title: Convallatoxin: a new P-glycoprotein substrate.
abstract: Digitalis-like compounds (DLCs), such as digoxin and digitoxin that are derived from digitalis species, are currently used to treat heart failure and atrial fibrillation, but have a narrow therapeutic index. Drug-drug interactions at the transporter level are frequent causes of DLCs toxicity. P-glycoprotein (P-gp, ABCB1) is the primary transporter of digoxin and its inhibitors influence pharmacokinetics and disposition of digoxin in the human body; however, the involvement of P-gp in the disposition of other DLCs is currently unknown. In present study, the transport of fourteen DLCs by human P-gp was studied using membrane vesicles originating from human embryonic kidney (HEK293) cells overexpressing P-gp. DLCs were quantified by liquid chromatography-mass spectrometry (LC-MS). The Lily of the Valley toxin, convallatoxin, was identified as a P-gp substrate (Km: 1.1±0.2 mM) in the vesicular assay. Transport of convallatoxin by P-gp was confirmed in rat in vivo, in which co-administration with the P-gp inhibitor elacridar, resulted in increased concentrations in brain and kidney cortex. To address the interaction of convallatoxin with P-gp on a molecular level, the effect of nine alanine mutations was compared with the substrate N-methyl quinidine (NMQ). Phe343 appeared to be more important for transport of NMQ than convallatoxin, while Val982 was particularly relevant for convallatoxin transport. We identified convallatoxin as a new P-gp substrate and recognized Val982 as an important amino acid involved in its transport. These results contribute to a better understanding of the interaction of DLCs with P-gp.
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Elnaz
authors.initials: E
authors.lastname: Gozalpour
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Rick
authors.initials: R
authors.lastname: Greupink
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Albert
authors.initials: A
authors.lastname: Bilos
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Vivienne
authors.initials: V
authors.lastname: Verweij
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Jeroen J M W
authors.initials: JJ
authors.lastname: van den Heuvel
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Rosalinde
authors.initials: R
authors.lastname: Masereeuw
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
authors.forename: Frans G M
authors.initials: FG
authors.lastname: Russel
authors.affiliation: Department of Pharmacology and Toxicology 149, Radboud University Medical Centre, Radboud Institute for Molecular Life Sciences, PO Box 9101, 6500 HB Nijmegen, The Netherlands. Electronic address: jan.koenderink@radboudumc.nl.
authors.forename: Jan B
authors.initials: JB
authors.lastname: Koenderink
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000502:physiology; D001921:Brain / Q000378:metabolism; D002460:Cell Line; D004077:Digoxin / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007672:Kidney Cortex / Q000378:metabolism; D008297:Male; D026901:Membrane Transport Proteins / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013328:Strophanthins / Q000378:metabolism*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D026901:Membrane Transport Proteins; D013328:Strophanthins; D004077:Digoxin; C000505:convallatoxin
keywords: Convallatoxin; Convallatoxin (Pubchem CID: 441852); Cymarin (Pubchem CID: 539061); Digitalis-like compounds; Digitoxigenin (Pubchem CID: 4369270); Digitoxin (Pubchem CID: 441207); Digoxigenin (Pubchem CID: 15478); Digoxin (Pubchem CID: 2724385); Lily of the Valley; Mutagenesis; Ouabagenin (Pubchem CID: 262968); Ouabain (Pubchem CID: 439501); P-glycoprotein; Proscillaridin A (Pubchem CID: 16219784); Strophanthidin (Pubchem CID: 6185); Vesicular transport assay