title: Molecular analysis and structure-activity relationship modeling of the substrate/inhibitor interaction site of plasma membrane monoamine transporter.
abstract: Plasma membrane monoamine transporter (PMAT) is a new polyspecific transporter that interacts with a wide range of structurally diverse organic cations. To map the physicochemical descriptors of cationic compounds that allow interaction with PMAT, we systematically analyzed the interactions between PMAT and three series of structural analogs of known organic cation substrates including phenylalkylamines, n-tetraalkylammonium (n-TAA) compounds, and β-carbolines. Our results showed that phenylalkylamines with a distance between the aromatic ring and the positively charged amine nitrogen atom of ∼6.4 Å confer optimal interactions with PMAT, whereas studies with n-TAA compounds revealed an excellent correlation between IC(50) values and hydrophobicity. The five β-carbolines that we tested, which possess a pyridinium-like structure and are structurally related to the neurotoxin 1-methyl-4-phenylpyridinium, inhibited PMAT with high affinity (IC(50) values of 39.1-65.5 μM). Cytotoxicity analysis further showed that cells expressing PMAT are 14- to 15-fold more sensitive to harmalan and norharmanium, suggesting that these two β-carbolines are also transportable substrates of PMAT. We then used computer-aided modeling to generate qualitative and quantitative three-dimensional pharmacophore models on the basis of 23 previously reported and currently identified PMAT inhibitors and noninhibitors. These models are characterized by a hydrogen bond donor and two to three hydrophobic features with distances between the hydrogen bond donor and hydrophobic features ranging between 5.20 and 7.02 Å. The consistency between the mapping results and observed PMAT affinity of a set of test compounds indicates that the models performed well in inhibitor prediction and could be useful for future virtual screening of new PMAT inhibitors.
authors.affiliation: Department of Pharmaceutics, University of Washington, H272J Health Sciences Building, Seattle, WA 98195, USA.
authors.forename: Horace T B
authors.initials: HT
authors.lastname: Ho
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Pan
authors.forename: Zhiyi
authors.initials: Z
authors.lastname: Cui
authors.forename: Haichuan
authors.initials: H
authors.lastname: Duan
authors.forename: Peter W
authors.initials: PW
authors.lastname: Swaan
authors.forename: Joanne
authors.initials: J
authors.lastname: Wang
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001555:Benzene Derivatives / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002243:Carbolines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D002460:Cell Line; D003001:Cloning, Molecular; D004285:Dogs; D004353:Drug Evaluation, Preclinical; D033705:Equilibrative Nucleoside Transport Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D008958:Models, Molecular; D008968:Molecular Conformation; D000644:Quaternary Ammonium Compounds / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D000814:Aniline Compounds; D001555:Benzene Derivatives; D002243:Carbolines; D033705:Equilibrative Nucleoside Transport Proteins; D000644:Quaternary Ammonium Compounds; C495988:SLC29A4 protein, human; C045323:harmalan