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Miwa S, Takikawa H, Takeuchi R, Mizunuma R, Matsuoka K, Ogawa H, Kato H, Takasu K. Structure-ATPase Activity Relationship of Rhodamine Derivatives as Potent Inhibitors of P-Glycoprotein CmABCB1. ACS Med Chem Lett 2024; 15:287-293. [PMID: 38352840 PMCID: PMC10860176 DOI: 10.1021/acsmedchemlett.3c00526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 01/05/2024] [Accepted: 01/13/2024] [Indexed: 02/16/2024] Open
Abstract
Understanding the transport and inhibition mechanisms of substrates by P-glycoprotein (P-gp) is one of the important approaches in addressing multidrug resistance (MDR). In this study, we evaluated a variety of rhodamine derivatives as potential P-gp inhibitors targeting CmABCB1, a P-gp homologue, with a focus on their ATPase activity. Notably, a Q-rhodamine derivative with an o,o'-dimethoxybenzyl ester moiety (RhQ-DMB) demonstrated superior affinity and inhibitory activity, which was further confirmed by a drug susceptibility assay in yeast strains expressing CmABCB1. Results from a tryptophan fluorescence quenching experiment using a CmABCB1 mutant suggested that RhQ-DMB effectively enters and binds to the inner chamber of CmABCB1. These findings underscore the promising potential of RhQ-DMB as a tool for future studies aimed at elucidating the substrate-bound state of CmABCB1.
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Affiliation(s)
- Sorachi Miwa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hiroshi Takikawa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Rina Takeuchi
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Ryo Mizunuma
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Keita Matsuoka
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Haruo Ogawa
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hiroaki Kato
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
- RIKEN Harima Institute at SPring-8, Hyogo 679-5148 Japan
| | - Kiyosei Takasu
- Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
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Inoue Y, Yamaguchi T, Otsuka T, Utsunomiya Y, Pan D, Ogawa H, Kato H. Structure-based alteration of tryptophan residues of the multidrug transporter CmABCB1 to assess substrate binding using fluorescence spectroscopy. Protein Sci 2022; 31:e4331. [PMID: 35634783 PMCID: PMC9123602 DOI: 10.1002/pro.4331] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Revised: 03/01/2022] [Accepted: 04/06/2022] [Indexed: 09/17/2023]
Abstract
ABCB1, also known as P-glycoprotein, is an essential component of many physiological barriers and extrudes a variety of hydrophobic chemicals out of the cell. Structures of ABCB1 provided insights into the structural changes that occur upon ATP binding and the characteristic architecture of the substrate binding site. Yet, the structure-function relationship between substrate binding and transporting still remains largely obscured because there is no robust method for accurately measuring substrate binding constants. The methods currently used cannot identify whether the bound substrates are located in the inner chamber of the molecule in the transmembrane region or not because of the low spatial resolution. Here, we report a system for measuring the affinity of substrate binding to the Cyanidioschyzon merolae ABCB1 (CmABCB1) using site-specific tryptophan (Trp) fluorescence quenching. We designed a CmABCB1 mutant with an extrinsic Trp residue introduced into the inner chamber. Trp fluorescence was quenched by three substrates and one inhibitor, including rhodamine 6G, in a saturable fashion, allowing for accurate estimation of the dissociation constant (KD ) for each molecule. The KD for rhodamine 6G is similar to that determined using a reciprocal fluorescence quenching assay using rhodamine 6G fluorescence, suggesting that Trp fluorescence of the mutant was quenched by the interaction between the extrinsic Trp and substrates bound in the inner chamber. Structural comparison of the ABCB1 structures suggests that the system presented in this study could be ideal method of choice to determine the substrate binding affinities of compounds bound to the chamber of mammalian ABCB1.
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Affiliation(s)
- Yoshiki Inoue
- Department of Structural Biology, Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Tomohiro Yamaguchi
- Department of Structural Biology, Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Tetsuo Otsuka
- Department of Structural Biology, Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Yuto Utsunomiya
- Department of Structural Biology, Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Dongqing Pan
- Department of Structural Biology, Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Haruo Ogawa
- Department of Structural Biology, Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
| | - Hiroaki Kato
- Department of Structural Biology, Graduate School of Pharmaceutical SciencesKyoto UniversityKyotoJapan
- Advanced Photon Technology DivisionRIKEN Harima Institute at SPring‐8Sayo‐gunHyogoJapan
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