Organic Anion Transporting Polypeptide 2B1 (OATP2B1) Genetic Variants: In Vitro Functional Characterization and Association With Circulating Concentrations of Endogenous Substrates.

Richard B Kim,Daniel P Taylor,Jaymie Mailloux,Samantha Medwid,Rommel G Tirona,Ute I Schwarz,Hayley R Price

doi:10.3389/fphar.2021.713567

Abstract

Organic anion transporting polypeptide 2B1 (OATP2B1, gene SLCO2B1) is an uptake transporter that is thought to determine drug disposition and in particular, the oral absorption of medications. At present, the clinical relevance of SLCO2B1 genetic variation on pharmacokinetics is poorly understood. We sought to determine the functional activity of 5 of the most common missense OATP2B1 variants (c.76_84del, c.601G>A, c.917G>A, c.935G>A, and c.1457C>T) and a predicted dysfunctional variant (c.332G>A) in vitro. Furthermore, we measured the basal plasma concentrations of endogenous OATP2B1 substrates, namely estrone sulfate, dehydroepiandrosterone sulfate (DHEAS), pregnenolone sulfate, coproporphyrin I (CPI), and CPIII, and assessed their relationships with SLCO2B1 genotypes in 93 healthy participants. Compared to reference OATP2B1, the transport activities of the c.332G>A, c.601G>A and c.1457C>T variants were reduced among the substrates examined (estrone sulfate, DHEAS, CPI, CPIII and rosuvastatin), although there were substrate-dependent effects. Lower transport function of OATP2B1 variants could be explained by diminished cell surface expression. Other OATP2B1 variants (c.76-84del, c.917G>A and c.935G>A) had similar activity to the reference transporter. In the clinical cohort, the SLCO2B1 c.935G>A allele was associated with both higher plasma CPI (42%) and CPIII (31%) concentrations, while SLCO2B1 c.917G>A was linked to lower plasma CPIII by 28% after accounting for the effects of age, sex, and SLCO1B1 genotypes. No association was observed between SLCO2B1 variant alleles and estrone sulfate or DHEAS plasma concentrations, however 45% higher plasma pregnenolone sulfate level was associated with SLCO2B1 c.1457C>T. Taken together, we found that the impacts of OATP2B1 variants on transport activities in vitro were not fully aligned with their associations to plasma concentrations of endogenous substrates in vivo. Additional studies are required to determine whether circulating endogenous substrates reflect OATP2B1 activity.

Highlights

Organic anion transporting peptide 2B1 (OATP2B1, previously known as OATP-B, gene name SLCO2B1) is a member of the solute transporting carrier (SLC) superfamily
We explored the possibility that genetic variations in SLCO2B1 are associated with the plasma concentrations of its endogenous substrates, namely, estrone sulfate, dehydroepiandrosterone sulfate (DHEAS), pregnenolone sulfate, coproporphyrin I (CPI) and CPIII
OATP2B1-mediated cellular accumulation of substrates was evidenced by 9.5, 1.5, 2.0, 5.2-and 6.5-fold greater cellular uptake for estrone sulfate, DHEAS, CPI, CPIII and rosuvastatin, respectively, when compared to blank vector control cells (Figure 2)

Summary

Introduction

Organic anion transporting peptide 2B1 (OATP2B1, previously known as OATP-B, gene name SLCO2B1) is a member of the solute transporting carrier (SLC) superfamily. OATP2B1 is ubiquitously expressed throughout the body in organs including intestine, liver, kidney, brain, heart, skeletal muscle, lung, placenta, pancreas and macrophages (Tamai et al, 2000; Kullak-Ublick et al, 2001; St-Pierre et al, 2002; Grube et al, 2006b; Niessen et al, 2009; Seki et al, 2009; Knauer et al, 2010; Hussner et al, 2015; Kim M. et al, 2017; Nakano et al, 2019). There is significant experimental support for the relevance of intestinal OATP2B1 to drug absorption (McFeely et al, 2019), the impact of this transporter on drug distribution and elimination in other tissues where it is expressed, remains significantly less understood (Kinzi et al, 2021)

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