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Abudureyimu M, Luo X, Jiang L, Jin X, Pan C, Yu W, Ge J, Zhang Y, Ren J. FBXL4 protects against HFpEF through Drp1-Mediated regulation of mitochondrial dynamics and the downstream SERCA2a. Redox Biol 2024; 70:103081. [PMID: 38359748 PMCID: PMC10878117 DOI: 10.1016/j.redox.2024.103081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 02/08/2024] [Accepted: 02/08/2024] [Indexed: 02/17/2024] Open
Abstract
AIMS Heart failure with preserved ejection fraction (HFpEF) is a devastating health issue although limited knowledge is available for its pathogenesis and therapeutics. Given the perceived involvement of mitochondrial dysfunction in HFpEF, this study was designed to examine the role of mitochondrial dynamics in the etiology of HFpEF. METHOD AND RESULTS Adult mice were placed on a high fat diet plus l-NAME in drinking water ('two-hit' challenge to mimic obesity and hypertension) for 15 consecutive weeks. Mass spectrometry revealed pronounced changes in mitochondrial fission protein Drp1 and E3 ligase FBXL4 in 'two-hit' mouse hearts. Transfection of FBXL4 rescued against HFpEF-compromised diastolic function, cardiac geometry, and mitochondrial integrity without affecting systolic performance, in conjunction with altered mitochondrial dynamics and integrity (hyperactivation of Drp1 and unchecked fission). Mass spectrometry and co-IP analyses unveiled an interaction between FBXL4 and Drp1 to foster ubiquitination and degradation of Drp1. Truncated mutants of FBXL4 (Delta-Fbox) disengaged interaction between FBXL4 and Drp1. Metabolomic and proteomics findings identified deranged fatty acid and glucose metabolism in HFpEF patients and mice. A cellular model was established with concurrent exposure of high glucose and palmitic acid as a 'double-damage' insult to mimic diastolic anomalies in HFpEF. Transfection of FBXL4 mitigated 'double-damage'-induced cardiomyocyte diastolic dysfunction and mitochondrial injury, the effects were abolished and mimicked by Drp1 knock-in and knock-out, respectively. HFpEF downregulated sarco(endo)plasmic reticulum (SR) Ca2+ uptake protein SERCA2a while upregulating phospholamban, RYR1, IP3R1, IP3R3 and Na+-Ca2+ exchanger with unaltered SR Ca2+ load. FBXL4 ablated 'two-hit' or 'double-damage'-induced changes in SERCA2a, phospholamban and mitochondrial injury. CONCLUSION FBXL4 rescued against HFpEF-induced cardiac remodeling, diastolic dysfunction, and mitochondrial injury through reverting hyperactivation of Drp1-mediated mitochondrial fission, underscoring the therapeutic promises of FBXL4 in HFpEF.
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Affiliation(s)
- Miyesaier Abudureyimu
- Cardiovascular Department, Shanghai Xuhui Central Hospital, Fudan University, Shanghai, 200031, China; National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China
| | - Xuanming Luo
- National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China; Department of General Surgery, Shanghai Xuhui Central Hospital, Fudan University, Shanghai, 200031, China
| | - Lingling Jiang
- Cardiovascular Department, Shanghai Xuhui Central Hospital, Fudan University, Shanghai, 200031, China; National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China
| | - Xuejuan Jin
- National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China; Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, 200032, China
| | - Cuizhen Pan
- National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China; Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, 200032, China
| | - Wei Yu
- Xianning Medical College, Hubei University of Science and Technology, Xianning, 437100, China
| | - Junbo Ge
- National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China; Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, 200032, China
| | - Yingmei Zhang
- National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China; Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, 200032, China
| | - Jun Ren
- National Clinical Research Center for Interventional Medicine, Shanghai, 200032, China; Department of Cardiology, Zhongshan Hospital, Fudan University, Shanghai Institute of Cardiovascular Diseases, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, National Health Commission, Shanghai, 200032, China; Key Laboratory of Viral Heart Diseases, Chinese Academy of Medical Sciences, Shanghai, 200032, China.
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2
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Kulkarni P, Nguyen-Dien GT, Kozul KL, Pagan JK. FBXL4: safeguarding against mitochondrial depletion through suppression of mitophagy. Autophagy 2024:1-3. [PMID: 38423516 DOI: 10.1080/15548627.2024.2318077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024] Open
Abstract
Mitophagy is a critical mitochondrial quality control process that selectively removes dysfunctional or excess mitochondria through the autophagy-lysosome system. The process is tightly controlled to ensure cellular and physiological homeostasis. Insufficient mitophagy can result in failure to remove damaged mitochondria and consequent cellular degeneration, but it is equally important to appropriately restrain mitophagy to prevent excessive mitochondrial depletion. Here, we discuss our recent discovery that the SKP1-CUL1-F-box (SCF)-FBXL4 (F-box and leucine-rich repeat protein 4) E3 ubiquitin ligase localizes to the mitochondrial outer membrane, where it constitutively mediates the ubiquitination and degradation of BNIP3L/NIX and BNIP3 mitophagy receptors to suppress mitophagy. The post-translational regulation of BNIP3L and BNIP3 is disrupted in mitochondrial DNA depletion syndrome 13 (MTDPS13), a multi-systemic disorder caused by mutations in the FBXL4 gene and characterized by elevated mitophagy and mitochondrial DNA/mtDNA depletion in patient fibroblasts. Our results demonstrate that mitophagy is not solely stimulated in response to specific conditions but is instead also actively suppressed through the continuous degradation of BNIP3L and BNIP3 mediated by the SCF-FBXL4 ubiquitin ligase. Thus, cellular conditions or signaling events that prevent the FBXL4-mediated turnover of BNIP3L and BNIP3 on specific mitochondria are expected to facilitate their selective removal.
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Affiliation(s)
- Prajakta Kulkarni
- Faculty of Medicine, School of Biomedical Sciences, University of Queensland, Brisbane, QLD, Australia
| | - Giang Thanh Nguyen-Dien
- Faculty of Medicine, School of Biomedical Sciences, University of Queensland, Brisbane, QLD, Australia
- Department of Biotechnology, School of Biotechnology, Viet Nam National University-International University, Ho Chi Minh City, Vietnam
| | - Keri-Lyn Kozul
- Faculty of Medicine, School of Biomedical Sciences, University of Queensland, Brisbane, QLD, Australia
| | - Julia K Pagan
- Faculty of Medicine, School of Biomedical Sciences, University of Queensland, Brisbane, QLD, Australia
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
- Faculty of Medicine, The University of Queensland Frazer Institute, Brisbane, QLD, Australia
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3
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Gao K, Xu X, Wang C. FBXL4 mutation-caused mitochondrial DNA depletion syndrome is driven by BNIP3/BNIP3L-dependent excessive mitophagy. Trends Mol Med 2024; 30:113-116. [PMID: 38123379 DOI: 10.1016/j.molmed.2023.11.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2023] [Revised: 11/29/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023]
Abstract
Encephalomyopathic mitochondrial DNA (mtDNA) depletion syndrome 13 (MTDPS13) is an autosomal recessive disorder arising from biallelic F-box and leucine-rich repeat (LRR) protein 4 (FBXL4) gene mutations. Recent advances have shown that excessive BCL2 interacting protein 3 (BNIP3)/ BCL2 interacting protein 3 like (BNIP3L)-dependent mitophagy underlies the molecular pathogenesis of MTDPS13. Here, we provide an overview of these groundbreaking findings and discuss potential therapeutic strategies for this fatal disease.
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Affiliation(s)
- Kun Gao
- Department of Clinical Laboratory, Shanghai First Maternity and Infant Hospital, School of Medicine, Tongji University, Shanghai, China.
| | - Xiayun Xu
- State Key Laboratory of Genetic Engineering, MOE Engineering Research Center of Gene Technology, Shanghai Engineering Research Center of Industrial Microorganisms, School of Life Sciences, Fudan University, Shanghai, China
| | - Chenji Wang
- State Key Laboratory of Genetic Engineering, MOE Engineering Research Center of Gene Technology, Shanghai Engineering Research Center of Industrial Microorganisms, School of Life Sciences, Fudan University, Shanghai, China.
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4
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Sun Y, Cao Y, Wan H, Memetimin A, Cao Y, Li L, Wu C, Wang M, Chen S, Li Q, Ma Y, Dong M, Jiang H. A mitophagy sensor PPTC7 controls BNIP3 and NIX degradation to regulate mitochondrial mass. Mol Cell 2024; 84:327-344.e9. [PMID: 38151018 DOI: 10.1016/j.molcel.2023.11.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 09/15/2023] [Accepted: 11/29/2023] [Indexed: 12/29/2023]
Abstract
Mitophagy mediated by BNIP3 and NIX critically regulates mitochondrial mass. Cellular BNIP3 and NIX levels are tightly controlled by SCFFBXL4-mediated ubiquitination to prevent excessive mitochondrial loss and lethal disease. Here, we report that knockout of PPTC7, a mitochondrial matrix protein, hyperactivates BNIP3-/NIX-mediated mitophagy and causes perinatal lethality that is rescued by NIX knockout in mice. Biochemically, the PPTC7 precursor is trapped by BNIP3 and NIX to the mitochondrial outer membrane, where PPTC7 scaffolds assembly of a substrate-PPTC7-SCFFBXL4 holocomplex to degrade BNIP3 and NIX, forming a homeostatic regulatory loop. PPTC7 possesses an unusually weak mitochondrial targeting sequence to facilitate its outer membrane retention and mitophagy control. Starvation upregulates PPPTC7 expression in mouse liver to repress mitophagy, which critically maintains hepatic mitochondrial mass, bioenergetics, and gluconeogenesis. Collectively, PPTC7 functions as a mitophagy sensor that integrates homeostatic and physiological signals to dynamically control BNIP3 and NIX degradation, thereby maintaining mitochondrial mass and cellular homeostasis.
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Affiliation(s)
- Yuqiu Sun
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China; National Institute of Biological Sciences, Beijing 102206, China; Beijing Key Laboratory of Cell Biology for Animal Aging, Beijing 102206, China
| | - Yu Cao
- College of Life Sciences, Beijing Normal University, Beijing 100875, China; National Institute of Biological Sciences, Beijing 102206, China; Beijing Key Laboratory of Cell Biology for Animal Aging, Beijing 102206, China
| | - Huayun Wan
- National Institute of Biological Sciences, Beijing 102206, China; Beijing Key Laboratory of Cell Biology for Animal Aging, Beijing 102206, China
| | - Adalet Memetimin
- National Institute of Biological Sciences, Beijing 102206, China
| | - Yang Cao
- National Institute of Biological Sciences, Beijing 102206, China
| | - Lin Li
- National Institute of Biological Sciences, Beijing 102206, China
| | - Chongyang Wu
- National Institute of Biological Sciences, Beijing 102206, China
| | - Meng Wang
- National Institute of Biological Sciences, Beijing 102206, China
| | - She Chen
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China; National Institute of Biological Sciences, Beijing 102206, China
| | - Qi Li
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China; National Institute of Biological Sciences, Beijing 102206, China
| | - Yan Ma
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China; National Institute of Biological Sciences, Beijing 102206, China
| | - Mengqiu Dong
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China; National Institute of Biological Sciences, Beijing 102206, China; Beijing Key Laboratory of Cell Biology for Animal Aging, Beijing 102206, China
| | - Hui Jiang
- Tsinghua Institute of Multidisciplinary Biomedical Research, Tsinghua University, Beijing 102206, China; National Institute of Biological Sciences, Beijing 102206, China; Beijing Key Laboratory of Cell Biology for Animal Aging, Beijing 102206, China.
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5
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Alotaibi M, Alqasmi A, Albassam F, Alkahtani T, Alqahtany M, Alkhaldi M. The First Reported Case of a Child with Two Different Rare Metabolic Disorders: Very Long-Chain Acyl-CoA Dehydrogenase Deficiency and Encephalomyopathic Mitochondrial DNA Depletion Syndrome 13. Glob Med Genet 2023; 10:278-281. [PMID: 37822418 PMCID: PMC10564565 DOI: 10.1055/s-0043-1775979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/13/2023] Open
Abstract
One of the most common inborn errors in fatty acid β oxidation (FAO) is a very long-chain acyl-coenzyme A dehydrogenase (VLCAD) deficiency. It is autosomal recessive. The enzyme used in the first phase of FAO is VLCAD. The enzyme is responsible for β oxidation spiral pathway's initial step, the dehydrogenation process of long-chain fatty acyl-CoA. The phenotypes include hypoglycemia, hepatomegaly, cardiomyopathy, and occasionally abrupt mortality. Most VLCAD deficiencies in newborns are now detected during the neonatal period due to the development of newborn screening programs. Mitochondrial DNA depletion syndromes (MTDPS) are one of the rarest metabolic disorders. It is an autosomal recessive disease caused by defects in genes necessary for the maintenance of mitochondrial DNA (mtDNA). One of these FBXL4 (F-box and leucine-rich repeat protein 4) variants causes encephalomyopathic mtDNA depletion syndrome 13 (MTDPS13), which presents as a failure to thrive, severe global developmental delay, hypotonia, early infantile onset of encephalopathy, and lactic acidosis. We report here the case of a Saudi infant born to consanguineous parents who presented to us with severe failure to thrive, profound neurodevelopmental delays, and facial dysmorphic features. Whole-exome sequencing (WES) showed the infants had MTDPS13. The FBXL4 variant c.1698A > G p. (Ile566Met) has previously been described as a disease that causes developmental delay and lactic acidosis, and another variant has also been detected in the patient. The ACADVL variant c.134C > A p. (Ser45*) has previously been described to cause VLCAD deficiency. A comprehensive literature review showed our patient to be the first case of MTDPS13 and VLCAD reported to date worldwide.
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Affiliation(s)
- Maha Alotaibi
- Department of Genetic, Children Hospital, King Saud Medical City, Riyadh, Saudi Arabia
| | - Amal Alqasmi
- Department of Pediatric Neurology and Epilepsy, King Saud Medical City, Riyadh, Saudi Arabia
| | - Faisal Albassam
- Collage of Medicine, AlMaarefa University, Riyadh, Saudi Arabia
| | - Turki Alkahtani
- Collage of Medicine, AlMaarefa University, Riyadh, Saudi Arabia
| | - Muath Alqahtany
- Collage of Medicine, AlMaarefa University, Riyadh, Saudi Arabia
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6
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Nguyen‐Dien GT, Kozul K, Cui Y, Townsend B, Kulkarni PG, Ooi SS, Marzio A, Carrodus N, Zuryn S, Pagano M, Parton RG, Lazarou M, Millard SS, Taylor RW, Collins BM, Jones MJK, Pagan JK. FBXL4 suppresses mitophagy by restricting the accumulation of NIX and BNIP3 mitophagy receptors. EMBO J 2023; 42:e112767. [PMID: 37161784 PMCID: PMC10308361 DOI: 10.15252/embj.2022112767] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 04/19/2023] [Accepted: 04/20/2023] [Indexed: 05/11/2023] Open
Abstract
To maintain both mitochondrial quality and quantity, cells selectively remove damaged or excessive mitochondria through mitophagy, which is a specialised form of autophagy. Mitophagy is induced in response to diverse conditions, including hypoxia, cellular differentiation and mitochondrial damage. However, the mechanisms that govern the removal of specific dysfunctional mitochondria under steady-state conditions to fine-tune mitochondrial content are not well understood. Here, we report that SCFFBXL4 , an SKP1/CUL1/F-box protein ubiquitin ligase complex, localises to the mitochondrial outer membrane in unstressed cells and mediates the constitutive ubiquitylation and degradation of the mitophagy receptors NIX and BNIP3 to suppress basal levels of mitophagy. We demonstrate that the pathogenic variants of FBXL4 that cause encephalopathic mtDNA depletion syndrome (MTDPS13) do not efficiently interact with the core SCF ubiquitin ligase machinery or mediate the degradation of NIX and BNIP3. Thus, we reveal a molecular mechanism whereby FBXL4 actively suppresses mitophagy by preventing NIX and BNIP3 accumulation. We propose that the dysregulation of NIX and BNIP3 turnover causes excessive basal mitophagy in FBXL4-associated mtDNA depletion syndrome.
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Affiliation(s)
- Giang Thanh Nguyen‐Dien
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
- Department of Biotechnology, School of BiotechnologyViet Nam National University‐International UniversityHo Chi Minh CityVietnam
| | - Keri‐Lyn Kozul
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
| | - Yi Cui
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
| | - Brendan Townsend
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
| | | | - Soo Siang Ooi
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
| | - Antonio Marzio
- Department of Biochemistry and Molecular PharmacologyNew York University Grossman School of MedicineNew YorkNYUSA
- Perlmutter Cancer CenterNew York University Grossman School of MedicineNew YorkNYUSA
- Department of Pathology and Lab Medicine, Meyer Cancer CenterWeill Cornell MedicineNew YorkNYUSA
| | - Nissa Carrodus
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
| | - Steven Zuryn
- Clem Jones Centre for Ageing Dementia Research, Queensland Brain InstituteThe University of QueenslandBrisbaneQLDAustralia
| | - Michele Pagano
- Department of Biochemistry and Molecular PharmacologyNew York University Grossman School of MedicineNew YorkNYUSA
- Perlmutter Cancer CenterNew York University Grossman School of MedicineNew YorkNYUSA
| | - Robert G Parton
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
- Centre for Microscopy and MicroanalysisUniversity of QueenslandBrisbaneQLDAustralia
| | - Michael Lazarou
- Walter and Eliza Hall Institute of Medical ResearchParkvilleVICAustralia
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery InstituteMonash UniversityMelbourneVICAustralia
- Department of Medical BiologyUniversity of MelbourneMelbourneVICAustralia
| | - S Sean Millard
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle upon TyneUK
- NHS Highly Specialised Service for Rare Mitochondrial DisordersNewcastle upon Tyne Hospitals NHS Foundation TrustNewcastle upon TyneUK
| | - Brett M Collins
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
| | - Mathew JK Jones
- The University of Queensland Diamantina Institute, Faculty of MedicineThe University of QueenslandBrisbaneQLDAustralia
- School of Chemistry & Molecular BiosciencesUniversity of QueenslandBrisbaneQLDAustralia
| | - Julia K Pagan
- Faculty of Medicine, School of Biomedical SciencesUniversity of QueenslandBrisbaneQLDAustralia
- Institute for Molecular BioscienceThe University of QueenslandBrisbaneQLDAustralia
- The University of Queensland Diamantina Institute, Faculty of MedicineThe University of QueenslandBrisbaneQLDAustralia
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7
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Cao Y, Zheng J, Wan H, Sun Y, Fu S, Liu S, He B, Cai G, Cao Y, Huang H, Li Q, Ma Y, Chen S, Wang F, Jiang H. A mitochondrial SCF- FBXL4 ubiquitin E3 ligase complex degrades BNIP3 and NIX to restrain mitophagy and prevent mitochondrial disease. EMBO J 2023; 42:e113033. [PMID: 36896912 PMCID: PMC10308365 DOI: 10.15252/embj.2022113033] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 02/14/2023] [Accepted: 02/17/2023] [Indexed: 03/11/2023] Open
Abstract
Mitophagy is a fundamental quality control mechanism of mitochondria. Its regulatory mechanisms and pathological implications remain poorly understood. Here, via a mitochondria-targeted genetic screen, we found that knockout (KO) of FBXL4, a mitochondrial disease gene, hyperactivates mitophagy at basal conditions. Subsequent counter screen revealed that FBXL4-KO hyperactivates mitophagy via two mitophagy receptors BNIP3 and NIX. We determined that FBXL4 functions as an integral outer-membrane protein that forms an SCF-FBXL4 ubiquitin E3 ligase complex. SCF-FBXL4 ubiquitinates BNIP3 and NIX to target them for degradation. Pathogenic FBXL4 mutations disrupt SCF-FBXL4 assembly and impair substrate degradation. Fbxl4-/- mice exhibit elevated BNIP3 and NIX proteins, hyperactive mitophagy, and perinatal lethality. Importantly, knockout of either Bnip3 or Nix rescues metabolic derangements and viability of the Fbxl4-/- mice. Together, beyond identifying SCF-FBXL4 as a novel mitochondrial ubiquitin E3 ligase restraining basal mitophagy, our results reveal hyperactivated mitophagy as a cause of mitochondrial disease and suggest therapeutic strategies.
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Affiliation(s)
- Yu Cao
- College of Life SciencesBeijing Normal UniversityBeijingChina
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Jing Zheng
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Huayun Wan
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Yuqiu Sun
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Song Fu
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- Graduate School of Peking Union Medical CollegeBeijingChina
| | - Shanshan Liu
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
| | - Baiyu He
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- College of Life SciencesChina Agriculture UniversityBeijingChina
| | - Gaihong Cai
- National Institute of Biological SciencesBeijingChina
| | - Yang Cao
- National Institute of Biological SciencesBeijingChina
| | - Huanwei Huang
- National Institute of Biological SciencesBeijingChina
| | - Qi Li
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Yan Ma
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - She Chen
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Fengchao Wang
- National Institute of Biological SciencesBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
| | - Hui Jiang
- College of Life SciencesBeijing Normal UniversityBeijingChina
- National Institute of Biological SciencesBeijingChina
- Beijing Key Laboratory of Cell Biology for Animal AgingBeijingChina
- Tsinghua Institute of Multidisciplinary Biomedical ResearchTsinghua UniversityBeijingChina
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8
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Elcocks H, Brazel AJ, McCarron KR, Kaulich M, Husnjak K, Mortiboys H, Clague MJ, Urbé S. FBXL4 ubiquitin ligase deficiency promotes mitophagy by elevating NIX levels. EMBO J 2023; 42:e112799. [PMID: 37102372 PMCID: PMC10308357 DOI: 10.15252/embj.2022112799] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Revised: 03/17/2023] [Accepted: 04/09/2023] [Indexed: 04/28/2023] Open
Abstract
Selective autophagy of mitochondria, mitophagy, is linked to mitochondrial quality control and as such is critical to a healthy organism. We have used a CRISPR/Cas9 approach to screen human E3 ubiquitin ligases for influence on mitophagy under both basal cell culture conditions and upon acute mitochondrial depolarization. We identify two cullin-RING ligase substrate receptors, VHL and FBXL4, as the most profound negative regulators of basal mitophagy. We show that these converge, albeit via different mechanisms, on control of the mitophagy adaptors BNIP3 and BNIP3L/NIX. FBXL4 restricts NIX and BNIP3 levels via direct interaction and protein destabilization, while VHL acts through suppression of HIF1α-mediated transcription of BNIP3 and NIX. Depletion of NIX but not BNIP3 is sufficient to restore mitophagy levels. Our study contributes to an understanding of the aetiology of early-onset mitochondrial encephalomyopathy that is supported by analysis of a disease-associated mutation. We further show that the compound MLN4924, which globally interferes with cullin-RING ligase activity, is a strong inducer of mitophagy, thus providing a research tool in this context and a candidate therapeutic agent for conditions linked to mitochondrial dysfunction.
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Affiliation(s)
- Hannah Elcocks
- Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative BiologyUniversity of LiverpoolLiverpoolUK
| | - Ailbhe J Brazel
- Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative BiologyUniversity of LiverpoolLiverpoolUK
- Present address:
Department of BiologyMaynooth UniversityMaynoothIreland
| | - Katy R McCarron
- Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative BiologyUniversity of LiverpoolLiverpoolUK
| | - Manuel Kaulich
- Institute of Biochemistry IIGoethe University, Medical Faculty, University HospitalFrankfurt am MainGermany
- Frankfurt Cancer InstituteFrankfurt am MainGermany
| | - Koraljka Husnjak
- Institute of Biochemistry IIGoethe University, Medical Faculty, University HospitalFrankfurt am MainGermany
| | - Heather Mortiboys
- Sheffield Institute for Translational Neuroscience (SITraN)University of SheffieldSheffieldUK
| | - Michael J Clague
- Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative BiologyUniversity of LiverpoolLiverpoolUK
| | - Sylvie Urbé
- Molecular Physiology and Cell Signalling, Institute of Systems, Molecular and Integrative BiologyUniversity of LiverpoolLiverpoolUK
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9
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Köse E, Köse M, Edizer S, Akışın Z, Yılmaz ZB, Şahin A, Genel F. Different clinical presentation in a patient with two novel pathogenic variants of the FBXL4 gene. Turk J Pediatr 2021; 62:652-656. [PMID: 32779419 DOI: 10.24953/turkjped.2020.04.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The recently described FBXL4-related encephalomyopathic mitochondrial DNA depletion syndrome 13 (MTDPS13) manifests with severe encephalopathy, early-onset lactic acidosis, hypotonia, developmental delay and feeding difficulty. Less than 100 cases with FBXL4-related MTDPS13 and 47 pathogenic mutations in the FBXL4 gene have been identified thus far. Here, we describe a patient diagnosed with MTDPS13 with two novel variants of the FBXL4 gene. CASE A 51-day-old male was admitted with the complaint of bloody stool. His physical examination revealed facial dysmorphic features, developmental delay and truncal hypotonia with lack of head control. Laboratory investigations showed anemia, neutropenia, metabolic acidosis with hyperlactatemia, elevated fumaric acid, 2-ketoglutaric acid in urine and elevated alanine level in plasma which were consistent with mitochondrial dysfunction. Brain magnetic resonance imaging (MRI) showed large ventricles, thin corpus callosum and poor myelination. Drug-resistant epilepsy developed during the clinical follow-up. Ketogenic diet was initiated for intractable epilepsy; which was then interrupted due to severe metabolic acidosis. Compound heterozygous pathogenic variants were detected in the FBXL4 gene [p.Gly258* (c.772G > T, Exon 5)/p.Trp354Ser (c.1061G > C, Exon 6)] with whole-exome sequencing. CONCLUSION We detected two novel variants of the FBXL4 gene. To the best of our knowledge, this is the first case in the literature that presented with gastrointestinal bleeding as an encephalomyopathic form of mitochondrial DNA depletion syndromes and for whom ketogenic diet was initiated due to intractable epilepsy, which was not reported in previous cases.
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Affiliation(s)
- Engin Köse
- Division of Pediatric Metabolism and Nutrition, Department of Pediatrics, Ankara University Faculty of Medicine, Ankara
| | - Melis Köse
- Division of Pediatric Metabolism and Nutrition, Department of Pediatrics, Katip Çelebi University Faculty of Medicine, İzmir
| | - Selvinaz Edizer
- Divisions of Pediatric Neurology, Dr. Behçet Uz Children Research and Training Hospital, İzmir, Turkey
| | - Zeynep Akışın
- Nutrition and Dietetics, Dr. Behçet Uz Children Research and Training Hospital, İzmir, Turkey
| | - Zehra Burcu Yılmaz
- Department of Pediatrics, Dr. Behçet Uz Children Research and Training Hospital, İzmir, Turkey
| | - Ahmet Şahin
- Department of Pediatrics, Dr. Behçet Uz Children Research and Training Hospital, İzmir, Turkey
| | - Ferah Genel
- Department of Allergy and Immunology, Dr. Behçet Uz Children Research and Training Hospital, İzmir, Turkey
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Oncul U, Kose E, Eminoglu FT. A Mild Phenotype of Mitochondrial DNA Depletion Syndrome Type 13 with a Novel FBXL4 Variant. Mol Syndromol 2021; 12:294-299. [PMID: 34602956 PMCID: PMC8436661 DOI: 10.1159/000515928] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Accepted: 03/16/2021] [Indexed: 11/19/2022] Open
Abstract
Mitochondrial DNA depletion syndromes (MDDS) are a group of rare genetic disorders caused by defects in multiple genes involved in mitochondrial DNA maintenance. Among these, FBXL4 gene variants result in encephalomyopathic mtDNA depletion syndrome 13 (MTDPS13), which commonly presents as a combination of failure to thrive, neurodevelopmental delays, encephalopathy, hypotonia, a pattern of mild facial dysmorphisms, and persistent lactic acidosis. To date, 53 pathogenic FBXL4 variants and 100 cases have been described in the literature. In the present case report, we report on a 4.5-year-old boy with MTDPS13 and a novel variant. The patient had a history of antenatal hydrocephalus, severe developmental delay and mental motor retardation with psychomotor delay, severe hypotonia, mild left ventricular hypertrophic cardiomyopathy, mild facial dysmorphism, and elevated lactate levels. Symptoms suggested mitochondrial myopathy; subsequently, whole-exome sequencing was performed and a novel homozygous variant FBXL4 (NM_012160.4): c.486T>G (p.Tyr162Ter) was identified. While most of the patients with FBLX4 gene mutation have severe clinical manifestation and die at a very young age, clinical progress of our case was milder than previously reported. MDDS are very rare and can present with many different clinical signs and symptoms. In this report, we identified a novel pathogenic variant in the FBXL4 gene. This report shows that patients with FBLX4 gene mutations may present with a milder clinical phenotype than previously reported.
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Affiliation(s)
- Ummuhan Oncul
- Department of Pediatric Metabolism, Faculty of Medicine, Ankara University, Ankara, Turkey
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11
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Wang S, Lin L, Wang Y, Wang A, Liu Z, Wu S, Lan X, Jia J, Zhang Y, Yuan F, Wang C, Luo X, Sun X, Avula SK, Tolaymat A, Liu C, Ren Y, Chen Y. Novel homozygous mutation in the FBXL4 gene is associated with mitochondria DNA depletion syndrome-13. J Neurol Sci 2020; 416:116948. [PMID: 32559514 DOI: 10.1016/j.jns.2020.116948] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 05/24/2020] [Accepted: 05/25/2020] [Indexed: 10/24/2022]
Abstract
BACKGROUND Mitochondrial DNA depletion syndrome-13 (MTDPS13) is caused by mutations in FBXL4 (F-box and leucine-rich repeat protein 4), a nuclear gene encoding an F-box protein that plays a role in maintaining mtDNA integrity and stability. METHODS We identified a novel homozygous FBXL4 gene mutation, c.993dupA (p.L332Tfs*3), in a 1-year-old girl of Han Chinese descent. We performed three-dimensional protein structural analysis and targeted mtDNA next-generation sequencing. We analysed FBXL4 expression and mitochondrial DNA level, and reviewed mutations reported in FBXL4-related literature. RESULTS This mutation resulted in premature termination of translation and loss of 288 amino acids from C-terminus. A three-dimensional structural analysis revealed that conserved LRR domains were lost in mutant FBXL4 protein, which likely affected its ability to form protein-protein interactions. There were no differences in FBXL4 mRNA expression levels between the patient and her parents. There were no mtDNA mutations in either the patient or her parents. However, ND1/GAPDH ratio in lymphocytes and urine, which represents mtDNA/nuclear DNA ratio, showed that the number of mitochondrial genomes was significantly lower in the patient than in her parents or wild-type subjects. CONCLUSION Homozygous FBXL4 gene mutation, c.993dupA, can cause mitochondrial dysfunction, and LRR region is especially important for FBXL4 protein function.
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Affiliation(s)
- Simei Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China; Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | - Longlong Lin
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Yilin Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Anqi Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Zhao Liu
- Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | - Shengnan Wu
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Xiaoping Lan
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Jia Jia
- Shanghai Center for Bioinformation Technology, Shanghai 201202, China
| | - Yuanfeng Zhang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Fang Yuan
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Chunmei Wang
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Xiaona Luo
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Xiaomin Sun
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Sreenivas K Avula
- Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | - Abdullah Tolaymat
- Division of Pediatric Neurology, Department of Pediatrics, University of Illinois and Children's Hospital of Illinois, Peoria, IL 61637, USA
| | | | - Yun Ren
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China
| | - Yucai Chen
- Department of Neurology, Shanghai Children's Hospital, Shanghai JiaoTong University, Shanghai 200062, China.
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12
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Alsina D, Lytovchenko O, Schab A, Atanassov I, Schober FA, Jiang M, Koolmeister C, Wedell A, Taylor RW, Wredenberg A, Larsson NG. FBXL4 deficiency increases mitochondrial removal by autophagy. EMBO Mol Med 2020; 12:e11659. [PMID: 32525278 PMCID: PMC7338799 DOI: 10.15252/emmm.201911659] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 05/11/2020] [Accepted: 05/14/2020] [Indexed: 01/29/2023] Open
Abstract
Pathogenic variants in FBXL4 cause a severe encephalopathic syndrome associated with mtDNA depletion and deficient oxidative phosphorylation. To gain further insight into the enigmatic pathophysiology caused by FBXL4 deficiency, we generated homozygous Fbxl4 knockout mice and found that they display a predominant perinatal lethality. Surprisingly, the few surviving animals are apparently normal until the age of 8–12 months when they gradually develop signs of mitochondrial dysfunction and weight loss. One‐year‐old Fbxl4 knockouts show a global reduction in a variety of mitochondrial proteins and mtDNA depletion, whereas lysosomal proteins are upregulated. Fibroblasts from patients with FBXL4 deficiency and human FBXL4 knockout cells also have reduced steady‐state levels of mitochondrial proteins that can be attributed to increased mitochondrial turnover. Inhibition of lysosomal function in these cells reverses the mitochondrial phenotype, whereas proteasomal inhibition has no effect. Taken together, the results we present here show that FBXL4 prevents mitochondrial removal via autophagy and that loss of FBXL4 leads to decreased mitochondrial content and mitochondrial disease.
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Affiliation(s)
- David Alsina
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Oleksandr Lytovchenko
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Aleksandra Schab
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Ilian Atanassov
- Proteomics Core Facility, Max Planck Institute for Biology of Ageing, Cologne, Germnay
| | - Florian A Schober
- Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden.,Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
| | - Min Jiang
- Key Laboratory of Growth Regulation and Translation Research of Zhejiang Province, School of Life Sciences, Westlake University, Hangzhou, China
| | - Camilla Koolmeister
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden
| | - Anna Wedell
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden.,Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Robert W Taylor
- Wellcome Centre for Mitochondrial Research, Translational and Clinical Research Institute, Newcastle University, Newcastle upon Tyne, UK
| | - Anna Wredenberg
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden.,Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
| | - Nils-Göran Larsson
- Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.,Max Planck Institute Biology of Ageing - Karolinska Institutet Laboratory, Karolinska Institutet, Stockholm, Sweden.,Centre for Inherited Metabolic Diseases, Karolinska University Hospital, Stockholm, Sweden
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13
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Carraro U. Thirty years of translational research in Mobility Medicine: Collection of abstracts of the 2020 Padua Muscle Days. Eur J Transl Myol 2020; 30:8826. [PMID: 32499887 PMCID: PMC7254447 DOI: 10.4081/ejtm.2019.8826] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 01/22/2020] [Indexed: 12/11/2022] Open
Abstract
More than half a century of skeletal muscle research is continuing at Padua University (Italy) under the auspices of the Interdepartmental Research Centre of Myology (CIR-Myo), the European Journal of Translational Myology (EJTM) and recently also with the support of the A&CM-C Foundation for Translational Myology, Padova, Italy. The Volume 30(1), 2020 of the EJTM opens with the collection of abstracts for the conference "2020 Padua Muscle Days: Mobility Medicine 30 years of Translational Research". This is an international conference that will be held between March 18-21, 2020 in Euganei Hills and Padova in Italy. The abstracts are excellent examples of translational research and of the multidimensional approaches that are needed to classify and manage (in both the acute and chronic phases) diseases of Mobility that span from neurologic, metabolic and traumatic syndromes to the biological process of aging. One of the typical aim of Physical Medicine and Rehabilitation is indeed to reduce pain and increase mobility enough to enable impaired persons to walk freely, garden, and drive again. The excellent contents of this Collection of Abstracts reflect the high scientific caliber of researchers and clinicians who are eager to present their results at the PaduaMuscleDays. A series of EJTM Communications will also add to this preliminary evidence.
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Affiliation(s)
- Ugo Carraro
- Interdepartmental Research Centre of Myology (CIR-Myo), Department of Biomedical Sciences, University of Padova, Italy
- A&C M-C Foundation for Translational Myology, Padova, Italy
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14
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Nardi N, Proulx F, Brunel-Guiton C, Oligny LL, Piché N, Mitchell GA, Joyal JS. Fulminant Necrotizing Enterocolitis and Multiple Organ Dysfunction in a Toddler with Mitochondrial DNA Depletion Syndrome-13. J Pediatr Intensive Care 2019; 9:54-59. [PMID: 31984159 DOI: 10.1055/s-0039-1697620] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Accepted: 08/15/2019] [Indexed: 12/13/2022] Open
Abstract
Necrotizing enterocolitis (NEC) is exceptional after the neonatal period. A toddler with encephalopathy, mitochondrial myopathy, and hypertrophic cardiomyopathy developed fatal NEC and multiple organ dysfunction within 48 hours of the introduction of enteral feeding. She was subsequently found to have pathogenic mutations in FBXL4 , a cause of mitochondrial DNA depletion syndrome-13. Intestinal dysmotility in the context of deficient mitochondrial respiration may have contributed to the development of NEC. Current paradigms call for early introduction of enteral nutrition to reinstate energy homeostasis. Enteral feeding should be administered with caution during metabolic crises of patients with mitochondrial DNA depletion syndromes.
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Affiliation(s)
- Nicolas Nardi
- Department of Pediatrics, Sainte-Justine Hospital, University of Montreal, Montreal, Canada
| | - François Proulx
- Department of Pediatrics, Sainte-Justine Hospital, University of Montreal, Montreal, Canada
| | | | - Luc L Oligny
- Department of Pediatric Pathology, Sainte-Justine Hospital, University of Montreal, Montreal, Canada
| | - Nelson Piché
- Department of Pediatric Surgery, Sainte-Justine Hospital, University of Montreal, Montreal, Canada
| | - Grant A Mitchell
- Department of Pediatrics, Sainte-Justine Hospital, University of Montreal, Montreal, Canada
| | - Jean Sébastien Joyal
- Department of Pediatrics, Sainte-Justine Hospital, University of Montreal, Montreal, Canada
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15
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Sabouny R, Wong R, Lee-Glover L, Greenway SC, Sinasac DS, Khan A, Shutt TE. Characterization of the C584R variant in the mtDNA depletion syndrome gene FBXL4, reveals a novel role for FBXL4 as a regulator of mitochondrial fusion. Biochim Biophys Acta Mol Basis Dis 2019; 1865:165536. [PMID: 31442532 DOI: 10.1016/j.bbadis.2019.165536] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 07/16/2019] [Accepted: 08/18/2019] [Indexed: 12/16/2022]
Abstract
Mutations in FBXL4 (F-Box and Leucine rich repeat protein 4), a nuclear-encoded mitochondrial protein with an unknown function, cause mitochondrial DNA depletion syndrome. We report two siblings, from consanguineous parents, harbouring a previously uncharacterized homozygous variant in FBXL4 (c.1750 T > C; p.Cys584Arg). Both patients presented with encephalomyopathy, lactic acidosis and cardiac hypertrophy, which are reported features of FBXL4 impairment. Remarkably, dichloroacetate (DCA) administration to the younger sibling improved metabolic acidosis and reversed cardiac hypertrophy. Characterization of FBXL4 patient fibroblasts revealed severe bioenergetic defects, mtDNA depletion, fragmentation of mitochondrial networks, and abnormalities in mtDNA nucleoids. These phenotypes, observed with other pathogenic FBXL4 variants, confirm the pathogenicity of the p.Cys584Arg variant. Although treating FBXL4 fibroblasts with DCA improved extracellular acidification, in line with reduced lactate levels in patients, DCA treatment did not improve any of the other mitochondrial functions. Nonetheless, we highlight DCA as a potentially effective drug for the management of elevated lactate and cardiomyopathy in patients with pathogenic FBXL4 variants. Finally, as the exact mechanism through which FBXL4 mutations lead to mtDNA depletion was unknown, we tested the hypothesis that FBXL4 promotes mitochondrial fusion. Using a photo-activatable GFP fusion assay, we found reduced mitochondrial fusion rates in cells harbouring a pathogenic FBXL4 variant. Meanwhile, overexpression of wildtype FBXL4, but not the p.Cys584Arg variant, promoted mitochondrial hyperfusion. Thus, we have uncovered a novel function for FBXL4 in promoting mitochondrial fusion, providing important mechanistic insights into the pathogenic mechanism underlying FBXL4 dysfunction.
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Affiliation(s)
- Rasha Sabouny
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada.
| | - Rachel Wong
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Laurie Lee-Glover
- Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Steven C Greenway
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Cardiac Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada; Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - David S Sinasac
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | | | - Aneal Khan
- Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada
| | - Timothy E Shutt
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada; Alberta Children's Hospital Research Institute, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
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16
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Kuptanon C, Srichomthong C, Ittiwut C, Wechapinan T, Sri-Udomkajorn S, Iamopas O, Phokaew C, Suphapeetiporn K, Shotelersuk V. Whole exome sequencing revealed mutations in FBXL4, UNC80, and ADK in Thai patients with severe intellectual disabilities. Gene 2019; 696:21-7. [PMID: 30771478 DOI: 10.1016/j.gene.2019.01.049] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 12/25/2018] [Accepted: 01/04/2019] [Indexed: 01/20/2023]
Abstract
Intellectual disabilities (ID) are etiologically heterogeneous. Advanced molecular techniques could be helpful in identification of the underlying genetic defects. We aimed to characterize clinical and molecular features of three Thai patients with ID. Patient 1 had ID, hypotonia and lactic acidosis. Patient 2 had ID and growth failure. Patient 3 had ID, seizure, diarrhea and hypoglycemia. Whole exome sequencing found that Patient 1 was homozygous for a nonsense, c.1303C>T (p.Arg435Ter), mutation in FBXL4, a gene responsible for encephalomyopathic mitochondrial DNA depletion syndrome-13 (MTDPS13). Patient 2 was compound heterozygous for two novel mutations, c.3226C>T (p.Arg1076Ter) and c.3205C>T (p.Arg1069Ter), in UNC80, a known gene of infantile hypotonia with psychomotor retardation and characteristic facies-2 (IHPRF2). Patient 3 was homozygous for a novel missense, c.427T>C (p.Cys143Arg), mutation in ADK, a known gene of adenosine kinase deficiency leading to hypermethioninemia. This study expands the mutational spectra of ID genes.
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17
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Ballout RA, Al Alam C, Bonnen PE, Huemer M, El-Hattab AW, Shbarou R. FBXL4-Related Mitochondrial DNA Depletion Syndrome 13 (MTDPS13): A Case Report With a Comprehensive Mutation Review. Front Genet 2019; 10:39. [PMID: 30804983 PMCID: PMC6370620 DOI: 10.3389/fgene.2019.00039] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 01/18/2019] [Indexed: 01/28/2023] Open
Abstract
Mitochondrial DNA depletion syndromes (MTDPS) are a group of rare genetic disorders caused by defects in multiple genes involved in mitochondrial DNA (mtDNA) maintenance. Among those, FBXL4 mutations result in the encephalomyopathic mtDNA depletion syndrome 13 (MTDPS13; OMIM #615471), which commonly presents as a combination of failure to thrive, neurodevelopmental delays, encephalopathy, hypotonia, and persistent lactic acidosis. We report here the case of a Lebanese infant presenting to us with profound neurodevelopmental delays, generalized hypotonia, facial dysmorphic features, and extreme emaciation. Whole-exome sequencing (WES) showed the girl as having MTDPS13 with an underlying FBXL4 missense mutation that has been previously reported only twice in unrelated individuals (c.1303C > T). Comprehensive literature search marked our patient as being the 94th case of MTDPS13 reported to date worldwide, and the first from Lebanon. We include at the end of this report a comprehensive mutation review table of all the pathological FBXL4 mutations reported in the literature, using it to highlight, for the first time, a possible founder effect of Arab origins to the disorder, being most prevalent in patients of Arab descent as shown in our mutation table. Finally, we provide a direct comparison of the disorder's clinical manifestations across two unrelated patients harboring the same disease-causing mutation as our patient, emphasizing the remarkable variability in genotype-to-phenotype correlation characteristic of the disease.
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Affiliation(s)
- Rami A Ballout
- Faculty of Medicine, American University of Beirut, Beirut, Lebanon
| | - Chadi Al Alam
- Division of Pediatric Neurology, Department of Pediatrics, American University of Beirut Medical Center, Beirut, Lebanon
| | - Penelope E Bonnen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Martina Huemer
- Department of Pediatrics, Landeskrankenhaus Bregenz, Bregenz, Austria.,Division of Metabolism, University Children's Hospital Zürich, Zurich, Switzerland
| | - Ayman W El-Hattab
- Genetics Clinic, KidsHeart Medical Center, Dubai, United Arab Emirates
| | - Rolla Shbarou
- Division of Pediatric Neurology, Department of Pediatrics, American University of Beirut Medical Center, Beirut, Lebanon
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18
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El-Hattab AW, Suleiman J, Almannai M, Scaglia F. Mitochondrial dynamics: Biological roles, molecular machinery, and related diseases. Mol Genet Metab 2018; 125:315-321. [PMID: 30361041 DOI: 10.1016/j.ymgme.2018.10.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 10/15/2018] [Indexed: 01/09/2023]
Abstract
Mitochondria are dynamic organelles that undergo fusion, fission, movement, and mitophagy. These processes are essential to maintain the normal mitochondrial morphology, distribution, and function. Mitochondrial fusion allows the exchange of intramitochondrial material, whereas the fission process is required to replicate the mitochondria during cell division, facilitate the transport and distribution of mitochondria, and allow the isolation of damaged organelles. Mitochondrial mobility is essential for mitochondrial distribution depending on the cellular metabolic demands. Mitophagy is needed for the elimination of dysfunctional and damaged mitochondria to maintain a healthy mitochondrial population. The mitochondrial dynamic processes are mediated by a number of nuclear-encoded proteins that function in mitochondrial transport, fusion, fission, and mitophagy. Disorders of mitochondrial dynamics are caused by pathogenic variants in the genes encoding these proteins. These diseases have a high clinical variability, and range in severity from isolated optic atrophy to lethal encephalopathy. These disorders include defects in mitochondrial fusion (caused by pathogenic variants in MFN2, OPA1, YME1L1, MSTO1, and FBXL4), mitochondrial fission (caused by pathogenic variants in DNM1L and MFF), and mitochondrial autophagy (caused by pathogenic variants in PINK1 and PRKN). In this review, the molecular machinery and biological roles of mitochondrial dynamic processes are discussed. Subsequently, the currently known diseases related to mitochondrial dynamic defects are presented.
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Affiliation(s)
- Ayman W El-Hattab
- Division of Clinical Genetics and Metabolic Disorders, Pediatrics Department, Tawam Hospital, Al-Ain, United Arab Emirates
| | - Jehan Suleiman
- Division of Neurology, Pediatrics Department, Tawam Hospital, Al Ain, United Arab Emirates
| | - Mohammed Almannai
- Medical Genetics Division, King Fahad Medical City, Riyadh, Saudi Arabia
| | - Fernando Scaglia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA; Texas Children's Hospital, Houston, TX, USA; Joint BCM-CUHK Center of Medical Genetics, Prince of Wales Hospital, ShaTin, Hong Kong Special Administrative Region.
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19
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Morton SU, Neilan EG, Peake RWA, Shi J, Schmitz-Abe K, Towne M, Markianos K, Prabhu SP, Agrawal PB. Hyperammonemia as a Presenting Feature in Two Siblings with FBXL4 Variants. JIMD Rep 2016; 35:7-15. [PMID: 27858371 DOI: 10.1007/8904_2016_17] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 10/03/2016] [Accepted: 10/05/2016] [Indexed: 01/13/2023] Open
Abstract
Early-onset mitochondrial encephalomyopathy is a rare disorder that presents in the neonatal period with lactic acidosis, hypotonia, and developmental delay. Sequence variants in the nuclear-encoded gene FBXL4 have been previously demonstrated to be a cause of early-onset mitochondrial encephalomyopathy in several unrelated families. We have identified a pair of siblings with mutations in FBXL4 who each presented in the neonatal period with hyperammonemia, low plasma levels of aspartate, low urine levels of tricarboxylic acid cycle intermediates suggesting a defect in anaplerosis, and cerebellar hypoplasia in addition to lactic acidosis and other classic signs of mitochondrial encephalomyopathy. After initial clinical stabilization, both subjects continued to have episodic exacerbations characterized by lactic acidosis and hyperammonemia. Previously reported cases of FBXL4 mutations are reviewed and compared with these affected siblings. These two new cases add to the spectrum of disease caused by mutations in FBLX4 and suggest possible benefit from anaplerotic therapies.
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Affiliation(s)
- Sarah U Morton
- Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Hunnewell 4, Boston, MA, 02115, USA.,Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Edward G Neilan
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Roy W A Peake
- Department of Laboratory Medicine, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Jiahai Shi
- Department of Biomedical Sciences, City University of Hong Kong, Pok Fu Lam, Hong Kong
| | - Klaus Schmitz-Abe
- Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Meghan Towne
- Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA.,Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Kyriacos Markianos
- Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Hunnewell 4, Boston, MA, 02115, USA.,Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Sanjay P Prabhu
- Department of Radiology, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Pankaj B Agrawal
- Division of Newborn Medicine, Boston Children's Hospital and Harvard Medical School, 300 Longwood Ave, Hunnewell 4, Boston, MA, 02115, USA. .,Gene Discovery Core, The Manton Center for Orphan Disease Research, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA. .,Division of Genetics and Genomics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA.
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