Thesis supervisor: Katalin Goda
Location of studies (in Hungarian): University of Debrecen Abbreviation of location of studies: DEAOK
Description of the research topic:
The human ABCG2 protein (also known as Breast Cancer Resistance Protein (BCRP)) is a primary active transporter belonging to the ATP-binding cassette (ABC) protein superfamily. It can expel large variety of chemically unrelated, mainly hydrophobic or amphipathic compounds from cells, such as chemotherapeutic drugs used for the treatment of various diseases. ABCG2 is expressed in tissues with barrier functions including the blood-brain barrier, blood-testis barrier, intestine, liver, placenta, and kidneys. Based on its tissue localization and broad substrate spectrum ABCG2 plays an important role in the absorption, distribution, elimination, and toxicity (ADME-Tox) of chemotherapeutic drugs used for the treatment of various diseases. In addition, its expression in tumor tissues correlates with an unfavourable prognosis of tumor chemotherapy. On the other hand, genetic polymorphisms leading to decreased expression and/or impaired function of ABCG2 may result in various pathological conditions including hyperuricemia and gout.
The ABCG2 gene codes a “half transporter” consisting of one NBD and one TMD that form a dimer to make a functionally active transporter. Based on structural studies, in absence of ATP, apo-ABCG2 adopts an inward-facing (IF) state, wherein the substrate binding cavity is open towards the cytosolic side, while ATP-bound ABCG2 is in an outward-facing (OF) state, allowing the release of substrates to the extracellular side. Although the recent boom of structural studies, especially the cryo-EM technique served high-resolution structures of different ABCG2 conformers, the details of the structural and energetic interplay between the NBDs and TMDs remains unclear.
We would like to contribute to an improved understanding of ABCG2 function by elucidating the crosstalk between the NBDs and the TMDs. For studying the conformational changes of NBDs, we aim to develop a fluorescence resonance energy transfer (FRET)-based system, while the conformation changes of TMDs will be followed by measuring reactivity to a conformation selective monoclonal antibody (5D3) recognizing the IF ABCG2 conformer. In addition, we would like to develop a protocol for the functional integration of ABCG2 into membrane mimetic nanoparticles (nanodiscs) to serve a simple, reproducible system for FRET measurements.
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