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Redeker KEM, Schröder S, Dücker C, Brockmöller J, Gebauer L. Targeted mutagenesis of negatively charged amino acids outlining the substrate translocation path within the human organic cation transporter 3. Biochem Pharmacol 2024; 223:116188. [PMID: 38580166 DOI: 10.1016/j.bcp.2024.116188] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2023] [Revised: 03/12/2024] [Accepted: 04/02/2024] [Indexed: 04/07/2024]
Abstract
Recently published cryo-EM structures of human organic cation transporters of the SLC22 family revealed seven, sequentially arranged glutamic and aspartic acid residues, which may be relevant for interactions with positively charged substrates. We analyzed the functional consequences of removing those negative charges by creating D155N, E232Q, D382N, E390Q, E451Q, E459Q, and D478N mutants of OCT3. E232Q, E459Q, and D478N resulted in a lack of localization in the outer cell membrane and no relevant uptake activity. However, D155N and E451Q showed a substrate-specific loss of transport activity, whereas E390Q had no remaining activity despite correct membrane localization. In contrast, D382N showed almost wild-type-like uptake. D155 is located at the entrance to the substrate binding pocket and could, therefore be involved in guiding cationic substrates towards the inside of the binding pocket. For E390, we confirm its critical function for transporter function as it was recently shown for the corresponding position in OCT1. Interestingly, E451 seems to be located at the bottom of the binding pocket in the outward-open confirmation of the transporter. Substrate-specific loss of transport activity of the E451Q variant suggests an essential role in the transport cycle of specific substances as part of an opportunistic binding site. In general, our study highlights the impact of the cryo-EM structures in guiding mutagenesis studies to understand the molecular level of transporter-ligand interactions, and it also confirms the importance of testing multiple substrates in mutagenesis studies of polyspecific OCTs.
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Affiliation(s)
- Kyra-Elisa M Redeker
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany.
| | - Sophie Schröder
- Department for Epigenetics and Systems Medicine in Neurodegenerative Diseases, German Center for Neurodegenerative Diseases (DZNE), D-37075 Göttingen, Germany
| | - Christof Dücker
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany
| | - Jürgen Brockmöller
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany
| | - Lukas Gebauer
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany
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Pochini L, Barone F, Console L, Brunocilla C, Galluccio M, Scalise M, Indiveri C. OCTN1 (SLC22A4) displays two different transport pathways for organic cations or zwitterions. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184263. [PMID: 38092232 DOI: 10.1016/j.bbamem.2023.184263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 11/15/2023] [Accepted: 12/08/2023] [Indexed: 12/19/2023]
Abstract
BACKGROUND OCTN1 belongs to the SLC22 family, which includes transporters for cationic, zwitterionic, and anionic substrates. OCTN1 function and role in cells are still poorly understood. Not only cations, such as TEA, but also zwitterions, such as carnitine and ergothioneine, figure among transported molecules. METHODS In this work, we carried out transport assays measuring [14C]-TEA and [3H]-Carnitine in proteoliposomes reconstituted with the recombinant human OCTN1 in the presence of Na+ or other cations. The homology model of OCTN1 was built using the structure of OCT3 as a template for docking analysis. RESULTS TEA and carnitine did not inhibit each other. Moreover, carnitine uptake was not affected by the presence of Na+ and TEBA, whereas TEA was strongly inhibited by both compounds. Computational data revealed that TEA, Na+, and carnitine can interact with E381 in the OCTN1 substrate site. Differently from TEA, in the presence of Na+, carnitine is still able to interact with the binding site via R469. CONCLUSIONS The lack of mutual inhibition of the two prototype substrates, the different effect of Na+ and TEBA on their transport reaction, together with the computational analysis supports the existence of two transport pathways for cations and zwitterions. GENERAL SIGNIFICANCE The results shed new light on the transport mechanisms of OCTN1, helping to get further insights into the structure/function relationships. The described results correlate well with previous and very recent findings on the polyspecificity of the OCT group of transporters belonging to the same family.
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Affiliation(s)
- Lorena Pochini
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Laboratory of Biochemistry, Molecular Biotechnology, and Molecular Biology, University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy; National Research Council (CNR), Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), via Amendola 122/O, 70126 Bari, Italy
| | - Francesca Barone
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Laboratory of Biochemistry, Molecular Biotechnology, and Molecular Biology, University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy
| | - Lara Console
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Laboratory of Biochemistry, Molecular Biotechnology, and Molecular Biology, University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy
| | - Chiara Brunocilla
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Laboratory of Biochemistry, Molecular Biotechnology, and Molecular Biology, University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy
| | - Michele Galluccio
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Laboratory of Biochemistry, Molecular Biotechnology, and Molecular Biology, University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy
| | - Mariafrancesca Scalise
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Laboratory of Biochemistry, Molecular Biotechnology, and Molecular Biology, University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy.
| | - Cesare Indiveri
- Department DiBEST (Biologia, Ecologia, Scienze della Terra) Laboratory of Biochemistry, Molecular Biotechnology, and Molecular Biology, University of Calabria, Via Bucci 4C, 6C, 87036 Arcavacata di Rende, Italy; National Research Council (CNR), Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies (IBIOM), via Amendola 122/O, 70126 Bari, Italy.
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Gebauer L, Jensen O, Rafehi M, Brockmöller J. Stereoselectivity in Cell Uptake by SLC22 Organic Cation Transporters 1, 2, and 3. J Med Chem 2023; 66:15990-16001. [PMID: 38052451 PMCID: PMC10726348 DOI: 10.1021/acs.jmedchem.3c01436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Revised: 10/30/2023] [Accepted: 11/24/2023] [Indexed: 12/07/2023]
Abstract
Stereoselectivity can be most relevant in drug metabolism and receptor binding. Although drug membrane transport might be equally important for small-molecule pharmacokinetics, the extent of stereoselectivity in membrane transport is largely unknown. Here, we characterized the stereoselective transport of 18 substrates of SLC22 organic cation transporters (OCTs) 1, 2, and 3. OCT2 and OCT3 showed highly stereoselective cell uptake with several substrates and, interestingly, often with opposite stereoselectivity. In contrast, transport by OCT1 was less stereoselective, although (R)-tamsulosin was transported by OCT1 with higher apparent affinity than the (S)-enantiomer. Using OCT1 and CYP2D6 co-overexpressing cells, an additive effect of the stereoselectivities was demonstrated. This indicates that pharmacokinetic stereoselectivity may be the result of combined effects in transport and metabolism. This study highlights that the pronounced polyspecificity of OCTs not contradicts stereoselectivity in the transport. Nevertheless, stereoselectivity is highly substrate-specific and for most substrates and OCTs, there was no major selectivity.
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Affiliation(s)
- Lukas Gebauer
- Institute of Clinical Pharmacology, University Medical Center Göttingen, Göttingen D-37075, Germany
| | - Ole Jensen
- Institute of Clinical Pharmacology, University Medical Center Göttingen, Göttingen D-37075, Germany
| | - Muhammad Rafehi
- Institute of Clinical Pharmacology, University Medical Center Göttingen, Göttingen D-37075, Germany
| | - Jürgen Brockmöller
- Institute of Clinical Pharmacology, University Medical Center Göttingen, Göttingen D-37075, Germany
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Gebauer L, Jensen O, Rafehi M, Brockmöller J. Stereoselective Inhibition of High- and Low-Affinity Organic Cation Transporters. Mol Pharm 2023; 20:6289-6300. [PMID: 37962560 DOI: 10.1021/acs.molpharmaceut.3c00691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Many drugs have chiral centers and are therapeutically applied as racemates. Thus, the stereoselectivity in their interactions with membrane transporters needs to be addressed. Here, we studied stereoselectivity in inhibiting organic cation transporters (OCTs) 1, 2, and 3 and the high-affinity monoamine transporters (MATs) NET and SERT. Selectivity by the inhibition of 35 pairs of enantiomers significantly varied among the three closely related OCTs. OCT1 inhibition was nonselective in almost all cases, whereas OCT2 was stereoselectively inhibited by 45% of the analyzed drugs. However, the stereoselectivity of the OCT2 was only moderate with the highest selectivity observed for pramipexole. The (R)-enantiomer inhibited OCT2 4-fold more than the (S)-enantiomer. OCT3 showed the greatest stereoselectivity in its inhibition. (R)-Tolterodine and (S)-zolmitriptan inhibited OCT3 11-fold and 25-fold more than their respective counterparts. Interestingly, in most cases, the pharmacodynamically active enantiomer was also the stronger OCT inhibitor. In addition, stereoselectivity in the OCT inhibition appeared not to depend on the transported substrate. For high-affinity MATs, our data confirmed the stereoselective inhibition of NET and SERT by several antidepressants. However, the stereoselectivity measured here was generally lower than that reported in the literature. Unexpectedly, the high-affinity MATs were not significantly more stereoselectively inhibited than the polyspecific OCTs. Combining our in vitro OCT inhibition data with available stereoselective pharmacokinetic analyses revealed different risks of drug-drug interactions, especially at OCT2. For the tricyclic antidepressant doxepine, only the (E)-isomer showed an increased risk of drug-drug interactions according to guidelines from regulatory authorities for renal transporters. However, most chiral drugs show only minor stereoselectivity in the inhibition of OCTs in vitro, which is unlikely to translate into clinical consequences.
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Affiliation(s)
- Lukas Gebauer
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany
| | - Ole Jensen
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany
| | - Muhammad Rafehi
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany
| | - Jürgen Brockmöller
- Institute of Clinical Pharmacology, University Medical Center Göttingen, D-37075 Göttingen, Germany
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Ahmed F, Vranic M, Hetty S, Mathioudaki A, Patsoukaki V, Fanni G, Pereira MJ, Eriksson JW. Increased OCT3 Expression in Adipose Tissue With Aging: Implications for Catecholamine and Lipid Turnover and Insulin Resistance in Women. Endocrinology 2023; 165:bqad172. [PMID: 37972266 PMCID: PMC10690730 DOI: 10.1210/endocr/bqad172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 11/09/2023] [Accepted: 11/09/2023] [Indexed: 11/19/2023]
Abstract
BACKGROUND Catecholamine-stimulated lipolysis is reduced with aging, which may promote adiposity and insulin resistance. Organic cation transporter 3 (OCT3), which is inhibited by estradiol (E2), mediates catecholamine transport into adipocytes for degradation, thus decreasing lipolysis. In this study, we investigated the association of OCT3 mRNA levels in subcutaneous adipose tissue (SAT) with aging and markers of insulin resistance in women. METHODS SAT biopsies were obtained from 66 women with (19) or without (47) type 2 diabetes (age 22-76 years, 20.0-40.1 kg/m2). OCT3 mRNA and protein levels were measured for group comparisons and correlation analysis. SAT was incubated with E2 and OCT3 mRNA levels were measured. Associations between OCT3 single nucleotide polymorphisms (SNPs) and diabetes-associated traits were assessed. RESULTS OCT3 mRNA and protein levels in SAT increased with aging. SAT from postmenopausal women had higher levels of OCT3 than premenopausal women, and there was a dose-dependent reduction in OCT3 mRNA levels in SAT treated with E2. OCT3 mRNA levels were negatively associated with markers of insulin resistance, and ex vivo lipolysis. OCT3 SNPs were associated with BMI, waist to hip ratio, and circulating lipids (eg, triglycerides). CONCLUSION OCT3 mRNA and protein levels in SAT increased with aging, and mRNA levels were negatively associated with markers of insulin resistance. E2 incubation downregulated OCT3 mRNA levels, which may explain lower OCT3 mRNA in premenopausal vs postmenopausal women. High OCT3 protein levels in adipose tissue may result in increased catecholamine degradation, and this can contribute to the reduction in lipolysis observed in women with aging.
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Affiliation(s)
- Fozia Ahmed
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
| | - Milica Vranic
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
| | - Susanne Hetty
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
| | - Argyri Mathioudaki
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
| | - Vagia Patsoukaki
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
| | - Giovanni Fanni
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
| | - Maria J Pereira
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
| | - Jan W Eriksson
- Department of Medical Sciences, Clinical Diabetology and Metabolism, Uppsala University, 751 85 Uppsala, Sweden
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Parvez MM, Sadighi A, Ahn Y, Keller SF, Enoru JO. Uptake Transporters at the Blood-Brain Barrier and Their Role in Brain Drug Disposition. Pharmaceutics 2023; 15:2473. [PMID: 37896233 PMCID: PMC10610385 DOI: 10.3390/pharmaceutics15102473] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Revised: 10/03/2023] [Accepted: 10/05/2023] [Indexed: 10/29/2023] Open
Abstract
Uptake drug transporters play a significant role in the pharmacokinetic of drugs within the brain, facilitating their entry into the central nervous system (CNS). Understanding brain drug disposition is always challenging, especially with respect to preclinical to clinical translation. These transporters are members of the solute carrier (SLC) superfamily, which includes organic anion transporter polypeptides (OATPs), organic anion transporters (OATs), organic cation transporters (OCTs), and amino acid transporters. In this systematic review, we provide an overview of the current knowledge of uptake drug transporters in the brain and their contribution to drug disposition. Here, we also assemble currently available proteomics-based expression levels of uptake transporters in the human brain and their application in translational drug development. Proteomics data suggest that in association with efflux transporters, uptake drug transporters present at the BBB play a significant role in brain drug disposition. It is noteworthy that a significant level of species differences in uptake drug transporters activity exists, and this may contribute toward a disconnect in inter-species scaling. Taken together, uptake drug transporters at the BBB could play a significant role in pharmacokinetics (PK) and pharmacodynamics (PD). Continuous research is crucial for advancing our understanding of active uptake across the BBB.
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Affiliation(s)
- Md Masud Parvez
- Department of Quantitative, Translational & ADME Sciences (QTAS), AbbVie Biotherapeutics, San Francisco, CA 94080, USA; (M.M.P.)
| | - Armin Sadighi
- Department of Quantitative, Translational & ADME Sciences (QTAS), AbbVie Biotherapeutics, San Francisco, CA 94080, USA; (M.M.P.)
| | - Yeseul Ahn
- Department of Pharmaceutical Sciences, Jerry H. Hodge School of Pharmacy, Texas Tech University Health Sciences Center, 1300 S Coulter St., Amarillo, TX 79106, USA
- Center for Blood-Brain Barrier Research, Jerry H. Hodge School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA
| | - Steve F. Keller
- Department of Quantitative, Translational & ADME Sciences (QTAS), AbbVie Biotherapeutics, San Francisco, CA 94080, USA; (M.M.P.)
| | - Julius O. Enoru
- Department of Quantitative, Translational & ADME Sciences (QTAS), AbbVie Biotherapeutics, San Francisco, CA 94080, USA; (M.M.P.)
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Yee SW, Macdonald C, Mitrovic D, Zhou X, Koleske ML, Yang J, Silva DB, Grimes PR, Trinidad D, More SS, Kachuri L, Witte JS, Delemotte L, Giacomini KM, Coyote-Maestas W. The full spectrum of OCT1 (SLC22A1) mutations bridges transporter biophysics to drug pharmacogenomics. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.06.543963. [PMID: 37333090 PMCID: PMC10274788 DOI: 10.1101/2023.06.06.543963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Membrane transporters play a fundamental role in the tissue distribution of endogenous compounds and xenobiotics and are major determinants of efficacy and side effects profiles. Polymorphisms within these drug transporters result in inter-individual variation in drug response, with some patients not responding to the recommended dosage of drug whereas others experience catastrophic side effects. For example, variants within the major hepatic Human organic cation transporter OCT1 (SLC22A1) can change endogenous organic cations and many prescription drug levels. To understand how variants mechanistically impact drug uptake, we systematically study how all known and possible single missense and single amino acid deletion variants impact expression and substrate uptake of OCT1. We find that human variants primarily disrupt function via folding rather than substrate uptake. Our study revealed that the major determinants of folding reside in the first 300 amino acids, including the first 6 transmembrane domains and the extracellular domain (ECD) with a stabilizing and highly conserved stabilizing helical motif making key interactions between the ECD and transmembrane domains. Using the functional data combined with computational approaches, we determine and validate a structure-function model of OCT1s conformational ensemble without experimental structures. Using this model and molecular dynamic simulations of key mutants, we determine biophysical mechanisms for how specific human variants alter transport phenotypes. We identify differences in frequencies of reduced function alleles across populations with East Asians vs European populations having the lowest and highest frequency of reduced function variants, respectively. Mining human population databases reveals that reduced function alleles of OCT1 identified in this study associate significantly with high LDL cholesterol levels. Our general approach broadly applied could transform the landscape of precision medicine by producing a mechanistic basis for understanding the effects of human mutations on disease and drug response.
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Affiliation(s)
- Sook Wah Yee
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Christian Macdonald
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Darko Mitrovic
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, 12121 Solna, Sweden
| | - Xujia Zhou
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Megan L Koleske
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Jia Yang
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Dina Buitrago Silva
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Patrick Rockefeller Grimes
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Donovan Trinidad
- Department of Medicine, Division of Infectious Disease, University of California, San Francisco, United States
| | - Swati S More
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
- Current address: Center for Drug Design (CDD), College of Pharmacy, University of Minnesota, Minnesota, United States
| | - Linda Kachuri
- Epidemiology and Population Health, Stanford University, California, United States
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, United States
| | - John S Witte
- Epidemiology and Population Health, Stanford University, California, United States
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, United States
| | - Lucie Delemotte
- Science for Life Laboratory, Department of Applied Physics, KTH Royal Institute of Technology, 12121 Solna, Sweden
| | - Kathleen M Giacomini
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
| | - Willow Coyote-Maestas
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, United States
- Quantitative Biosciences Institute, University of California, San Francisco, United States
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Combined and independent effects of OCT1 and CYP2D6 on the cellular disposition of drugs. Biomed Pharmacother 2023; 161:114454. [PMID: 36871537 DOI: 10.1016/j.biopha.2023.114454] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 02/20/2023] [Accepted: 02/26/2023] [Indexed: 03/06/2023] Open
Abstract
The organic cation transporter 1 (OCT1) mediates the cell uptake and cytochrome P450 2D6 (CYP2D6) the metabolism of many cationic substrates. Activities of OCT1 and CYP2D6 are affected by enormous genetic variation and frequent drug-drug interactions. Single or combined deficiency of OCT1 and CYP2D6 might result in dramatic differences in systemic exposure, adverse drug reactions, and efficacy. Thus, one should know what drugs are affected to what extent by OCT1, CYP2D6 or both. Here, we compiled all data on CYP2D6 and OCT1 drug substrates. Among 246 CYP2D6 substrates and 132 OCT1 substrates, we identified 31 shared substrates. In OCT1 and CYP2D6 single and double-transfected cells, we studied which, OCT1 or CYP2D6, is more critical for a given drug and whether there are additive, antagonistic or synergistic effects. In general, OCT1 substrates were more hydrophilic than CYP2D6 substrates and smaller in size. Inhibition studies showed unexpectedly pronounced inhibition of substrate depletion by shared OCT1/CYP2D6 inhibitors. In conclusion, there is a distinct overlap in the OCT1/CYP2D6 substrate and inhibitor spectra, so in vivo pharmacokinetics and -dynamics of shared substrates may be significantly affected by frequent OCT1- and CYP2D6-polymorphisms and by comedication with shared inhibitors.
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Redeker KEM, Jensen O, Gebauer L, Meyer-Tönnies MJ, Brockmöller J. Atypical Substrates of the Organic Cation Transporter 1. Biomolecules 2022; 12:1664. [PMID: 36359014 PMCID: PMC9687798 DOI: 10.3390/biom12111664] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 10/27/2022] [Accepted: 11/02/2022] [Indexed: 10/29/2023] Open
Abstract
The human organic cation transporter 1 (OCT1) is expressed in the liver and mediates hepatocellular uptake of organic cations. However, some studies have indicated that OCT1 could transport neutral or even anionic substrates. This capability is interesting concerning protein-substrate interactions and the clinical relevance of OCT1. To better understand the transport of neutral, anionic, or zwitterionic substrates, we used HEK293 cells overexpressing wild-type OCT1 and a variant in which we changed the putative substrate binding site (aspartate474) to a neutral amino acid. The uncharged drugs trimethoprim, lamivudine, and emtricitabine were good substrates of hOCT1. However, the uncharged drugs zalcitabine and lamotrigine, and the anionic levofloxacin, and prostaglandins E2 and F2α, were transported with lower activity. Finally, we could detect only extremely weak transport rates of acyclovir, ganciclovir, and stachydrine. Deleting aspartate474 had a similar transport-lowering effect on anionic substrates as on cationic substrates, indicating that aspartate474 might be relevant for intra-protein, rather than substrate-protein, interactions. Cellular uptake of the atypical substrates by the naturally occurring frequent variants OCT1*2 (methionine420del) and OCT1*3 (arginine61cysteine) was similarly reduced, as it is known for typical organic cations. Thus, to comprehensively understand the substrate spectrum and transport mechanisms of OCT1, one should also look at organic anions.
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Affiliation(s)
- Kyra-Elisa Maria Redeker
- Institute of Clinical Pharmacology, University Medical Centre Göttingen, 37075 Göttingen, Germany
| | - Ole Jensen
- Institute of Clinical Pharmacology, University Medical Centre Göttingen, 37075 Göttingen, Germany
| | - Lukas Gebauer
- Institute of Clinical Pharmacology, University Medical Centre Göttingen, 37075 Göttingen, Germany
| | - Marleen Julia Meyer-Tönnies
- Department of General Pharmacology, Institute of Pharmacology, Centre of Drug Absorption and Transport (C-DAT), University Medical Centre Greifswald, 17487 Greifswald, Germany
| | - Jürgen Brockmöller
- Institute of Clinical Pharmacology, University Medical Centre Göttingen, 37075 Göttingen, Germany
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Sachkova A, Jensen O, Dücker C, Ansari S, Brockmöller J. The mystery of the human proton-organic cation antiporter: One transport protein or many? Pharmacol Ther 2022; 239:108283. [DOI: 10.1016/j.pharmthera.2022.108283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 09/20/2022] [Accepted: 09/20/2022] [Indexed: 10/14/2022]
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