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Novel CYP2B6 Enzyme Variants in a Rwandese Population: Functional Characterization and Assessment of In Silico Prediction Tools

Authors


  • Additional Supporting Information may be found in the online version of this article.

  • Communicated by Daniel W. Nebert

  • Contract grant sponsors: Luxembourg Fonds National de la Recherche (FNR grant TR-PHD BFR08/072); the German Federal Ministry of Education and Research (Virtual Liver Network grant 0315755); the Robert Bosch Foundation, Stuttgart, Germany.

Correspondence to: Kathrin Klein, Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology Stuttgart and University Tuebingen, Auerbachstr 112, D-70376 Stuttgart, Germany. E-mail: kathrin.klein@ikp-stuttgart.de

ABSTRACT

Cytochrome P450 CYP2B6 is a highly polymorphic enzyme that metabolizes numerous drugs, pesticides, and environmental toxins. Sequence analysis of a Rwandese population identified eight functionally uncharacterized nonsynonymous variants c.329G>T (p.G110V), c.341T>C (p.I114T), c.444G>T (p.E148D), c.548T>G (p.V183G), c.637T>C (p.F213L), c.758G>A (p.R253H), c.835G>C (p.A279P), and c.1459C>A (p.R487S), and five novel alleles termed CYP2B6*33 to CYP2B6*37 were assigned. Recombinant expression in COS-1 cells and functional characterization using the antidepressant bupropion and the antiretroviral efavirenz (EFV) as substrates demonstrated complete or almost complete loss-of-function for variants p.G110V, p.I114T, p.V183G, and p.F213L, whereas p.E148D, p.R253H, p.A279P, and p.R487S variants were functional. The data were used to assess the predictive power of eight online available functional prediction programs for amino-acid changes. Although none of the programs correctly predicted the functionality of all variants, substrate docking simulation analyses indicated similar conformational changes by all four deleterious mutations within the enzyme's active site, thus explaining lack of enzymatic function for both substrates. Because low-activity alleles of CYP2B6 are associated with impaired EFV metabolism and adverse drug response, these results are of potential utility for personalized treatment strategies in HIV/AIDS therapy.

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