Mitochondrial ribosomal stress in lung diseases

Injury Death ◽

Atp Production ◽

Mitochondrial Ribosome ◽

Ribosomal Stress

Mitochondria are involved in a variety of critical cellular functions, and their impairment drives cell injury. The mitochondrial ribosome (mitoribosome) is responsible for the protein synthesis of mitochondrial DNA encoded genes. These proteins are involved in oxidative phosphorylation, respiration, and ATP production required in the cell. Mitoribosome components originate from both mitochondrial and nuclear genomes. Their dysfunction can be caused by impaired mitochondrial protein synthesis or mitoribosome misassembly, leading to a decline in mitochondrial translation. This decrease can trigger mitochondrial ribosomal stress and contribute to pulmonary cell injury, death, and diseases. This review focuses on the contribution of the impaired mitoribosome structural components and function to respiratory disease pathophysiology. We present recent findings in the fields of lung cancer, chronic obstructive pulmonary disease, interstitial lung disease, and asthma. We also include reports on the mitoribosome dysfunction in pulmonary hypertension, high altitude pulmonary edema, bacterial and viral infections. Studies of the mitoribosome alterations in respiratory diseases can lead to novel therapeutic targets.

Chronic ethanol feeding causes depression of mitochondrial elongation factor Tu in the rat liver: implications for the mitochondrial ribosome

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00108.2010 ◽

2011 ◽

Vol 300 (5) ◽

pp. G815-G822 ◽

Cited By ~ 5

Author(s):

Brian Weiser ◽

Gregory Gonye ◽

Peter Sykora ◽

Sara Crumm ◽

Alan Cahill

Keyword(s):

Protein Synthesis ◽

Mitochondrial Protein ◽

Elongation Factor ◽

Chronic Ethanol ◽

Male Rats ◽

Hepatic Energy Metabolism ◽

Mitochondrial Ribosome ◽

Ethanol Feeding

Chronic ethanol feeding is known to negatively impact hepatic energy metabolism. Previous studies have indicated that the underlying lesion responsible for this may lie at the level of the mitoribosome. The aim of this study was to characterize the structure of the hepatic mitoribosome in alcoholic male rats and their isocalorically paired controls. Our experiments revealed that chronic ethanol feeding resulted in a significant depletion of both structural (death-associated protein 3) and functional [elongation factor thermo unstable (EF-Tu)] mitoribosomal proteins. In addition, significant increases were found in nucleotide elongation factor thermo stable (EF-Ts) and structural mitochondrial ribosomal protein L12 (MRPL12). The increase in MRPL12 was found to correlate with an increase in the levels of the 39S large mitoribosomal subunit. These changes were accompanied by decreased levels of nuclear- and mitochondrially encoded respiratory subunits, decreased amounts of intact respiratory complexes, decreased hepatic ATP levels, and depressed mitochondrial translation. Mathematical modeling of ethanol-mediated changes in EF-Tu and EF-Ts using prederived kinetic data predicted that the ethanol-mediated decrease in EF-Tu levels could completely account for the impaired mitochondrial protein synthesis. In conclusion, chronic ethanol feeding results in a depletion of mitochondrial EF-Tu levels within the liver that is mathematically predicted to be responsible for the impaired mitochondrial protein synthesis seen in alcoholic animals.

Cardiolipin is required for membrane docking of mitochondrial ribosomes and protein synthesis

Journal of Cell Science ◽

10.1242/jcs.240374 ◽

2020 ◽

Vol 133 (14) ◽

pp. jcs240374 ◽

Cited By ~ 2

Author(s):

Richard G. Lee ◽

Junjie Gao ◽

Stefan J. Siira ◽

Anne-Marie Shearwood ◽

Judith A. Ermer ◽

...

Keyword(s):

Protein Synthesis ◽

Stress Responses ◽

Protein Complexes ◽

Mitochondrial Protein ◽

Mitochondrial Morphology ◽

Inner Membrane ◽

Mitochondrial Ribosomes ◽

Mitochondrial Inner Membrane ◽

Mitochondrial Ribosome

ABSTRACTThe mitochondrial inner membrane contains a unique phospholipid known as cardiolipin (CL), which stabilises the protein complexes embedded in the membrane and supports its overall structure. Recent evidence indicates that the mitochondrial ribosome may associate with the inner membrane to facilitate co-translational insertion of the hydrophobic oxidative phosphorylation (OXPHOS) proteins into the inner membrane. We generated three mutant knockout cell lines for the CL biosynthesis gene Crls1 to investigate the effects of CL loss on mitochondrial protein synthesis. Reduced CL levels caused altered mitochondrial morphology and transcriptome-wide changes that were accompanied by uncoordinated mitochondrial translation rates and impaired respiratory chain supercomplex formation. Aberrant protein synthesis was caused by impaired formation and distribution of mitochondrial ribosomes. Reduction or loss of CL resulted in divergent mitochondrial and endoplasmic reticulum stress responses. We show that CL is required to stabilise the interaction of the mitochondrial ribosome with the membrane via its association with OXA1 (also known as OXA1L) during active translation. This interaction facilitates insertion of newly synthesised mitochondrial proteins into the inner membrane and stabilises the respiratory supercomplexes.

Exploring the Ability of LARS2 Carboxy-Terminal Domain in Rescuing the MELAS Phenotype

Life ◽

10.3390/life11070674 ◽

2021 ◽

Vol 11 (7) ◽

pp. 674

Author(s):

Francesco Capriglia ◽

Francesca Rizzo ◽

Giuseppe Petrosillo ◽

Veronica Morea ◽

Giulia d’Amati ◽

...

Keyword(s):

Protein Synthesis ◽

Molecular Mechanisms ◽

Mitochondrial Protein ◽

Trna Synthetase ◽

Terminal Domain ◽

Carboxy Terminal Domain ◽

Mitochondrial Functions ◽

Carboxy Terminal

The m.3243A>G mutation within the mitochondrial mt-tRNALeu(UUR) gene is the most prevalent variant linked to mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome. This pathogenic mutation causes severe impairment of mitochondrial protein synthesis due to alterations of the mutated tRNA, such as reduced aminoacylation and a lack of post-transcriptional modification. In transmitochondrial cybrids, overexpression of human mitochondrial leucyl-tRNA synthetase (LARS2) has proven effective in rescuing the phenotype associated with m.3243A>G substitution. The rescuing activity resides in the carboxy-terminal domain (Cterm) of the enzyme; however, the precise molecular mechanisms underlying this process have not been fully elucidated. To deepen our knowledge on the rescuing mechanisms, we demonstrated the interactions of the Cterm with mutated mt-tRNALeu(UUR) and its precursor in MELAS cybrids. Further, the effect of Cterm expression on mitochondrial functions was evaluated. We found that Cterm ameliorates de novo mitochondrial protein synthesis, whilst it has no effect on mt-tRNALeu(UUR) steady-state levels and aminoacylation. Despite the complete recovery of cell viability and the increase in mitochondrial translation, Cterm-overexpressing cybrids were not able to recover bioenergetic competence. These data suggest that, in our MELAS cell model, the beneficial effect of Cterm may be mediated by factors that are independent of the mitochondrial bioenergetics.

Using mitoribosomal profiling to investigate human mitochondrial translation

Wellcome Open Research ◽

10.12688/wellcomeopenres.13119.2 ◽

2018 ◽

Vol 2 ◽

pp. 116

Author(s):

Fei Gao ◽

Maria Wesolowska ◽

Reuven Agami ◽

Koos Rooijers ◽

Fabricio Loayza-Puch ◽

...

Keyword(s):

Gene Expression ◽

Protein Synthesis ◽

Codon Position ◽

Mitochondrial Protein ◽

Base Pairs ◽

Suboptimal Structure ◽

Human Counterpart ◽

Steady State Levels

Background: Gene expression in human mitochondria has various idiosyncratic features. One of these was recently revealed as the unprecedented recruitment of a mitochondrially-encoded tRNA as a structural component of the large mitoribosomal subunit. In porcine particles this is mt-tRNAPhe whilst in humans it is mt-tRNAVal. We have previously shown that when a mutation in mt-tRNAVal causes very low steady state levels, there is preferential recruitment of mt-tRNAPhe. We have investigated whether this altered mitoribosome affects intra-organellar protein synthesis. Methods: By using mitoribosomal profiling we have revealed aspects of mitoribosome behaviour with its template mt-mRNA under both normal conditions as well as those where the mitoribosome has incorporated mt-tRNAPhe. Results: Analysis of the mitoribosome residency on transcripts under control conditions reveals that although mitochondria employ only 22 mt-tRNAs for protein synthesis, the use of non-canonical wobble base pairs at codon position 3 does not cause any measurable difference in mitoribosome occupancy irrespective of the codon. Comparison of the profile of aberrant mt-tRNAPhe containing mitoribosomes with those of controls that integrate mt-tRNAVal revealed that the impaired translation seen in the latter was not due to stalling on triplets encoding either of these amino acids. The alterations in mitoribosome interactions with start codons was not directly attributable to the either the use of non-cognate initiation codons or the presence or absence of 5’ leader sequences, except in the two bicistronic RNA units, RNA7 and RNA14 where the initiation sites are internal. Conclusions: These data report the power of mitoribosomal profiling in helping to understand the subtleties of mammalian mitochondrial protein synthesis. Analysis of profiles from the mutant mt-tRNAVal cell line suggest that despite mt-tRNAPhe being preferred in the porcine mitoribosome, its integration into the human counterpart results in a suboptimal structure that modifies its interaction with mt-mRNAs.

Mitochondrial OXPHOS Biogenesis: Co-Regulation of Protein Synthesis, Import, and Assembly Pathways

International Journal of Molecular Sciences ◽

10.3390/ijms21113820 ◽

2020 ◽

Vol 21 (11) ◽

pp. 3820 ◽

Cited By ~ 1

Author(s):

Jia Xin Tang ◽

Kyle Thompson ◽

Robert W. Taylor ◽

Monika Oláhová

Keyword(s):

Gene Expression ◽

Protein Synthesis ◽

Protein Import ◽

Acyl Carrier Protein ◽

Early Stage ◽

Mitochondrial Gene ◽

Mitochondrial Protein ◽

Fine Tuning ◽

Oxphos Complex

The assembly of mitochondrial oxidative phosphorylation (OXPHOS) complexes is an intricate process, which—given their dual-genetic control—requires tight co-regulation of two evolutionarily distinct gene expression machineries. Moreover, fine-tuning protein synthesis to the nascent assembly of OXPHOS complexes requires regulatory mechanisms such as translational plasticity and translational activators that can coordinate mitochondrial translation with the import of nuclear-encoded mitochondrial proteins. The intricacy of OXPHOS complex biogenesis is further evidenced by the requirement of many tightly orchestrated steps and ancillary factors. Early-stage ancillary chaperones have essential roles in coordinating OXPHOS assembly, whilst late-stage assembly factors—also known as the LYRM (leucine–tyrosine–arginine motif) proteins—together with the mitochondrial acyl carrier protein (ACP)—regulate the incorporation and activation of late-incorporating OXPHOS subunits and/or co-factors. In this review, we describe recent discoveries providing insights into the mechanisms required for optimal OXPHOS biogenesis, including the coordination of mitochondrial gene expression with the availability of nuclear-encoded factors entering via mitochondrial protein import systems.

Oxygen and pH regulation of protein synthesis in mitochondria from Artemia franciscana embryos

Biochemical Journal ◽

10.1042/bj3130207 ◽

1996 ◽

Vol 313 (1) ◽

pp. 207-213 ◽

Cited By ~ 25

Author(s):

Kurt E. KWAST ◽

Steven C. HAND

Keyword(s):

Protein Synthesis ◽

Ph Regulation ◽

Mitochondrial Protein ◽

Oxygen Limitation ◽

Oxygen Availability ◽

Artemia Franciscana ◽

Synthesis Rate ◽

Protein Synthesis Rate ◽

Purine Nucleotides

To identify factors responsible for the down-regulation of mitochondrial biosynthetic processes during anoxia in encysted Artemia franciscana embryos, the effects of oxygen limitation and pH on protein synthesis were investigated in isolated mitochondria. At the optimal pH of 7.5, exposure of mitochondria to anoxia decreases the protein synthesis rate by 79%. Rates were suppressed by a further 10% at pH 6.8, the intracellular pH (pHi) measured under anoxia in vivo. Matrix pH, measured under identical conditions, was 8.43±0.01 at an extramitochondrial pH of 7.9 (mean±S.E.M., n = 3), 8.05±0.01 at pH 7.5, and 7.10±0.01 at pH 6.8. The matrix pH did not vary (P ≥0.20) as a function of oxygen availability during the 1 h assays. Intramitochondrial purine nucleotides varied little as a function of pH. In contrast, after 1 h of protein synthesis under anoxia, ATP levels decreased by up to 40%,. whereas AMP, ADP and GDP concentrations increased, and GTP and GMP concentrations remained relatively constant. The addition of 1 mM ATP at the onset of anoxia maintained the ATP/ADP ratio at the aerobic value, but did not stabilize the GTP/GDP ratio or rescue rates of protein synthesis. Thus, at present, we cannot eliminate the possibility that the decrease in the GTP/GDP ratio during anoxia may contribute to the suppression of protein synthesis. The effect of anoxia was reversible; the rate of protein synthesis upon reoxygenation after a 30 min bout of anoxia was comparable (P = 0.14) with the pre-anoxic rate (193±17 and 174±6 pmol of leucine per mg of protein respectively; mean±S.E.M., n = 3). The array of mitochondrial translation products did not differ qualitatively as a function of either oxygen availability or pH. Finally, similar pH profiles for protein synthesis were obtained with either [3H]leucine or [3H]histidine (known to use different transporters). Consequently, it is improbable that the pH-sensitivity of protein synthesis can be explained by a specific protein effect on the import of the radiolabelled amino acid used. In summary, both oxygen limitation and acidic pH suppress rates of mitochondrial protein synthesis and are likely to contribute to the arrest of mitochondrial anabolic processes during anoxia-induced quiescence in A. franciscana embryos.

Insulin stimulates mitochondrial protein synthesis and respiration in isolated perfused rat heart.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1990.259.3.e413 ◽

1990 ◽

Vol 259 (3) ◽

pp. E413

Author(s):

E E McKee ◽

B L Grier

Keyword(s):

Protein Synthesis ◽

Mitochondrial Protein ◽

Control Level ◽

Respiratory Control ◽

Mitochondrial Proteins ◽

Rat Hearts ◽

Perfused Rat Hearts ◽

Perfused Hearts

The rates of synthesis of mitochondrial proteins by both the cytoplasmic and mitochondrial protein synthetic systems, as well as parameters of respiration, were measured and compared in mitochondria isolated from fresh, control perfused, and insulin-perfused rat hearts. The respiratory control ratio (RCR) in mitochondria from fresh hearts was 8.1 +/- 0.4 and decreased to 6.0 +/- 0.2 (P less than 0.001 vs. fresh) in mitochondria from control perfused hearts and to 6.7 +/- 0.2 (P less than 0.005 vs. fresh and P less than 0.02 vs. control perfused) for mitochondria from hearts perfused in the presence of insulin. A positive correlation between the RCR and the rate of mitochondrial translation was demonstrated in mitochondria from fresh hearts. In mitochondria isolated from control perfused hearts, the rate of protein synthesis decreased to 84 +/- 3% of the fresh rate after 30 min of perfusion and fell further to 64 +/- 3% after 3 h of perfusion. The inclusion of insulin in the perfusion buffer stimulated mitochondrial protein synthesis 1.2-fold by 1 h (P less than 0.005) and 1.34-fold by 3 h of perfusion (P less than 0.001). The addition of insulin to 1-h control perfused hearts shifted the rate of mitochondrial protein synthesis from the control level to the insulin-perfused level within 30 min of additional perfusion, whereas 1 h was required to shift the RCR values of these mitochondria from control levels to insulin-perfused levels. Thus, whereas RCR was a useful predictor of mitochondrial translation rates, it did not account for the effects of insulin on mitochondrial translation.(ABSTRACT TRUNCATED AT 250 WORDS)

Mrpl36 Is Important for Generation of Assembly Competent Proteins during Mitochondrial Translation

Molecular Biology of the Cell ◽

10.1091/mbc.e08-12-1162 ◽

2009 ◽

Vol 20 (10) ◽

pp. 2615-2625 ◽

Cited By ~ 32

Author(s):

Martin Prestele ◽

Frank Vogel ◽

Andreas S. Reichert ◽

Johannes M. Herrmann ◽

Martin Ott

Keyword(s):

Protein Synthesis ◽

Respiratory Chain ◽

Large Subunit ◽

Critical Role ◽

Respiratory Chain Complexes ◽

Ribosomal Subunits ◽

Terminal Domain ◽

Chain Complexes ◽

Mitochondrial Ribosome

The complexes of the respiratory chain represent mosaics of nuclear and mitochondrially encoded components. The processes by which synthesis and assembly of the various subunits are coordinated remain largely elusive. During evolution, many proteins of the mitochondrial ribosome acquired additional domains pointing at specific properties or functions of the translation machinery in mitochondria. Here, we analyzed the function of Mrpl36, a protein associated with the large subunit of the mitochondrial ribosome. This protein, homologous to the ribosomal protein L31 from bacteria, contains a mitochondria-specific C-terminal domain that is not required for protein synthesis per se; however, its absence decreases stability of Mrpl36. Cells lacking this C-terminal domain can still synthesize proteins, but these translation products fail to be properly assembled into respiratory chain complexes and are rapidly degraded. Surprisingly, overexpression of Mrpl36 seems to even increase the efficiency of mitochondrial translation. Our data suggest that Mrpl36 plays a critical role during translation that determines the rate of respiratory chain assembly. This important function seems to be carried out by a stabilizing activity of Mrpl36 on the interaction between large and small ribosomal subunits, which could influence accuracy of protein synthesis.

Glutamyl-tRNAGln amidotransferase is essential for mammalian mitochondrial translation in vivo

Biochemical Journal ◽

10.1042/bj20131107 ◽

2014 ◽

Vol 460 (1) ◽

pp. 91-101 ◽

Cited By ~ 20

Author(s):

Lucía Echevarría ◽

Paula Clemente ◽

Rosana Hernández-Sierra ◽

María Esther Gallardo ◽

Miguel A. Fernández-Moreno ◽

...

Keyword(s):

Protein Synthesis ◽

Mammalian Cells ◽

Mitochondrial Protein ◽

Indirect Pathway ◽

Mitochondrial Translation

We have demonstrated that in mitochondria of mammalian cells the aminoacylation of tRNAGln is produced by an indirect pathway involving the enzyme glutamyl-tRNAGln amidotransferase. Misaminoacylated Glu-tRNAGln is rejected from the ribosomes maintaining the fidelity of the mitochondrial protein synthesis.

NOA1 is an essential GTPase required for mitochondrial protein synthesis

Molecular Biology of the Cell ◽

10.1091/mbc.e10-07-0643 ◽

2011 ◽

Vol 22 (1) ◽

pp. 1-11 ◽

Cited By ~ 37

Author(s):

Mateusz Kolanczyk ◽

Markus Pech ◽

Tomasz Zemojtel ◽

Hiroshi Yamamoto ◽

Ivan Mikula ◽

...

Keyword(s):

Protein Synthesis ◽

Mammalian Cells ◽

Gradient Centrifugation ◽

Mitochondrial Protein ◽

In Vitro Assays ◽

Developmental Defect ◽

Mitochondrial Functions ◽

Mitochondrial Ribosome

Nitric oxide associated-1 (NOA1) is an evolutionarily conserved guanosine triphosphate (GTP) binding protein that localizes predominantly to mitochondria in mammalian cells. On the basis of bioinformatic analysis, we predicted its possible involvement in ribosomal biogenesis, although this had not been supported by any experimental evidence. Here we determine NOA1 function through generation of knockout mice and in vitro assays. NOA1-deficient mice exhibit midgestation lethality associated with a severe developmental defect of the embryo and trophoblast. Primary embryonic fibroblasts isolated from NOA1 knockout embryos show deficient mitochondrial protein synthesis and a global defect of oxidative phosphorylation (OXPHOS). Additionally, Noa1–/– cells are impaired in staurosporine-induced apoptosis. The analysis of mitochondrial ribosomal subunits from Noa1–/– cells by sucrose gradient centrifugation and Western blotting showed anomalous sedimentation, consistent with a defect in mitochondrial ribosome assembly. Furthermore, in vitro experiments revealed that intrinsic NOA1 GTPase activity was stimulated by bacterial ribosomal constituents. Taken together, our data show that NOA1 is required for mitochondrial protein synthesis, likely due to its yet unidentified role in mitoribosomal biogenesis. Thus, NOA1 is required for such basal mitochondrial functions as adenosine triphosphate (ATP) synthesis and apoptosis.