Functional characterization of common protein variants in the efflux transporter ABCC11 and identification of T546M as functionally damaging variant
- Pharmacogenomics J. 2016 Apr;16(2):193-201. doi: 10.1038/tpj.2015.27.
- 1. Dr Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart and University of Tübingen, Stuttgart, Germany.
- 2. Department of Pharmacology, Center of Drug Absorption and Transport (C_DAT), University Medicine of Greifswald, Greifswald, Germany.
- 3. RIKEN Center for Life Science Technologies, Yokohama, Japan.
- 4. Department of Clinical Pharmacology, Institute of Experimental and Clinical Pharmacology and Toxicology, University Hospital of Tübingen, Tübingen, Germany.
Multidrug resistance protein 8 (ABCC11) is an efflux transporter for anionic lipophilic compounds, conferring resistance to Antiviral and Anticancer agents like 5-fluorouracil (5-FU). ABCC11 missense variants may contribute to variability in drug response but functional consequences, except for the 'earwax variant' c.538G>A, are unknown. Using the 'Screen and Insert' technology, we generated human embryonic kidney 293 cells stably expressing ABCC11 missense variants frequently occurring in different ethnic populations: c.57G>A, c.538G>A, c.950C>A, c.1637C>T, c.1942G>A, c.4032A>G. A series of in silico prediction analyses and in vitro plasma membrane vesicle uptake, immunoblotting and immunolocalization experiments were undertaken to investigate functional consequences. We identified c.1637C>T (T546M), previously associated with 5-FU-related toxicity, as a novel functionally damaging ABCC11 variant exhibiting markedly reduced transport function of 5-FdUMP, the active cytotoxic metabolite of 5-FU. Detailed analysis of 14 subpopulations revealed highest allele frequencies of c.1637C>T in Europeans and Americans (up to 11%) compared with Africans and Asians (up to 3%).