Characterization of the C584R variant in the mtDNA depletion syndrome gene FBXL4, reveals a novel role for FBXL4 as a regulator of mitochondrial fusion

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.Cys548Arg 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...
Source: Biochimica et Biophysica Acta (BBA) Molecular Basis of Disease - Category: Molecular Biology Source Type: research

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Abstract NADH:ubiquinone oxidoreductase, more commonly referred to as mitochondrial complex I (CI), is the largest discrete enzyme of the oxidative phosphorylation system (OXPHOS). It is localized to the mitochondrial inner membrane. CI oxidizes NADH generated from the tricarboxylic acid cycle to NAD+, in a series of redox reactions that culminates in the reduction of ubiquinone, and the transport of protons from the matrix across the inner membrane to the intermembrane space. The resulting proton-motive force is consumed by ATP synthase to generate ATP, or harnessed to transport ions, metabolites and proteins int...
Source: Cellular and Molecular Life Sciences : CMLS - Category: Cytology Authors: Tags: Cell Mol Life Sci Source Type: research
In conclusions, our present study firstly showed that liver-secreted exosomal miR-122 played a critical role in the development of metabolic cardiomyopathy, and miR-122/mitochondrial Arl-2 signaling affected cardiac energy homeostasis.
Source: Clinical Science - Category: Biomedical Science Authors: Tags: PublishAheadOfPrint Source Type: research
In this study, we found that ectopic ATP synthase was more sensitive to CIT treatment than mitochondrial ATP synthase in H9c2 cardiomyocytes. CIT inhibited the transcriptional activity of peroxisome proliferator activated receptor gamma (PPAR-γ) in mice hearts and H9c2 cells. PPAR-γ agonist attenuated the inhibitory effect of CIT on mechanistic target of rapamycin complex 2 (mTORC2) and stimulatory effect of CIT on autophagy in cardiomyocytes. CIT induced apoptosis through lysosomal-mitochondrial axis in cardiomyocytes. PPAR-γ agonist and autophagy inhibitor alleviated CIT-induced apoptosis and accelerate...
Source: Chemico Biological Interactions - Category: Biochemistry Source Type: research
In this study, we found that ectopic ATP synthase was more sensitive to CIT treatment than mitochondrial ATP synthase in H9c2 cardiomyocytes. CIT inhibited the transcriptional activity of peroxisome proliferator activated receptor gamma (PPAR-γ) in mice hearts and H9c2 cells. PPAR-γ agonist attenuated the inhibitory effect of CIT on mechanistic target of rapamycin complex 2 (mTORC2) and stimulatory effect of CIT on autophagy in cardiomyocytes. CIT induced apoptosis through lysosomal-mitochondrial axis in cardiomyocytes. PPAR-γ agonist and autophagy inhibitor alleviated CIT-induced apoptosis and accelerate...
Source: Chemico-Biological Interactions - Category: Molecular Biology Authors: Tags: Chem Biol Interact Source Type: research
In conclusion, with study of the frailty syndrome still in its infancy, frailty analysis remains a major challenge. It is a challenge that needs to be overcome in order to shed light on the multiple mechanisms involved in the pathogenesis of this syndrome. Although several mechanisms contribute to frailty, immune system alteration seems to play a central role: this syndrome is characterized by increased levels of pro-inflammatory markers and the resulting pro-inflammatory status can have negative effects on various organs. Future studies should aim to better clarify the immune system alteration in frailty, and seek to esta...
Source: Fight Aging! - Category: Research Authors: Tags: Newsletters Source Type: blogs
Publication date: Available online 27 July 2019Source: Redox BiologyAuthor(s): Jiankai Zhong, Ying Tan, Jianhua Lu, Jichen Liu, Xiaochan Xiao, Pinji Zhu, Sainan Chen, Sulin Zheng, Yuying Chen, Yunzhao Hu, Zhigang GuoAbstractThe basic pathophysiological mechanisms underlying septic cardiomyopathy have not yet been completely clarified. Disease-specific treatments are lacking, and care is still based on supportive modalities. The aim of our study was to assess the protective effects of melatonin on septic cardiomyopathy, with a focus on the interactions between receptor-interacting protein kinase 3 (Ripk3), the mitochondria,...
Source: Redox Biology - Category: Biology Source Type: research
Abstract Diabetes mellitus (DM) has become an increasingly common disease with high disability and mortality rates. Diabetes complications are the main cause of diabetes death and about 50% of diabetic patients died from heart disease in developed countries reported by World Health Organization. Diabetic cardiomyopathy (DCM) has been considered as a high incidence and serious complication of DM and plays a key role in the incidence and development of diabetes related heart failure. Metabolism dysregulation is regarded as an important and earlier factor occurred in the pathogenesis of DCM. Insulin resistance, oxida...
Source: Current Protein and Peptide Science - Category: Biochemistry Authors: Tags: Curr Protein Pept Sci Source Type: research
Abstract The cytochrome C oxidase assembly protein SCO1 gene encodes a mitochondrial protein essential for the mammalian energy metabolism. Only three pedigrees of SCO1mutations have thus far been reported. They all presented with lactate acidosis and encephalopathy. Two had hepatopathy and hypotonia, and the other presented with intrauterine growth retardation and hypertrophic cardiomyopathy leading to cardiac failure. Mitochondrial disease may manifest in neonates, but early diagnosis has so far been difficult. Here, we present a novel mutation in the SCO1 gene: in-frame deletion (Gly106del)with a different phen...
Source: Neonatology - Category: Perinatology & Neonatology Authors: Tags: Neonatology Source Type: research
ConclusionsBased on the population data and our case series, COQ4-related mitochondriopathy is likely an underrecognized condition. We recommend including the COQ4 c.370G > A variant as a part of the screening process for mitochondriopathy in Chinese populations.
Source: Clinica Chimica Acta - Category: Laboratory Medicine Source Type: research
Abstract Hydrogen sulfide (H2S) is reported to be effective in the management of the myocardial ischemia-reperfusion (I/R) injury via PI3K/GSK3β pathway in normal rats. However, its efficacy against I/R in the presence of diabetic cardiomyopathy is relatively obscure. Thus, the present work aimed to find out H2S-mediated cardioprotection against I/R in diabetic cardiomyopathy and to evaluate its mode of action using Langendorff isolated heart perfusion system. The present work includes three groups of rat, viz. (i) normal, (ii) diabetes mellitus (DM: streptozotocin: 35 mg/kg; normal diet), and (iii) diab...
Source: Cardiovascular Toxicology - Category: Cardiology Authors: Tags: Cardiovasc Toxicol Source Type: research
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