首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Friedreich ataxia (FRDA) is an autosomal recessive, multi-systemic degenerative disease that results from reduced synthesis of the mitochondrial protein frataxin. Frataxin has been intensely studied since its deficiency was linked to FRDA in 1996. The defining properties of frataxin – (i) the ability to bind iron, (ii) the ability to interact with, and donate iron to, other iron-binding proteins, and (iii) the ability to oligomerize, store iron and control iron redox chemistry – have been extensively characterized with different frataxin orthologs and their interacting protein partners. This very large body of biochemical and structural data [reviewed in (Bencze et al., 2006)] supports equally extensive biological evidence that frataxin is critical for mitochondrial iron metabolism and overall cellular iron homeostasis and antioxidant protection [reviewed in (Wilson, 2006)]. However, the precise biological role of frataxin remains a matter of debate. Here, we review seminal and recent data that strongly link frataxin to the synthesis of iron–sulfur cluster cofactors (ISC), as well as controversial data that nevertheless link frataxin to additional iron-related processes. Finally, we discuss how defects in ISC synthesis could be a major (although likely not unique) contributor to the pathophysiology of FRDA via (i) loss of ISC-dependent enzymes, (ii) mitochondrial and cellular iron dysregulation, and (iii) enhanced iron-mediated oxidative stress. This article is part of a Special Issue entitled ‘Mitochondrial function and dysfunction in neurodegeneration’.  相似文献   

2.
Friedreich ataxia is an inherited, severe, progressive neuro- and cardiodegenerative disorder for which there currently is no approved therapy. Friedreich ataxia is caused by the decreased expression and/or function of frataxin, a mitochondrial matrix protein that binds iron and is involved in the formation of iron-sulfur clusters. Decreased frataxin function leads to decreased iron-sulfur cluster formation, mitochondrial iron accumulation, cytosolic iron depletion, oxidative stress, and mitochondrial dysfunction. Cloning of the disease gene for Friedreich ataxia and elucidation of many aspects of the biochemical defects underlying the disorder have led to several major therapeutic initiatives aimed at increasing frataxin expression, reversing mitochondrial iron accumulation, and alleviating oxidative stress. These initiatives are in preclinical and clinical development and are reviewed herein.  相似文献   

3.
Friedreich ataxia is the most common hereditary ataxia. The signs and symptoms of the disorder derive from decreased expression of the protein frataxin, which is involved in iron metabolism. Frataxin chaperones iron for iron-sulfur cluster biogenesis and detoxifies iron in the mitochondrial matrix. Decreased expression of frataxin is associated with impairments of iron-sulfur cluster biogenesis and heme synthesis, as well as with mitochondrial dysfunction and oxidative stress. Compounds currently in clinical trials are directed toward improving mitochondrial function and lessening oxidative stress. Iron chelators and compounds that increase frataxin expression are under evaluation. Further elucidation of frataxin's function should lead to additional therapeutic approaches.  相似文献   

4.
Friedreich ataxia (FRDA), the most common autosomal recessive inherited ataxic disorder, is the consequence of deficiency of the mitochondrial protein frataxin, typically caused by homozygous intronic GAA expansions in the corresponding gene. The yeast frataxin homologue (yfh1p) is required for cellular respiration. Yfh1p appears to regulate mitochondrial iron homeostasis and protect from free radical toxicity. Complete loss of frataxin in knockout mice leads to early embryonic lethality, indicating an important role for frataxin during development. Heterozygous littermates with partial frataxin deficiency are apparently healthy and have no obvious phenotype. Here we evaluate iron metabolism and sensitivity to dietary and parenteral iron loading in heterozygote frataxin knockout mice (Fx(+/-)). Iron concentrations in the liver, heart, pancreas and spleen, and cellular iron distribution patterns were compared between wild type and Fx(+/-) mice. Response to parenteral iron challenge was not different between Fx(+/-) mice and wild type littermates, while sporadic iron deposits were observed in the hearts of dietary iron-loaded Fx(+/-) mice. Finally, we evaluated the effect of partial frataxin deficiency on susceptibility to cardiac damage in the mouse model of hereditary hemochromatosis (HH), the Hfe knockout mice. HH, an iron overload disease, is one of the most frequent genetic diseases in populations of European origin. By breeding Hfe(-/-) with Fx(+/-) mice, we obtained compound mutant mice lacking both Hfe and one frataxin allele. Sparse iron deposits in areas of mild to moderate cardiac fibrosis were found in the majority of these mice. However, they did not develop any neurological symptoms. Our studies indicate an association between frataxin deficiency, iron deposits and cardiac fibrosis, but no obvious association between iron accumulation and neurodegeneration similar to FRDA could be detected in our model. In addition, these results suggest that frataxin mutations may have a modifier role in HH, that predisposes to cardiomyopathy.  相似文献   

5.
6.
Understanding the role of frataxin in mitochondria is key to an understanding of the pathogenesis of Friedreich ataxia. Frataxins are small essential proteins whose deficiency causes a range of metabolic disturbances, which include oxidative stress, deficit of iron-sulphur clusters, and defects in heme synthesis, sulfur amino acid and energy metabolism, stress response, and mitochondrial function. Structural studies carried out on different orthologues have shown that the frataxin fold consists of a flexible N-terminal region present only in eukaryotes and in a highly conserved C-terminal globular domain. Frataxins bind iron directly but with very unusual properties: iron coordination is achieved solely by glutamates and aspartates exposed on the protein surface. It has been suggested that frataxin function is that of a ferritin-like protein, an iron chaperone of the ironsulphur cluster machinery and heme metabolism and/or a controller of cellular oxidative stress. To understand FRDA pathogenesis and to design novel therapeutic strategies, we must first precisely identify the cellular role of frataxin.  相似文献   

7.
Friedreich’s ataxia, the most common hereditary ataxia, is caused by expansion of a GAA triplet located within the first intron of the frataxin gene on chromosome 9q13. There is a clear correlation between size of the expanded repeat and severity of the phenotype. Frataxin is a mitochondrial protein that plays a role in iron homeostasis. Deficiency of frataxin results in mitochondrial iron accumulation, defects in specific mitochondrial enzymes, enhanced sensitivity to oxidative stress, and eventually free-radical mediated cell death. Friedreich’s ataxia is considered a nuclear encoded mitochondrial disease.

This review discusses the major and rapid progress made in Friedreich’s ataxia from gene mapping and identification of the gene to pathogenesis and encouraging therapeutic implications.  相似文献   


8.
Friedreich ataxia (FRDA) is the most common hereditary autosomal recessive ataxia, but is also a multisystemic condition with frequent presence of cardiomyopathy or diabetes. It has been linked to expansion of a GAA-triplet repeat in the first intron of the FXN gene, leading to a reduced level of frataxin, a mitochondrial protein which, by controlling both iron entry and/or sulfide production, is essential to properly assemble and protect the Fe-S cluster during the initial stage of biogenesis. Several data emphasize the role of oxidative damage in FRDA, but better understanding of pathophysiological consequences of FXN mutations has led to develop animal models. Conditional knockout models recapitulate important features of the human disease but lack the genetic context, GAA repeat expansion-based knock-in and transgenic models carry a GAA repeat expansion but they only show a very mild phenotype. Cells derived from FRDA patients constitute the most relevant frataxin-deficient cell model as they carry the complete frataxin locus together with GAA repeat expansions and regulatory sequences. Induced pluripotent stem cell (iPSC)-derived neurons present a maturation delay and lower mitochondrial membrane potential, while cardiomyocytes exhibit progressive mitochondrial degeneration, with frequent dark mitochondria and proliferation/accumulation of normal mitochondria. Efforts in developing therapeutic strategies can be divided into three categories: iron chelators, antioxidants and/or stimulants of mitochondrial biogenesis, and frataxin level modifiers. A promising therapeutic strategy that is currently the subject of intense research is to directly target the heterochromatin state of the GAA repeat expansion with histone deacytelase inhibitors (HDACi) to restore frataxin levels.  相似文献   

9.
Friedreich's ataxia (FRDA) is caused by point mutations or trinucleotide repeat expansions in both alleles of the gene encoding frataxin. Studies of frataxin homologues in lower eukaryotes suggest that mitochondrial iron accumulation may underlie the pathophysiology of FRDA. To evaluate the possible role of iron-chelation therapy for FRDA, we measured serum iron and ferritin concentration in 10 FRDA patients. The measurements were within normal limits, suggesting that iron-chelation therapy for FRDA may be problematic.  相似文献   

10.
The possible causes of abnormal iron metabolism in patients with Friedreich's ataxia are considered. Reduced expression of a frataxin homologue in yeast is associated with mitochondrial iron accumulation at the expense of cytosolic iron, and the same phenomenon can be demonstrated in these patients. A decrease in cytosolic iron causes the expression of a high-affinity iron-uptake protein, and therefore Friedreich's ataxia can be considered to be a disease of abnormal intracellular iron distribution. Friedreich's ataxia is of autosomal recessive inheritance, and the gene associated with it has been mapped to chromosome 9. This encodes the protein frataxin which regulates mitochondrial iron transport. The commonest mutation causing this disorder is an expanded GAA repeat in the gene for this protein. Different point mutations may account for some of the variations in the phenotypic features that are often found, and these variations are discussed. These findings have raised therapeutic possibilities in a condition for which previously there was no specific treatment. There are intracellular enzymes which are very sensitive to injury by oxygen-free radicals. Treatment has therefore been tried with ibebenone which acts as a free-radical scavenger, with some evidence of improvement. Iron chelating agents, such as deferoxamine, have also been given, but the finding of normal serum iron and ferritin casts doubt on the rationale of this. However the finding that the accumulation of iron in the mitochondria of the cells in patients with this form of ataxia will cause oxidative stress and cell death, gives hope for more effective treatment in the future, possibly with gene therapy.  相似文献   

11.
Friedreich ataxia, the most common type of inherited ataxia, is itself caused in most cases by a large expansion of an intronic GAA repeat, resulting in decreased expression of the target frataxin gene. The autosomal recessive inheritance of the disease gives this triplet repeat mutation some unique features of natural history and evolution. Frataxin is a mitochondrial protein that has homologues in yeast and even in gram-negative bacteria. Yeast organisms deficient in the frataxin homologue accumulate iron in mitochondria and show increased sensitivity to oxidative stress. This suggests that Friedreich ataxia is caused by mitochondrial dysfunction and free radical toxicity.  相似文献   

12.
Friedreich ataxia is the most common human ataxia and results from inadequate production of the frataxin protein, most often the result of a triplet expansion in the nuclear FXN gene. The gene cannot be transcribed to generate the messenger ribonucleic acid for frataxin. Frataxin is an iron-binding protein targeted to the mitochondrial matrix. In its absence, multiple iron-sulfur-dependent proteins in mitochondria and the cytosol lack proper assembly, destroying mitochondrial and nuclear function. Mitochondrial oxidant stress may also participate in ongoing cellular injury. Although progressive and debilitative ataxia is the most prominent clinical finding, hypertrophic cardiomyopathy with heart failure is the most common cause of early death in this disease. There is no cure. In this review the authors cover recent basic and clinical findings regarding the heart in Friedreich ataxia, offer recommendations for clinical management of the cardiomyopathy in this disease, and point out new research directions to advance the field.  相似文献   

13.
Dürr A 《Lancet neurology》2002,1(6):370-374
Friedreich's ataxia (FA) is the most prevalent cerebellar ataxia in children and adults in Europe. FA is one of a growing number of diseases known to be caused by triplet-repeat expansions. The causative mutation is a GAA trinucleotide-repeat expansion in the first intron of the frataxin gene. The mitochondrial localisation of frataxin and decreased oxidation activity in vivo and in vitro show that FA is a mitochondrial disease. Frataxin is involved in iron metabolism and may protect mitochondria from oxidative damage. The understanding of the disease has only just begun and possible treatments are within reach. In this review I discuss the clinical knowledge of FA and recent developments that have helped to elucidate the pathogenesis of the disease and made the first therapeutic attempts possible.  相似文献   

14.
Friedreich ataxia (FRDA) is an autosomal recessive inherited neurodegenerative disorder leading to reduced expression of the mitochondrial protein frataxin. Previous studies showed frataxin upregulation in FRDA following treatment with recombinant human erythropoietin (rhuEPO). Dose-response interactions between frataxin and rhuEPO have not been studied until to date. We administered escalating rhuEPO single doses (5,000, 10,000 and 30,000?IU) in monthly intervals to five adult FRDA patients. Measurements of frataxin, serum erythropoietin levels, iron metabolism and mitochondrial function were carried out. Clinical outcome was assessed using the "Scale for the assessment and rating of ataxia". We found maximal erythropoietin serum concentrations 24?h after rhuEPO application which is comparable to healthy subjects. Frataxin levels increased significantly over 3?months, while ataxia rating did not reveal clinical improvement. All FRDA patients had considerable ferritin decrease. NADH/NAD ratio, an indicator of mitochondrial function, increased following rhuEPO treatment. In addition to frataxin upregulation in response to continuous low-dose rhuEPO application shown in previous studies, our results indicate for a long-lasting frataxin increase after single high-dose rhuEPO administration. To detect frataxin-derived neuroprotective effects resulting in clinically relevant improvement, well-designed studies with extended time frame are required.  相似文献   

15.
Friedreich's ataxia (FRDA) is an autosomal recessive inherited disorder characterized by progressive gait and limb ataxia, dysarthria, areflexia, loss of vibratory and position sense, and a progressive motor weakness of central origin. Additional features include hypertrophic cardiomyopathy and diabetes. Large GAA repeat expansions in the first intron of the FXN gene are the most common mutation underlying FRDA. Patients show severely reduced levels of a FXN-encoded mitochondrial protein called frataxin. Frataxin deficiency is associated with abnormalities of iron metabolism: decreased iron-sulfur cluster (ISC) biogenesis, accumulation of iron in mitochondria and depletion in the cytosol, enhanced cellular iron uptake. Some models have also shown reduced heme synthesis. Evidence for oxidative stress has been reported. Respiratory chain dysfunction aggravates oxidative stress by increasing leakage of electrons and the formation of superoxide. In vitro studies have demonstrated that Frataxin deficient cells not only generate more free radicals, but also show a reduced capacity to mobilize antioxidant defenses. The search for experimental drugs increasing the amount of frataxin is a very active and timely area of investigation. In cellular and in animal model systems, the replacement of frataxin function seems to alleviate the symptoms or even completely reverse the phenotype. Therefore, drugs increasing the amount of frataxin are attractive candidates for novel therapies. This review will discuss recent findings on FRDA pathogenesis, frataxin function, new treatments, as well as recent animal and cellular models. Controversial aspects are also discussed.  相似文献   

16.
The discovery of the genetic cause of Friedreich ataxia has significantly affected our understanding of the disorder at both the clinical and basic science levels. Friedreich ataxia results from a deficiency of functional frataxin, a protein that appears to be involved in mitochondrial iron homeostasis. This leads to iron accumulation and mitochondrial abnormalities with consequent oxidant damage. The clinical spectrum of Friedreich ataxia has also expanded with the recognition of broader phenotypic features, including the absence of classical Friedreich ataxia features, later age at onset, and spasticity instead of ataxia. Although no proven therapy is yet available, antioxidants are a potential method for therapeutic intervention.  相似文献   

17.
Childhood ataxia is characterized by impaired balance and coordination primarily because of cerebellar dysfunction. Friedreich ataxia, a form of childhood ataxia, is the most common multisystem autosomal recessive disease. Most of these patients are homozygous for the GAA repeat expansion located on the first intron of the frataxin gene on chromosome 9. Mutations in the frataxin gene impair mitochondrial function, increase reactive oxygen species, and trigger redistribution of iron in the mitochondria and cytosol. Targeted therapies for Friedreich ataxia are undergoing testing. In addition, a centralized database, patient registry, and natural history study have been launched to support clinical trials in Friedreich ataxia. The 2011 Neurobiology of Disease in Children symposium, held in conjunction with the 40th annual Child Neurology Society meeting, aimed to (1) describe clinical features surrounding Friedreich ataxia, including cardiomyopathy and genetics; (2) discuss recent advances in the understanding of the pathogenesis of Friedreich ataxia and developments of clinical trials; (3) review new investigations of characteristic symptoms; and (4) establish clinical and biochemical overlaps in neurodegenerative diseases and possible directions for future basic, translational, and clinical studies.  相似文献   

18.
Rescue of the Friedreich's ataxia knockout mouse by human YAC transgenesis   总被引:3,自引:0,他引:3  
We have generated and characterised transgenic mice that contain the entire Friedreich's ataxia gene (FRDA) within a human YAC clone of 370 kb. In an effort to overcome the embryonic lethality of homozygous Frda knockout mice and to study the behaviour of human frataxin in a mouse cellular environment, we bred the FRDA YAC transgene onto the null mouse background. Phenotypically normal offspring that express only YAC-derived human frataxin were identified. The human frataxin was expressed in the appropriate tissues at levels comparable to the endogenous mouse frataxin, and it was correctly processed and localised to mitochondria. Biochemical analysis of heart tissue demonstrated preservation of mitochondrial respiratory chain function, together with some increase in citrate synthase and aconitase activities. Thus, we have demonstrated that human frataxin can effectively substitute for endogenous murine frataxin in the null mutant. Our studies are of immediate consequence for the generation of Friedreich's ataxia transgenic mouse models, and further contribute to the accumulating knowledge of human-mouse functional gene replacement systems. Electronic Publication  相似文献   

19.
Friedreich ataxia is due to insufficient levels of frataxin, a mitochondrial iron chaperone that shields this metal from reactive oxygen species (ROS) and renders it bioavailable as Fe II. Frataxin participates in the synthesis of iron-sulfur clusters (ISCs), cofactors of several enzymes, including mitochondrial and cytosolic aconitase, complexes I, II and III of the respiratory chain, and ferrochelatase. It also plays a role in the maintenance of ISCs, in particular for mitochondrial aconitase. A role of frataxin in heme synthesis has been postulated, but is controversial. Insufficient frataxin leads to deficit of ISC enzymes and energy deficit. Iron levels increase in mitochondria. Oxidative stress may result from respiratory chain dysfunction and from direct reaction between iron and ROS. Stress pathways are activated that may lead to apoptosis or other forms of cell death. The basis for the selective vulnerability of specific neurons, like sensory neurons, is still unknown.  相似文献   

20.
Friedreich’s ataxia is an inherited neurological disorder characterised by mitochondrial dysfunction and increased susceptibility to oxidative stress. At present, no therapy has been shown to reduce disease progression. Strategies being trialled to treat Friedreich’s ataxia include drugs that improve mitochondrial function and reduce oxidative injury. In addition, stem cells have been investigated as a potential therapeutic approach. We have used siRNA-induced knockdown of frataxin in SH-SY5Y cells as an in vitro cellular model for Friedreich’s ataxia. Knockdown of frataxin protein expression to levels detected in patients with the disorder was achieved, leading to decreased cellular viability, increased susceptibility to hydrogen peroxide-induced oxidative stress, dysregulation of key anti-oxidant molecules and deficiencies in both cell proliferation and differentiation. Bone marrow stem cells are being investigated extensively as potential treatments for a wide range of neurological disorders, including Friedreich’s ataxia. The potential neuroprotective effects of bone marrow-derived mesenchymal stem cells were therefore studied using our frataxin-deficient cell model. Soluble factors secreted by mesenchymal stem cells protected against cellular changes induced by frataxin deficiency, leading to restoration in frataxin levels and anti-oxidant defences, improved survival against oxidative stress and stimulated both cell proliferation and differentiation down the Schwann cell lineage. The demonstration that mesenchymal stem cell-derived factors can restore cellular homeostasis and function to frataxin-deficient cells further suggests that they may have potential therapeutic benefits for patients with Friedreich’s ataxia.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号