Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELAS
The mitochondrial regulator MNRR1 is reduced in several pathologies, including the mitochondrial heteroplasmic disease MELAS, and genetic restoration of its level normalizes the pathological phenotype. Here, we investigate the upstream mechanism that reduces MNRR1 levels. We have identified the hypo...
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MDPI AG
2025-07-01
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| author | Neeraja Purandare Vignesh Pasupathi Yue Xi Vikram Rajan Caleb Vegh Steven Firestine Tamas Kozicz Andrew M. Fribley Lawrence I. Grossman Siddhesh Aras |
| author_facet | Neeraja Purandare Vignesh Pasupathi Yue Xi Vikram Rajan Caleb Vegh Steven Firestine Tamas Kozicz Andrew M. Fribley Lawrence I. Grossman Siddhesh Aras |
| author_sort | Neeraja Purandare |
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| description | The mitochondrial regulator MNRR1 is reduced in several pathologies, including the mitochondrial heteroplasmic disease MELAS, and genetic restoration of its level normalizes the pathological phenotype. Here, we investigate the upstream mechanism that reduces MNRR1 levels. We have identified the hypoxic regulator HIF2α to bind the MNRR1 promoter and inhibit transcription by competing with RBPJκ. In MELAS cells, there is a pseudohypoxic state that transcriptionally induces <i>HIF2α</i> and stabilizes HIF2α protein. MELAS cybrids harboring the m.3243A > G mutation display reduced levels of prolyl hydroxylase 3 (PHD3), which contributes to the HIF2α stabilization. These results prompted a search for compounds that could increase MNRR1 levels pharmacologically. The screening of a 2400-compound library uncovered the antifungal drug nitazoxanide and its metabolite tizoxanide as enhancers of <i>MNRR1</i> transcription. We show that treating MELAS cybrids with tizoxanide restores cellular respiration, enhances mitophagy, and, importantly, shifts heteroplasmy toward wild-type mtDNA. Furthermore, in fibroblasts from MELAS patients, the compound improves mitochondrial biogenesis, enhances autophagy, and protects from LPS-induced inflammation. Mechanistically, nitazoxanide reduces HIF2α levels by increasing PHD3. Chemical activation of MNRR1 is thus a potential strategy to improve mitochondrial deficits seen in MELAS. Finally, our data suggests a broader physiological pathway wherein two proteins, induced under severe (1% O2; HIF2α) and moderate (4% O2; MNRR1) hypoxic conditions, regulate each other inversely. |
| format | Article |
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| institution | DOAJ |
| issn | 2073-4409 |
| language | English |
| publishDate | 2025-07-01 |
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| series | Cells |
| spelling | doaj-art-41575ca6b91c422bad9719d8bebf88b82025-08-20T02:45:34ZengMDPI AGCells2073-44092025-07-011414107810.3390/cells14141078Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELASNeeraja Purandare0Vignesh Pasupathi1Yue Xi2Vikram Rajan3Caleb Vegh4Steven Firestine5Tamas Kozicz6Andrew M. Fribley7Lawrence I. Grossman8Siddhesh Aras9Center for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI 48201, USACenter for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI 48201, USADepartment of Pediatrics, School of Medicine, Wayne State University, Detroit, MI 48201, USACenter for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI 48201, USACenter for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI 48201, USADepartment of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, MI 48201, USADepartment of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USADepartment of Pediatrics, School of Medicine, Wayne State University, Detroit, MI 48201, USACenter for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI 48201, USACenter for Molecular Medicine and Genetics, School of Medicine, Wayne State University, Detroit, MI 48201, USAThe mitochondrial regulator MNRR1 is reduced in several pathologies, including the mitochondrial heteroplasmic disease MELAS, and genetic restoration of its level normalizes the pathological phenotype. Here, we investigate the upstream mechanism that reduces MNRR1 levels. We have identified the hypoxic regulator HIF2α to bind the MNRR1 promoter and inhibit transcription by competing with RBPJκ. In MELAS cells, there is a pseudohypoxic state that transcriptionally induces <i>HIF2α</i> and stabilizes HIF2α protein. MELAS cybrids harboring the m.3243A > G mutation display reduced levels of prolyl hydroxylase 3 (PHD3), which contributes to the HIF2α stabilization. These results prompted a search for compounds that could increase MNRR1 levels pharmacologically. The screening of a 2400-compound library uncovered the antifungal drug nitazoxanide and its metabolite tizoxanide as enhancers of <i>MNRR1</i> transcription. We show that treating MELAS cybrids with tizoxanide restores cellular respiration, enhances mitophagy, and, importantly, shifts heteroplasmy toward wild-type mtDNA. Furthermore, in fibroblasts from MELAS patients, the compound improves mitochondrial biogenesis, enhances autophagy, and protects from LPS-induced inflammation. Mechanistically, nitazoxanide reduces HIF2α levels by increasing PHD3. Chemical activation of MNRR1 is thus a potential strategy to improve mitochondrial deficits seen in MELAS. Finally, our data suggests a broader physiological pathway wherein two proteins, induced under severe (1% O2; HIF2α) and moderate (4% O2; MNRR1) hypoxic conditions, regulate each other inversely.https://www.mdpi.com/2073-4409/14/14/1078drug repurposingheteroplasmyhypoxia |
| spellingShingle | Neeraja Purandare Vignesh Pasupathi Yue Xi Vikram Rajan Caleb Vegh Steven Firestine Tamas Kozicz Andrew M. Fribley Lawrence I. Grossman Siddhesh Aras Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELAS Cells drug repurposing heteroplasmy hypoxia |
| title | Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELAS |
| title_full | Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELAS |
| title_fullStr | Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELAS |
| title_full_unstemmed | Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELAS |
| title_short | Pseudohypoxia-Stabilized HIF2α Transcriptionally Inhibits <i>MNRR1</i>, a Druggable Target in MELAS |
| title_sort | pseudohypoxia stabilized hif2α transcriptionally inhibits i mnrr1 i a druggable target in melas |
| topic | drug repurposing heteroplasmy hypoxia |
| url | https://www.mdpi.com/2073-4409/14/14/1078 |
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