Interaction of ABCG2 with EMMPRIN and alpha-1-acid glycoprotein
Background
ABCG2 is a member of the ATP binding cassette family of membrane transporters and is one of at least three so-called multidrug pumps, capable of effluxing a broad range of substrates from cells [1]. Understanding the activity of multidrug pumps is a critical requirement for drug discovery as these transporters are known to affect the bioavailability of many pharmaceuticals. Additionally, these multidrug pumps have a recognised role in contributing to the failure of cancer chemotherapy by conferring multidrug resistance (MDR) upon tumours. For a decade or more my lab has been interested in the protein:drug interactions in ABCG2[2]; more recently we have become interested in ABCG2’s protein:protein interactions and there are two current lines of research that we would investigate in this “Magnify” project.
Could ABCG2-interacting proteins stabilise the transporter and speed up the transport rate?We are presently investigating ABCG2’s interaction with another membrane protein, EMMPRIN (CD147, basigin). Although widely recognised as an activator of matrix metalloproteinases there is growing evidence that its interaction partners are considerably wider than this family of extracellular enzymes (e.g. [3]). We hypothesise that it may have a general chaperone function for ABCG2 and may act to increase expression of ABCG2 at the cell membrane, either by facilitating ER trafficking, or by stabilising plasma membrane ABCG2. We are investigating this in our lab by expression of EMMPRIN into HEK293T cells clonally isolated to express low levels of ABCG2 to determine if there is increased cell surface expression of the transporter. We would also investigate if the stability of ABCG2 was enhanced following EMMPRIN expression by thermostability assays.
A second protein:protein interaction we are investigating is with the acute phase plasma protein alpha 1-acid glycoprotein (AAG). Our hypothesis is based upon existing evidence that interaction of ABCG2 with plasma proteins may facilitate the rate of transport by the protein, by preventing the immediate cellular re-entry of exported (but hydrophobic) drug substrates [4]. In our lab we are investigating this in HEK293T cells clonally isolated to express high levels of ABCG2 and determining the transport/efflux rate of typical ABCG2 substrates (e.g. mitoxantrone) in the presence or absence of increasing concentrations of AAG.
In the Magnify project the student would work alongside PGR student(s) in the lab working on these two streams of research.
References
[1] B. Sarkadi, L. Homolya, G. Szakacs, A. Varadi, Human multidrug resistance ABCB and ABCG transporters: participation in a chemoimmunity defense system, Physiol Rev 86(4) (2006) 1179-236.
[2] P. Kapoor, D.A. Briggs, M.H. Cox, I.D. Kerr, Disruption of the Unique ABCG-Family NBD:NBD Interface Impacts Both Drug Transport and ATP Hydrolysis, Int J Mol Sci 21(3) (2020).
[3] S.J. Fairweather, N. Shah, S. Brӧer, Heteromeric Solute Carriers: Function, Structure, Pathology and Pharmacology, Adv Exp Med Biol 21 (2021) 13-127.
[4] M.J. Szafraniec, L. Fiedor, One ring is not enough to rule them all. Albumin-dependent ABCG2-mediated transport of chlorophyll-derived photosensitizers, Eur J Pharm Sci 167 (2021) 106001.
Training: In addition to acquiring multiple laboratory techniques (cell culture, protein gels, thermostabililty and transport assays etc) the student would participate in fortnightly laboratory meetings and gain skills in data analysis and presentation.