The molecular chaperone Hsp78 confers compartment-specific thermotolerance to mitochondria.

Hsp78, a member of the family of Clp/Hsp100 proteins, exerts chaperone functions in mitochondria of S. cerevisiae which overlap with those of mitochondrial Hsp70. In the present study, the role of Hsp78 under extreme stress was analyzed. Whereas deletion of HSP78 does not affect cell growth at temperatures up to 39 decrees C and cellular thermotolerance at 50 degrees C, Hsp78 is crucial for maintenance of respiratory competence and for mitochondrial genome integrity under severe temperature stress (mitochondrial thermotolerance). Mitochondrial protein synthesis is identified as a thermosensitive process. Reactivation of mitochondrial protein synthesis after heat stress depends on the presence of Hsp78, though Hsp78 does not confer protection against heat-inactivation to this process. Hsp78 appears to act in concert with other mitochondrial chaperone proteins since a conditioning pretreatment of the cells to induce the cellular heat shock response is required to maintain mitochondrial functions under severe temperature stress. When expressed in the cytosol, Hsp78 can substitute for the homologous heat shock protein Hsp104 in mediating cellular thermotolerance, suggesting a conserved mode of action of the two proteins. Thus, proteins of the Clp/Hsp100-family located in the cytosol and within mitochondria confer compartment-specific protection against heat damage to the cell.

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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 ◽

Mitochondrial Protein Synthesis ◽

Mitochondrial Translation ◽

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.

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Physiological Role of the N-terminal Processed P4501A1 Targeted to Mitochondria in Erythromycin Metabolism and Reversal of Erythromycin-mediated Inhibition of Mitochondrial Protein Synthesis

Journal of Biological Chemistry ◽

10.1074/jbc.274.10.6617 ◽

1999 ◽

Vol 274 (10) ◽

pp. 6617-6625 ◽

Cited By ~ 39

Author(s):

Hindupur K. Anandatheerthavarada ◽

C. Vijayasarathy ◽

Shripad V. Bhagwat ◽

Gopa Biswas ◽

Jayati Mullick ◽

...

Keyword(s):

Protein Synthesis ◽

Mitochondrial Protein ◽

Physiological Role ◽

Mitochondrial Protein Synthesis

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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 Protein Synthesis ◽

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.

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Role of the mitochondrial protein synthesis in the catabolite repression of the petite-negative yeast K. lactis

Biochemical and Biophysical Research Communications ◽

10.1016/0006-291x(78)90682-4 ◽

1978 ◽

Vol 80 (2) ◽

pp. 340-348 ◽

Cited By ~ 26

Author(s):

I. Ferrero ◽

C. Rossi ◽

M.P. Landini ◽

P.P. Puglisi

Keyword(s):

Protein Synthesis ◽

Catabolite Repression ◽

Mitochondrial Protein ◽

Mitochondrial Protein Synthesis ◽

Petite Negative Yeast

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MITOCHONDRIAL PROTEIN SYNTHESIS IN HELA CELLS

The Journal of Cell Biology ◽

10.1083/jcb.60.3.755 ◽

1974 ◽

Vol 60 (3) ◽

pp. 755-763 ◽

Cited By ~ 17

Author(s):

Jonas B. Galper

Keyword(s):

Protein Synthesis ◽

Ethidium Bromide ◽

Mitochondrial Protein ◽

Specific Protein ◽

Mitochondrial Proteins ◽

Mitochondrial Protein Synthesis ◽

Initiator Trna ◽

Low Concentrations ◽

Separate Protein

HeLa cell mitochondrial proteins have been shown to be the products of two separate protein-synthesizing systems; one, the general cellular mechanism, sensitive to inhibition by cycloheximide, the other, a specific mitochondrial system subject to inhibition by low concentrations of chloramphenicol (Galper, J. B., and J. E. Darnell. 1971. J. Mol. Biol 57:363). Preliminary data have suggested that a mitochondrial N-formyl-methionyl-tRNA (f-Met-tRNA) might be the initiator tRNA in the latter (Galper, J. B., and J. E. Darnell. 1969. Biochem. Biophys. Res. Commun. 34:205; 1971. J. Mol. Biol. 57:363). It is demonstrated here that the synthesis of these endogenous mitochondrial proteins is also subject to inhibition by ethidium bromide and decays with a half-life of 1½–2 h in cultures incubated with low concentrations of this dye. The role of formylated f-Met-tRNA as the initiator tRNA in the synthesis of mitochondrial proteins is supported by data from several experiments. The rates of ethidium bromide inhibition of both the charging of f-Met-tRNA and of the synthesis of mitochondrial proteins are strikingly similar. Inhibition by aminopterin of the formylation of f-Met-tRNA greatly depresses the rate of mitochondrial-specific protein synthesis. In the absence of the synthesis of these proteins, respiration, the levels of cytochromes a–a3 and b, and the number of mitochondrial cristae are decreased. The implications of these findings as they relate to mitochondrial biogenesis are discussed.

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Role of Mitochondrial RNA Polymerase in the Toxicity of Nucleotide Inhibitors of Hepatitis C Virus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01922-15 ◽

2015 ◽

Vol 60 (2) ◽

pp. 806-817 ◽

Cited By ~ 33

Author(s):

Joy Y. Feng ◽

Yili Xu ◽

Ona Barauskas ◽

Jason K. Perry ◽

Shekeba Ahmadyar ◽

...

Keyword(s):

Protein Synthesis ◽

Hepatitis C Virus ◽

Hepatitis C ◽

Adverse Events ◽

Mitochondrial Protein ◽

Mitochondrial Rna ◽

Mitochondrial Toxicity ◽

Mitochondrial Protein Synthesis ◽

Mitochondrial Rna Polymerase

ABSTRACTToxicity has emerged during the clinical development of many but not all nucleotide inhibitors (NI) of hepatitis C virus (HCV). To better understand the mechanism for adverse events, clinically relevant HCV NI were characterized in biochemical and cellular assays, including assays of decreased viability in multiple cell lines and primary cells, interaction with human DNA and RNA polymerases, and inhibition of mitochondrial protein synthesis and respiration. NI that were incorporated by the mitochondrial RNA polymerase (PolRMT) inhibited mitochondrial protein synthesis and showed a corresponding decrease in mitochondrial oxygen consumption in cells. The nucleoside released by the prodrug balapiravir (R1626), 4′-azido cytidine, was a highly selective inhibitor of mitochondrial RNA transcription. The nucleotide prodrug of 2′-C-methyl guanosine, BMS-986094, showed a primary effect on mitochondrial function at submicromolar concentrations, followed by general cytotoxicity. In contrast, NI containing multiple ribose modifications, including the active forms of mericitabine and sofosbuvir, were poor substrates for PolRMT and did not show mitochondrial toxicity in cells. In general, these studies identified the prostate cell line PC-3 as more than an order of magnitude more sensitive to mitochondrial toxicity than the commonly used HepG2 cells. In conclusion, analogous to the role of mitochondrial DNA polymerase gamma in toxicity caused by some 2′-deoxynucleotide analogs, there is an association between HCV NI that interact with PolRMT and the observation of adverse events. More broadly applied, the sensitive methods for detecting mitochondrial toxicity described here may help in the identification of mitochondrial toxicity prior to clinical testing.

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