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Jayaram DT, Sivaram P, Biswas P, Dai Y, Sweeny EA, Stuehr DJ. Heme allocation in eukaryotic cells relies on mitochondrial heme export through FLVCR1b to cytosolic GAPDH. RESEARCH SQUARE 2024:rs.3.rs-4314324. [PMID: 38746106 PMCID: PMC11092803 DOI: 10.21203/rs.3.rs-4314324/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
Heme is an iron-containing cofactor essential for life. In eukaryotes heme is generated in the mitochondria and must leave this organelle to reach protein targets in other cell compartments. Mitochondrial heme binding by cytosolic GAPDH was recently found essential for heme distribution in eukaryotic cells. Here, we sought to uncover how mitochondrial heme reaches GAPDH. Experiments involving a human cell line and a novel GAPDH reporter construct whose heme binding in live cells can be followed by fluorescence revealed that the mitochondrial transmembrane protein FLVCR1b exclusively transfers mitochondrial heme to GAPDH through a direct protein-protein interaction that rises and falls as heme transfers. In the absence of FLVCR1b, neither GAPDH nor downstream hemeproteins received any mitochondrial heme. Cell expression of TANGO2 was also required, and we found it interacts with FLVCR1b to likely support its heme exporting function. Finally, we show that purified GAPDH interacts with FLVCR1b in isolated mitochondria and triggers heme transfer to GAPDH and its downstream delivery to two client proteins. Identifying FLVCR1b as the sole heme source for GAPDH completes the path by which heme is exported from mitochondria, transported, and delivered into protein targets within eukaryotic cells.
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Affiliation(s)
| | - Pranav Sivaram
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA
| | - Pranjal Biswas
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA
| | - Yue Dai
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA
| | - Elizabeth A. Sweeny
- Department of Biochemistry, The Medical College of Wisconsin, Milwaukee, WI 53226, USA
| | - Dennis J. Stuehr
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA
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Biswas P, Palazzo J, Schlanger S, Jayaram DT, Islam S, Page RC, Stuehr DJ. Visualizing mitochondrial heme flow through GAPDH in living cells and its regulation by NO. Redox Biol 2024; 71:103120. [PMID: 38507973 PMCID: PMC10966083 DOI: 10.1016/j.redox.2024.103120] [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: 01/16/2024] [Revised: 02/08/2024] [Accepted: 02/22/2024] [Indexed: 03/22/2024] Open
Abstract
Iron protoporphyrin IX (heme) is a redox-active cofactor that is bound in mammalian cells by GAPDH and allocated by a process influenced by physiologic levels of NO. This impacts the activity of many heme proteins including indoleamine dioxygenase-1 (IDO1), a redox enzyme involved in immune response and tumor growth. To gain further understanding we created a tetra-Cys human GAPDH reporter construct (TC-hGAPDH) which after labeling could indicate its heme binding by fluorescence quenching. When purified or expressed in a human cell line, TC-hGAPDH had properties like native GAPDH and heme binding quenched its fluorescence by 45-65%, allowing it to report on GAPDH binding of mitochondrially-generated heme in live cells in real time. In cells with active mitochondrial heme synthesis, low-level NO exposure increased heme allocation to IDO1 while keeping the TC-hGAPDH heme level constant due to replenishment by mitochondria. When mitochondrial heme synthesis was blocked, low NO caused a near complete transfer of the existing heme in TC-hGAPDH to IDO1 in a process that required IDO1 be able to bind the heme and have an active hsp90 present. Higher NO exposure had the opposite effect and caused IDO1 heme to transfer back to TC-hGAPDH. This demonstrated: (i) flow of mitochondrial heme through GAPDH is tightly coupled to target delivery, (ii) NO up- or down-regulates IDO1 activity by promoting a conserved heme exchange with GAPDH that goes in either direction according to the NO exposure level. The ability to drive a concentration-dependent, reversible protein heme exchange is unprecedented and reveals a new role for NO in biology.
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Affiliation(s)
- Pranjal Biswas
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Joseph Palazzo
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Simon Schlanger
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, 44195, USA
| | | | - Sidra Islam
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, 44195, USA
| | - Richard C Page
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH, 45056, USA
| | - Dennis J Stuehr
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, 44195, 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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Islam S, Jayaram DT, Biswas P, Stuehr DJ. Functional maturation of cytochromes P450 3A4 and 2D6 relies on GAPDH- and Hsp90-Dependent heme allocation. J Biol Chem 2024; 300:105633. [PMID: 38199567 PMCID: PMC10840333 DOI: 10.1016/j.jbc.2024.105633] [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: 09/21/2023] [Revised: 11/20/2023] [Accepted: 12/15/2023] [Indexed: 01/12/2024] Open
Abstract
Cytochrome P450 3A4 and 2D6 (EC 1.14.13.97 and 1.14.14.1; CYP3A4 and 2D6) are heme-containing enzymes that catalyze the oxidation of a wide number of xenobiotic and drug substrates and thus broadly impact human biology and pharmacologic therapies. Although their activities are directly proportional to their heme contents, little is known about the cellular heme delivery and insertion processes that enable their maturation to functional form. We investigated the potential involvement of GAPDH and chaperone Hsp90, based on our previous studies linking these proteins to intracellular heme allocation. We studied heme delivery and insertion into CYP3A4 and 2D6 after they were transiently expressed in HEK293T and GlyA CHO cells or when naturally expressed in HEPG2 cells in response to rifampicin, and also investigated their associations with GAPDH and Hsp90 in cells. The results indicate that GAPDH and its heme binding function is involved in delivery of mitochondria-generated heme to apo-CYP3A4 and 2D6, and that cell chaperone Hsp90 is additionally involved in driving their heme insertions. Uncovering how cells allocate heme to CYP3A4 and 2D6 provides new insight on their maturation processes and how this may help to regulate their functions in health and disease.
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Affiliation(s)
- Sidra Islam
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio, USA
| | | | - Pranjal Biswas
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio, USA
| | - Dennis J Stuehr
- Department of Inflammation and Immunity, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio, USA.
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Biswas P, Palazzo J, Schlanger S, Jayaram DT, Islam S, Page RC, Stuehr DJ. Visualizing Mitochondrial Heme Flow through GAPDH to Targets in Living Cells and its Regulation by NO. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.10.575067. [PMID: 38260356 PMCID: PMC10802506 DOI: 10.1101/2024.01.10.575067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Iron protoporphyrin IX (heme) is an essential cofactor that is chaperoned in mammalian cells by GAPDH in a process regulated by NO. To gain further understanding we generated a tetra-Cys human GAPDH reporter construct (TC-hGAPDH) which after being expressed and labeled with fluorescent FlAsH reagent could indicate heme binding by fluorescence quenching. When purified or expressed in HEK293T mammalian cells, FlAsH-labeled TC-hGAPDH displayed physical, catalytic, and heme binding properties like native GAPDH and its heme binding (2 mol per tetramer) quenched its fluorescence by 45-65%. In live HEK293T cells we could visualize TC-hGAPDH binding mitochondrially-generated heme and releasing it to the hemeprotein target IDO1 by monitoring cell fluorescence in real time. In cells with active mitochondrial heme synthesis, a low-level NO exposure increased heme allocation into IDO1 while keeping steady the level of heme-bound TC-hGAPDH. When mitochondrial heme synthesis was blocked at the time of NO exposure, low NO caused cells to reallocate existing heme from TC-hGAPDH to IDO1 by a mechanism requiring IDO1 be present and able to bind heme. Higher NO exposure had an opposite effect and caused cells to reallocate existing heme from IDO1 to TC-hGAPDH. Thus, with TC-hGAPDH we could follow mitochondrial heme as it travelled onto and through GAPDH to a downstream target (IDO1) in living cells, and to learn that NO acted at or downstream from the GAPDH heme complex to promote a heme reallocation in either direction depending on the level of NO exposure.
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