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Mitchell-White JI, Briggs DA, Mistry SJ, Mbiwan HA, Kellam B, Holliday ND, Briddon SJ, Kerr ID. A time-resolved Förster resonance energy transfer assay to investigate drug and inhibitor binding to ABCG2. Arch Biochem Biophys 2024; 753:109915. [PMID: 38307314 DOI: 10.1016/j.abb.2024.109915] [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: 10/27/2023] [Revised: 12/21/2023] [Accepted: 01/17/2024] [Indexed: 02/04/2024]
Abstract
The human ATP-binding cassette (ABC) transporter, ABCG2, is responsible for multidrug resistance in some tumours. Detailed knowledge of its activity is crucial for understanding drug transport and resistance in cancer, and has implications for wider pharmacokinetics. The binding of substrates and inhibitors is a key stage in the transport cycle of ABCG2. Here, we describe a novel binding assay using a high affinity fluorescent inhibitor based on Ko143 and time-resolved Förster resonance energy transfer (TR-FRET) to measure saturation binding to ABCG2. This binding is displaced by Ko143 and other known ABCG2 ligands, and is sensitive to the addition of AMP-PNP, a non-hydrolysable ATP analogue. This assay complements the arsenal of methods for determining drug:ABCG2 interactions and has the possibility of being adaptable for other multidrug pumps.
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Affiliation(s)
- James I Mitchell-White
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK; Centre of Membrane Proteins and Receptors, Universities of Birmingham and Nottingham, The Midlands, UK.
| | - Deborah A Briggs
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK
| | - Sarah J Mistry
- School of Pharmacy, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Hannah A Mbiwan
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK; School of Pharmacy, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Barrie Kellam
- School of Pharmacy, University of Nottingham, Nottingham, NG7 2UH, UK
| | - Nicholas D Holliday
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK
| | - Stephen J Briddon
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK; Centre of Membrane Proteins and Receptors, Universities of Birmingham and Nottingham, The Midlands, UK
| | - Ian D Kerr
- School of Life Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, NG7 2UH, UK.
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Analysis of Sequence Divergence in Mammalian ABCGs Predicts a Structural Network of Residues That Underlies Functional Divergence. Int J Mol Sci 2021; 22:ijms22063012. [PMID: 33809494 PMCID: PMC8001107 DOI: 10.3390/ijms22063012] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 03/08/2021] [Accepted: 03/12/2021] [Indexed: 12/17/2022] Open
Abstract
The five members of the mammalian G subfamily of ATP-binding cassette transporters differ greatly in their substrate specificity. Four members of the subfamily are important in lipid transport and the wide substrate specificity of one of the members, ABCG2, is of significance due to its role in multidrug resistance. To explore the origin of substrate selectivity in members 1, 2, 4, 5 and 8 of this subfamily, we have analysed the differences in conservation between members in a multiple sequence alignment of ABCG sequences from mammals. Mapping sets of residues with similar patterns of conservation onto the resolved 3D structure of ABCG2 reveals possible explanations for differences in function, via a connected network of residues from the cytoplasmic to transmembrane domains. In ABCG2, this network of residues may confer extra conformational flexibility, enabling it to transport a wider array of substrates.
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Khunweeraphong N, Mitchell-White J, Szöllősi D, Hussein T, Kuchler K, Kerr ID, Stockner T, Lee JY. Picky ABCG5/G8 and promiscuous ABCG2 - a tale of fatty diets and drug toxicity. FEBS Lett 2020; 594:4035-4058. [PMID: 32978801 PMCID: PMC7756502 DOI: 10.1002/1873-3468.13938] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Accepted: 09/03/2020] [Indexed: 12/20/2022]
Abstract
Structural data on ABCG5/G8 and ABCG2 reveal a unique molecular architecture for subfamily G ATP‐binding cassette (ABCG) transporters and disclose putative substrate‐binding sites. ABCG5/G8 and ABCG2 appear to use several unique structural motifs to execute transport, including the triple helical bundles, the membrane‐embedded polar relay, the re‐entry helices, and a hydrophobic valve. Interestingly, ABCG2 shows extreme substrate promiscuity, whereas ABCG5/G8 transports only sterol molecules. ABCG2 structures suggest a large internal cavity, serving as a binding region for substrates and inhibitors, while mutational and pharmacological analyses support the notion of multiple binding sites. By contrast, ABCG5/G8 shows a collapsed cavity of insufficient size to hold substrates. Indeed, mutational analyses indicate a sterol‐binding site at the hydrophobic interface between the transporter and the lipid bilayer. In this review, we highlight key differences and similarities between ABCG2 and ABCG5/G8 structures. We further discuss the relevance of distinct and shared structural features in the context of their physiological functions. Finally, we elaborate on how ABCG2 and ABCG5/G8 could pave the way for studies on other ABCG transporters.
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Affiliation(s)
- Narakorn Khunweeraphong
- Max Perutz Labs Vienna, Campus Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, Vienna, Austria.,CCRI-St. Anna Children's Cancer Research Institute, Vienna, Austria
| | - James Mitchell-White
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
| | - Dániel Szöllősi
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Toka Hussein
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Karl Kuchler
- Max Perutz Labs Vienna, Campus Vienna Biocenter, Center for Medical Biochemistry, Medical University of Vienna, Vienna, Austria
| | - Ian D Kerr
- School of Life Sciences, Queen's Medical Centre, University of Nottingham, Nottingham, UK
| | - Thomas Stockner
- Center for Physiology and Pharmacology, Institute of Pharmacology, Medical University of Vienna, Vienna, Austria
| | - Jyh-Yeuan Lee
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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