PhD Scientific Days 2024

Poster Session F - Molecular Medicine 3.

Examination of potential regulatory regions of the ABCG2 multidrug transporter

Text of the abstract

ABCG2 is a multidrug transporter protein responsible for the export of endo- and xenobiotics from various cells in the human body. It plays a protective role in the blood-brain barrier, stem cells, the intestine, and the placenta. Among the substrates of ABCG2 are a wide range of commonly used drugs and chemotherapeutics, thus, this transporter also contributes to multidrug resistance in cancer cells. Due to its effect on ADME-tox properties, examining interactions with ABCG2 is recommended when a new drug is developed and authorized. This protein also participates in urate secretion, and a common missense variant, Q141K-ABCG2 is an important factor in the development of gout.
In this work we have examined two regions in the ABCG2 structure with potentially important regulatory properties. A disordered loop in ABCG2 is affected by a naturally occurring mutation (K360del), and this region contains four consecutive lysines and a documented phosphorylation site (T362). We found that the K360del variant increased ABCG2 plasma membrane expression and accelerated cellular trafficking. The neighboring (K357-K360) lysine-to-alanine variants showed slightly decreased, variable expression levels compared to the wild type. However, transport function and localization in polarized cells were not affected. Another potential regulatory region examined here includes leucine residues (L554 and L555), a so-called di-leucine plug or valve, potentially affecting the ABCG2 transport mechanism. When performing a detailed mutational analysis in mammalian cells, we followed ABCG2 surface expression and transport function by flow cytometry and examined protein stability and glycosylation by Western blotting. ABCG2 ATPase activity and cholesterol modulation were examined in an insect cell expression system. Our data demonstrate the importance of this region in ABCG2 stability and function, while no major changes in substrate handling, transport, or ATPase coupling were observed. These results should contribute to a better understanding of the structure and function of ABCG2.
PREPARED WITH THE PROFESSIONAL SUPPORT OF THE DOCTORAL STUDENT SCHOLARSHIP PROGRAM OF THE CO-OPERATIVE DOCTORAL PROGRAM OF THE MINISTRY OF CULTURE AND INNOVATION FINANCED FROM THE NATIONAL RESEARCH, DEVELOPMENT AND INNOVATION FUND.