| Structural highlights
Function
ABCG2_HUMAN High-capacity urate exporter functioning in both renal and extrarenal urate excretion. Plays a role in porphyrin homeostasis as it is able to mediates the export of protoporhyrin IX (PPIX) both from mitochondria to cytosol and from cytosol to extracellular space, and cellular export of hemin, and heme. Xenobiotic transporter that may play an important role in the exclusion of xenobiotics from the brain. Appears to play a major role in the multidrug resistance phenotype of several cancer cell lines. Implicated in the efflux of numerous drugs and xenobiotics: mitoxantrone, the photosensitizer pheophorbide, camptothecin, methotrexate, azidothymidine (AZT), and the anthracyclines daunorubicin and doxorubicin.[1] [2] [3] [4]
Publication Abstract from PubMed
ABCG2 is an ATP-binding cassette transporter that exports a wide range of xenobiotic compounds and has been recognized as a contributing factor for multidrug resistance in cancer cells. Substrate and inhibitor interactions with ABCG2 have been extensively studied and small molecule inhibitors have been developed that prevent the export of anticancer drugs from tumor cells. Here, we explore the potential for inhibitors that target sites other than the substrate binding pocket of ABCG2. We developed novel nanobodies against ABCG2 and used functional analyses to select three inhibitory nanobodies (Nb8, Nb17 and Nb96) for structural studies by single particle cryo-electron microscopy. Our results showed that these nanobodies allosterically bind to different regions of the nucleotide binding domains. Two copies of Nb8 bind to the apex of the NBDs preventing them from fully closing. Nb17 binds near the two-fold axis of the transporter and interacts with both NBDs. Nb96 binds to the side of the NBD and immobilizes a region connected to key motifs involved in ATP binding and hydrolysis. All three nanobodies prevent the transporter from undergoing conformational changes required for substrate transport. These findings advance our understanding of the molecular basis of modulation of ABCG2 by external binders, which may contribute to the development of a new generation of inhibitors. Furthermore, this is the first example of modulation of human multidrug resistance transporters by nanobodies.
Structural basis of the allosteric inhibition of human ABCG2 by nanobodies.,Irobalieva RN, Manolaridis I, Jackson SM, Ni D, Pardon E, Stahlberg H, Steyaert J, Locher KP J Mol Biol. 2023 Aug 17:168234. doi: 10.1016/j.jmb.2023.168234. PMID:37597690[5]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Zhang W, Mojsilovic-Petrovic J, Andrade MF, Zhang H, Ball M, Stanimirovic DB. The expression and functional characterization of ABCG2 in brain endothelial cells and vessels. FASEB J. 2003 Nov;17(14):2085-7. Epub 2003 Sep 4. PMID:12958161 doi:http://dx.doi.org/10.1096/fj.02-1131fje
- ↑ Desuzinges-Mandon E, Arnaud O, Martinez L, Huche F, Di Pietro A, Falson P. ABCG2 transports and transfers heme to albumin through its large extracellular loop. J Biol Chem. 2010 Oct 22;285(43):33123-33. doi: 10.1074/jbc.M110.139170. Epub, 2010 Aug 12. PMID:20705604 doi:http://dx.doi.org/10.1074/jbc.M110.139170
- ↑ Nakayama A, Matsuo H, Takada T, Ichida K, Nakamura T, Ikebuchi Y, Ito K, Hosoya T, Kanai Y, Suzuki H, Shinomiya N. ABCG2 is a high-capacity urate transporter and its genetic impairment increases serum uric acid levels in humans. Nucleosides Nucleotides Nucleic Acids. 2011 Dec;30(12):1091-7. doi:, 10.1080/15257770.2011.633953. PMID:22132962 doi:http://dx.doi.org/10.1080/15257770.2011.633953
- ↑ Kobuchi H, Moriya K, Ogino T, Fujita H, Inoue K, Shuin T, Yasuda T, Utsumi K, Utsumi T. Mitochondrial localization of ABC transporter ABCG2 and its function in 5-aminolevulinic acid-mediated protoporphyrin IX accumulation. PLoS One. 2012;7(11):e50082. doi: 10.1371/journal.pone.0050082. Epub 2012 Nov 26. PMID:23189181 doi:http://dx.doi.org/10.1371/journal.pone.0050082
- ↑ Irobalieva RN, Manolaridis I, Jackson SM, Ni D, Pardon E, Stahlberg H, Steyaert J, Locher KP. Structural basis of the allosteric inhibition of human ABCG2 by nanobodies. J Mol Biol. 2023 Aug 17:168234. PMID:37597690 doi:10.1016/j.jmb.2023.168234
|
