scholarly journals Rim2, a pyrimidine nucleotide exchanger, is needed for iron utilization in mitochondria

2011 ◽  
Vol 440 (1) ◽  
pp. 137-146 ◽  
Author(s):  
Heeyong Yoon ◽  
Yan Zhang ◽  
Jayashree Pain ◽  
Elise R. Lyver ◽  
Emmanuel Lesuisse ◽  
...  
Keyword(s):  
Iron Transport ◽  
Wild Type ◽  
Mitochondrial Carrier ◽  
Pyrimidine Nucleotide ◽  
Mitochondrial Transporter ◽  
Mitochondrial Iron ◽  
Mitochondrial Carrier Protein ◽  
Synthetically Lethal ◽  
Yeast Mutants ◽  
Iron Utilization

Mitochondria transport and utilize iron for the synthesis of haem and Fe–S clusters. Although many proteins are known to be involved in these processes, additional proteins are likely to participate. To test this hypothesis, in the present study we used a genetic screen looking for yeast mutants that are synthetically lethal with the mitochondrial iron carriers Mrs3 and Mrs4. Several genes were identified, including an isolate mutated for Yfh1, the yeast frataxin homologue. All such triple mutants were complemented by increased expression of Rim2, another mitochondrial carrier protein. Rim2 overexpression was able to enhance haem and Fe–S cluster synthesis in wild-type or Δmrs3/Δmrs4 backgrounds. Conversely Rim2 depletion impaired haem and Fe–S cluster synthesis in wild-type or Δmrs3/Δmrs4 backgrounds, indicating a unique requirement for this mitochondrial transporter for these processes. Rim2 was previously shown to mediate pyrimidine exchange in and out of vesicles. In the present study we found that isolated mitochondria lacking Rim2 exhibited concordant iron defects and pyrimidine transport defects, although the connection between these two functions is not explained. When organellar membranes were ruptured to bypass iron transport, haem synthesis from added iron and porphyrin was still markedly deficient in Rim2-depleted mitochondrial lysate. The results indicate that Rim2 is a pyrimidine exchanger with an additional unique function in promoting mitochondrial iron utilization.

scholarly journals Role of YHM1, encoding a mitochondrial carrier protein, in iron distribution of yeast

2004 ◽  
Vol 378 (2) ◽  
pp. 599-607 ◽  
Author(s):  
Emmanuel LESUISSE ◽  
Elise R. LYVER ◽  
Simon A. B. KNIGHT ◽  
Andrew DANCIS
Keyword(s):  
Protein Family ◽  
Carrier Protein ◽  
Ferric Reductase ◽  
Mitochondrial Carrier ◽  
Mitochondrial Dna Damage ◽  
Cellular Iron ◽  
Mitochondrial Transporter ◽  
Large Protein Family ◽  
Mitochondrial Carrier Protein ◽  
Mitochondrial Carrier Proteins

Mitochondrial carrier proteins are a large protein family, consisting of 35 members in Saccharomyces cerevisiae. Members of this protein family have been shown to transport varied substrates from cytoplasm to mitochondria or mitochondria to cytoplasm, although many family members do not have assigned substrates. We speculated whether one or more of these transporters will play a role in iron metabolism. Haploid yeast strains each deleted for a single mitochondrial carrier protein were analysed for alterations in iron homoeostasis. The strain deleted for YHM1 was characterized by increased and misregulated surface ferric reductase and high-affinity ferrous transport activities. Siderophore uptake from different sources was also increased, and these effects were dependent on the AFT1 iron sensor regulator. Mutants of YHM1 converted into rho°, consistent with secondary mitochondrial DNA damage from mitochondrial iron accumulation. In fact, in the Δyhm1 mutant, iron was found to accumulate in mitochondria. The accumulated iron showed decreased availability for haem synthesis, measured in isolated mitochondria using endogenously available metals and added porphyrins. The phenotypes of Δyhm1 mutants indicate a role for this mitochondrial transporter in cellular iron homoeostasis.

The mitochondrial carrier Rim2 co-imports pyrimidine nucleotides and iron

2013 ◽  
Vol 455 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Elisabeth M. Froschauer ◽  
Nicole Rietzschel ◽  
Melanie R. Hassler ◽  
Markus Binder ◽  
Rudolf J. Schweyen ◽  
...  
Keyword(s):  
Metal Ions ◽  
Divalent Metal ◽  
Divalent Metal Ions ◽  
Protein Maturation ◽  
Pyrimidine Nucleotides ◽  
Mitochondrial Carrier ◽  
S Protein ◽  
Pyrimidine Nucleotide ◽  
Iron Supply ◽  
Mitochondrial Iron

Mitochondrial iron uptake is of key importance both for organelle function and cellular iron homoeostasis. The mitochondrial carrier family members Mrs3 and Mrs4 (homologues of vertebrate mitoferrin) function in organellar iron supply, yet other low efficiency transporters may exist. In Saccharomyces cerevisiae, overexpression of RIM2 (MRS12) encoding a mitochondrial pyrimidine nucleotide transporter can overcome the iron-related phenotypes of strains lacking both MRS3 and MRS4. In the present study we show by in vitro transport studies that Rim2 mediates the transport of iron and other divalent metal ions across the mitochondrial inner membrane in a pyrimidine nucleotide-dependent fashion. Mutations in the proposed substrate-binding site of Rim2 prevent both pyrimidine nucleotide and divalent ion transport. These results document that Rim2 catalyses the co-import of pyrimidine nucleotides and divalent metal ions including ferrous iron. The deletion of RIM2 alone has no significant effect on mitochondrial iron supply, Fe–S protein maturation and haem synthesis. However, RIM2 deletion in mrs3/4Δ cells aggravates their Fe–S protein maturation defect. We conclude that under normal physiological conditions Rim2 does not play a significant role in mitochondrial iron acquisition, yet, in the absence of the main iron transporters Mrs3 and Mrs4, this carrier can supply the mitochondrial matrix with iron in a pyrimidine-nucleotide-dependent fashion.

scholarly journals SEC3 Mutations Are Synthetically Lethal With Profilin Mutations and Cause Defects in Diploid-Specific Bud-Site Selection

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 495-510 ◽  
Author(s):  
B K Haarer ◽  
A Corbett ◽  
Y Kweon ◽  
A S Petzold ◽  
P Silver ◽  
...  
Keyword(s):  
Site Selection ◽  
Secretory Pathway ◽  
Wild Type ◽  
Synthetic Lethal ◽  
Abnormal Growth ◽  
Colony Color ◽  
Synthetically Lethal ◽  
Homozygous Diploid ◽  
Bud Site ◽  
Wild Type Yeast

Abstract Replacement of the wild-type yeast profilin gene (PFY1) with a mutated form (pfy1-111) that has codon 72 changed to encode glutamate rather than arginine results in defects similar to, but less severe than, those that result from complete deletion of the profilin gene. We have used a colony color-sectoring assay to identify mutations that cause pfy1-111, but not wild-type, cells to be inviable. These profilin synthetic lethal (psl) mutations result in various degrees of abnormal growth, morphology, and temperature sensitivity in PFY1 cells. We have examined psl1 strains in the most detail. Interestingly, these strains display a diploid-specific defect in bud-site selection; haploid strains bud normally, while homozygous diploid strains show a dramatic increase in random budding. We discovered that PSL1 is the late secretory gene, SEC3, and have found that mutations in several other late secretory genes are also synthetically lethal with pfy1-111. Our results are likely to reflect an interdependence between the actin cytoskeleton and secretory processes in directing cell polarity and growth. Moreover, they indicate that the secretory pathway is especially crucial for maintaining budding polarity in diploids.

scholarly journals The calcium-dependent ATP-Mg/Pi mitochondrial carrier is a target of glucose-induced calcium signalling in Saccharomyces cerevisiae

2005 ◽  
Vol 392 (3) ◽  
pp. 537-544 ◽  
Author(s):  
Santiago Cavero ◽  
Javier Traba ◽  
Araceli Del Arco ◽  
Jorgina Satrústegui
Keyword(s):  
Calcium Binding ◽  
Mitochondrial Protein ◽  
Calcium Signalling ◽  
Cytosolic Calcium ◽  
Calcium Signal ◽  
Transport Activity ◽  
Wild Type ◽  
Binding Motifs ◽  
Mitochondrial Carrier ◽  
Calcium Dependent

Sal1p is a mitochondrial protein that belongs to the SCaMC (short calcium-binding mitochondrial carrier) subfamily of mitochondrial carriers. The presence of calcium-binding motifs facing the extramitochondrial space allows the regulation of the transport activity of these carriers by cytosolic calcium and provides a new mechanism to transduce calcium signals in mitochondria without the requirement of calcium entry in the organelle. We have studied its transport activity, finding that it is a carboxyatractyloside-resistant ATP-Mg carrier. Mitochondria from a disruption mutant of SAL1 have a 50% reduction in the uptake of ATP. We have also found a clear stimulation of ATP-transport activity by calcium, with an S0.5 of approx. 30 μM. Our results also suggest that Sal1p is a target of the glucose-induced calcium signal which is non-essential in wild-type cells, but becomes essential for transport of ATP into mitochondria in yeast lacking ADP/ATP translocases.

scholarly journals The mitochondrial iron exporter genes MMT1 and MMT2 in yeast are transcriptionally regulated by Aft1 and Yap1

2020 ◽  
Vol 295 (6) ◽  
pp. 1716-1726 ◽  
Author(s):  
Liangtao Li ◽  
Sophie Bertram ◽  
Jerry Kaplan ◽  
Xuan Jia ◽  
Diane M. Ward
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Promoter Region ◽  
Iron Transport ◽  
Mitochondrial Proteins ◽  
Upstream Region ◽  
Iron Sulfur Cluster ◽  
High Affinity ◽  
Iron Sulfur ◽  
Mitochondrial Iron

Budding yeast (Saccharomyces cerevisiae) responds to low cytosolic iron by up-regulating the expression of iron import genes; iron import can reflect iron transport into the cytosol or mitochondria. Mmt1 and Mmt2 are nuclearly encoded mitochondrial proteins that export iron from the mitochondria into the cytosol. Here we report that MMT1 and MMT2 expression is transcriptionally regulated by two pathways: the low-iron-sensing transcription factor Aft1 and the oxidant-sensing transcription factor Yap1. We determined that MMT1 and MMT2 expression is increased under low-iron conditions and decreased when mitochondrial iron import is increased through overexpression of the high-affinity mitochondrial iron importer Mrs3. Moreover, loss of iron-sulfur cluster synthesis induced expression of MMT1 and MMT2. We show that exposure to the oxidant H2O2 induced MMT1 expression but not MMT2 expression and identified the transcription factor Yap1 as being involved in oxidant-mediated MMT1 expression. We defined Aft1- and Yap1-dependent transcriptional sites in the MMT1 promoter that are necessary for low-iron- or oxidant-mediated MMT1 expression. We also found that the MMT2 promoter contains domains that are important for regulating its expression under low-iron conditions, including an upstream region that appears to partially repress expression under low-iron conditions. Our findings reveal that MMT1 and MMT2 are induced under low-iron conditions and that the low-iron regulator Aft1 is required for this induction. We further uncover an Aft1-binding site in the MMT1 promoter sufficient for inducing MMT1 transcription and identify an MMT2 promoter region required for low iron induction.

Functional properties of transfected human DMT1 iron transporter

2000 ◽  
Vol 279 (6) ◽  
pp. G1265-G1273 ◽  
Author(s):  
Mark T. Worthington ◽  
Lauren Browne ◽  
Emily H. Battle ◽  
Roger Qi Luo
Keyword(s):  
Transition Metals ◽  
Iron Uptake ◽  
Iron Transport ◽  
Potential Role ◽  
Human Gene ◽  
Wild Type ◽  
Ph Optimum ◽  
Transfected Cells ◽  
Proton Current ◽  
Intestinal Enterocytes

Recently, mutation of the DMT1 gene has been discovered to cause ineffective intestinal iron uptake and abnormal body iron metabolism in the anemic Belgrade rat and mkmouse. DMT1 transports first-series transition metals, but only iron turns on an inward proton current. The process of iron transport was studied by transfection of human DMT1 into the COS-7 cell line. Native and epitope-tagged human DMT1 led to increased iron uptake. The human gene with the Belgrade rat mutation was found to have one-fifth of the activity of the wild-type protein. The pH optimum of human DMT1 iron uptake was 6.75, which is equivalent to the pH of the duodenal brush border. The transporter demonstrates uptake without saturation from 0 to 50 μM iron, recapitulating earlier studies of isolated intestinal enterocytes. Diethylpyrocarbonate inhibition of iron uptake in DMT1-transfected cells suggests a functional role for histidine residues. Finally, a model is presented that incorporates the selectivity of the DMT1 transporter for transition metals and a potential role for the inward proton current.

scholarly journals Peroxisome Maintenance Depends on De Novo Peroxisome Formation in Yeast Mutants Defective in Peroxisome Fission and Inheritance

2019 ◽  
Vol 20 (16) ◽  
pp. 4023 ◽  
Author(s):  
Justyna P. Wróblewska ◽  
Ida J. van der Klei
Keyword(s):  
De Novo ◽  
Hansenula Polymorpha ◽  
Yeast Cells ◽  
Wild Type ◽  
Double Deletion ◽  
Mother Cells ◽  
Yeast Mutants ◽  
Rescue Mechanism ◽  
Wild Type Yeast ◽  
In Cells

There is an ongoing debate on how peroxisomes form: by growth and fission of pre-existing peroxisomes or de novo from another membrane. It has been proposed that, in wild type yeast cells, peroxisome fission and careful segregation of the organelles over mother cells and buds is essential for organelle maintenance. Using live cell imaging we observed that cells of the yeast Hansenula polymorpha, lacking the peroxisome fission protein Pex11, still show peroxisome fission and inheritance. Also, in cells of mutants without the peroxisome inheritance protein Inp2 peroxisome segregation can still occur. In contrast, peroxisome fission and inheritance were not observed in cells of a pex11 inp2 double deletion strain. In buds of cells of this double mutant, new organelles likely appear de novo. Growth of pex11 inp2 cells on methanol, a growth substrate that requires functional peroxisomes, is retarded relative to the wild type control. Based on these observations we conclude that in H. polymorpha de novo peroxisome formation is a rescue mechanism, which is less efficient than organelle fission and inheritance to maintain functional peroxisomes.

scholarly journals Genetics and Virulence Association of the Shigella flexneri Sit Iron Transport System

2009 ◽  
Vol 77 (5) ◽  
pp. 1992-1999 ◽  
Author(s):  
Carolyn R. Fisher ◽  
Nicola M. L. L. Davies ◽  
Elizabeth E. Wyckoff ◽  
Zhengyu Feng ◽  
Edwin V. Oaks ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Transport System ◽  
Iron Transport ◽  
Shigella Flexneri ◽  
Lung Model ◽  
Mouse Lung ◽  
Wild Type ◽  
Insertion Elements ◽  
Wild Type Parent

ABSTRACT The sit-encoded iron transport system is present within pathogenicity islands in all Shigella spp. and some pathogenic Escherichia coli strains. The islands contain numerous insertion elements and sequences with homology to bacteriophage genes. The Shigella flexneri sit genes can be lost as a result of deletion within the island. The formation of deletions was dependent upon RecA and occurred at relatively high frequency. This suggests that the sit region is inherently unstable, yet sit genes are maintained in all of the clinical isolates tested. Characterization of the sitABCD genes in S. flexneri indicates that they encode a ferrous iron transport system, although the genes are induced aerobically. The sit genes provide a competitive advantage to S. flexneri growing within epithelial cells, and a sitA mutant is outcompeted by the wild type in cultured epithelial cells. The Sit system is also required for virulence in a mouse lung model. The sitA mutant was able to infect the mice and induce a protective immune response but was avirulent compared to its wild-type parent strain.

scholarly journals Recombination Can either Help Maintain Very Short Telomeres or Generate Longer Telomeres in Yeast Cells with Weak Telomerase Activity

2011 ◽  
Vol 10 (8) ◽  
pp. 1131-1142 ◽  
Author(s):  
Evelina Basenko ◽  
Zeki Topcu ◽  
Michael J. McEachern
Keyword(s):  
Homologous Recombination ◽  
Telomere Length ◽  
Telomerase Activity ◽  
Telomere Maintenance ◽  
Yeast Cells ◽  
Colony Morphology ◽  
Wild Type ◽  
Telomeric Repeats ◽  
Yeast Mutants ◽  
Derivatives Of

ABSTRACT Yeast mutants lacking telomerase are able to elongate their telomeres through processes involving homologous recombination. In this study, we investigated telomeric recombination in several mutants that normally maintain very short telomeres due to the presence of a partially functional telomerase. The abnormal colony morphology present in some mutants was correlated with especially short average telomere length and with a requirement for RAD52 for indefinite growth. Better-growing derivatives of some of the mutants were occasionally observed and were found to have substantially elongated telomeres. These telomeres were composed of alternating patterns of mutationally tagged telomeric repeats and wild-type repeats, an outcome consistent with amplification occurring via recombination rather than telomerase. Our results suggest that recombination at telomeres can produce two distinct outcomes in the mutants we studied. In occasional cells, recombination generates substantially longer telomeres, apparently through the roll-and-spread mechanism. However, in most cells, recombination appears limited to helping to maintain very short telomeres. The latter outcome likely represents a simplified form of recombinational telomere maintenance that is independent of the generation and copying of telomeric circles.

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