title: Insights Into the Molecular Mechanism of Triptan Transport by P-glycoprotein.
abstract: The P-glycoprotein (Pgp) transporter reduces the penetration of a chemically diverse range of neurotherapeutics at the blood-brain barrier, but the molecular features of drugs and drug-Pgp interactions that drive transport remain to be clarified. In particular, the triptan neurotherapeutics, eletriptan (ETT) and sumatriptan (STT), were identified to have a >10-fold difference in transport rates despite being from the same drug class. Consistent with these transport differences, ETT activated Pgp-mediated ATP hydrolysis ∼2-fold, whereas STT slightly inhibited Pgp-mediated ATP hydrolysis by ∼10%. The interactions between them were also noncompetitive, suggesting that they occupy different binding sites on the transporter. Despite these differences, protein fluorescence spectroscopy revealed that the drugs have similar affinity to the transporter. NMR with Pgp and the drugs showed that they have distinct interactions with the transporter. Tertiary conformational changes probed by acrylamide quenching of Pgp tryptophan fluorescence with the drugs and a nonhydrolyzable ATP analog implied that the STT-bound Pgp must undergo larger conformational changes to hydrolyze ATP than ETT-bound Pgp. These results and previous transport studies were used to build a conformationally driven model for triptan transport with Pgp where STT presents a higher conformational barrier for ATP hydrolysis and transport than ETT.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, Georgia 30602.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Wilt
authors.affiliation: Department of Biomanufacturing and Bioprocessing, University of Georgia, Athens, Georgia 30602.
authors.forename: Diana
authors.initials: D
authors.lastname: Nguyen
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, University of Georgia, Athens, Georgia 30602. Electronic address: audie@uga.edu.
authors.forename: Arthur G
authors.initials: AG
authors.lastname: Roberts
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000737:chemistry / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism; D006868:Hydrolysis; D051379:Mice; D011487:Protein Conformation / Q000187:drug effects; D011759:Pyrrolidines / Q000378:metabolism / Q000493:pharmacokinetics*; D017366:Serotonin Receptor Agonists / Q000378:metabolism / Q000493:pharmacokinetics*; D018170:Sumatriptan / Q000378:metabolism / Q000493:pharmacokinetics*; D014363:Tryptamines / Q000378:metabolism / Q000493:pharmacokinetics*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D011759:Pyrrolidines; D017366:Serotonin Receptor Agonists; D014363:Tryptamines; C115647:eletriptan; D000255:Adenosine Triphosphate; D018170:Sumatriptan
keywords: ABC transporters; P-glycoprotein; fluorescence; nuclear magnetic resonance (NMR)