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Polymorphisms in the mitochondrial ribosome recycling factor EF-G2mt/MEF2 compromise cell respiratory function and increase atorvastatin toxicity.

Callegari S, Gregory PA, Sykes MJ, Bellon J, Andrews S, McKinnon RA, de Barros Lopes MA - PLoS Genet. (2012)

Bottom Line: However, a significant proportion of users suffer side effects of varying severity that commonly affect skeletal muscle.Although these mutations do not produce an obvious growth phenotype, three mutations reveal an atorvastatin-sensitive phenotype and further analysis uncovers a decreased respiratory capacity.These findings constitute the first reported phenotype associated with SNPs in the EF-G2mt gene and implicate the human EF-G2mt gene as a pharmacogenetic candidate gene for statin toxicity in humans.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy and Medical Sciences, Division of Health Sciences, University of South Australia, Adelaide, South Australia, Australia.

ABSTRACT
Mitochondrial translation, essential for synthesis of the electron transport chain complexes in the mitochondria, is governed by nuclear encoded genes. Polymorphisms within these genes are increasingly being implicated in disease and may also trigger adverse drug reactions. Statins, a class of HMG-CoA reductase inhibitors used to treat hypercholesterolemia, are among the most widely prescribed drugs in the world. However, a significant proportion of users suffer side effects of varying severity that commonly affect skeletal muscle. The mitochondria are one of the molecular targets of statins, and these drugs have been known to uncover otherwise silent mitochondrial mutations. Based on yeast genetic studies, we identify the mitochondrial translation factor MEF2 as a mediator of atorvastatin toxicity. The human ortholog of MEF2 is the Elongation Factor Gene (EF-G) 2, which has previously been shown to play a specific role in mitochondrial ribosome recycling. Using small interfering RNA (siRNA) silencing of expression in human cell lines, we demonstrate that the EF-G2mt gene is required for cell growth on galactose medium, signifying an essential role for this gene in aerobic respiration. Furthermore, EF-G2mt silenced cell lines have increased susceptibility to cell death in the presence of atorvastatin. Using yeast as a model, conserved amino acid variants, which arise from non-synonymous single nucleotide polymorphisms (SNPs) in the EF-G2mt gene, were generated in the yeast MEF2 gene. Although these mutations do not produce an obvious growth phenotype, three mutations reveal an atorvastatin-sensitive phenotype and further analysis uncovers a decreased respiratory capacity. These findings constitute the first reported phenotype associated with SNPs in the EF-G2mt gene and implicate the human EF-G2mt gene as a pharmacogenetic candidate gene for statin toxicity in humans.

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Related in: MedlinePlus

In silico model of the human EF-G2mt protein.(A) Model depicting four of the five amino acid variants that were functionally characterised in this study. (B) Five newly discovered variants that have yet to be functionally characterised. Helices are shown as ribbons, beta-sheets are depicted as flat broad arrows and loops and coils appear as thin tubes. The five protein domains of the EF-G2mt protein are distinguished by different colours. Domain I, the GTP binding domain is shown in blue, domain II is purple, domain III is orange, domain IV is cyan and domain V is green. Model was visualised using the Visual Molecular Dynamics program (VMD), version 1.8.7 (University of Illinois).
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pgen-1002755-g007: In silico model of the human EF-G2mt protein.(A) Model depicting four of the five amino acid variants that were functionally characterised in this study. (B) Five newly discovered variants that have yet to be functionally characterised. Helices are shown as ribbons, beta-sheets are depicted as flat broad arrows and loops and coils appear as thin tubes. The five protein domains of the EF-G2mt protein are distinguished by different colours. Domain I, the GTP binding domain is shown in blue, domain II is purple, domain III is orange, domain IV is cyan and domain V is green. Model was visualised using the Visual Molecular Dynamics program (VMD), version 1.8.7 (University of Illinois).

Mentions: The crystal structure of the human EF-G2mt protein has not yet been elucidated. Therefore, to gain insight into the molecular effects of the five chosen amino acid variations, a computational model of the EF-G2mt protein was constructed using the SWISS-MODEL server [41]. The model is based on the experimentally determined crystal structure of the Thermus. thermophilus EF-G protein [42] which shares 39 percent identity with the human EF-G2mt protein and four of the five EF-G2mt protein domains. As the N-terminal and C-terminal regions of the EF-G2mt protein share particularly low homology with the template, the initial 65 and final 10 amino acid residues could not be accurately modelled. For this reason, the location of amino acid variant EF-G2mtR774Q, positioned very close to the C-terminus, was omitted (Figure 7A). Stereochemical quality of the model was assessed by generating a Ramachandran plot using PROCHECK. Eighty seven percent of residues fall within the most favoured regions of the plot, indicating ideal stereochemistry.


Polymorphisms in the mitochondrial ribosome recycling factor EF-G2mt/MEF2 compromise cell respiratory function and increase atorvastatin toxicity.

Callegari S, Gregory PA, Sykes MJ, Bellon J, Andrews S, McKinnon RA, de Barros Lopes MA - PLoS Genet. (2012)

In silico model of the human EF-G2mt protein.(A) Model depicting four of the five amino acid variants that were functionally characterised in this study. (B) Five newly discovered variants that have yet to be functionally characterised. Helices are shown as ribbons, beta-sheets are depicted as flat broad arrows and loops and coils appear as thin tubes. The five protein domains of the EF-G2mt protein are distinguished by different colours. Domain I, the GTP binding domain is shown in blue, domain II is purple, domain III is orange, domain IV is cyan and domain V is green. Model was visualised using the Visual Molecular Dynamics program (VMD), version 1.8.7 (University of Illinois).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3375252&req=5

pgen-1002755-g007: In silico model of the human EF-G2mt protein.(A) Model depicting four of the five amino acid variants that were functionally characterised in this study. (B) Five newly discovered variants that have yet to be functionally characterised. Helices are shown as ribbons, beta-sheets are depicted as flat broad arrows and loops and coils appear as thin tubes. The five protein domains of the EF-G2mt protein are distinguished by different colours. Domain I, the GTP binding domain is shown in blue, domain II is purple, domain III is orange, domain IV is cyan and domain V is green. Model was visualised using the Visual Molecular Dynamics program (VMD), version 1.8.7 (University of Illinois).
Mentions: The crystal structure of the human EF-G2mt protein has not yet been elucidated. Therefore, to gain insight into the molecular effects of the five chosen amino acid variations, a computational model of the EF-G2mt protein was constructed using the SWISS-MODEL server [41]. The model is based on the experimentally determined crystal structure of the Thermus. thermophilus EF-G protein [42] which shares 39 percent identity with the human EF-G2mt protein and four of the five EF-G2mt protein domains. As the N-terminal and C-terminal regions of the EF-G2mt protein share particularly low homology with the template, the initial 65 and final 10 amino acid residues could not be accurately modelled. For this reason, the location of amino acid variant EF-G2mtR774Q, positioned very close to the C-terminus, was omitted (Figure 7A). Stereochemical quality of the model was assessed by generating a Ramachandran plot using PROCHECK. Eighty seven percent of residues fall within the most favoured regions of the plot, indicating ideal stereochemistry.

Bottom Line: However, a significant proportion of users suffer side effects of varying severity that commonly affect skeletal muscle.Although these mutations do not produce an obvious growth phenotype, three mutations reveal an atorvastatin-sensitive phenotype and further analysis uncovers a decreased respiratory capacity.These findings constitute the first reported phenotype associated with SNPs in the EF-G2mt gene and implicate the human EF-G2mt gene as a pharmacogenetic candidate gene for statin toxicity in humans.

View Article: PubMed Central - PubMed

Affiliation: School of Pharmacy and Medical Sciences, Division of Health Sciences, University of South Australia, Adelaide, South Australia, Australia.

ABSTRACT
Mitochondrial translation, essential for synthesis of the electron transport chain complexes in the mitochondria, is governed by nuclear encoded genes. Polymorphisms within these genes are increasingly being implicated in disease and may also trigger adverse drug reactions. Statins, a class of HMG-CoA reductase inhibitors used to treat hypercholesterolemia, are among the most widely prescribed drugs in the world. However, a significant proportion of users suffer side effects of varying severity that commonly affect skeletal muscle. The mitochondria are one of the molecular targets of statins, and these drugs have been known to uncover otherwise silent mitochondrial mutations. Based on yeast genetic studies, we identify the mitochondrial translation factor MEF2 as a mediator of atorvastatin toxicity. The human ortholog of MEF2 is the Elongation Factor Gene (EF-G) 2, which has previously been shown to play a specific role in mitochondrial ribosome recycling. Using small interfering RNA (siRNA) silencing of expression in human cell lines, we demonstrate that the EF-G2mt gene is required for cell growth on galactose medium, signifying an essential role for this gene in aerobic respiration. Furthermore, EF-G2mt silenced cell lines have increased susceptibility to cell death in the presence of atorvastatin. Using yeast as a model, conserved amino acid variants, which arise from non-synonymous single nucleotide polymorphisms (SNPs) in the EF-G2mt gene, were generated in the yeast MEF2 gene. Although these mutations do not produce an obvious growth phenotype, three mutations reveal an atorvastatin-sensitive phenotype and further analysis uncovers a decreased respiratory capacity. These findings constitute the first reported phenotype associated with SNPs in the EF-G2mt gene and implicate the human EF-G2mt gene as a pharmacogenetic candidate gene for statin toxicity in humans.

Show MeSH
Related in: MedlinePlus