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

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          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.

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          The mutational constraint spectrum quantified from variation in 141,456 humans

          Genetic variants that inactivate protein-coding genes are a powerful source of information about the phenotypic consequences of gene disruption: genes that are crucial for the function of an organism will be depleted of such variants in natural populations, whereas non-essential genes will tolerate their accumulation. However, predicted loss-of-function variants are enriched for annotation errors, and tend to be found at extremely low frequencies, so their analysis requires careful variant annotation and very large sample sizes 1 . Here we describe the aggregation of 125,748 exomes and 15,708 genomes from human sequencing studies into the Genome Aggregation Database (gnomAD). We identify 443,769 high-confidence predicted loss-of-function variants in this cohort after filtering for artefacts caused by sequencing and annotation errors. Using an improved model of human mutation rates, we classify human protein-coding genes along a spectrum that represents tolerance to inactivation, validate this classification using data from model organisms and engineered human cells, and show that it can be used to improve the power of gene discovery for both common and rare diseases.
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            SLCO1B1 variants and statin-induced myopathy--a genomewide study.

            Lowering low-density lipoprotein cholesterol with statin therapy results in substantial reductions in cardiovascular events, and larger reductions in cholesterol may produce larger benefits. In rare cases, myopathy occurs in association with statin therapy, especially when the statins are administered at higher doses and with certain other medications. We carried out a genomewide association study using approximately 300,000 markers (and additional fine-mapping) in 85 subjects with definite or incipient myopathy and 90 controls, all of whom were taking 80 mg of simvastatin daily as part of a trial involving 12,000 participants. Replication was tested in a trial of 40 mg of simvastatin daily involving 20,000 participants. The genomewide scan yielded a single strong association of myopathy with the rs4363657 single-nucleotide polymorphism (SNP) located within SLCO1B1 on chromosome 12 (P=4x10(-9)). SLCO1B1 encodes the organic anion-transporting polypeptide OATP1B1, which has been shown to regulate the hepatic uptake of statins. The noncoding rs4363657 SNP was in nearly complete linkage disequilibrium with the nonsynonymous rs4149056 SNP (r(2)=0.97), which has been linked to statin metabolism. The prevalence of the rs4149056 C allele in the population was 15%. The odds ratio for myopathy was 4.5 (95% confidence interval [CI], 2.6 to 7.7) per copy of the C allele, and 16.9 (95% CI, 4.7 to 61.1) in CC as compared with TT homozygotes. More than 60% of these myopathy cases could be attributed to the C variant. The association of rs4149056 with myopathy was replicated in the trial of 40 mg of simvastatin daily, which also showed an association between rs4149056 and the cholesterol-lowering effects of simvastatin. No SNPs in any other region were clearly associated with myopathy. We have identified common variants in SLCO1B1 that are strongly associated with an increased risk of statin-induced myopathy. Genotyping these variants may help to achieve the benefits of statin therapy more safely and effectively. (Current Controlled Trials number, ISRCTN74348595.) 2008 Massachusetts Medical Society
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              Organic anion transporting polypeptide 1B1: a genetically polymorphic transporter of major importance for hepatic drug uptake.

              The importance of membrane transporters for drug pharmacokinetics has been increasingly recognized during the last decade. Organic anion transporting polypeptide 1B1 (OATP1B1) is a genetically polymorphic influx transporter expressed on the sinusoidal membrane of human hepatocytes, and it mediates the hepatic uptake of many endogenous compounds and xenobiotics. Recent studies have demonstrated that OATP1B1 plays a major, clinically important role in the hepatic uptake of many drugs. A common single-nucleotide variation (coding DNA c.521T>C, protein p.V174A, rs4149056) in the SLCO1B1 gene encoding OATP1B1 decreases the transporting activity of OATP1B1, resulting in markedly increased plasma concentrations of, for example, many statins, particularly of active simvastatin acid. The variant thereby enhances the risk of statin-induced myopathy and decreases the therapeutic indexes of statins. However, the effect of the SLCO1B1 c.521T>C variant is different on different statins. The same variant also markedly affects the pharmacokinetics of several other drugs. Furthermore, certain SLCO1B1 variants associated with an enhanced clearance of methotrexate increase the risk of gastrointestinal toxicity by methotrexate in the treatment of children with acute lymphoblastic leukemia. Certain drugs (e.g., cyclosporine) potently inhibit OATP1B1, causing clinically significant drug interactions. Thus, OATP1B1 plays a major role in the hepatic uptake of drugs, and genetic variants and drug interactions affecting OATP1B1 activity are important determinants of individual drug responses. In this article, we review the current knowledge about the expression, function, substrate characteristics, and pharmacogenetics of OATP1B1 as well as its role in drug interactions, in parts comparing with those of other hepatocyte-expressed organic anion transporting polypeptides, OATP1B3 and OATP2B1.
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                Author and article information

                Contributors
                Journal
                Front Pharmacol
                Front Pharmacol
                Front. Pharmacol.
                Frontiers in Pharmacology
                Frontiers Media S.A.
                1663-9812
                14 September 2021
                2021
                : 12
                : 713567
                Affiliations
                [ 1 ]Department of Physiology & Pharmacology, University of Western Ontario, London, ON, Canada
                [ 2 ]Division of Clinical Pharmacology, Department of Medicine, University of Western Ontario, London, ON, Canada
                [ 3 ]Department of Oncology, Schulich School of Medicine, University of Western Ontario, London, ON, Canada
                Author notes

                Edited by: Caroline Flora Samer, Geneva University Hospitals (HUG), Switzerland

                Reviewed by: Volker Martin Lauschke, Karolinska Institutet (KI), Sweden

                Bo Liu, Sichuan University, China

                *Correspondence: Rommel G. Tirona, rommel.tirona@ 123456schulich.uwo.ca

                This article was submitted to Pharmacogenetics and Pharmacogenomics, a section of the journal Frontiers in Pharmacology

                Article
                713567
                10.3389/fphar.2021.713567
                8476882
                34594217
                7493f1b3-20bb-42c2-92c2-fec9294ecd85
                Copyright © 2021 Medwid, Price, Taylor, Mailloux, Schwarz, Kim and Tirona.

                This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

                History
                : 23 May 2021
                : 23 August 2021
                Funding
                Funded by: Canadian Institutes of Health Research , doi 10.13039/501100000024;
                Categories
                Pharmacology
                Original Research

                Pharmacology & Pharmaceutical medicine
                drug transporter,genetic variant,endogenous substrates,organic anion transporting polypeptide 2b1 (oatp2b1),pharmacogenenomics and personalised medicine

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