A Developmentally Regulated Aconitase Related to Iron-regulatory Protein-1 Is Localized in the Cytoplasm and in the Mitochondrion of Trypanosoma brucei

Saas, Joachim; Ziegelbauer, Karl; Haeseler, Arndt von; Fast, Beate; Boshart, Michael

doi:10.1074/jbc.275.4.2745

Cited by 85 publications

(72 citation statements)

References 106 publications

(83 reference statements)

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“…A recent study shows that aconitase along with other glyoxylate and Krebs cycle enzymes are increased in A. thaliana during infection with Pseudomonas syringae, suggesting a role for aconitase in plant defense against pathogens (40). In T. brucei, IRP-1 expression is developmentally regulated, increasing in procyclic stage when Krebs cycle enzymes also increase (17). Whether IRP-1 functions in a glyoxylate pathway in T. brucei is unclear.…”

Section: Fig 6 Aconitase Activity Is Regulated By Iron In Wormsmentioning

confidence: 99%

“…Our data show that GEI-22/ACO-1 lacks RNA binding activity, which is consistent with the lack of discernible IREs in the C. elegans genome. Other IRP-1s, such as T. brucei (17), A. thaliana (13), and Nicotiana tabacum (15), were shown to be aconitases, but RNA binding activity was not reported, and it is probable that these proteins also do not bind RNA. However, some nonvertebrate IRP-1s bind RNA.…”

Section: Fig 6 Aconitase Activity Is Regulated By Iron In Wormsmentioning

confidence: 99%

“…IRP-1s share a high degree of amino acid identity among different species. For example, mammalian IRP-1s are Ͼ90% identical and are highly homologous to IRP-1s from other organisms, including Caenorhabditis elegans (64% identity) (16), Arabidopsis thaliana (59% identity) plants (13), Trypanosome brucei (64% identity) (17), and Escherichia coli (52% identity) (10). In contrast, IRP-1s share only ϳ20% amino acid identity to mitochondrial aconitases.…”

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confidence: 99%

“…IRP-1s have been identified in a wide variety of organisms, including bacteria (10 -12), plants (13)(14)(15), and animals (16,17). IRP-1s share a high degree of amino acid identity among different species.…”

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confidence: 99%

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Cytosolic Aconitase and Ferritin Are Regulated by Iron inCaenorhabditis elegans

Gourley

Parker

Jones

et al. 2003

Journal of Biological Chemistry

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Iron regulatory protein-1 (IRP-1) is a cytosolic RNAbinding protein that is a regulator of iron homeostasis in mammalian cells. IRP-1 binds to RNA structures, known as iron-responsive elements, located in the untranslated regions of specific mRNAs, and it regulates the translation or stability of these mRNAs. Iron regulates IRP-1 activity by converting it from an RNA-binding apoprotein into a [4Fe-4S] cluster protein exhibiting aconitase activity. IRP-1 is widely found in prokaryotes and eukaryotes. Here, we report the biochemical characterization and regulation of an IRP-1 homolog in Caenorhabditis elegans (GEI-22/ACO-1). GEI-22/ACO-1 is expressed in the cytosol of cells of the hypodermis and the intestine. Like mammalian IRP-1/aconitases, GEI-22/ ACO-1 exhibits aconitase activity and is post-translationally regulated by iron. Although GEI-22/ACO-1 shares striking resemblance to mammalian IRP-1, it fails to bind RNA. This is consistent with the lack of iron-responsive elements in the C. elegans ferritin genes, ftn-1 and ftn-2. While mammalian ferritin H and L mRNAs are translationally regulated by iron, the amounts of C. elegans ftn-1 and ftn-2 mRNAs are increased by iron and decreased by iron chelation. Excess iron did not significantly alter worm development but did shorten their life span. These studies indicated that iron homeostasis in C. elegans shares some similarities with those of vertebrates.Iron is an essential element required for growth and survival of most organisms. The importance of iron is implicit in the role it plays in oxygen transport and heme synthesis as well as its ability to serve as a cofactor for enzymes involved in a variety of biological processes including DNA synthesis, energy production, and neurotransmitter synthesis. Abnormally high concentration of cellular iron is toxic due to its ability to catalyze the generation of free radicals that damage DNA, lipids, and proteins. In humans, the accumulation of excess cellular iron can result in cirrhosis, arthritis, cardiomyopathy, diabetes mellitus, and increased risk of cancer and heart disease. To provide adequate iron for cellular needs yet prevent the accumulation of excess iron, the concentration of iron within cells is tightly controlled.In vertebrates, the iron regulatory proteins 1 and 2 (IRP-1 and IRP-2) 1 regulate iron homeostasis. IRPs are cytosolic RNAbinding proteins that regulate the translation or the stability of mRNAs encoding proteins involved in iron and energy homeostasis (1-4). IRPs bind to RNA stem-loop structures, known as iron-responsive elements (IREs), that are located in either the 5Ј-or 3Ј-untranslated regions (UTRs) of specific mRNAs. These mRNAs encode proteins involved in iron storage (ferritin), iron utilization (erythroid aminolevilunate synthase and mitochondrial aconitase), and iron transport (transferrin receptor and divalent metal transporter-1). When iron is scarce, IRP binding to the 5Ј IRE in ferritin mRNA represses translation, whereas IRP binding to the 3Ј IREs in the transferrin receptor mRNA...

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Section: Fig 6 Aconitase Activity Is Regulated By Iron In Wormsmentioning

confidence: 99%

Section: Fig 6 Aconitase Activity Is Regulated By Iron In Wormsmentioning

confidence: 99%

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confidence: 99%

mentioning

confidence: 99%

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Cytosolic Aconitase and Ferritin Are Regulated by Iron inCaenorhabditis elegans

Gourley

Parker

Jones

et al. 2003

Journal of Biological Chemistry

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“…Saccharomyces cerevisiae contains only a single aconitase gene, encoding a mitochondrial enzyme, though low amounts of aconitase can be detected in the cytosol (14). Aconitase activity in both mitochondria and cytosol is also documented for the more primitive protozoan parasites Trypanosoma brucei and Plasmodium falciparum, each of which contains a single aconitase gene (15,16). Conversely, mitochondrial and cytosolic aconitases are encoded by different genes in Caenorhabditis elegans (17,18).…”

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confidence: 99%

Of Two Cytosolic Aconitases Expressed in Drosophila, Only One Functions as an Iron-regulatory Protein

Lind

Missirlis

Melefors

et al. 2006

Journal of Biological Chemistry

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In mammalian cells, iron homeostasis is largely regulated by post-transcriptional control of gene expression through the binding of iron-regulatory proteins (IRP1 and IRP2) to iron-responsive elements (IREs) contained in the untranslated regions of target mRNAs. IRP2 is the dominant iron sensor in mammalian cells under normoxia, but IRP1 is the more ancient protein in evolutionary terms and has an additional function as a cytosolic aconitase. The Caenorhabditis elegans genome does not contain an IRP2 homolog or identifiable IREs; its IRP1 homolog has aconitase activity but does not bind to mammalian IREs. The Drosophila genome offers an evolutionary intermediate containing two IRP1-like proteins (IRP-1A and IRP-1B) and target genes with IREs. Here, we used purified recombinant IRP-1A and IRP-1B from Drosophila melanogaster and showed that only IRP-1A can bind to IREs, although both proteins possess aconitase activity. These results were also corroborated in whole-fly homogenates from transgenic flies that overexpress IRP-1A and IRP-1B in their fat bodies. Ubiquitous and muscle-specific overexpression of IRP-1A, but not of IRP-1B, resulted in pre-adult lethality, underscoring the importance of the biochemical difference between the two proteins. Domain-swap experiments showed that multiple amino acid substitutions scattered throughout the IRP1 domains are synergistically required for conferring IRE binding activity. Our data suggest that as a first step during the evolution of the IRP/IRE system, the ancient cytosolic aconitase was duplicated in insects with one variant acquiring IRE-specific binding.Iron is required for aerobic metabolism and is actively sensed, sequestered, and regulated by organisms, including hosts and pathogens, that often compete for metal acquisition (1). In multicellular organisms, signals exist for systemic control of iron metabolism (2). One of the central regulators of cellular iron metabolism is the IRP/IRE system (3). In brief, absence of iron is sensed by IRP1 and IRP2, which then bind to ironresponsive elements (IREs) 4 in the 5Ј-untranslated regions of mRNAs encoding several storage or consumer iron proteins, inhibiting their translation. IRP1 and IRP2 also bind to IREs in the 3Ј-untranslated regions of mRNAs encoding proteins that function in cellular iron import, stabilizing the transcripts and enhancing iron sequestration. There is much interest in defining how IRP1 and IRP2 sense iron levels. IRP1 interconverts between an iron-sulfur protein with aconitase activity and the apoprotein that binds to the IRE (4). IRP2 has an additional 73-amino acid domain inserted in the protein and has no aconitase activity (5, 6). Extensive analysis of knock-out mice has led to the conclusion that IRP2 dominates mammalian cellular iron metabolism (7). IRP1 also contributes to the regulation of cellular iron metabolism, albeit to a lesser extent, because its iron-sulfur cluster is efficiently repaired and the protein functions mostly as an aconitase (8 -10). It is also well established that b...

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A proteomic approach to identify developmentally regulated proteins in Leishmania infantum

2002

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We used comparative two-dimensional gel electrophoresis (2-DE) and mass spectrometry methodologies to highlight and identify proteins that are differentially expressed in the intracellular stage of the parasite Leishmania donovani infantum, a causative agent of visceral leishmaniasis. During its digenetic life cycle, Leishmania alternates between the alimentary tract of the sandfly vector as an extracellular promastigote and the acidic phagolysosomes of macrophage cells as an intracellular amastigote. Proteins differentially expressed in the intracellular form of the parasite are thought to be important for intracellular survival and pathogenesis. We used narrow pH range strips for isoelectric focusing to resolve soluble proteins of both developmental stages of L. infantum. More than 62 proteins differentially expressed in amastigotes were detected among approximately 2000 protein spots resolved by 2-DE. A quadrupole time-of-flight analysis of few selected protein spots, specifically expressed in the amastigote stage, permitted the identification of two proteins, part of the energetic metabolism pathways, the isocitrate dehydrogenase and the glycolytic enzyme triosephosphate isomerase. The kinetic parameters of these two enzymes were measured in both developmental stages of the parasite and their activity was indeed found to be higher in amastigotes. These findings bring a new insight in our understanding of metabolic and energy requirements of the intracellular form of Leishmania. Comparative analysis of the proteome of both developmental stages of the protozoan parasite Leishmania should permit the identification of protein candidates for the development of vaccines and new drugs.

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A Developmentally Regulated Aconitase Related to Iron-regulatory Protein-1 Is Localized in the Cytoplasm and in the Mitochondrion of Trypanosoma brucei

Cited by 85 publications

References 106 publications

Cytosolic Aconitase and Ferritin Are Regulated by Iron inCaenorhabditis elegans

Cytosolic Aconitase and Ferritin Are Regulated by Iron inCaenorhabditis elegans

Of Two Cytosolic Aconitases Expressed in Drosophila, Only One Functions as an Iron-regulatory Protein

A proteomic approach to identify developmentally regulated proteins in Leishmania infantum

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