Targeting Mitochondrial Protein Expression as a Future Approach for Cancer Therapy

Extensive metabolic remodeling is a fundamental feature of cancer cells. Although early reports attributed such remodeling to a loss of mitochondrial functions, it is now clear that mitochondria play central roles in cancer development and progression, from energy production to synthesis of macromolecules, from redox modulation to regulation of cell death. Biosynthetic pathways are also heavily affected by the metabolic rewiring, with protein synthesis dysregulation at the hearth of cellular transformation. Accumulating evidence in multiple organisms shows that the metabolic functions of mitochondria are tightly connected to protein synthesis, being assembly and activity of respiratory complexes highly dependent on de novo synthesis of their components. In turn, protein synthesis within the organelle is tightly connected with the cytosolic process. This implies an entire network of interactions and fine-tuned regulations that build up a completely under-estimated level of complexity. We are now only preliminarily beginning to reconstitute such regulatory level in human cells, and to perceive its role in diseases. Indeed, disruption or alterations of these connections trigger conditions of proteotoxic and energetic stress that could be potentially exploited for therapeutic purposes. In this review, we summarize the available literature on the coordinated regulation of mitochondrial and cytosolic mRNA translation, and their effects on the integrity of the mitochondrial proteome and functions. Finally, we highlight the potential held by this topic for future research directions and for the development of innovative therapeutic approaches.

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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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MITOCHONDRIAL PROTEIN PROFILE AND ITS ROLE IN PATHOLOGIC PROCESSES

Bulletin of Siberian Medicine ◽

10.20538/1682-0363-2013-3-5-17 ◽

2013 ◽

Vol 12 (3) ◽

pp. 5-17

Author(s):

Ye. A. Kosterina ◽

I. I. Kozenkov ◽

V. A. Kasymov ◽

P. A. Kamensky ◽

I. N. Dominova ◽

...

Keyword(s):

Molecular Mechanisms ◽

Protein Profile ◽

Mitochondrial Protein ◽

Proteome Profiling ◽

Mitochondrial Proteome ◽

Mitochondrial Functions ◽

Precursor Proteins ◽

Real Size ◽

Pathologic Processes

Mitochondria import hundreds of different precursor proteins from the cytosol, and only 13 proteins are encoded by mtDNA itself. Recent investigations demonstrated real size of mitochondrial proteome and complexity of their functions There are many methods using for mitochondrial proteome profiling, that help to understand a molecular mechanisms of mitochondrial functions and identify the causes of disruptions that lead to different disorders. In this review we discuss a recent data in the field of mitochondrial proteomics.

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

The Journal of Cell Biology ◽

10.1083/jcb.134.6.1375 ◽

1996 ◽

Vol 134 (6) ◽

pp. 1375-1386 ◽

Cited By ~ 74

Author(s):

M Schmitt ◽

W Neupert ◽

T Langer

Keyword(s):

Protein Synthesis ◽

Heat Shock ◽

Temperature Stress ◽

Mitochondrial Protein ◽

Heat Inactivation ◽

Mitochondrial Protein Synthesis ◽

Extreme Stress ◽

Mitochondrial Functions ◽

Mitochondrial Hsp70

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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Hepatic carnitine palmitoyltransferase turnover and translation rates in fed, starved, streptozotocin-diabetic and diethylhexyl phthalate-treated rats

Biochemical Journal ◽

10.1042/bj2460641 ◽

1987 ◽

Vol 246 (3) ◽

pp. 641-649 ◽

Cited By ~ 15

Author(s):

P S Brady ◽

L J Brady

Keyword(s):

Protein Synthesis ◽

Mitochondrial Protein ◽

Mrna Translation ◽

Liver Weight ◽

Diabetic Rats ◽

Carnitine Palmitoyltransferase ◽

Diethylhexyl Phthalate ◽

Mild Diabetes ◽

Streptozotocin Diabetic Rats

Hepatic carnitine palmitoyltransferase (CPT) turnover was studied in control and in non-ketotic hyperglycaemic streptozotocin-diabetic rats. The degradation constant (kd) and half-life (t1/2) did not appear to be altered by mild diabetes. The hepatic CPT (micrograms/g of liver) was not increased by the mild, non-ketotic, diabetes. However, the total hepatic CPT (micrograms/liver) was 37% greater in the diabetic animals, owing to the increased liver weight. This resulted from a 40% increase in the synthesis constant (ks). Hepatic CPT activity (total detergent-solubilized) and translation rates were measured in fed, starved (48 h), non-ketotic diabetic, ketotic diabetic and diethylhexyl phthalate (DEHP)-treated rats. CPT activity (m units/mg of mitochondrial protein) was not significantly increased with non-ketotic diabetes (44% increase, but non-significant), but was increased approx. 2-fold with starvation and ketotic diabetes, and 3.5-fold with DEHP treatment. CPT expressed as units/liver was increased non-significantly (23%) in non-ketotic and starved rats, similar to the turnover study, but was significantly increased with ketotic diabetes and with DEHP treatment. mRNA-translation activity for CPT was elevated in all states to a somewhat greater extent than was activity. It was concluded that protein synthesis as a product of increased CPT-mRNA translation activity is a major means of long-term regulation.

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Mitochondrial hypoxic stress induces widespread RNA editing by APOBEC3G in lymphocyte

10.1101/389791 ◽

2018 ◽

Cited By ~ 3

Author(s):

Shraddha Sharma ◽

Jianmin Wang ◽

Scott Portwood ◽

Eduardo Cortes-Gomez ◽

Orla Maguire ◽

...

Keyword(s):

T Cells ◽

Rna Editing ◽

De Novo ◽

Cytidine Deaminase ◽

Mrna Translation ◽

Hypoxic Stress ◽

Mrna Editing ◽

Metabolic Remodeling ◽

Editing Enzyme ◽

Normal Health

AbstractProtein recoding by RNA editing is required for normal health and evolutionary adaptation. However, de novo induction of RNA editing in response to environmental factors is an uncommon phenomenon. While APOBEC3A edits many mRNAs in monocytes/macrophages in response to hypoxia and interferons, the physiological significance of such editing is unclear. Here we show that the related APOBEC3G cytidine deaminase induces site-specific C-to-U RNA editing in natural killer (NK), CD8+ T cells and lymphoma cell lines upon cellular crowding and hypoxia. RNASeq analysis of hypoxic NK cells reveals widespread C-to-U recoding mRNA editing that is enriched for genes involved in mRNA translation. APOBEC3G promotes Warburg-like metabolic remodeling and reduces proliferation of HuT78 T cells under similar conditions. Hypoxia-induced RNA editing by APOBEC3G can be mimicked by the inhibition of mitochondrial respiration, and occurs independently of HIF-1α. Thus, APOBEC3G is an endogenous RNA editing enzyme, which is induced by mitochondrial hypoxic stress to promote adaptation in lymphocytes.

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A high-density human mitochondrial proximity interaction network

10.1101/2020.04.01.020479 ◽

2020 ◽

Cited By ~ 4

Author(s):

Hana Antonicka ◽

Zhen-Yuan Lin ◽

Alexandre Janer ◽

Woranontee Weraarpachai ◽

Anne-Claude Gingras ◽

...

Keyword(s):

High Resolution ◽

Correlation Analysis ◽

Mitochondrial Protein ◽

Interaction Network ◽

Mitochondrial Proteins ◽

Site Formation ◽

List Type ◽

Mitochondrial Proteome ◽

Mitochondrial Functions ◽

The Matrix

SummaryWe used BioID, a proximity-dependent biotinylation assay, to interrogate 100 mitochondrial baits from all mitochondrial sub-compartments to create a high resolution human mitochondrial proximity interaction network. We identified 1465 proteins, producing 15626 unique high confidence proximity interactions. Of these, 528 proteins were previously annotated as mitochondrial, nearly half of the mitochondrial proteome defined by Mitocarta 2.0. Bait-bait analysis showed a clear separation of mitochondrial compartments, and correlation analysis among preys across all baits allowed us to identify functional clusters involved in diverse mitochondrial functions, and to assign uncharacterized proteins to specific modules. We demonstrate that this analysis can assign isoforms of the same mitochondrial protein to different mitochondrial sub-compartments, and show that some proteins may have multiple cellular locations. Outer membrane baits showed specific proximity interactions with cytosolic proteins and proteins in other organellar membranes, suggesting specialization of proteins responsible for contact site formation between mitochondria and individual organelles. This proximity network will be a valuable resource for exploring the biology of uncharacterized mitochondrial proteins, the interactions of mitochondria with other cellular organelles, and will provide a framework to interpret alterations in sub-mitochondrial environments associated with mitochondrial disease.Bullet pointsWe created a high resolution human mitochondrial protein proximity map using BioIDBait-bait analysis showed that the map has sub-compartment resolution and correlation analysis of preys identified functional clusters and assigned proteins to specific modulesWe identified isoforms of matrix and IMS proteins with multiple cellular localizations and an endonuclease that localizes to both the matrix and the OMMOMM baits showed specific interactions with non-mitochondrial proteins reflecting organellar contact sites and protein dual localization

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

The Journal of Cell Biology ◽

10.1083/jcb.201504062 ◽

2015 ◽

Vol 211 (2) ◽

pp. 373-389 ◽

Cited By ~ 48

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.

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De novo mutations in TOMM70, a receptor of the mitochondrial import translocase, cause neurological impairment

Human Molecular Genetics ◽

10.1093/hmg/ddaa081 ◽

2020 ◽

Vol 29 (9) ◽

pp. 1568-1579 ◽

Cited By ~ 1

Author(s):

Debdeep Dutta ◽

Lauren C Briere ◽

Oguz Kanca ◽

Paul C Marcogliese ◽

Melissa A Walker ◽

...

Keyword(s):

White Matter ◽

Protein Import ◽

De Novo ◽

Mitochondrial Protein ◽

Neurological Impairment ◽

Loss Of Function ◽

De Novo Mutations ◽

Coding Region ◽

Mitochondrial Protein Import ◽

Mitochondrial Proteome

Abstract The translocase of outer mitochondrial membrane (TOMM) complex is the entry gate for virtually all mitochondrial proteins and is essential to build the mitochondrial proteome. TOMM70 is a receptor that assists mainly in mitochondrial protein import. Here, we report two individuals with de novo variants in the C-terminal region of TOMM70. While both individuals exhibited shared symptoms including hypotonia, hyper-reflexia, ataxia, dystonia and significant white matter abnormalities, there were differences between the two individuals, most prominently the age of symptom onset. Both individuals were undiagnosed despite extensive genetics workups. Individual 1 was found to have a p.Thr607Ile variant while Individual 2 was found to have a p.Ile554Phe variant in TOMM70. To functionally assess both TOMM70 variants, we replaced the Drosophila Tom70 coding region with a Kozak-mini-GAL4 transgene using CRISPR-Cas9. Homozygous mutant animals die as pupae, but lethality is rescued by the mini-GAL4-driven expression of human UAS-TOMM70 cDNA. Both modeled variants lead to significantly less rescue indicating that they are loss-of-function alleles. Similarly, RNAi-mediated knockdown of Tom70 in the developing eye causes roughening and synaptic transmission defect, common findings in neurodegenerative and mitochondrial disorders. These phenotypes were rescued by the reference, but not the variants, of TOMM70. Altogether, our data indicate that de novo loss-of-function variants in TOMM70 result in variable white matter disease and neurological phenotypes in affected individuals.

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