scholarly journals Quality control of mitochondrial protein synthesis is required for membrane integrity and cell fitness

2015 ◽  
Vol 211 (2) ◽  
pp. 373-389 ◽  
Author(s):  
Uwe Richter ◽  
Taina Lahtinen ◽  
Paula Marttinen ◽  
Fumi Suomi ◽  
Brendan J. Battersby
Keyword(s):  
Quality Control ◽  
Protein Synthesis ◽  
Oxidative Phosphorylation ◽  
De Novo ◽  
Mitochondrial Protein ◽  
Membrane Integrity ◽  
Mitochondrial Proteins ◽  
Protein Accumulation ◽  
Mitochondrial Protein Synthesis ◽  
Inner Membrane

Mitochondrial ribosomes synthesize a subset of hydrophobic proteins required for assembly of the oxidative phosphorylation complexes. This process requires temporal and spatial coordination and regulation, so quality control of mitochondrial protein synthesis is paramount to maintain proteostasis. We show how impaired turnover of de novo mitochondrial proteins leads to aberrant protein accumulation in the mitochondrial inner membrane. This creates a stress in the inner membrane that progressively dissipates the mitochondrial membrane potential, which in turn stalls mitochondrial protein synthesis and fragments the mitochondrial network. The mitochondrial m-AAA protease subunit AFG3L2 is critical to this surveillance mechanism that we propose acts as a sensor to couple the synthesis of mitochondrial proteins with organelle fitness, thus ensuring coordinated assembly of the oxidative phosphorylation complexes from two sets of ribosomes.

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

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 ◽  
Mitochondrial Protein Synthesis ◽  
Mitochondrial Translation ◽  
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)

scholarly journals MITOCHONDRIAL PROTEIN SYNTHESIS IN HELA CELLS

1974 ◽  
Vol 60 (3) ◽  
pp. 755-763 ◽  
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.

Discrete electrophoretic products of mitochondrial protein synthesis in the Chinese hamster ovary cell line

1977 ◽  
Vol 55 (10) ◽  
pp. 1064-1074 ◽  
Author(s):  
R. W. Yatscoff ◽  
K. B. Freeman
Keyword(s):  
Protein Synthesis ◽  
Cell Line ◽  
Electrophoretic Mobility ◽  
Chinese Hamster Ovary ◽  
Mitochondrial Protein ◽  
Chinese Hamster ◽  
Mitochondrial Proteins ◽  
Mitochondrial Protein Synthesis ◽  
Cho Cell ◽  
Cho Cell Line

Mitochondrial proteins labelled with [35S]methionine for 1 h in whole Chinese hamster ovary (CHO) cells in the presence of cycloheximide or emetine, known inhibitors of cytosolic protein synthesis, have been enumerated and characterized by their electrophoretic mobility in sodium dodecyl sulfate slab gel electrophoresis. Ten distinct electrophoretic bands were observed. The components were relatively stable during a 2 h postlabelling period. The same 10 bands were also seen with the CHO cell line tsH1, labelled at 40 °C, a temperature at which cytosolic but not mitochondrial protein synthesis is inhibited in this cell line, and with isolated mitochondria labelled in the presence of cycloheximide. An 11th band was present when [3H]leucine but not [35S] methionine was used for labelling. The width of the major band suggested that it consists of two components making a total of at least 12 proteins synthesized in mitochondria. The molecular weights of these mitochondrial proteins ranged from 5000 to 50000 and there was a sixfold difference in the relative molar amounts synthesized in a 1-h period in the presence of [3H]leucine or [3SS] methionine.No differences in number or electrophoretic mobility of the mitochondrially synthesized proteins were found among the seven CHO cell lines examined. These results suggest the stability of the mitochondrial genome in the CHO cell line.

Products of mitochondrial protein synthesis in Tetrahymena

1979 ◽  
Vol 57 (4) ◽  
pp. 314-320 ◽  
Author(s):  
Paul G. Young ◽  
Neil P. Hunter
Keyword(s):  
Protein Synthesis ◽  
Gel Electrophoresis ◽  
Trichloroacetic Acid ◽  
Polyacrylamide Gel Electrophoresis ◽  
Mitochondrial Protein ◽  
Sodium Dodecyl ◽  
Apparent Molecular Weight ◽  
Mitochondrial Proteins ◽  
Mitochondrial Protein Synthesis ◽  
Chloroform Methanol

The products of mitochondrial protein synthesis have been investigated in Tetrahymena after labelling with [35S]methionine in the presence of cycloheximide. The labelled proteins were analyzed by sodium dodecyl sulfate slab polyacrylamide gel electrophoresis. We have identified 13 electrophoretically discrete bands as well as 4 other bands with a more variable occurrence. These proteins ranged in apparent molecular weight from 8100 to 57 500. The cycloheximide-resistant incorporation could be blocked with chloramphenicol. The mitochondrial proteins appeared to be in a disaggregated state and were stable to agents such as trichloroacetic acid (hot or cold) and chloroform–methanol. The pattern of proteins was similar following labelling times ranging from 30 min to 3 h.

scholarly journals Mitochondrial stress response triggered by defects in protein synthesis quality control

2019 ◽  
Vol 2 (1) ◽  
pp. e201800219 ◽  
Author(s):  
Uwe Richter ◽  
Kah Ying Ng ◽  
Fumi Suomi ◽  
Paula Marttinen ◽  
Taina Turunen ◽  
...  
Keyword(s):  
Quality Control ◽  
Protein Synthesis ◽  
Stress Response ◽  
Expression System ◽  
Mitochondrial Protein ◽  
Clinical Syndrome ◽  
Control Mechanisms ◽  
Mitochondrial Protein Synthesis ◽  
Mitochondrial Ribosomes ◽  
Form And Function

Mitochondria have a compartmentalized gene expression system dedicated to the synthesis of membrane proteins essential for oxidative phosphorylation. Responsive quality control mechanisms are needed to ensure that aberrant protein synthesis does not disrupt mitochondrial function. Pathogenic mutations that impede the function of the mitochondrial matrix quality control protease complex composed of AFG3L2 and paraplegin cause a multifaceted clinical syndrome. At the cell and molecular level, defects to this quality control complex are defined by impairment to mitochondrial form and function. Here, we establish the etiology of these phenotypes. We show how disruptions to the quality control of mitochondrial protein synthesis trigger a sequential stress response characterized first by OMA1 activation followed by loss of mitochondrial ribosomes and by remodelling of mitochondrial inner membrane ultrastructure. Inhibiting mitochondrial protein synthesis with chloramphenicol completely blocks this stress response. Together, our data establish a mechanism linking major cell biological phenotypes of AFG3L2 pathogenesis and show how modulation of mitochondrial protein synthesis can exert a beneficial effect on organelle homeostasis.

Mitochondrial protein synthesis during thyroxine-induced cardiac hypertrophy

1990 ◽  
Vol 258 (3) ◽  
pp. E511-E518 ◽  
Author(s):  
A. C. Leung ◽  
E. E. McKee
Keyword(s):  
Protein Synthesis ◽  
Cardiac Hypertrophy ◽  
Total Protein ◽  
Time Course ◽  
Mitochondrial Protein ◽  
Hormone Treatment ◽  
Mitochondrial Proteins ◽  
Mitochondrial Protein Synthesis ◽  
Perfused Heart ◽  
Intact Heart

The goal of this paper was to determine the effects of 3,5,3'-triiodothyronine (T3)-thyroxine-induced cardiac hypertrophy on the rates of synthesis of mitochondrial proteins by both the cytoplasmic and mitochondrial protein synthesis systems and to compare the results with total protein synthesis and cardiac enlargement. Daily injections of T3-thyroxine in the rat resulted in a 25% increase in the growth of the ventricle compared with controls. The cytoplasmic synthesis of both mitochondrial and total proteins as measured in the isolated perfused heart was stimulated by T3-thyroxine injection to a peak of 155 and 146%, respectively, of vehicle-injected controls after 3 days of hormone treatment. This peak was followed by a gradual decline in stimulation in total protein synthesis to 132% of control by 9 days of injection, whereas the decline in stimulation of cytoplasmic synthesis of mitochondrial proteins was significantly steeper, falling to 119% of vehicle control. The rate of protein synthesis within the mitochondrial compartment was also measured during the time course of T3-thyroxine-induced hypertrophy. These rates were measured in an isolated intact heart mitochondrial protein synthesis system described and characterized in the companion papers [E. E. McKee, B. L. Grier, G. S. Thompson, and J. D. McCourt. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E492-E502, 1990; and E. E. McKee, B. L. Grier, G. S. Thompson, A. C. F. Leung, and J. D. McCourt. Am. J. Physiol. 258 (Endocrinol. Metab. 21): E503-E510, 1990]. Rates of mitochondrial protein synthesis were dramatically stimulated by T3-thyroxine injection.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Mitochondrial Retrograde Signaling: Triggers, Pathways, and Outcomes

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Fernanda Marques da Cunha ◽  
Nicole Quesada Torelli ◽  
Alicia J. Kowaltowski
Keyword(s):  
Protein Synthesis ◽  
Mitochondrial Protein ◽  
Retrograde Signaling ◽  
Mitochondrial Proteins ◽  
Mitochondrial Protein Synthesis ◽  
Compensatory Responses ◽  
Mitochondrial Retrograde Signaling ◽  
Effector Pathways

Mitochondria are essential organelles for eukaryotic homeostasis. Although these organelles possess their own DNA, the vast majority (>99%) of mitochondrial proteins are encoded in the nucleus. This situation makes systems that allow the communication between mitochondria and the nucleus a requirement not only to coordinate mitochondrial protein synthesis during biogenesis but also to communicate eventual mitochondrial malfunctions, triggering compensatory responses in the nucleus. Mitochondria-to-nucleus retrograde signaling has been described in various organisms, albeit with differences in effector pathways, molecules, and outcomes, as discussed in this review.

scholarly journals Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis.

2021 ◽  
Author(s):  
Kah Ying Ng ◽  
Uwe Richter ◽  
Christopher Jackson ◽  
Sara Seneca ◽  
Brendan Battersby
Keyword(s):  
Quality Control ◽  
Protein Synthesis ◽  
Mitochondrial Gene ◽  
Mitochondrial Protein ◽  
Control Mechanisms ◽  
Mitochondrial Protein Synthesis ◽  
Primary Defect ◽  
Pathogenic Variants ◽  
Heterogenous Group ◽  
Quality Control Mechanism

Pathogenic variants that disrupt human mitochondrial protein synthesis are associated with a clinically heterogenous group of diseases. Despite an impairment in oxidative phosphorylation being a common phenotype, the underlying molecular pathogenesis is more complex than simply a bioenergetic deficiency. Currently, we have limited mechanistic understanding on the scope by which a primary defect in mitochondrial protein synthesis contributes to organelle dysfunction. Since the proteins encoded in the mitochondrial genome are hydrophobic and need co-translational insertion into a lipid bilayer, responsive quality control mechanisms are required to resolve aberrations that arise with the synthesis of truncated and misfolded proteins. Here, we show that defects in the OXA1L-mediated insertion of MT-ATP6 nascent chains into the mitochondrial inner membrane are rapidly resolved by the AFG3L2 protease complex. Using pathogenic MT-ATP6 variants, we then reveal discrete steps in this quality control mechanism and the differential functional consequences to mitochondrial gene expression. The inherent ability of a given cell type to recognize and resolve impairments in mitochondrial protein synthesis may in part contribute at the molecular level to the wide clinical spectrum of these disorders.

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