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Structural basis of organic cation transporter-3 inhibition.

ABSTRACT: Organic cation transporters (OCTs) facilitate the translocation of catecholamines, drugs and xenobiotics across the plasma membrane in various tissues throughout the human body. OCT3 plays a key role in low-affinity, high-capacity uptake of monoamines in most tissues including heart, brain and liver. Its deregulation plays a role in diseases. Despite its importance, the structural basis of OCT3 function and its inhibition has remained enigmatic. Here we describe the cryo-EM structure of human OCT3 at 3.2 Å resolution. Structures of OCT3 bound to two inhibitors, corticosterone and decynium-22, define the ligand binding pocket and reveal common features of major facilitator transporter inhibitors. In addition, we relate the functional characteristics of an extensive collection of previously uncharacterized human genetic variants to structural features, thereby providing a basis for understanding the impact of OCT3 polymorphisms.

SUBMITTER: Khanppnavar B

PROVIDER: S-EPMC9640557 | biostudies-literature | 2022 Nov

REPOSITORIES: biostudies-literature

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Structural basis of organic cation transporter-3 inhibition.

Khanppnavar Basavraj B Maier Julian J Herborg Freja F Gradisch Ralph R Lazzarin Erika E Luethi Dino D Yang Jae-Won JW Qi Chao C Holy Marion M Jäntsch Kathrin K Kudlacek Oliver O Schicker Klaus K Werge Thomas T Gether Ulrik U Stockner Thomas T Korkhov Volodymyr M VM Sitte Harald H HH

Nature communications 20221107 1

Organic cation transporters (OCTs) facilitate the translocation of catecholamines, drugs and xenobiotics across the plasma membrane in various tissues throughout the human body. OCT3 plays a key role in low-affinity, high-capacity uptake of monoamines in most tissues including heart, brain and liver. Its deregulation plays a role in diseases. Despite its importance, the structural basis of OCT3 function and its inhibition has remained enigmatic. Here we describe the cryo-EM structure of human OC ...[more]

PMID: 36344565

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Project description:The organic cation transporter (OCT) 3 is widely expressed in various organs in humans, and involved in the disposition of many exogenous and endogenous compounds. Several lines of evidence have suggested that OCT3 expressed in the brain plays an important role in the regulation of neurotransmission. Relative to wild-type (WT) animals, Oct3 knockout (KO) mice have displayed altered behavioral and neurochemical responses to psychostimulants such as amphetamine (AMPH) and methamphetamine. In the present study, both in vitro and in vivo approaches were utilized to explore potential mechanisms underlying the disparate neuropharmacological effects observed following AMPH exposure in Oct3 KO mice. In vitro uptake studies conducted in OCT3 transfected cells indicated that dextroamphetamine (d-AMPH) is not a substrate of OCT3. However, OCT3 was determined to be a high-capacity and low-affinity transporter for the neurotransmitters dopamine (DA), norepinephrine (NE), and serotonin (5-HT). Inhibition studies demonstrated that d-AMPH exerts relatively weak inhibitory effects on the OCT3-mediated uptake of DA, NE, 5-HT, and the model OCT3 substrate 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide. The IC(50) values were determined to be 41.5 +/- 7.5 and 24.1 +/- 7.0 microM for inhibiting DA and 5-HT uptake, respectively, while 50% inhibition of NE and 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide uptake was not achieved by even the highest concentration of d-AMPH applied (100 microM). Furthermore, the disposition of d-AMPH in various tissues including the brain, liver, heart, kidney, muscle, intestine, spleen, testis, uterus, and plasma were determined in both male and female Oct3 KO and WT mice. No significant difference was observed between either genotypes or sex in all tested organs and tissues. Our findings suggest that OCT3 is not a prominent factor influencing the disposition of d-AMPH. Additionally, based upon the inhibitory potency observed in vitro, d-AMPH is unlikely to inhibit the uptake of monoamines mediated by OCT3 in the brain. Differentiated neuropharmacological effects of AMPHs noted between Oct3 KO and WT mice appear to be due to the absence of Oct3 mediated uptake of neurotransmitters in the KO mice.

Project description:The importance of the organic cation transporter OCT2 in the renal excretion of cationic drugs raises the possibility of drug-drug interactions (DDIs) in which an inhibitor (perpetrator) drug decreases OCT2-dependent renal clearance of a victim (substrate) drug. In fact, there are clinically significant interactions for drugs that are known substrates of OCT2 such as metformin. To identify drugs as inhibitors for OCT2, individual drugs or entire drug libraries have been investigated in vitro by using experimental probe substrates such as 1-methyl-4-phenylpyridinium (MPP+) or 4-4-dimethylaminostyryl-N-methylpyridinium (ASP+). It has been questioned whether the inhibition data obtained with an experimental probe substrate such as MPP+ or ASP+ might be used to predict the inhibition against other, clinical relevant substrates such as metformin. Here we compared the OCT2 inhibition profile data for the substrates metformin, MPP+ and ASP+. We used human embryonic kidney (HEK 293) cells stably overexpressing human OCT2 as the test system to screen 125 frequently prescribed drugs as inhibitors of OCT2-mediated metformin and MPP+ uptake. Data on inhibition of OCT2-mediated ASP+ uptake were obtained from previous literature. A moderate correlation between the inhibition of OCT2-mediated MPP+, ASP+, and metformin uptake was observed (pairwise rs between 0.27 and 0.48, all P < 0.05). Of note, the correlation in the inhibition profile between structurally similar substrates such as MPP+ and ASP+ (Tanimoto similarity T = 0.28) was even lower (rs = 0.27) than the correlation between structurally distinct substrates, such as ASP+ and metformin (T = 0.01; rs = 0.48) or MPP+ and metformin (T = 0.01; rs = 0.40). We identified selective as well as universal OCT2 inhibitors, which inhibited transport by more than 50% of one substrate only or of all substrates, respectively. Our data suggest that the predictive value for drug-drug interactions using experimental substrates rather than the specific victim drug is limited.

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Structural basis of organic cation transporter-3 inhibition.

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Structural basis of organic cation transporter-3 inhibition.

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