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Belot A, Puy H, Hamza I, Bonkovsky HL. Update on heme biosynthesis, tissue-specific regulation, heme transport, relation to iron metabolism and cellular energy. Liver Int 2024. [PMID: 38888238 DOI: 10.1111/liv.15965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 04/19/2024] [Accepted: 04/23/2024] [Indexed: 06/20/2024]
Abstract
Heme is a primordial macrocycle upon which most aerobic life on Earth depends. It is essential to the survival and health of nearly all cells, functioning as a prosthetic group for oxygen-carrying proteins and enzymes involved in oxidation/reduction and electron transport reactions. Heme is essential for the function of numerous hemoproteins and has numerous other roles in the biochemistry of life. In mammals, heme is synthesised from glycine, succinyl-CoA, and ferrous iron in a series of eight steps. The first and normally rate-controlling step is catalysed by 5-aminolevulinate synthase (ALAS), which has two forms: ALAS1 is the housekeeping form with highly variable expression, depending upon the supply of the end-product heme, which acts to repress its activity; ALAS2 is the erythroid form, which is regulated chiefly by the adequacy of iron for erythroid haemoglobin synthesis. Abnormalities in the several enzymes of the heme synthetic pathway, most of which are inherited partial enzyme deficiencies, give rise to rare diseases called porphyrias. The existence and role of heme importers and exporters in mammals have been debated. Recent evidence established the presence of heme transporters. Such transporters are important for the transfer of heme from mitochondria, where the penultimate and ultimate steps of heme synthesis occur, and for the transfer of heme from cytoplasm to other cellular organelles. Several chaperones of heme and iron are known and important for cell health. Heme and iron, although promoters of oxidative stress and potentially toxic, are essential cofactors for cellular energy production and oxygenation.
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Affiliation(s)
- Audrey Belot
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, School of Medicine, University of Maryland, Baltimore, Maryland, USA
| | - Herve Puy
- Centre Français des Porphyries, Assistance Publique-Hôpitaux de Paris (APHP), Université de Paris Cité, INSERM U1149, Paris, France
| | - Iqbal Hamza
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, School of Medicine, University of Maryland, Baltimore, Maryland, USA
- Department of Animal and Avian Sciences, University of Maryland, College Park, Maryland, USA
| | - Herbert L Bonkovsky
- Section on Gastroenterology & Hepatology, Department of Medicine, Wake Forest University School of Medicine, Atrium Health Wake Forest Baptist, Winston-Salem, North Carolina, USA
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Dunaway LS, Loeb SA, Petrillo S, Tolosano E, Isakson BE. Heme metabolism in nonerythroid cells. J Biol Chem 2024; 300:107132. [PMID: 38432636 PMCID: PMC10988061 DOI: 10.1016/j.jbc.2024.107132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/31/2024] [Accepted: 02/23/2024] [Indexed: 03/05/2024] Open
Abstract
Heme is an iron-containing prosthetic group necessary for the function of several proteins termed "hemoproteins." Erythrocytes contain most of the body's heme in the form of hemoglobin and contain high concentrations of free heme. In nonerythroid cells, where cytosolic heme concentrations are 2 to 3 orders of magnitude lower, heme plays an essential and often overlooked role in a variety of cellular processes. Indeed, hemoproteins are found in almost every subcellular compartment and are integral in cellular operations such as oxidative phosphorylation, amino acid metabolism, xenobiotic metabolism, and transcriptional regulation. Growing evidence reveals the participation of heme in dynamic processes such as circadian rhythms, NO signaling, and the modulation of enzyme activity. This dynamic view of heme biology uncovers exciting possibilities as to how hemoproteins may participate in a range of physiologic systems. Here, we discuss how heme is regulated at the level of its synthesis, availability, redox state, transport, and degradation and highlight the implications for cellular function and whole organism physiology.
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Affiliation(s)
- Luke S Dunaway
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Skylar A Loeb
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia, USA; Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, Virginia, USA
| | - Sara Petrillo
- Deptartment Molecular Biotechnology and Health Sciences and Molecular Biotechnology Center "Guido Tarone", University of Torino, Torino, Italy
| | - Emanuela Tolosano
- Deptartment Molecular Biotechnology and Health Sciences and Molecular Biotechnology Center "Guido Tarone", University of Torino, Torino, Italy
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, Virginia, USA; Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, Virginia, USA.
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Chen C, Hamza I. Notes from the Underground: Heme Homeostasis in C. elegans. Biomolecules 2023; 13:1149. [PMID: 37509184 PMCID: PMC10377359 DOI: 10.3390/biom13071149] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/13/2023] [Accepted: 07/14/2023] [Indexed: 07/30/2023] Open
Abstract
Heme is an iron-containing tetrapyrrole that plays a critical role in various biological processes, including oxygen transport, electron transport, signal transduction, and catalysis. However, free heme is hydrophobic and potentially toxic to cells. Organisms have evolved specific pathways to safely transport this essential but toxic macrocycle within and between cells. The bacterivorous soil-dwelling nematode Caenorhabditis elegans is a powerful animal model for studying heme-trafficking pathways, as it lacks the ability to synthesize heme but instead relies on specialized trafficking pathways to acquire, distribute, and utilize heme. Over the past 15 years, studies on this microscopic animal have led to the identification of a number of heme-trafficking proteins, with corresponding functional homologs in vertebrates. In this review, we provide a comprehensive overview of the heme-trafficking proteins identified in C. elegans and their corresponding homologs in related organisms.
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Affiliation(s)
- Caiyong Chen
- MOE Key Laboratory of Biosystems Homeostasis and Protection, College of Life Sciences, Zhejiang University, Hangzhou 310058, China
| | - Iqbal Hamza
- Center for Blood Oxygen Transport and Hemostasis, Department of Pediatrics, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
- Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA
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Hau RK, Wright SH, Cherrington NJ. Drug Transporters at the Human Blood-Testis Barrier. Drug Metab Dispos 2023; 51:560-571. [PMID: 36732077 PMCID: PMC10158500 DOI: 10.1124/dmd.122.001186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Revised: 01/06/2023] [Accepted: 01/26/2023] [Indexed: 02/04/2023] Open
Abstract
Transporters are involved in the movement of many physiologically important molecules across cell membranes and have a substantial impact on the pharmacological and toxicological effect of xenobiotics. Many transporters have been studied in the context of disposition to, or toxicity in, organs such as the kidney and liver; however, transporters in the testes are increasingly gaining recognition for their role in drug transport across the blood-testis barrier (BTB). The BTB is an epithelial membrane barrier formed by adjacent Sertoli cells (SCs) in the seminiferous tubules that form intercellular junctional complexes to protect developing germ cells from the external environment. Consequently, many charged or large polar molecules cannot cross this barrier without assistance from a transporter. SCs express a variety of drug uptake and efflux transporters to control the flux of endogenous and exogenous molecules across the BTB. Recent studies have identified several transport pathways in SCs that allow certain drugs to circumvent the human BTB. These pathways may exist in other species, such as rodents and nonhuman primates; however, there is (1) a lack of information on their expression and/or localization in these species, and (2) conflicting reports on localization of some transporters that have been evaluated in rodents compared with humans. This review outlines the current knowledge on the expression and localization of pharmacologically relevant drug transporters in human testes and calls attention to the insufficient and contradictory understanding of testicular transporters in other species that are commonly used in drug disposition and toxicity studies. SIGNIFICANCE STATEMENT: While the expression, localization, and function of many xenobiotic transporters have been studied in organs such as the kidney and liver, the characterization of transporters in the testes is scarce. This review summarizes the expression and localization of common pharmacologically-relevant transporters in human testes that have significant implications for the development of drugs that can cross the blood-testis barrier. Potential expression differences between humans and rodents highlighted here suggest rodents may be inappropriate for some testicular disposition and toxicity studies.
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Affiliation(s)
- Raymond K Hau
- College of Pharmacy, Department of Pharmacology & Toxicology (R.K.H., N.J.C.) and College of Medicine, Department of Physiology (S.H.W.), The University of Arizona, Tucson, Arizona
| | - Stephen H Wright
- College of Pharmacy, Department of Pharmacology & Toxicology (R.K.H., N.J.C.) and College of Medicine, Department of Physiology (S.H.W.), The University of Arizona, Tucson, Arizona
| | - Nathan J Cherrington
- College of Pharmacy, Department of Pharmacology & Toxicology (R.K.H., N.J.C.) and College of Medicine, Department of Physiology (S.H.W.), The University of Arizona, Tucson, Arizona
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Seike M, Asahara SI, Inoue H, Kudo M, Kanno A, Yokoi A, Suzuki H, Kimura-Koyanagi M, Kido Y, Ogawa W. l-Asparaginase regulates mTORC1 activity via a TSC2-dependent pathway in pancreatic beta cells. Biochem Biophys Res Commun 2023; 652:121-130. [PMID: 36842323 DOI: 10.1016/j.bbrc.2023.02.035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 02/09/2023] [Accepted: 02/14/2023] [Indexed: 02/18/2023]
Abstract
Eif2ak4, a susceptibility gene for type 2 diabetes, encodes GCN2, a molecule activated by amino acid deficiency. Mutations or deletions in GCN2 in pancreatic β-cells increase mTORC1 activity by decreasing Sestrin2 expression in a TSC2-independent manner. In this study, we searched for molecules downstream of GCN2 that suppress mTORC1 activity in a TSC2-dependent manner. To do so, we used a pull-down assay to identify molecules that competitively inhibit the binding of the T1462 phosphorylation site of TSC2 to 14-3-3. l-asparaginase was identified. Although l-asparaginase is frequently used as an anticancer drug for acute lymphoblastic leukemia, little is known about endogenous l-asparaginase. l-Asparaginase, which is expressed downstream of GCN2, was found to bind 14-3-3 and thereby to inhibit its binding to the T1462 phosphorylation site of TSC2 and contribute to TSC2 activation and mTORC1 inactivation upon TSC2 dephosphorylation. Further investigation of the regulation of mTORC1 activity in pancreatic β-cells by l-asparaginase should help to elucidate the mechanism of diabetes and insulin secretion failure during anticancer drug use.
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Affiliation(s)
- Masako Seike
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
| | - Shun-Ichiro Asahara
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
| | - Hiroyuki Inoue
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan.
| | - Michiyo Kudo
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan.
| | - Ayumi Kanno
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
| | - Aisha Yokoi
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
| | - Hirotaka Suzuki
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
| | - Maki Kimura-Koyanagi
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
| | - Yoshiaki Kido
- Division of Medical Chemistry, Department of Metabolism and Diseases, Kobe University Graduate School of Health Sciences, 7-10-2 Tomogaoka, Suma-ku, Kobe, Hyogo, 654-0142, Japan.
| | - Wataru Ogawa
- Division of Diabetes and Endocrinology, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, Hyogo, 650-0017, Japan.
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Vázquez-Meza H, Vilchis-Landeros MM, Vázquez-Carrada M, Uribe-Ramírez D, Matuz-Mares D. Cellular Compartmentalization, Glutathione Transport and Its Relevance in Some Pathologies. Antioxidants (Basel) 2023; 12:antiox12040834. [PMID: 37107209 PMCID: PMC10135322 DOI: 10.3390/antiox12040834] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 03/24/2023] [Accepted: 03/27/2023] [Indexed: 03/31/2023] Open
Abstract
Reduced glutathione (GSH) is the most abundant non-protein endogenous thiol. It is a ubiquitous molecule produced in most organs, but its synthesis is predominantly in the liver, the tissue in charge of storing and distributing it. GSH is involved in the detoxification of free radicals, peroxides and xenobiotics (drugs, pollutants, carcinogens, etc.), protects biological membranes from lipid peroxidation, and is an important regulator of cell homeostasis, since it participates in signaling redox, regulation of the synthesis and degradation of proteins (S-glutathionylation), signal transduction, various apoptotic processes, gene expression, cell proliferation, DNA and RNA synthesis, etc. GSH transport is a vital step in cellular homeostasis supported by the liver through providing extrahepatic organs (such as the kidney, lung, intestine, and brain, among others) with the said antioxidant. The wide range of functions within the cell in which glutathione is involved shows that glutathione’s role in cellular homeostasis goes beyond being a simple antioxidant agent; therefore, the importance of this tripeptide needs to be reassessed from a broader metabolic perspective.
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Abstract
An abundant metal in the human body, iron is essential for key biological pathways including oxygen transport, DNA metabolism, and mitochondrial function. Most iron is bound to heme but it can also be incorporated into iron-sulfur clusters or bind directly to proteins. Iron's capacity to cycle between Fe2+ and Fe3+ contributes to its biological utility but also renders it toxic in excess. Heme is an iron-containing tetrapyrrole essential for diverse biological functions including gas transport and sensing, oxidative metabolism, and xenobiotic detoxification. Like iron, heme is essential yet toxic in excess. As such, both iron and heme homeostasis are tightly regulated. Here we discuss molecular and physiologic aspects of iron and heme metabolism. We focus on dietary absorption; cellular import; utilization; and export, recycling, and elimination, emphasizing studies published in recent years. We end with a discussion on current challenges and needs in the field of iron and heme biology.
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Affiliation(s)
- Sohini Dutt
- Department of Animal and Avian Sciences and Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
| | - Iqbal Hamza
- Department of Animal and Avian Sciences and Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland, USA
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Wang Z, Zeng P, Zhou B. Identification and characterization of a heme exporter from the MRP family in Drosophila melanogaster. BMC Biol 2022; 20:126. [PMID: 35655259 PMCID: PMC9161523 DOI: 10.1186/s12915-022-01332-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 05/17/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The heme group constitutes a major functional form of iron, which plays vital roles in various biological processes including oxygen transport and mitochondrial respiration. Heme is an essential nutrient, but its pro-oxidant nature may have toxic cellular effects if present at high levels, and its synthesis is therefore tightly regulated. Deficiency and excess of heme both lead to pathological processes; however, our current understanding of metazoan heme transport is largely limited to work in mammals and the worm Caenorhabditis elegans, while functional analyses of heme transport in the genetically amenable Drosophila melanogaster and other arthropods have not been explored. RESULTS We implemented a functional screening in Schneider 2 (S2) cells to identify putative heme transporters of D. melanogaster. A few multidrug resistance-associated protein (MRP) members were found to be induced by hemin and/or involved in heme export. Between the two plasma membrane-resident heme exporters CG4562 and CG7627, the former is responsible for heme transit across the intestinal epithelium. CG4562 knockdown resulted in heme accumulation in the intestine and lethality that could be alleviated by heme synthesis inhibition, human MRP5 (hMRP5) expression, heme oxygenase (HO) expression, or zinc supplement. CG4562 is mainly expressed in the gastric caeca and the anterior part of the midgut, suggesting this is the major site of heme absorption. It thus appears that CG4562 is the functional counterpart of mammalian MRP5. Mutation analyses in the transmembrane and nucleotide binding domains of CG4562 characterized some potential binding sites and conservative ATP binding pockets for the heme transport process. Furthermore, some homologs in Aedes aegypti, including that of CG4562, have also been characterized as heme exporters. CONCLUSIONS Together, our findings suggest a conserved heme homeostasis mechanism within insects, and between insects and mammals. We propose the fly model may be a good complement to the existing platforms of heme studies.
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Affiliation(s)
- Zhiqing Wang
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Peng Zeng
- Institute for Immunology, Tsinghua-Peking Center for Life Sciences, School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Bing Zhou
- State Key Laboratory of Membrane Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
- Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
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