1
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Thévenod F, Lee WK. Cadmium transport by mammalian ATP-binding cassette transporters. Biometals 2024; 37:697-719. [PMID: 38319451 PMCID: PMC11101381 DOI: 10.1007/s10534-024-00582-5] [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: 09/15/2023] [Accepted: 01/04/2024] [Indexed: 02/07/2024]
Abstract
Cellular responses to toxic metals depend on metal accessibility to intracellular targets, reaching interaction sites, and the intracellular metal concentration, which is mainly determined by uptake pathways, binding/sequestration and efflux pathways. ATP-binding cassette (ABC) transporters are ubiquitous in the human body-usually in epithelia-and are responsible for the transfer of indispensable physiological substrates (e.g. lipids and heme), protection against potentially toxic substances, maintenance of fluid composition, and excretion of metabolic waste products. Derailed regulation and gene variants of ABC transporters culminate in a wide array of pathophysiological disease states, such as oncogenic multidrug resistance or cystic fibrosis. Cadmium (Cd) has no known physiological role in mammalians and poses a health risk due to its release into the environment as a result of industrial activities, and eventually passes into the food chain. Epithelial cells, especially within the liver, lungs, gastrointestinal tract and kidneys, are particularly susceptible to the multifaceted effects of Cd because of the plethora of uptake pathways available. Pertinent to their broad substrate spectra, ABC transporters represent a major cellular efflux pathway for Cd and Cd complexes. In this review, we summarize current knowledge concerning transport of Cd and its complexes (mainly Cd bound to glutathione) by the ABC transporters ABCB1 (P-glycoprotein, MDR1), ABCB6, ABCC1 (multidrug resistance related protein 1, MRP1), ABCC7 (cystic fibrosis transmembrane regulator, CFTR), and ABCG2 (breast cancer related protein, BCRP). Potential detoxification strategies underlying ABC transporter-mediated efflux of Cd and Cd complexes are discussed.
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Affiliation(s)
- Frank Thévenod
- Institute for Physiology, Pathophysiology and Toxicology & ZBAF, Witten/Herdecke University, 58453, Witten, Germany
- Physiology and Pathophysiology of Cells and Membranes, Medical School OWL, Bielefeld University, Morgenbreede 1, 33615, Bielefeld, Germany
| | - Wing-Kee Lee
- Physiology and Pathophysiology of Cells and Membranes, Medical School OWL, Bielefeld University, Morgenbreede 1, 33615, Bielefeld, Germany.
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2
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Choi SH, Lee SS, Lee HY, Kim S, Kim JW, Jin MS. Cryo-EM structure of cadmium-bound human ABCB6. Commun Biol 2024; 7:672. [PMID: 38822018 PMCID: PMC11143254 DOI: 10.1038/s42003-024-06377-1] [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: 09/22/2023] [Accepted: 05/23/2024] [Indexed: 06/02/2024] Open
Abstract
ATP-binding cassette transporter B6 (ABCB6), a protein essential for heme biosynthesis in mitochondria, also functions as a heavy metal efflux pump. Here, we present cryo-electron microscopy structures of human ABCB6 bound to a cadmium Cd(II) ion in the presence of antioxidant thiol peptides glutathione (GSH) and phytochelatin 2 (PC2) at resolutions of 3.2 and 3.1 Å, respectively. The overall folding of the two structures resembles the inward-facing apo state but with less separation between the two halves of the transporter. Two GSH molecules are symmetrically bound to the Cd(II) ion in a bent conformation, with the central cysteine protruding towards the metal. The N-terminal glutamate and C-terminal glycine of GSH do not directly interact with Cd(II) but contribute to neutralizing positive charges of the binding cavity by forming hydrogen bonds and van der Waals interactions with nearby residues. In the presence of PC2, Cd(II) binding to ABCB6 is similar to that observed with GSH, except that two cysteine residues of each PC2 molecule participate in Cd(II) coordination to form a tetrathiolate. Structural comparison of human ABCB6 and its homologous Atm-type transporters indicate that their distinct substrate specificity might be attributed to variations in the capping residues situated at the top of the substrate-binding cavity.
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Affiliation(s)
- Seung Hun Choi
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Sang Soo Lee
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Hyeon You Lee
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Subin Kim
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea
| | - Ji Won Kim
- Department of Life Sciences, POSTECH, 77 Cheongam-Ro, Nam-gu, Pohang, Republic of Korea
| | - Mi Sun Jin
- School of Life Sciences, GIST, 123 Cheomdangwagi-ro, Buk-gu, Gwangju, Republic of Korea.
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3
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Popescu RG, Dinischiotu A, Soare T, Vlase E, Marinescu GC. Nicotinamide Mononucleotide (NMN) Works in Type 2 Diabetes through Unexpected Effects in Adipose Tissue, Not by Mitochondrial Biogenesis. Int J Mol Sci 2024; 25:2594. [PMID: 38473844 DOI: 10.3390/ijms25052594] [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: 12/20/2023] [Revised: 02/01/2024] [Accepted: 02/14/2024] [Indexed: 03/14/2024] Open
Abstract
Nicotinamide mononucleotide (NMN) has emerged as a promising therapeutic intervention for age-related disorders, including type 2 diabetes. In this study, we confirmed the previously observed effects of NMN treatment on glucose uptake and investigated its underlying mechanisms in various tissues and cell lines. Through the most comprehensive proteomic analysis to date, we discovered a series of novel organ-specific effects responsible for glucose uptake as measured by the IPGTT: adipose tissue growing (suggested by increased protein synthesis and degradation and mTOR proliferation signaling upregulation). Notably, we observed the upregulation of thermogenic UCP1, promoting enhanced glucose conversion to heat in intermuscular adipose tissue while showing a surprising repressive effect on mitochondrial biogenesis in muscle and the brain. Additionally, liver and muscle cells displayed a unique response, characterized by spliceosome downregulation and concurrent upregulation of chaperones, proteasomes, and ribosomes, leading to mildly impaired and energy-inefficient protein synthesis machinery. Furthermore, our findings revealed remarkable metabolic rewiring in the brain. This involved increased production of ketone bodies, downregulation of mitochondrial OXPHOS and TCA cycle components, as well as the induction of well-known fasting-associated effects. Collectively, our data elucidate the multifaceted nature of NMN action, highlighting its organ-specific effects and their role in improving glucose uptake. These findings deepen our understanding of NMN's therapeutic potential and pave the way for novel strategies in managing metabolic disorders.
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Affiliation(s)
- Roua Gabriela Popescu
- Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, 050095 Bucharest, Romania
- Independent Research Association, 012416 Bucharest, Romania
- Blue Screen SRL, 012416 Bucharest, Romania
| | - Anca Dinischiotu
- Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, 050095 Bucharest, Romania
| | - Teodoru Soare
- Pathology Department, Faculty of Veterinary Medicine, University of Agronomic Sciences and Veterinary Medicine of Bucharest, 050097 Bucharest, Romania
| | - Ene Vlase
- Animals Facility Laboratory, Cantacuzino National Institute for Medico-Military Research and Development, 013821 Bucharest, Romania
| | - George Cătălin Marinescu
- Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Bucharest, 050095 Bucharest, Romania
- Independent Research Association, 012416 Bucharest, Romania
- Blue Screen SRL, 012416 Bucharest, Romania
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4
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Miyoshi K, Hishinuma E, Matsukawa N, Shirasago Y, Watanabe M, Sato T, Sato Y, Kumondai M, Kikuchi M, Koshiba S, Fukasawa M, Maekawa M, Mano N. Global Proteomics for Identifying the Alteration Pathway of Niemann-Pick Disease Type C Using Hepatic Cell Models. Int J Mol Sci 2023; 24:15642. [PMID: 37958627 PMCID: PMC10648601 DOI: 10.3390/ijms242115642] [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: 09/27/2023] [Revised: 10/24/2023] [Accepted: 10/25/2023] [Indexed: 11/15/2023] Open
Abstract
Niemann-Pick disease type C (NPC) is an autosomal recessive disorder with progressive neurodegeneration. Although the causative genes were previously identified, NPC has unclear pathophysiological aspects, and patients with NPC present various symptoms and onset ages. However, various novel biomarkers and metabolic alterations have been investigated; at present, few comprehensive proteomic alterations have been reported in relation to NPC. In this study, we aimed to elucidate proteomic alterations in NPC and perform a global proteomics analysis for NPC model cells. First, we developed two NPC cell models by knocking out NPC1 using CRISPR/Cas9 (KO1 and KO2). Second, we performed a label-free (LF) global proteomics analysis. Using the LF approach, more than 300 proteins, defined as differentially expressed proteins (DEPs), changed in the KO1 and/or KO2 cells, while the two models shared 35 DEPs. As a bioinformatics analysis, the construction of a protein-protein interaction (PPI) network and an enrichment analysis showed that common characteristic pathways such as ferroptosis and mitophagy were identified in the two model cells. There are few reports of the involvement of NPC in ferroptosis, and this study presents ferroptosis as an altered pathway in NPC. On the other hand, many other pathways and DEPs were previously suggested to be associated with NPC, supporting the link between the proteome analyzed here and NPC. Therapeutic research based on these results is expected in the future.
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Affiliation(s)
- Keitaro Miyoshi
- Faculty of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
| | - Eiji Hishinuma
- Advanced Research Center for Innovations in Next-Generation Medicine, Tohoku University, 2-1 Seiryo-machi, Aoba-Ku, Sendai 980-8573, Japan; (E.H.)
- Tohoku Medical Megabank Organization, Tohoku University, 2-1 Seiryo-machi, Aoba-Ku, Sendai 980-8573, Japan
| | - Naomi Matsukawa
- Tohoku Medical Megabank Organization, Tohoku University, 2-1 Seiryo-machi, Aoba-Ku, Sendai 980-8573, Japan
| | - Yoshitaka Shirasago
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Masahiro Watanabe
- Graduate School of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
| | - Toshihiro Sato
- Department of Pharmaceutical Sciences, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
| | - Yu Sato
- Department of Pharmaceutical Sciences, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
| | - Masaki Kumondai
- Department of Pharmaceutical Sciences, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
| | - Masafumi Kikuchi
- Faculty of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
- Graduate School of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
- Department of Pharmaceutical Sciences, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
| | - Seizo Koshiba
- Advanced Research Center for Innovations in Next-Generation Medicine, Tohoku University, 2-1 Seiryo-machi, Aoba-Ku, Sendai 980-8573, Japan; (E.H.)
- Tohoku Medical Megabank Organization, Tohoku University, 2-1 Seiryo-machi, Aoba-Ku, Sendai 980-8573, Japan
| | - Masayoshi Fukasawa
- Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1, Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Masamitsu Maekawa
- Faculty of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
- Advanced Research Center for Innovations in Next-Generation Medicine, Tohoku University, 2-1 Seiryo-machi, Aoba-Ku, Sendai 980-8573, Japan; (E.H.)
- Graduate School of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
- Department of Pharmaceutical Sciences, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
| | - Nariyasu Mano
- Faculty of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
- Graduate School of Pharmaceutical Sciences, Tohoku University, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
- Department of Pharmaceutical Sciences, Tohoku University Hospital, 1-1 Seiryo-machi, Aoba-Ku, Sendai 980-8574, Japan
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5
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Simon MA, Iordanov I, Szollosi A, Csanády L. Estimating the true stability of the prehydrolytic outward-facing state in an ABC protein. eLife 2023; 12:e90736. [PMID: 37782012 PMCID: PMC10569789 DOI: 10.7554/elife.90736] [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: 07/06/2023] [Accepted: 10/01/2023] [Indexed: 10/03/2023] Open
Abstract
CFTR, the anion channel mutated in cystic fibrosis patients, is a model ABC protein whose ATP-driven conformational cycle is observable at single-molecule level in patch-clamp recordings. Bursts of CFTR pore openings are coupled to tight dimerization of its two nucleotide-binding domains (NBDs) and in wild-type (WT) channels are mostly terminated by ATP hydrolysis. The slow rate of non-hydrolytic closure - which determines how tightly bursts and ATP hydrolysis are coupled - is unknown, as burst durations of catalytic site mutants span a range of ~200-fold. Here, we show that Walker A mutation K1250A, Walker B mutation D1370N, and catalytic glutamate mutations E1371S and E1371Q all completely disrupt ATP hydrolysis. True non-hydrolytic closing rate of WT CFTR approximates that of K1250A and E1371S. That rate is slowed ~15-fold in E1371Q by a non-native inter-NBD H-bond, and accelerated ~15-fold in D1370N. These findings uncover unique features of the NBD interface in human CFTR.
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Affiliation(s)
- Márton A Simon
- Department of Biochemistry, Semmelweis UniversityBudapestHungary
- HCEMM-SE Molecular Channelopathies Research GroupBudapestHungary
- HUN-REN-SE Ion Channel Research GroupBudapestHungary
| | - Iordan Iordanov
- Department of Biochemistry, Semmelweis UniversityBudapestHungary
- HCEMM-SE Molecular Channelopathies Research GroupBudapestHungary
- HUN-REN-SE Ion Channel Research GroupBudapestHungary
| | - Andras Szollosi
- Department of Biochemistry, Semmelweis UniversityBudapestHungary
- HCEMM-SE Molecular Channelopathies Research GroupBudapestHungary
- HUN-REN-SE Ion Channel Research GroupBudapestHungary
| | - László Csanády
- Department of Biochemistry, Semmelweis UniversityBudapestHungary
- HCEMM-SE Molecular Channelopathies Research GroupBudapestHungary
- HUN-REN-SE Ion Channel Research GroupBudapestHungary
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6
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Lee SS, Park JG, Jang E, Choi SH, Kim S, Kim JW, Jin MS. W546 stacking disruption traps the human porphyrin transporter ABCB6 in an outward-facing transient state. Commun Biol 2023; 6:960. [PMID: 37735522 PMCID: PMC10514269 DOI: 10.1038/s42003-023-05339-3] [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: 03/16/2023] [Accepted: 09/11/2023] [Indexed: 09/23/2023] Open
Abstract
Human ATP-binding cassette transporter subfamily B6 (ABCB6) is a mitochondrial ATP-driven pump that translocates porphyrins from the cytoplasm into mitochondria for heme biosynthesis. Within the transport pathway, a conserved aromatic residue W546 located in each monomer plays a pivotal role in stabilizing the occluded conformation via π-stacking interactions. Herein, we employed cryo-electron microscopy to investigate the structural consequences of a single W546A mutation in ABCB6, both in detergent micelles and nanodiscs. The results demonstrate that the W546A mutation alters the conformational dynamics of detergent-purified ABCB6, leading to entrapment of the transporter in an outward-facing transient state. However, in the nanodisc system, we observed a direct interaction between the transporter and a phospholipid molecule that compensates for the absence of the W546 residue, thereby facilitating the normal conformational transition of the transporter toward the occluded state following ATP hydrolysis. The findings also reveal that adoption of the outward-facing conformation causes charge repulsion between ABCB6 and the bound substrate, and rearrangement of key interacting residues at the substrate-binding site. Consequently, the affinity for the substrate is significantly reduced, facilitating its release from the transporter.
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Affiliation(s)
- Sang Soo Lee
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Jun Gyou Park
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Eunhong Jang
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Seung Hun Choi
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Subin Kim
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea
| | - Ji Won Kim
- Department of Life Sciences, POSTECH, 77 Cheongam-Ro, Nam-gu, Pohang, 37673, Republic of Korea
| | - Mi Sun Jin
- School of Life Sciences, GIST, 123 Cheomdan-gwagiro, Buk-gu, Gwangju, 61005, Republic of Korea.
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7
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Abstract
ABC transporters are essential for cellular physiology. Humans have 48 ABC genes organized into seven distinct families. Of these genes, 44 (in five distinct families) encode for membrane transporters, of which several are involved in drug resistance and disease pathways resulting from transporter dysfunction. Over the last decade, advances in structural biology have vastly expanded our mechanistic understanding of human ABC transporter function, revealing details of their molecular arrangement, regulation, and interactions, facilitated in large part by advances in cryo-EM that have rendered hitherto inaccessible targets amenable to high-resolution structural analysis. As a result, experimentally determined structures of multiple members of each of the five families of ABC transporters in humans are now available. Here we review this recent progress, highlighting the physiological relevance of human ABC transporters and mechanistic insights gleaned from their direct structure determination. We also discuss the impact and limitations of model systems and structure prediction methods in understanding human ABC transporters and discuss current challenges and future research directions.
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Affiliation(s)
- Amer Alam
- The Hormel Institute, University of Minnesota, Austin, Minnesota, USA
| | - Kaspar P Locher
- Institute of Molecular Biology and Biophysics, ETH Zurich, Switzerland;
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8
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The lysosomal transporter TAPL has a dual role as peptide translocator and phosphatidylserine floppase. Nat Commun 2022; 13:5851. [PMID: 36195619 PMCID: PMC9532399 DOI: 10.1038/s41467-022-33593-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Accepted: 09/23/2022] [Indexed: 11/08/2022] Open
Abstract
TAPL is a lysosomal ATP-binding cassette transporter that translocates a broad spectrum of polypeptides from the cytoplasm into the lysosomal lumen. Here we report that, in addition to its well-known role as a peptide translocator, TAPL exhibits an ATP-dependent phosphatidylserine floppase activity that is the possible cause of its high basal ATPase activity and of the lack of coupling between ATP hydrolysis and peptide efflux. We also present the cryo-EM structures of mouse TAPL complexed with (i) phospholipid, (ii) cholesteryl hemisuccinate (CHS) and 9-mer peptide, and (iii) ADP·BeF3. The inward-facing structure reveals that F449 protrudes into the cylindrical transport pathway and divides it into a large hydrophilic central cavity and a sizable hydrophobic upper cavity. In the structure, the peptide binds to TAPL in horizontally-stretched fashion within the central cavity, while lipid molecules plug vertically into the upper cavity. Together, our results suggest that TAPL uses different mechanisms to function as a peptide translocase and a phosphatidylserine floppase.
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9
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Hou W, Xu D, Wang L, Chen Y, Chen Z, Zhou C, Chen Y. Plastic structures for diverse substrates: A revisit of human
ABC
transporters. Proteins 2022; 90:1749-1765. [DOI: 10.1002/prot.26406] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 07/31/2022] [Accepted: 08/01/2022] [Indexed: 12/18/2022]
Affiliation(s)
- Wen‐Tao Hou
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Da Xu
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Liang Wang
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Yu Chen
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Zhi‐Peng Chen
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Cong‐Zhao Zhou
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Yuxing Chen
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
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10
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Kim S, Lee SS, Park JG, Kim JW, Ju S, Choi SH, Kim S, Kim NJ, Hong S, Kang JY, Jin MS. Structural Insights into Porphyrin Recognition by the Human ATP-Binding Cassette Transporter ABCB6. Mol Cells 2022; 45:575-587. [PMID: 35950458 PMCID: PMC9385563 DOI: 10.14348/molcells.2022.0040] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2022] [Revised: 04/07/2022] [Accepted: 04/07/2022] [Indexed: 11/27/2022] Open
Abstract
Human ABCB6 is an ATP-binding cassette transporter that regulates heme biosynthesis by translocating various porphyrins from the cytoplasm into the mitochondria. Here we report the cryo-electron microscopy (cryo-EM) structures of human ABCB6 with its substrates, coproporphyrin III (CPIII) and hemin, at 3.5 and 3.7 Å resolution, respectively. Metalfree porphyrin CPIII binds to ABCB6 within the central cavity, where its propionic acids form hydrogen bonds with the highly conserved Y550. The resulting structure has an overall fold similar to the inward-facing apo structure, but the two nucleotide-binding domains (NBDs) are slightly closer to each other. In contrast, when ABCB6 binds a metal-centered porphyrin hemin in complex with two glutathione molecules (1 hemin: 2 glutathione), the two NBDs end up much closer together, aligning them to bind and hydrolyze ATP more efficiently. In our structures, a glycine-rich and highly flexible "bulge" loop on TM helix 7 undergoes significant conformational changes associated with substrate binding. Our findings suggest that ABCB6 utilizes at least two distinct mechanisms to fine-tune substrate specificity and transport efficiency.
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Affiliation(s)
- Songwon Kim
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Sang Soo Lee
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Jun Gyou Park
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Ji Won Kim
- Department of Life Sciences, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea
| | - Seulgi Ju
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Seung Hun Choi
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Subin Kim
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Na Jin Kim
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Semi Hong
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
| | - Jin Young Kang
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Mi Sun Jin
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Korea
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11
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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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12
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Fan C, Rees DC. Glutathione binding to the plant AtAtm3 transporter and implications for the conformational coupling of ABC transporters. eLife 2022; 11:76140. [PMID: 35333177 PMCID: PMC9000953 DOI: 10.7554/elife.76140] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 03/23/2022] [Indexed: 11/13/2022] Open
Abstract
The ATP Binding Cassette (ABC) transporter of mitochondria (Atm) from Arabidopsis thaliana (AtAtm3) has been implicated in the maturation of cytosolic iron-sulfur proteins and heavy metal detoxification, plausibly by exporting glutathione derivatives. Using single-particle cryo-electron microscopy, we have determined four structures of AtAtm3 in three different conformational states: two inward-facing conformations (with and without bound oxidized glutathione (GSSG)), together with closed and outward-facing states stabilized by MgADP-VO4. These structures not only provide a structural framework for defining the alternating access transport cycle, but also reveal the paucity of cysteine residues in the glutathione binding site that could potentially form inhibitory mixed disulfides with GSSG. Despite extensive efforts, we were unable to prepare the ternary complex of AtAtm3 containing both GSSG and MgATP. A survey of structurally characterized type IV ABC transporters that includes AtAtm3 establishes that while nucleotides are found associated with all conformational states, they are effectively required to stabilize occluded, closed, and outward-facing conformations. In contrast, transport substrates have only been observed associated with inward-facing conformations. The absence of structures with dimerized nucleotide binding domains containing both nucleotide and transport substrate suggests that this form of the ternary complex exists only transiently during the transport cycle.
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Affiliation(s)
- Chengcheng Fan
- Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, United States
| | - Douglas C Rees
- Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena, United States
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Analysis of corticosteroid and antiepileptic drug treatment effects on heme biosynthesis mRNA expression in lower-grade gliomas: potential implications for 5-ALA metabolization. Photodiagnosis Photodyn Ther 2022; 38:102755. [PMID: 35149260 DOI: 10.1016/j.pdpdt.2022.102755] [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: 12/26/2021] [Revised: 01/22/2022] [Accepted: 02/07/2022] [Indexed: 11/24/2022]
Abstract
OBJECTIVES Intraoperative visualization of gliomas with 5-aminolevulinic acid (5-ALA) induced fluorescence constitutes a powerful technique. While visible fluorescence is typically observed in high-grade gliomas, fluorescence is considerably less common in lower-grade gliomas (LGGs) WHO grade II&III. Whereas the exact mechanisms determining fluorescence in LGGs are not fully understood, metabolization of non-fluorescent 5-ALA to fluorescent Protoporphyrin IX by specific heme biosynthesis enzymes/transporters has been identified as relevant mechanism influencing fluorescence behavior. Furthermore, recent in-vitro studies have suggested preoperative treatment with corticosteroids and anti-epileptic drugs (AED) as potential factors influencing 5-ALA induced fluorescence. METHODS The goal of this study was thus to investigate the effect of preoperative corticosteroid/AED treatment on heme biosynthesis mRNA expression in a clinically relevant patient population. For this purpose, we analyzed the mRNA expression levels of specific heme biosynthesis factors including ALAD, HMBS, UROS, UROD, CPOX, PPOX, FECH, ABCB6, ACG2, SLC15A1 and SLC15A2, ABCB1, ABCB10 in a cohort of LGGs from "The Cancer Genome Atlas". RESULTS Altogether, 403 patients with available data on preoperative corticosteroid/AED treatment and heme biosynthesis mRNA expression were identified. Regarding corticosteroid treatment, no significant differences in expression of any of the 11 investigated heme biosynthesis factors were found. In contrast, a marginal yet statistically significant increase in SLC15A1 levels and decrease in ABCB6 levels were observed in patients with preoperative AED treatment. CONCLUSION While no significant differences in heme biosynthesis mRNA expression were observed according to preoperative corticosteroid treatment, changes in SLC15A1 as well as ABCB6 expression were detected in patients treated with AED. However, since these alterations were minor and have opposing effects on 5-ALA metabolization, our findings do not support a distinct effect of AED and corticosteroid treatment on heme biosynthesis regulation in LGGs.
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Structural basis of acyl-CoA transport across the peroxisomal membrane by human ABCD1. Cell Res 2022; 32:214-217. [PMID: 34754073 PMCID: PMC8807786 DOI: 10.1038/s41422-021-00585-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Accepted: 10/18/2021] [Indexed: 02/03/2023] Open
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Sun Y, Li X. Cholesterol efflux mechanism revealed by structural analysis of human ABCA1 conformational states. NATURE CARDIOVASCULAR RESEARCH 2022; 1:238-245. [PMID: 37181814 PMCID: PMC10181854 DOI: 10.1038/s44161-022-00022-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
ATP-binding cassette transporter A1 (ABCA1) utilizes energy derived from ATP hydrolysis to export cholesterol and phospholipids from macrophages. ABCA1 plays a central role in the biosynthesis of high-density lipoprotein (HDL), which mediates reverse cholesterol transport and prevents detrimental lipid deposition. Mutations in ABCA1 cause Tangier disease characterized by a remarkable reduction in the amount of HDL in blood. Here we present cryo-electron microscopy structures of human ABCA1 in ATP-bound and nucleotide-free states. Structural comparison reveals that ATP molecules pull the nucleotide-binding domains together, inducing movements of transmembrane helices 1, 2, 7 and 8 through a series of salt-bridge interactions. Subsequently, extracellular domains (ECDs) undergo a rotation and introduce conformational changes in the ECD-transmembrane interface. In addition, while we observe a sterol-like molecule in ECDs, no such density was observed in the structure of an HDL-deficiency mutant ABCA1Y482C, demonstrating the physiological importance of ECDs and a putative interaction mode between ABCA1 and its lipid acceptors. Thus, these structures, along with cholesterol efflux assays, advance the understanding ABCA1-mediated reverse cholesterol transport.
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Affiliation(s)
- Yingyuan Sun
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Xiaochun Li
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Correspondence and requests for materials should be addressed to Xiaochun Li.
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Ricci A, Di Pierro E, Marcacci M, Ventura P. Mechanisms of Neuronal Damage in Acute Hepatic Porphyrias. Diagnostics (Basel) 2021; 11:diagnostics11122205. [PMID: 34943446 PMCID: PMC8700611 DOI: 10.3390/diagnostics11122205] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 11/22/2021] [Accepted: 11/24/2021] [Indexed: 01/12/2023] Open
Abstract
Porphyrias are a group of congenital and acquired diseases caused by an enzymatic impairment in the biosynthesis of heme. Depending on the specific enzyme involved, different types of porphyrias (i.e., chronic vs. acute, cutaneous vs. neurovisceral, hepatic vs. erythropoietic) are described, with different clinical presentations. Acute hepatic porphyrias (AHPs) are characterized by life-threatening acute neuro-visceral crises (acute porphyric attacks, APAs), featuring a wide range of neuropathic (central, peripheral, autonomic) manifestations. APAs are usually unleashed by external "porphyrinogenic" triggers, which are thought to cause an increased metabolic demand for heme. During APAs, the heme precursors δ-aminolevulinic acid (ALA) and porphobilinogen (PBG) accumulate in the bloodstream and urine. Even though several hypotheses have been developed to explain the protean clinical picture of APAs, the exact mechanism of neuronal damage in AHPs is still a matter of debate. In recent decades, a role has been proposed for oxidative damage caused by ALA, mitochondrial and synaptic ALA toxicity, dysfunction induced by relative heme deficiency on cytochromes and other hemeproteins (i.e., nitric oxide synthases), pyridoxal phosphate functional deficiency, derangements in the metabolic pathways of tryptophan, and other factors. Since the pathway leading to the biosynthesis of heme is inscribed into a complex network of interactions, which also includes some fundamental processes of basal metabolism, a disruption in any of the steps of this pathway is likely to have multiple pathogenic effects. Here, we aim to provide a comprehensive review of the current evidence regarding the mechanisms of neuronal damage in AHPs.
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Affiliation(s)
- Andrea Ricci
- Internal Medicine Unit, Department of Medical and Surgical Science for Children and Adults, University of Modena e Reggio Emilia, 41124 Modena, Italy; (A.R.); (M.M.)
| | - Elena Di Pierro
- Dipartimento di Medicina Interna, Fondazione IRCSS Cà Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy;
| | - Matteo Marcacci
- Internal Medicine Unit, Department of Medical and Surgical Science for Children and Adults, University of Modena e Reggio Emilia, 41124 Modena, Italy; (A.R.); (M.M.)
| | - Paolo Ventura
- Internal Medicine Unit, Department of Medical and Surgical Science for Children and Adults, University of Modena e Reggio Emilia, 41124 Modena, Italy; (A.R.); (M.M.)
- Correspondence: ; Tel.: +39-059-4225-542
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Rayner RE, Wellmerling J, Makena P, Zhao J, Prasad GL, Cormet-Boyaka E. Transcriptomic Response of Primary Human Bronchial Cells to Repeated Exposures of Cigarette and ENDS Preparations. Cell Biochem Biophys 2021; 80:217-228. [PMID: 34767151 DOI: 10.1007/s12013-021-01042-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 10/14/2021] [Indexed: 12/28/2022]
Abstract
Cigarette smoke deregulates several biological pathways by modulating gene expression in airway epithelial cells and altering the physiology of the airway epithelium. The effects of repeated exposures of electronic cigarette delivery systems (ENDS) on gene expression in airway epithelium are relatively unknown. In order to assess the effect of repeated exposures of ENDS, primary normal human bronchial epithelial (NHBE) cells grown at air-liquid interface (ALI) were exposed to cigarette and ENDS preparations daily for 10 days. Cigarette smoke preparations significantly altered gene expression in a dose-dependent manner compared to vehicle control, including genes linked to oxidative stress, xenobiotic metabolism, cancer pathways, epithelial-mesenchymal transition, fatty acid metabolism, degradation of collagen and extracellular matrix, O-glycosylation, and chemokines/cytokines, which are known pathways found to be altered in smokers. Conversely, ENDS preparations had minimal effect on transcriptional pathways. This study revealed that a sub-chronic exposure of primary NHBE cultures to cigarette and ENDS preparations differentially regulated genes and canonical pathways, with minimal effect observed with ENDS preparations compared to cigarette preparations. This study also demonstrates the versatility of primary NHBE cultures at ALI to evaluate repeat-dose exposures of tobacco products.
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Affiliation(s)
- Rachael E Rayner
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, 43210, USA
| | - Jack Wellmerling
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, 43210, USA
| | | | - Jing Zhao
- Department of Biomedical Informatics, The Ohio State University, Columbus, OH, 43210, USA
| | - G L Prasad
- Prasad Scientific Consulting LLC, Lewisville, NC, USA.,Prior employee of RAI Services Company, Winston-Salem, NC, USA
| | - Estelle Cormet-Boyaka
- Department of Veterinary Biosciences, The Ohio State University, Columbus, OH, 43210, USA.
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