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Atlante A, Valenti D. Mitochondria Have Made a Long Evolutionary Path from Ancient Bacteria Immigrants within Eukaryotic Cells to Essential Cellular Hosts and Key Players in Human Health and Disease. Curr Issues Mol Biol 2023; 45:4451-4479. [PMID: 37232752 PMCID: PMC10217700 DOI: 10.3390/cimb45050283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 05/04/2023] [Accepted: 05/17/2023] [Indexed: 05/27/2023] Open
Abstract
Mitochondria have made a long evolutionary path from ancient bacteria immigrants within the eukaryotic cell to become key players for the cell, assuming crucial multitasking skills critical for human health and disease. Traditionally identified as the powerhouses of eukaryotic cells due to their central role in energy metabolism, these chemiosmotic machines that synthesize ATP are known as the only maternally inherited organelles with their own genome, where mutations can cause diseases, opening up the field of mitochondrial medicine. More recently, the omics era has highlighted mitochondria as biosynthetic and signaling organelles influencing the behaviors of cells and organisms, making mitochondria the most studied organelles in the biomedical sciences. In this review, we will especially focus on certain 'novelties' in mitochondrial biology "left in the shadows" because, although they have been discovered for some time, they are still not taken with due consideration. We will focus on certain particularities of these organelles, for example, those relating to their metabolism and energy efficiency. In particular, some of their functions that reflect the type of cell in which they reside will be critically discussed, for example, the role of some carriers that are strictly functional to the typical metabolism of the cell or to the tissue specialization. Furthermore, some diseases in whose pathogenesis, surprisingly, mitochondria are involved will be mentioned.
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Affiliation(s)
- Anna Atlante
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), National Research Council (CNR), Via G. Amendola 122/O, 70126 Bari, Italy
| | - Daniela Valenti
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), National Research Council (CNR), Via G. Amendola 122/O, 70126 Bari, Italy
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Jacobs LJHC, Riemer J. Maintenance of small molecule redox homeostasis in mitochondria. FEBS Lett 2023; 597:205-223. [PMID: 36030088 DOI: 10.1002/1873-3468.14485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 08/18/2022] [Accepted: 08/21/2022] [Indexed: 01/26/2023]
Abstract
Compartmentalisation of eukaryotic cells enables fundamental otherwise often incompatible cellular processes. Establishment and maintenance of distinct compartments in the cell relies not only on proteins, lipids and metabolites but also on small redox molecules. In particular, small redox molecules such as glutathione, NAD(P)H and hydrogen peroxide (H2 O2 ) cooperate with protein partners in dedicated machineries to establish specific subcellular redox compartments with conditions that enable oxidative protein folding and redox signalling. Dysregulated redox homeostasis has been directly linked with a number of diseases including cancer, neurological disorders, cardiovascular diseases, obesity, metabolic diseases and ageing. In this review, we will summarise mechanisms regulating establishment and maintenance of redox homeostasis in the mitochondrial subcompartments of mammalian cells.
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Affiliation(s)
- Lianne J H C Jacobs
- Institute for Biochemistry and Center of Excellence for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany
| | - Jan Riemer
- Institute for Biochemistry and Center of Excellence for Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Germany
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Almannai M, Salah A, El-Hattab AW. Mitochondrial Membranes and Mitochondrial Genome: Interactions and Clinical Syndromes. MEMBRANES 2022; 12:membranes12060625. [PMID: 35736332 PMCID: PMC9229594 DOI: 10.3390/membranes12060625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/06/2022] [Accepted: 06/14/2022] [Indexed: 11/16/2022]
Abstract
Mitochondria are surrounded by two membranes; the outer mitochondrial membrane and the inner mitochondrial membrane. They are unique organelles since they have their own DNA, the mitochondrial DNA (mtDNA), which is replicated continuously. Mitochondrial membranes have direct interaction with mtDNA and are therefore involved in organization of the mitochondrial genome. They also play essential roles in mitochondrial dynamics and the supply of nucleotides for mtDNA synthesis. In this review, we will discuss how the mitochondrial membranes interact with mtDNA and how this interaction is essential for mtDNA maintenance. We will review different mtDNA maintenance disorders that result from defects in this crucial interaction. Finally, we will review therapeutic approaches relevant to defects in mitochondrial membranes.
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Affiliation(s)
- Mohammed Almannai
- Genetics and Precision Medicine Department, King Abdullah Specialized Children Hospital, Riyadh P.O. Box 22490, Saudi Arabia
- Correspondence:
| | - Azza Salah
- Department of Pediatrics, University Hospital Sharjah, Sharjah P.O. Box 72772, United Arab Emirates;
| | - Ayman W. El-Hattab
- Department of Pediatrics, University Hospital Sharjah, Sharjah P.O. Box 72772, United Arab Emirates;
- Department of Clinical Sciences, College of Medicine, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates;
- Genetics and Metabolic Department, KidsHeart Medical Center, Abu Dhabi P.O. Box 505193, United Arab Emirates
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An Updated View of Translocator Protein (TSPO). Int J Mol Sci 2017; 18:ijms18122640. [PMID: 29211020 PMCID: PMC5751243 DOI: 10.3390/ijms18122640] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Revised: 11/13/2017] [Accepted: 12/04/2017] [Indexed: 01/01/2023] Open
Abstract
Decades of study on the role of mitochondria in living cells have evidenced the importance of the 18 kDa mitochondrial translocator protein (TSPO), first discovered in the 1977 as an alternative binding site for the benzodiazepine diazepam in the kidneys. This protein participates in a variety of cellular functions, including cholesterol transport, steroid hormone synthesis, mitochondrial respiration, permeability transition pore opening, apoptosis, and cell proliferation. Thus, TSPO has become an extremely attractive subcellular target for the early detection of disease states that involve the overexpression of this protein and the selective mitochondrial drug delivery. This special issue was programmed with the aim of summarizing the latest findings about the role of TSPO in eukaryotic cells and as a potential subcellular target of diagnostics or therapeutics. A total of 9 papers have been accepted for publication in this issue, in particular, 2 reviews and 7 primary data manuscripts, overall describing the main advances in this field.
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Yamagoshi R, Yamamoto T, Hashimoto M, Sugahara R, Shiotsuki T, Miyoshi H, Terada H, Shinohara Y. Identification of amino acid residues of mammalian mitochondrial phosphate carrier important for its functional expression in yeast cells, as achieved by PCR-mediated random mutation and gap-repair cloning. Mitochondrion 2016; 32:1-9. [PMID: 27836624 DOI: 10.1016/j.mito.2016.11.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2016] [Revised: 09/02/2016] [Accepted: 11/07/2016] [Indexed: 11/28/2022]
Abstract
The mitochondrial phosphate carrier (PiC) of mammals, but not the yeast one, is synthesized with a presequence. The deletion of this presequence of the mammalian PiC was reported to facilitate the import of the carrier into yeast mitochondria, but the question as to whether or not mammalian PiC could be functionally expressed in yeast mitochondria was not addressed. In the present study, we first examined whether the defective growth on a glycerol plate of yeast cells lacking the yeast PiC gene could be reversed by the introduction of expression vectors of rat PiCs. The introduction of expression vectors encoding full-length rat PiC (rPiC) or rPiC lacking the presequence (ΔNrPiC) was ineffective in restoring growth on the glycerol plates. When we examined the expression levels of individual rPiCs in yeast mitochondria, ΔNrPiC was expressed at a level similar to that of yeast PiC, but that of rPiC was very low. These results indicated that ΔNrPiC expressed in yeast mitochondria is inert. Next, we sought to isolate "revertants" viable on the glycerol plate by expressing randomly mutated ΔNrPiC, and obtained two clones. These clones carried either of two mutations, F267S or F282S; and these mutations restored the transport function of ΔNrPiC in yeast mitochondria. These two Phe residues were conserved in human carrier (hPiC), and the transport function of ΔNhPiC expressed in yeast mitochondria was also markedly improved by their substitutions. Thus, substitution of F267S or F282S was concluded to be important for functional expression of mammalian PiCs in yeast mitochondria.
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Affiliation(s)
- Ryohei Yamagoshi
- Institute for Genome Research, Tokushima University, Kuramotocho-3, Tokushima 770-8503, Japan; Faculty of Pharmaceutical Sciences, Tokushima University, Shomachi-1, Tokushima 770-8505, Japan
| | - Takenori Yamamoto
- Institute for Genome Research, Tokushima University, Kuramotocho-3, Tokushima 770-8503, Japan; Faculty of Pharmaceutical Sciences, Tokushima University, Shomachi-1, Tokushima 770-8505, Japan
| | - Mitsuru Hashimoto
- Faculty of Pharmaceutical Science, Matsuyama University, Bunkyocho-4, Matsuyama 790-8578, Japan
| | - Ryohei Sugahara
- Insect Growth Regulation Research Unit, National Institute of Agrobiological Sciences, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Takahiro Shiotsuki
- Insect Growth Regulation Research Unit, National Institute of Agrobiological Sciences, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Hideto Miyoshi
- Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Hiroshi Terada
- Niigata University of Pharmacy and Applied Life Sciences, Niigata 956-8603, Japan
| | - Yasuo Shinohara
- Institute for Genome Research, Tokushima University, Kuramotocho-3, Tokushima 770-8503, Japan; Faculty of Pharmaceutical Sciences, Tokushima University, Shomachi-1, Tokushima 770-8505, Japan.
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Hopkins AM, Moghaddami M, Foster DJR, Proudman SM, Upton RN, Wiese MD. Intracellular CD3+ T Lymphocyte Teriflunomide Concentration Is Poorly Correlated with and Has Greater Variability Than Unbound Plasma Teriflunomide Concentration. Drug Metab Dispos 2016; 45:8-16. [PMID: 27742727 DOI: 10.1124/dmd.116.071985] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 10/13/2016] [Indexed: 01/12/2023] Open
Abstract
Leflunomide's active metabolite teriflunomide inhibits dihydro-oroate dehydrogenase, an enzyme essential to proliferation of T lymphocytes. As teriflunomide must reach the target site to have this effect, this study assessed the distribution of teriflunomide into T lymphocytes, as intracellular concentrations may be a superior response biomarker to plasma concentrations. CD3 MicroBeads (Miltenyi Biotec, Bergisch Gladbach, Germany) were used to extract CD3+ T cells from the peripheral blood of patients with rheumatoid arthritis who were taking a stable dose of leflunomide. Unbound plasma and intra-CD3+ T cell teriflunomide concentrations were quantified using liquid chromatography-mass spectrometry. Concentration (log transformed) and partition differences were assessed through paired Student t tests. Sixteen patients provided plasma steady-state teriflunomide samples, and eight provided a sample 6-12 weeks later. At time-point one, the geometric mean teriflunomide concentration (range) in CD3+ T cells was 18.12 μg/L (6.15-42.26 μg/L) compared with 69.75 μg/L (32.89-263.1 μg/L) unbound in plasma (P < 0.001). The mean partition coefficient (range) for unbound plasma teriflunomide into CD3+ T cells was 0.295 (0.092-0.632), which was significantly different from unity (P < 0.001). The median (range) change in teriflunomide concentration between the two time points was 14% (-10% to 40%) in unbound plasma and -29% (-69 to 138%) for CD3+ T cells. Because teriflunomide concentrations in CD3+ T cells were lower and displayed a higher intraindividual variability than the unbound plasma concentrations, its applicability as a therapeutic drug-monitoring marker may be limited.
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Affiliation(s)
- Ashley M Hopkins
- University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.)
| | - Mahin Moghaddami
- University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.)
| | - David J R Foster
- University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.)
| | - Susanna M Proudman
- University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.)
| | - Richard N Upton
- University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.)
| | - Michael D Wiese
- University of South Australia, Australian Centre for Pharmacometrics (A.M.H., D.J.R.F., R.N.U.) and Sansom Institute for Health Research (A.M.H., D.J.R.F., R.N.U., M.D.W), School of Pharmacy and Medical Sciences, Adelaide, South Australia, Australia; Arthritis Research Laboratory, Hanson Institute, SA Pathology, Adelaide, South Australia, Australia (M.M.); Discipline of Medicine, University of Adelaide, Adelaide, South Australia, Australia (M.M., S.M.P.); and Rheumatology Unit, Royal Adelaide Hospital, Adelaide, South Australia, Australia (S.M.P.)
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Whittaker JW. Intracellular trafficking of the pyridoxal cofactor. Implications for health and metabolic disease. Arch Biochem Biophys 2015; 592:20-6. [PMID: 26619753 DOI: 10.1016/j.abb.2015.11.031] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2015] [Revised: 11/09/2015] [Accepted: 11/16/2015] [Indexed: 01/01/2023]
Abstract
The importance of the vitamin B6-derived pyridoxal cofactor for human health has been established through more than 70 years of intensive biochemical research, revealing its fundamental roles in metabolism. B6 deficiency, resulting from nutritional limitation or impaired uptake from dietary sources, is associated with epilepsy, neuromuscular disease and neurodegeneration. Hereditary disorders of B6 processing are also known, and genetic defects in pathways involved in transport of B6 into the cell and its transformation to the pyridoxal-5'-phosphate enzyme cofactor can contribute to cardiovascular disease by interfering with homocysteine metabolism and the biosynthesis of vasomodulatory polyamines. Compared to the processes involved in cellular uptake and processing of the B6 vitamers, trafficking of the PLP cofactor across intracellular membranes is very poorly understood, even though the availability of PLP within subcellular compartments (particularly the mitochondrion) may have important health implications. The aim of this review is to concisely summarize the state of current knowledge of intracellular trafficking of PLP and to identify key directions for future research.
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Affiliation(s)
- James W Whittaker
- Institute of Environmental Health, Division of Environmental and Biomolecular Systems, Oregon Health and Science University, Portland, OR 97239-3098, USA.
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Whittaker MM, Penmatsa A, Whittaker JW. The Mtm1p carrier and pyridoxal 5'-phosphate cofactor trafficking in yeast mitochondria. Arch Biochem Biophys 2015; 568:64-70. [PMID: 25637770 DOI: 10.1016/j.abb.2015.01.021] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2014] [Revised: 01/21/2015] [Accepted: 01/22/2015] [Indexed: 12/23/2022]
Abstract
Biochemical communication between the cytoplasmic and mitochondrial subsystems of the cell depends on solute carriers in the mitochondrial inner membrane that transport metabolites between the two compartments. We have expressed and purified a yeast mitochondrial carrier protein (Mtm1p, YGR257cp), originally identified as a manganese ion carrier, for biochemical characterization aimed at resolving its function. High affinity, stoichiometric pyridoxal 5'-phosphate (PLP) cofactor binding was characterized by fluorescence titration and calorimetry, and the biochemical effects of mtm1 gene deletion on yeast mitochondria were investigated. The PLP status of the mitochondrial proteome (the mitochondrial 'PLP-ome') was probed by immunoblot analysis of mitochondria isolated from wild type (MTM1(+)) and knockout (MTM1(-)) yeast, revealing depletion of mitochondrial PLP in the latter. A direct activity assay of the enzyme catalyzing the first committed step of heme biosynthesis, the PLP-dependent mitochondrial enzyme 5-aminolevulinate synthase, extends these results, providing a specific example of PLP cofactor limitation. Together, these experiments support a role for Mtm1p in mitochondrial PLP trafficking and highlight the link between PLP cofactor transport and iron metabolism, a remarkable illustration of metabolic integration.
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Affiliation(s)
- Mei M Whittaker
- Institute of Environmental Health, Division of Environmental and Biomolecular Systems, Oregon Health and Science University, Portland, OR 97239-3098, USA
| | - Aravind Penmatsa
- Vollum Institute, Oregon Health and Science University, Portland, OR 97239-3098, USA
| | - James W Whittaker
- Institute of Environmental Health, Division of Environmental and Biomolecular Systems, Oregon Health and Science University, Portland, OR 97239-3098, USA.
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Flipphi M, Oestreicher N, Nicolas V, Guitton A, Vélot C. The Aspergillus nidulans acuL gene encodes a mitochondrial carrier required for the utilization of carbon sources that are metabolized via the TCA cycle. Fungal Genet Biol 2014; 68:9-22. [DOI: 10.1016/j.fgb.2014.04.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 04/24/2014] [Accepted: 04/29/2014] [Indexed: 10/25/2022]
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Abstract
The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.
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Rim2, a pyrimidine nucleotide exchanger, is needed for iron utilization in mitochondria. Biochem J 2011; 440:137-46. [PMID: 21777202 DOI: 10.1042/bj20111036] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
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.
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Piomboni P, Focarelli R, Stendardi A, Ferramosca A, Zara V. The role of mitochondria in energy production for human sperm motility. ACTA ACUST UNITED AC 2011; 35:109-24. [DOI: 10.1111/j.1365-2605.2011.01218.x] [Citation(s) in RCA: 245] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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Abnormal mitoferrin-1 expression in patients with erythropoietic protoporphyria. Exp Hematol 2011; 39:784-94. [PMID: 21627978 DOI: 10.1016/j.exphem.2011.05.003] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Revised: 04/08/2011] [Accepted: 04/16/2011] [Indexed: 11/23/2022]
Abstract
OBJECTIVE Most patients with erythropoietic protoporphyria have deficient ferrochelatase (FECH) activity due to changes in FECH DNA. We evaluated seven patients with erythropoietic protoporphyria phenotype in whom abnormalities of FECH DNA were not found by conventional analysis. The major focus was mitoferrin-1 (MFRN1), the mitochondrial transporter of Fe used for heme formation by FECH and for 2Fe2S cluster synthesis, which is critical to FECH activity/stability. MATERIALS AND METHODS Four patients had a deletion in ALAS2 that causes enzyme gain-of-function, resulting in increased formation of protoporphyrin; one had a heterozygous major deletion in FECH DNA. All had an abnormal transcript of MFRN1 in messenger RNA extracted from blood leukocytes and/or liver tissue. The abnormal transcript contained an insert of intron 2 that had a stop codon. The consequences of abnormal MFRN1 expression were examined using zebrafish and yeast MFRN-deficient strains and cultured lymphoblasts from the patients. RESULTS Abnormal human MFRN1 complementary DNA showed loss-of-function in zebrafish and yeast mutants, whereas normal human MFRN1 complementary DNA rescued both. Using cultured lymphoblasts, quantitative reverse transcription polymerase chain reaction showed increased formation of abnormal transcript that was accompanied by decreased formation of normal transcript and reduced FECH activity in patients compared to normal lines. A positive correlation coefficient (0.75) was found between FECH activity and normal MFRN1 messenger RNA in lymphoblasts. However, no obvious cause for increased formation of abnormal transcript was identified in MFRN1 exons and splice junctions. CONCLUSIONS Abnormal MFRN1 expression can contribute to erythropoietic protoporphyria phenotype in some patients, probably by causing a reduction in FECH activity.
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Wohlrab H. Homodimeric intrinsic membrane proteins. Identification and modulation of interactions between mitochondrial transporter (carrier) subunits. Biochem Biophys Res Commun 2010; 393:746-50. [PMID: 20171189 DOI: 10.1016/j.bbrc.2010.02.074] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2010] [Accepted: 02/11/2010] [Indexed: 11/28/2022]
Abstract
Transporter (carrier) proteins of the inner mitochondrial membrane link metabolic pathways within the matrix and the cytosol with transport/exchange of metabolites and inorganic ions. Their strict control of these fluxes is required for oxidative phosphorylation. Understanding the ternary complex transport mechanism with which most of these transporters function requires an accounting of the number and interactions of their subunits. The phosphate transporter (PTP, Mir1p) subunit readily forms homodimers with intersubunit affinities changeable by mutations. Cys28, likely at the subunit interface, is a site for mutations yielding transport inhibition or a channel-like transport mode. Such mutations yield a small increase or decrease in affinity between the subunits. The PTP inhibitor N-ethylmaleimide decreases subunit affinity by a small amount. PTP mutations that yield the highest (40%) and the lowest (2%) liposome incorporation efficiencies (LIE) are clustered near Cys28. Such mutant subunits show the lowest and highest subunit affinities respectively. The oxaloacetate transporter (Oac1p) subunit has an almost twofold lower affinity than the PTP subunit. The Oac1p, dicarboxylate (Dic1p) and PTP transporter subunits form heterodimers with even lower affinities. These results form a firm basis for detailed studies to establish the effect of subunit affinities on transport mode and activity and for the identification of the mechanism that prevents formation of heterodimers that surely will negatively impact oxidative phosphorylation and ATP levels with serious consequences for the cell.
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Affiliation(s)
- Hartmut Wohlrab
- Boston Biomedical Research Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 64 Grove Street, Watertown, MA 02472, USA.
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