Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter
The heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the biliary and transintestinal secretion of cholesterol and dietary plant sterols. Missense mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumul...
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| Format: | Article |
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MDPI AG
2020-11-01
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| Series: | International Journal of Molecular Sciences |
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| Online Access: | https://www.mdpi.com/1422-0067/21/22/8747 |
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| author | Bala M. Xavier Aiman A. Zein Angelica Venes Junmei Wang Jyh-Yeuan Lee |
| author_facet | Bala M. Xavier Aiman A. Zein Angelica Venes Junmei Wang Jyh-Yeuan Lee |
| author_sort | Bala M. Xavier |
| collection | DOAJ |
| description | The heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the biliary and transintestinal secretion of cholesterol and dietary plant sterols. Missense mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis. A new molecular framework was recently established by a crystal structure of human ABCG5/G8 and reveals a network of polar and charged amino acids in the core of the transmembrane domains, namely, a polar relay. In this study, we utilize genetic variants to dissect the mechanistic role of this transmembrane polar relay in controlling ABCG5/G8 function. We demonstrated a sterol-coupled ATPase activity of ABCG5/G8 by cholesteryl hemisuccinate (CHS), a relatively water-soluble cholesterol memetic, and characterized CHS-coupled ATPase activity of three loss-of-function missense variants, R543S, E146Q, and A540F, which are respectively within, in contact with, and distant from the polar relay. The results established an in vitro phenotype of the loss-of-function and missense mutations of ABCG5/G8, showing significantly impaired ATPase activity and loss of energy sufficient to weaken the signal transmission from the transmembrane domains. Our data provide a biochemical evidence underlying the importance of the polar relay and its network in regulating the catalytic activity of ABCG5/G8 sterol transporter. |
| first_indexed | 2024-03-10T14:43:59Z |
| format | Article |
| id | doaj.art-8b6c2866a61749feb8871ad97fd6635d |
| institution | Directory Open Access Journal |
| issn | 1661-6596 1422-0067 |
| language | English |
| last_indexed | 2024-03-10T14:43:59Z |
| publishDate | 2020-11-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | International Journal of Molecular Sciences |
| spelling | doaj.art-8b6c2866a61749feb8871ad97fd6635d2023-11-20T21:34:33ZengMDPI AGInternational Journal of Molecular Sciences1661-65961422-00672020-11-012122874710.3390/ijms21228747Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol TransporterBala M. Xavier0Aiman A. Zein1Angelica Venes2Junmei Wang3Jyh-Yeuan Lee4Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, CanadaDepartment of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, CanadaDepartment of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, CanadaDepartment of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, PA 15206, USADepartment of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, CanadaThe heterodimeric ATP-binding cassette (ABC) sterol transporter, ABCG5/G8, is responsible for the biliary and transintestinal secretion of cholesterol and dietary plant sterols. Missense mutations of ABCG5/G8 can cause sitosterolemia, a loss-of-function disorder characterized by plant sterol accumulation and premature atherosclerosis. A new molecular framework was recently established by a crystal structure of human ABCG5/G8 and reveals a network of polar and charged amino acids in the core of the transmembrane domains, namely, a polar relay. In this study, we utilize genetic variants to dissect the mechanistic role of this transmembrane polar relay in controlling ABCG5/G8 function. We demonstrated a sterol-coupled ATPase activity of ABCG5/G8 by cholesteryl hemisuccinate (CHS), a relatively water-soluble cholesterol memetic, and characterized CHS-coupled ATPase activity of three loss-of-function missense variants, R543S, E146Q, and A540F, which are respectively within, in contact with, and distant from the polar relay. The results established an in vitro phenotype of the loss-of-function and missense mutations of ABCG5/G8, showing significantly impaired ATPase activity and loss of energy sufficient to weaken the signal transmission from the transmembrane domains. Our data provide a biochemical evidence underlying the importance of the polar relay and its network in regulating the catalytic activity of ABCG5/G8 sterol transporter.https://www.mdpi.com/1422-0067/21/22/8747ABCG5ABCG8ATP-binding cassette transportercholesterolpolar relaysitosterolemia |
| spellingShingle | Bala M. Xavier Aiman A. Zein Angelica Venes Junmei Wang Jyh-Yeuan Lee Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter International Journal of Molecular Sciences ABCG5 ABCG8 ATP-binding cassette transporter cholesterol polar relay sitosterolemia |
| title | Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter |
| title_full | Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter |
| title_fullStr | Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter |
| title_full_unstemmed | Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter |
| title_short | Transmembrane Polar Relay Drives the Allosteric Regulation for ABCG5/G8 Sterol Transporter |
| title_sort | transmembrane polar relay drives the allosteric regulation for abcg5 g8 sterol transporter |
| topic | ABCG5 ABCG8 ATP-binding cassette transporter cholesterol polar relay sitosterolemia |
| url | https://www.mdpi.com/1422-0067/21/22/8747 |
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