In vitro characterization of SLCO2B1 genetic variants

OATP2B1, encoded by SLCO2B1, is a drug transporter expressed widely throughout the body in tissues such as the intestine and liver. Genetic variation of this transporter may lead to altered disposition of OATP2B1 substrate drugs, but especially the effects of rare variants are poorly understood. The aim of this study was to characterize the effects of naturally occurring missense single nucleotide variants of SLCO2B1 (c.601G>A, c.935G>A, c.953C>T, c.1175C>, c.1457C>T, c.1559G>C, c.1596C>A, and the c.601G>A + c.935G>A haplotype) on the in vitro functionality of OATP2B1. To characterize transport activity, cellular uptake of dibromofluorescein, 5-carboxyfluorescein, estrone sulfate, and rosuvastatin was compared in OATP2B1 reference- and variant-expressing HEK293 cells. The abundance of OATP2B1 variants in HEK293 crude membrane preparations was quantified with LC-MS/MS-based quantitative targeted absolute proteomics analysis. Variant c.1559G>C impaired OATP2B1-mediated uptake of all tested substrates almost completely, but protein abundance was not reduced to the same extent. Other studied variants had comparable or only modestly reduced protein abundance and transport function compared to reference OATP2B1. These results can be utilized to understand findings from clinical pharmacogenetic studies. More importantly, the results can aid in predicting the consequences of rare variants, such as the loss-of-function variant c.1559G>C, which can be difficult to detect in clinical studies.