Proteomic analysis of hearts from frataxin knockout mice: Marked rearrangement of energy metabolism, a response to cellular stress and altered expression of proteins involved in cell structure, motility and metabolism

Šuták, Robert; Xu, Xiangcong; Whitnall, Megan; Kashem, Mohammed A.; Vyoral, Daniel; Richardson, Des R.

doi:10.1002/pmic.200701049

Cited by 34 publications

(23 citation statements)

References 58 publications

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“…29 As already mentioned, FXN plays an important role in mitochondrial iron homeostasis. 12,13 In wild-type mice, we found increased levels of FXN mature protein after lesion, whereas the precursor form was not elevated. In contrast, although levels of the precursor protein were significantly increased in transgenic as compared to wildtype mice, the mature protein was not changed after lesion.…”

Section: Frataxin Overexpression Increases Rgc Survival After Acute Imentioning

confidence: 64%

“…10,11 Although the biological functions of FXN are still not fully understood, the protein serves important functions in iron homeostasis and biogenesis of iron-sulphur clusters in active sites of the complexes I and II of the mitochondrial electron transport chain and aconitase. 12,13 Cells that are deficient in FXN appear to be less efficient at generating natural antioxidant factors.14 There is evidence indicating that increasing FXN reduces the effects of oxidative stress and increases cell survival after oxidative stress-induced cell death. 3,4,15,16 Retinal ischemia/hypoxia is a complication of ocular diseases such as diabetic retinopathy, retinopathy of prematurity, and glaucoma.…”

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confidence: 99%

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Increased Frataxin Levels Protect Retinal Ganglion Cells After Acute Ischemia/Reperfusion in the Mouse Retina In Vivo

Schultz

Witte

Schmeer

2016

Invest. Ophthalmol. Vis. Sci.

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Citation: Schultz R, Witte OW, Schmeer C. Increased frataxin levels protect retinal ganglion cells after acute ischemia/reperfusion in the mouse retina in vivo. Invest Ophthalmol Vis Sci. 2016;57:4115-4124. DOI:10.1167/iovs.16-19260 PURPOSE. The mitochondrial protein frataxin (FXN) is highly expressed in metabolically active tissues and has been shown to improve cell survival in response to oxidative stress after ischemia. Retinal ischemia/hypoxia is a complication of ocular diseases such as diabetic retinopathy and glaucoma. There are no effective therapeutic approaches currently available. This study was performed to evaluate the neuroprotective effects of FXN after acute retinal ischemia/reperfusion in vivo. METHODS.Retinal ischemia/reperfusion was induced in adult wild-type and FXN-overexpressing mice by transient elevation of intraocular pressure (IOP) for 45 minutes. Expression of FXN was evaluated by quantitative (q)RT-PCR and Western blot analysis between 6 and 48 hours after ischemia. Retinal ganglion cell (RGC) survival was determined with immunofluorescent staining and fluorescence microscopy 14 days after lesion. Expression of hypoxiainducible factors Hif-1a and Hif-2a and of oxidative stress markers heme oxygenase-1 (Hmox1), glutathione peroxidase 1 (Gpx1), superoxidase dismutase 1 and 2 (Sod1, Sod2), and catalase was evaluated by qRT-PCR.RESULTS. Endogenous FXN levels were upregulated for up to 24 hours after retinal ischemia in vivo. Retinal ganglion cell survival was significantly improved in FXN-overexpressing mice 14 days after ischemia. Expression of antioxidative enzymes Gpx1, Sod2, and catalase was significantly increased in FXN-overexpressing mice after lesion. CONCLUSIONS.Retinal FXN levels are increased in response to ischemia. Furthermore, elevated FXN levels had a clear neuroprotective effect as shown by increased ganglion cell survival after acute retinal ischemia/reperfusion. Frataxin's neuroprotective effect was associated with an upregulation of antioxidative enzymes. The data suggest that FXN induces neuroprotection by decreasing oxidative stress.Keywords: frataxin, retinal ischemia, retinal ganglion cell, antioxidants F rataxin (FXN) is a nuclear-encoded mitochondrial protein highly conserved among eukaryotes. The mouse gene (Frda) encodes a 207-amino acid protein showing 73% amino acid identity to its human counterpart.1 It is abundantly expressed in metabolically active tissues such as liver, skeletal and cardiac muscle, and brain.1 In the retina of normal mice, immunoreactivity to FXN is found in the external and internal plexiform layers, the ganglion cell layer, and the inner nuclear layer.2 Frataxin deficiency is closely related to Friedreich ataxia (FRDA), a neurodegenerative disease associated with abnormal influx of iron into the mitochondria, which increases the susceptibility of the nervous system to oxidative stress. [3][4][5][6][7][8] Furthermore, complete absence of FXN leads to early embryonic lethality in transgenic mice. Conditional FXN knockout strains for st...

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Section: Frataxin Overexpression Increases Rgc Survival After Acute Imentioning

confidence: 64%

mentioning

confidence: 99%

Increased Frataxin Levels Protect Retinal Ganglion Cells After Acute Ischemia/Reperfusion in the Mouse Retina In Vivo

Schultz

Witte

Schmeer

2016

Invest. Ophthalmol. Vis. Sci.

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“…In this study, Fdxr up-regulation may be related to heme a synthesis, which is required for oxidative phosphorylation. Our proteomic studies have shown that frataxin depletion leads to energy metabolism deficiencies in MCK mutants, leading to metabolic compensation in an attempt to overcome the deficit (24). This may explain the Fdxr up-regulation.…”

Section: Frataxin Deficiency In the Heart Leads To Suppression Of Promentioning

confidence: 91%

“…Our aim was to explore the changes in iron metabolism due to frataxin deficiency. These mutants exhibit classical traits of the cardiomyopathy in Friedreich's ataxia, including cardiac hypertrophy, ISC enzyme deficiency, and marked mitochondrial iron accumulation (7,11,24). Thus, this model closely reflects the cardiac pathology in Friedreich's ataxia.…”

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confidence: 99%

Elucidation of the mechanism of mitochondrial iron loading in Friedreich's ataxia by analysis of a mouse mutant

Huang

Becker

Whitnall

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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231

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We used the muscle creatine kinase (MCK) conditional frataxin knockout mouse to elucidate how frataxin deficiency alters iron metabolism. This is of significance because frataxin deficiency leads to Friedreich's ataxia, a disease marked by neurologic and cardiologic degeneration. Using cardiac tissues, we demonstrate that frataxin deficiency leads to down-regulation of key molecules involved in 3 mitochondrial utilization pathways: iron-sulfur cluster (ISC) synthesis (iron-sulfur cluster scaffold protein1/2 and the cysteine desulferase Nfs1), mitochondrial iron storage (mitochondrial ferritin), and heme synthesis (5-aminolevulinate dehydratase, coproporphyrinogen oxidase, hydroxymethylbilane synthase, uroporphyrinogen III synthase, and ferrochelatase). This marked decrease in mitochondrial iron utilization and resultant reduced release of heme and ISC from the mitochondrion could contribute to the excessive mitochondrial iron observed. This effect is compounded by increased iron availability for mitochondrial uptake through (i) transferrin receptor1 up-regulation, increasing iron uptake from transferrin; (ii) decreased ferroportin1 expression, limiting iron export; (iii) increased expression of the heme catabolism enzyme heme oxygenase1 and down-regulation of ferritin-H and -L, both likely leading to increased ''free iron'' for mitochondrial uptake; and (iv) increased expression of the mammalian exocyst protein Sec15l1 and the mitochondrial iron importer mitoferrin-2 (Mfrn2), which facilitate cellular iron uptake and mitochondrial iron influx, respectively. Our results enable the construction of a model explaining the cytosolic iron deficiency and mitochondrial iron loading in the absence of frataxin, which is important for understanding the pathogenesis of Friedreich's ataxia.heme synthesis ͉ iron ͉ transferrin ͉ frataxin

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“…This ISC enzyme is critical for MIT energy metabolism and is markedly decreased in the mutant compared to WT (5,19). When we examined 8.5-weekold mice treated with vehicle or PIH/DFO, it was clear the chelators did not prevent the decrease in SDHA expression (Fig.…”

Section: Marked Alterations In Cytosolic 59 Fe Distribution Within Fementioning

confidence: 99%

The MCK mouse heart model of Friedreich's ataxia: Alterations in iron-regulated proteins and cardiac hypertrophy are limited by iron chelation

Whitnall

Rahmanto

Šuták

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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110

148

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There is no effective treatment for the cardiomyopathy of the most common autosomal recessive ataxia, Friedreich's ataxia (FA). The identification of potentially toxic mitochondrial (MIT) iron (Fe) deposits in FA suggests that Fe plays a role in its pathogenesis. This study used the muscle creatine kinase conditional frataxin (Fxn) knockout (mutant) mouse model that reproduces the classical traits associated with cardiomyopathy in FA. We examined the mechanisms responsible for the increased cardiac MIT Fe loading in mutants. Moreover, we explored the effect of Fe chelation on the pathogenesis of the cardiomyopathy. Our investigation showed that increased MIT Fe in the myocardium of mutants was due to marked transferrin Fe uptake, which was the result of enhanced transferrin receptor 1 expression. In contrast to the mitochondrion, cytosolic ferritin expression and the proportion of cytosolic Fe were decreased in mutant mice, indicating cytosolic Fe deprivation and markedly increased MIT Fe targeting. These studies demonstrated that loss of Fxn alters cardiac Fe metabolism due to pronounced changes in Fe trafficking away from the cytosol to the mitochondrion. Further work showed that combining the MITpermeable ligand pyridoxal isonicotinoyl hydrazone with the hydrophilic chelator desferrioxamine prevented cardiac Fe loading and limited cardiac hypertrophy in mutants but did not lead to overt cardiac Fe depletion or toxicity. Fe chelation did not prevent decreased succinate dehydrogenase expression in the mutants or loss of cardiac function. In summary, we show that loss of Fxn markedly alters cellular Fe trafficking and that Fe chelation limits myocardial hypertrophy in the mutant.ferritin ͉ iron chelators ͉ mitochondria ͉ transferrin receptor ͉ frataxin

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Proteomic analysis of hearts from frataxin knockout mice: Marked rearrangement of energy metabolism, a response to cellular stress and altered expression of proteins involved in cell structure, motility and metabolism

Cited by 34 publications

References 58 publications

Increased Frataxin Levels Protect Retinal Ganglion Cells After Acute Ischemia/Reperfusion in the Mouse Retina In Vivo

Increased Frataxin Levels Protect Retinal Ganglion Cells After Acute Ischemia/Reperfusion in the Mouse Retina In Vivo

Elucidation of the mechanism of mitochondrial iron loading in Friedreich's ataxia by analysis of a mouse mutant

The MCK mouse heart model of Friedreich's ataxia: Alterations in iron-regulated proteins and cardiac hypertrophy are limited by iron chelation

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