochondrial dysfunction caused by alterations in mitochondrial DNA (mtDNA) can lead to the initiation and progression of cancers and other diseases. These alterations include mutations and copy number variations. Especially, the mutations in D-loop, MT-ND1, and MT-ND5 affect mitochondrial functions and are widely detected in various cancers. Meanwhile, several other mutations have been correlated with muscular and neuronal diseases, especially MT-TL1 is deeply related. These pieces of evidence indicated mtDNA alterations in diseases show potential as a novel therapeutic target. mtDNA repair enzymes are the target for delaying or stalling the mtDNA damage-induced cancer progression and metastasis. Moreover, some mutations reveal a prognosis ability of the drug resistance. Current efforts aim to develop mitochondrial transplantation technique as a direct cure for deregulated mitochondria-associated diseases. This review summarizes the implications of mitochondrial dysfunction in cancers and other pathologies; and discusses the relevance of mitochondria-targeted therapies, along with their contribution as potential biomarkers.
    Keywords:  cancer; mitochondrial DNA; mutation; oxidative stress; predictor