MPV17 does not control cancer cell proliferation (original) (raw)
Related papers
MPV17 Loss Causes Deoxynucleotide Insufficiency and Slow DNA Replication in Mitochondria
PLoS genetics, 2016
MPV17 is a mitochondrial inner membrane protein whose dysfunction causes mitochondrial DNA abnormalities and disease by an unknown mechanism. Perturbations of deoxynucleoside triphosphate (dNTP) pools are a recognized cause of mitochondrial genomic instability; therefore, we determined DNA copy number and dNTP levels in mitochondria of two models of MPV17 deficiency. In Mpv17 ablated mice, liver mitochondria showed substantial decreases in the levels of dGTP and dTTP and severe mitochondrial DNA depletion, whereas the dNTP pool was not significantly altered in kidney and brain mitochondria that had near normal levels of DNA. The shortage of mitochondrial dNTPs in Mpv17-/- liver slows the DNA replication in the organelle, as evidenced by the elevated level of replication intermediates. Quiescent fibroblasts of MPV17-mutant patients recapitulate key features of the primary affected tissue of the Mpv17-/- mice, displaying virtual absence of the protein, decreased dNTP levels and mitoch...
European Journal of Human Genetics, 2014
Mitochondrial DNA (mtDNA) depletion syndromes (MDS) are severe autosomal recessive disorders associated with decreased mtDNA copy number in clinically affected tissues. The hepatocerebral form (mtDNA depletion in liver and brain) has been associated with mutations in the POLG, PEO1 (Twinkle), DGUOK and MPV17 genes, the latter encoding a mitochondrial inner membrane protein of unknown function. The aims of this study were to clarify further the clinical, biochemical, cellular and molecular genetic features associated with MDS due to MPV17 gene mutations. We identified 12 pathogenic mutations in the MPV17 gene, of which 11 are novel, in 17 patients from 12 families. All patients manifested liver disease. Poor feeding, hypoglycaemia, raised serum lactate, hypotonia and faltering growth were common presenting features. mtDNA depletion in liver was demonstrated in all seven cases where liver tissue was available. Mosaic mtDNA depletion was found in primary fibroblasts by PicoGreen staining. These results confirm that MPV17 mutations are an important cause of hepatocerebral mtDNA depletion syndrome, and provide the first demonstration of mosaic mtDNA depletion in human MPV17 mutant fibroblast cultures. We found that a severe clinical phenotype was associated with profound tissue-specific mtDNA depletion in liver, and, in some cases, mosaic mtDNA depletion in fibroblasts.
MPV17 Mutations Are Associated With a Quiescent Energetic Metabolic Profile
Frontiers in Cellular Neuroscience
Mutations in the MPV17 gene are associated with hepatocerebral form of mitochondrial depletion syndrome. The mechanisms through which MPV17 mutations cause respiratory chain dysfunction and mtDNA depletion is still unclear. The MPV17 gene encodes an inner membrane mitochondrial protein that was recently described to function as a non-selective channel. Although its exact function is unknown, it is thought to be important in the maintenance of mitochondrial membrane potential (ΔΨm). To obtain more information about the role of MPV17 in human disease, we investigated the effect of MPV17 knockdown and of selected known MPV17 mutations associated with MPV17 disease in vitro. We used different approaches in order to evaluate the cellular consequences of MPV17 deficiency. We found that lower levels of MPV17 were associated with impaired mitochondrial respiration and with a quiescent energetic metabolic profile. All the mutations studied destabilized the protein, resulting in reduced prote...
Pigment cell & melanoma research, 2017
The family of non-coding mitochondrial RNAs (ncmtRNA) are differentially expressed according to proliferative status. Normal proliferating cells express sense (SncmtRNA) and antisense ncmtRNAs (ASncmtRNAs), whereas tumor cells express SncmtRNA and downregulate ASncmtRNAs. Knockdown of ASncmtRNAs with oligonucleotides induces apoptotic cell death of tumor cells, leaving normal cells unaffected, suggesting a potential application for developing a novel cancer therapy. In this study, we knocked down the ASncmtRNAs in melanoma cell lines with a lentiviral-encoded shRNA approach. Transduction with lentiviral constructs targeted to the ASncmtRNAs induced apoptosis in murine B16F10 and human A375 melanoma cells in vitro and significantly retarded primary tumor growth in vivo. Moreover, the treatment drastically reduced the number of lung metastatic foci in a tail vein injection assay, compared to controls. These results provide additional proof-of-concept to the knockdown of ncmtRNAs for c...
Targeting Mitochondrial Therapy in the Regulation of HPV Infection and HPV-Related Cancers
Pathogens
It has been previously proposed that some types of cancer cells reprogram their metabolic pathways, favoring the metabolism of glucose by aerobic glycolysis (Warburg effect) instead of oxidative phosphorylation, mainly because the mitochondria of these cells are damaged, thus displaying mitochondrial dysfunction. However, in several cancers, the mitochondria do not exhibit any dysfunction and are also necessary for the tumor’s growth and maintenance. Remarkably, if the mitochondria are dysfunctional, specific processes associated with the release of cytochrome c (cyt c), such as apoptosis, are significantly impaired. In these cases, cellular biotherapies such as mitochondrial transplantation could restore the intrinsic apoptotic processes necessary for the elimination of cancers. On the other hand, if the mitochondria are in good shape, drugs that target the mitochondria are a valid option for treating the related cancers. Famously, the mitochondria are targeted by the human papillo...
The Journal of biological chemistry, 2015
The human MPV17-related mitochondrial DNA depletion syndrome (MDDS) is an inherited autosomal recessive disease caused by mutations in the inner mitochondrial membrane protein MPV17. Although more than 30 MPV17 gene mutations were shown to be associated with MDDS, the function of MPV17 is still unknown. Mice deficient in Mpv17 show signs of premature aging. In the present study we used electrophysiological measurements with recombinant MPV17 to reveal that this protein forms a non-selective channel with a pore diameter of 1.8 nm, and located the channel's selectivity filter. The channel was weakly cation-selective and showed several sub-conductance states. Voltage-dependent gating of the channel was regulated by redox conditions, pH, and affected in mutants mimicking a phosphorylated state. Likewise, the mitochondrial membrane potential (Delta Psi m) and the cellular production of reactive oxygen species were higher in embryonic fibroblasts from Mpv17-/- mice. However, despite o...
2012
Background: Antisense mitochondrial ncRNAs are down-regulated during oncogenesis by unknown mechanisms. Results: High risk HPV E2 oncogene induces down-regulation of the antisense transcripts. Additionally, E6 and E7 induce expression of a new sense mitochondrial ncRNA. Conclusion: HPV oncogenes modulate expression of mitochondrial ncRNAs. Significance: During non-viral oncogenesis, cellular factor(s), analogously to E2, could induce down-regulation of the antisense mitochondrial ncRNAs. The study of RNA and DNA oncogenic viruses has proved invaluable in the discovery of key cellular pathways that are rendered dysfunctional during cancer progression. An example is high risk human papillomavirus (HPV), the etiological agent of cervical cancer. The role of HPV oncogenes in cellular immortalization and transformation has been extensively investigated. We reported the differential expression of a family of human mitochondrial non-coding RNAs (ncRNAs) between normal and cancer cells. Normal cells express a sense mitochondrial ncRNA (SncmtRNA) that seems to be required for cell proliferation and two antisense transcripts (ASncmtRNAs). In contrast, the ASncmtRNAs are down-regulated in cancer cells. To shed some light on the mechanisms that trigger down-regulation of the ASncmtRNAs, we studied human keratinocytes (HFK) immortalized with HPV. Here we show that immortalization of HFK with HPV-16 or 18 causes down-regulation of the ASnc-mtRNAs and induces the expression of a new sense transcript named SncmtRNA-2. Transduction of HFK with both E6 and E7 is sufficient to induce expression of SncmtRNA-2. Moreover, E2 oncogene is involved in down-regulation of the ASncmtRNAs. Knockdown of E2 in immortalized cells reestablishes in a reversible manner the expression of the ASncmtRNAs, suggesting that endogenous cellular factors(s) could play functions analogous to E2 during non-HPV-induced oncogenesis. Cancer is characterized by a dysregulation of cell cycle control mechanisms, resulting in uncontrolled cell growth. Oncogenes and tumor suppressors, when functioning together properly, regulate progression of normal cell proliferation. In cancer, however, mutations result in constitutive activation of oncogenes, inactivation of tumor suppressors, immortality, resistance to apoptosis, invasiveness, and metastasis (1). About 15-20% of cancers are associated with infection by DNA and RNA oncogenic viruses (2-4), and the study of these pathogens has been invaluable in the discovery of key cellular pathways that become dysfunctional during cancer progression. For example, oncoproteins E6 and E7 from high risk human papillomavirus (HPV) 3-16 or-18 disable tumor suppressors p53 and Rb and up-regulate telomerase, fundamental changes for cell immortalization (5, 6). Interestingly, an apparently important step in the induction of cancer by oncogenic viruses is the specific interaction of some viral oncogenes with mitochondria, an organelle that has been implicated for decades in carcinogenesis (7, 8). Human cells express a unique family of sense and antisense mitochondrial ncRNAs containing long inverted repeats (IRs) (9, 10). The sense transcript or SncmtRNA (hereafter referred to as SncmtRNA-1), which contains an 815-nt IR and consequently a stem-loop structure (9), is expressed in normal proliferating cells and tumor cells but not in resting cells. This correlation between cell proliferation and expression of the SncmtRNA-1 suggests a function for this transcript in cell cycle * This work was supported by Fondecyt Grants 11090060, 1085210, and
Molecular Therapy, 2014
Mutations in human MPV17 cause a hepatocerebral form of mitochondrial DNA depletion syndrome (MDS) hallmarked by early-onset liver failure, leading to premature death. Liver transplantation and frequent feeding using slow-release carbohydrates are the only available therapies, although surviving patients eventually develop slowly progressive peripheral and central neuropathy. The physiological role of Mpv17, including its functional link to mitochondrial DNA (mtDNA) maintenance, is still unclear. We show here that Mpv17 is part of a high molecular weight complex of unknown composition, which is essential for mtDNA maintenance in critical tissues, i.e. liver, of a Mpv17 knockout mouse model. On a standard diet, Mpv17 −/− mouse shows hardly any symptom of liver dysfunction, but a ketogenic diet (KD) leads these animals to liver cirrhosis and failure. However, when expression of human MPV17 is carried out by adeno-associated virus (AAV)-mediated gene replacement, the Mpv17 knockout mice are able to reconstitute the Mpv17-containing supramolecular complex, restore liver mtDNA copy number and oxidative phosphorylation (OXPHOS) proficiency, and prevent liver failure induced by the KD. These results open new therapeutic perspectives for the treatment of MPV17-related liver-specific MDS.
Cancer Research, 2005
The role of mitochondrial dysfunction in cancer has been a subject of great interest and much ongoing investigation. Although most cancer cells harbor somatic mutations in mitochondrial DNA (mtDNA), the question of whether such mutations contribute to the promotion of carcinomas remains unsolved. Here we used trans-mitochondrial hybrids (cybrids) containing a common HeLa nucleus and mtDNA of interest to compare the role of mtDNA against the common nuclear background. We constructed cybrids with or without a homoplasmic pathogenic point mutation at nucleotide position 8,993 or 9,176 in the mtDNA ATP synthase subunit 6 gene (MTATP6) derived from patients with mitochondrial encephalomyopathy. When the cybrids were transplanted into nude mice, the MTATP6 mutations conferred an advantage in the early stage of tumor growth. The mutant cybrids also increased faster than wild type in culture. To complement the mtDNA mutations, we transfected a wild-type nuclear version of MTATP, whose codons were converted to the universal genetic codes containing a mitochondrial target sequence, into the nucleus of cybrids carrying mutant MTATP6. The restoration of MTATP slowed down the growth of tumor in transplantation. Conversely, expression of a mutant nuclear version of MTATP6 in the wild-type cybrids declined respiration and accelerated the tumor growth. These findings showed that the advantage in tumor growth depended upon the MTATP6 function but was not due to secondary nuclear mutations caused by the mutant mitochondria. Because apoptosis occurred less frequently in the mutant versus wild-type cybrids in cultures and tumors, the pathogenic mtDNA mutations seem to promote tumors by preventing apoptosis. (Cancer Res 2005; 65(5): 1655-63)
Cell growth & differentiation : the molecular biology journal of the American Association for Cancer Research, 1996
A differentiated human colonic epithelial cell has undergone relatively stable molecular, biochemical, and cellular alterations resulting in the acquisition of structures, activities, and functions that characterize it as one of at least three mature phenotypes: a columnar absorptive, secretory, or enteroendocrine cell. We have shown previously that induction of HT29 cells with the short-chain fatty acid sodium butyrate elevates alkaline phosphatase activity, a marker of the absorptive cell phenotype, and increases mitochondrial gene expression. Furthermore, this induction is accompanied by subsequent apoptosis and cell shedding. In this report, we have investigated the effects of forskolin, a potent inducer of the MUC2 gene in HT29 cells, a marker of the secretory phenotype, and have shown that neither apoptosis nor mitochondrial gene expression are significantly stimulated. Thus, differentiation along the secretory cell lineage may not play a major role in apoptosis of colonic epi...