Extra-mitochondrial localisation of frataxin and its association with IscU1 during enterocyte-like differentiation of the human colon adenocarcinoma cell line Caco-2

Acquaviva, Fabio; Biase, Irene De; Nezi, Luigi; Ruggiero, Giuseppina; Tatangelo, Fabiana; Pisano, Carmela; Monticelli, Antonella; Garbi, Corrado; Acquaviva, Angela Maria; Cocozza, Sérgio

doi:10.1242/jcs.02516

Cited by 59 publications

(50 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…It will therefore be interesting to directly analyze the cellular role of huCfd1 and clarify the relative tasks of the two related proteins. In contrast, a functional involvement of cytosolic duplicates of mitochondrial ISC assembly components in the maturation of extramitochondrial Fe/S proteins was proposed (1,39,69). However, in contrast to the strong effects observed for the depletion of huNbp35 and IOP1, specific RNAi knockdown of the cytosolic version of huIsu1 did not impair Fe/S cluster maturation on IRP1 (70).…”

Section: Discussionmentioning

confidence: 85%

“…In human cells, the majority of the ISC assembly components huNfs1, huIsu1, huNfu1, and frataxin are present inside mitochondria, and yet low amounts have been detected in the cytosol and/or nucleus (1,39,69). Hence, a spatial duplication of the ISC assembly machinery has been proposed, suggesting a maturation mechanism in the cytosol-nucleus resembling that within mitochondria (54,71).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Human Nbp35 Is Essential for both Cytosolic Iron-Sulfur Protein Assembly and Iron Homeostasis

Stehling¹,

Netz²,

Niggemeyer³

et al. 2008

Molecular and Cellular Biology

118

View full text Add to dashboard Cite

The maturation of cytosolic iron-sulfur (Fe/S) proteins in mammalian cells requires components of the mitochondrial iron-sulfur cluster assembly and export machineries. Little is known about the cytosolic components that may facilitate the assembly process. Here, we identified the cytosolic soluble P-loop NTPase termed huNbp35 (also known as Nubp1) as an Fe/S protein, and we defined its role in the maturation of Fe/S proteins in HeLa cells. Depletion of huNbp35 by RNA interference decreased cell growth considerably, indicating its essential function. The deficiency in huNbp35 was associated with an impaired maturation of the cytosolic Fe/S proteins glutamine phosphoribosylpyrophosphate amidotransferase and iron regulatory protein 1 (IRP1), while mitochondrial Fe/S proteins remained intact. Consequently, huNbp35 is specifically involved in the formation of extramitochondrial Fe/S proteins. The impaired maturation of IRP1 upon huNbp35 depletion had profound consequences for cellular iron metabolism, leading to decreased cellular H-ferritin, increased transferrin receptor levels, and higher transferrin uptake. These properties clearly distinguished huNbp35 from its yeast counterpart Nbp35, which is essential for cytosolic-nuclear Fe/S protein assembly but plays no role in iron regulation. huNbp35 formed a complex with its close homologue huCfd1 (also known as Nubp2) in vivo, suggesting the existence of a heteromeric P-loop NTPase complex that is required for both cytosolic Fe/S protein assembly and cellular iron homeostasis.

show abstract

Section: Discussionmentioning

confidence: 85%

mentioning

confidence: 99%

Human Nbp35 Is Essential for both Cytosolic Iron-Sulfur Protein Assembly and Iron Homeostasis

Stehling¹,

Netz²,

Niggemeyer³

et al. 2008

Molecular and Cellular Biology

118

View full text Add to dashboard Cite

show abstract

“…Hence, FISH can be coupled to immunofluorescence, and it is possible to quantitatively monitor mitochondrial DNA, RNA and proteins simultaneously. The mitochondrial porin VDAC is frequently used for assessing the mitochondrial mass (Acquaviva et al, 2005), but its presence elsewhere than in mitochondria (De Pinto et al, 2010, see also supplementary material Fig. S1) led us to use TOM22 instead (Fig.…”

Section: Mtrip Reveals Heterogeneity In Mitochondrial Transcriptionmentioning

confidence: 99%

Large heterogeneity of mitochondrial DNA transcription and initiation of replication exposed by single-cell imaging

Châtre

Ricchetti

2012

Journal of Cell Science

View full text Add to dashboard Cite

SummaryMitochondrial DNA (mtDNA) replication and transcription are crucial for cell function, but these processes are poorly understood at the single-cell level. We describe a novel fluorescence in situ hybridization protocol, called mTRIP (mitochondrial transcription and replication imaging protocol), that reveals simultaneously mtDNA and RNA, and that can also be coupled to immunofluorescence for in situ protein examination. mTRIP reveals mitochondrial structures engaged in initiation of DNA replication by identification of a specific sequence in the regulatory D-loop, as well as unique transcription profiles in single human cells. We observe and quantify at least three classes of mitochondrial structures: (i) replication initiation active and transcript-positive (Ia-Tp); (ii) replication initiation silent and transcript-positive (Is-Tp); and (iii) replication initiation silent and transcript-negative (Is-Tn). Thus, individual mitochondria are dramatically heterogeneous within the same cell. Moreover, mTRIP exposes a mosaic of distinct nucleic acid patterns in the D-loop, including H-strand versus L-strand transcripts, and uncoupled rRNA transcription and mtDNA initiation of replication, which might have functional consequences in the regulation of the mtDNA. Finally, mTRIP identifies altered mtDNA processing in cells with unbalanced mtDNA content and function, including in human mitochondrial disorders. Thus, mTRIP reveals qualitative and quantitative alterations that provide additional tools for elucidating the dynamics of mtDNA processing in single cells and mitochondrial dysfunction in diseases.

show abstract

“…At least four processing products of FXN have thus far been characterized in vitro and/or in vivo. These products, which include FXN , FXN 56 -210 , FXN 78 -210 , and FXN , are normally generated upon mitochondrial import (19 -21), although FXN was also detected in the cytoplasmic fraction of cultured human cells (22,23). The amino termini of FXN and FXN 56 -210 were initially defined by our group via processing of radiolabeled FXN with purified mitochondrial processing peptidase (MPP).…”

Section: From the Departments Of Pediatric And Adolescent Medicine And mentioning

confidence: 99%

Normal and Friedreich Ataxia Cells Express Different Isoforms of Frataxin with Complementary Roles in Iron-Sulfur Cluster Assembly

Gakh

Bedekovics

Duncan

et al. 2010

Journal of Biological Chemistry

123

View full text Add to dashboard Cite

Friedreich ataxia (FRDA) is an autosomal recessive degenerative disease caused by insufficient expression of frataxin (FXN), a mitochondrial iron-binding protein required for Fe-S cluster assembly. The development of treatments to increase FXN levels in FRDA requires elucidation of the steps involved in the biogenesis of functional FXN. The FXN mRNA is translated to a precursor polypeptide that is transported to the mitochondrial matrix and processed to at least two forms, FXN Friedreich ataxia (FRDA) 2 (OMIM number 229300) is an autosomal recessive disease with an estimated incidence of 1:40,000. Most FRDA patients are apparently healthy at birth and during the first 5-10 years of life; then their gait becomes increasingly unsteady and wide-based and their voluntary movements uncoordinated. Many patients develop hypertrophic cardiomyopathy as well as diabetes, muscle weakness, and skeletal deformities. Although cognitive functions remain largely intact during disease progression, patients develop significant communication difficulties due to dysarthria, which is often compounded by vision and hearing loss. The majority of patients eventually become wheelchair-bound and dependent on others for most daily activities. Cardiac failure is a frequent cause of death at a young age (1).The FRDA locus encodes a mitochondrial protein designated frataxin (FXN), which is expressed at much lower levels in FRDA patients compared with normal individuals (2). In most patients, FXN deficiency results from the presence of an expanded GAA repeat in the first intron of the FRDA gene (2) that causes transcriptional silencing (reviewed in Ref.3). Although FXN is ubiquitously expressed, certain cells (dorsal root ganglia neurons, cardiomyocytes, and pancreatic beta cells) are exquisitely sensitive to frataxin depletion, and the degenerative loss of these particular cells accounts for the major clinical aspects of FRDA (1).Extensive biochemical studies have shown that frataxins across species are conserved iron-binding proteins that can either provide iron for Fe-S cluster assembly and heme synthesis or store iron as a stable mineral (reviewed in Ref. 4). The loss of these properties accounts for impaired iron utilization and increased iron toxicity linked to frataxin deficiency in the mitochondria of such diverse organisms as Saccharomyces cerevisiae, Drosophila, mouse, and humans (5-8). In humans, the mitochondrial alterations caused by FXN deficiency lead to tissue-specific changes in various cellular pathways involved in antioxidant, metabolic, and inflammatory responses, thereby amplifying the pathophysiology of FRDA and promoting disease progression (9 -13).

show abstract

Extra-mitochondrial localisation of frataxin and its association with IscU1 during enterocyte-like differentiation of the human colon adenocarcinoma cell line Caco-2

Cited by 59 publications

References 42 publications

Human Nbp35 Is Essential for both Cytosolic Iron-Sulfur Protein Assembly and Iron Homeostasis

Human Nbp35 Is Essential for both Cytosolic Iron-Sulfur Protein Assembly and Iron Homeostasis

Large heterogeneity of mitochondrial DNA transcription and initiation of replication exposed by single-cell imaging

Normal and Friedreich Ataxia Cells Express Different Isoforms of Frataxin with Complementary Roles in Iron-Sulfur Cluster Assembly

Contact Info

Product

Resources

About