title: Polymorphic variants of MRP4/ABCC4 differentially modulate the transport of methylated arsenic metabolites and physiological organic anions.
abstract: Broad inter-individual variation exists in susceptibility to arsenic-induced tumours, likely involving differences in the ability of individuals to eliminate this metalloid. We recently identified human multidrug resistance protein 4 (MRP4/ABCC4) as a novel pathway for the cellular export of dimethylarsinic acid (DMAV), the major urinary arsenic metabolite in humans, and the diglutathione conjugate of the highly toxic monomethylarsonous acid [MMA(GS)2]. These findings, together with the basolateral and apical membrane localization of MRP4 in hepatocytes and renal proximal tubule cells, respectively, suggest a role for MRP4 in the urinary elimination of hepatic arsenic metabolites. Accordingly, we have now investigated the influence of non-synonymous single nucleotide polymorphisms (SNPs) on MRP4 levels, cellular localization, and arsenical transport. Of eight MRP4 variants (C171G-, G187W-, K304N-, G487E-, Y556C-, E757K-, V776I- and C956S-MRP4) characterized, two (V776I- and C956S-MRP4) did not localize appropriately to the plasma membrane of HEK293T and LLC-PK1 cells. Characterization of the six correctly localized mutants revealed that MMA(GS)2transport by C171G-, G187W-, and K304N-MRP4 was 180%, 73%, and 30% of WT-MRP4 activity, respectively, whereas DMAVtransport by K304N- and Y556C-MRP4 was 30% and 184% of WT-MRP4, respectively. Transport of the prototypical physiological MRP4 substrates prostaglandin E2and 17β-estradiol 17-(β-d-glucuronide) by the six variants was also differentially affected. Thus, MRP4 variants have differing abilities to transport arsenic and endogenous metabolites through both altered function and membrane localization. Further investigation is warranted to determine if genetic variations in ABCC4 contribute to inter-individual differences in susceptibility to arsenic-induced (and potentially other) diseases.
authors.affiliation: Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada. Electronic address: mbanerje@ualberta.ca.
authors.forename: Mayukh
authors.initials: M
authors.lastname: Banerjee
authors.affiliation: Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada. Electronic address: marensi@ualberta.ca.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Marensi
authors.affiliation: Department of Pathology and Molecular Medicine and Division of Cancer Biology and Genetics, Queen's University, Kingston, ON K7L 3N6, Canada. Electronic address: conseilg@queensu.ca.
authors.forename: Gwenaëlle
authors.initials: G
authors.lastname: Conseil
authors.affiliation: Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, 10-102 Clinical Sciences Building, University of Alberta, Edmonton, AB T6G 2G3, Canada. Electronic address: xc.le@ualberta.ca.
authors.forename: X Chris
authors.initials: XC
authors.lastname: Le
authors.affiliation: Department of Pathology and Molecular Medicine and Division of Cancer Biology and Genetics, Queen's University, Kingston, ON K7L 3N6, Canada. Electronic address: spc.cole@queensu.ca.
authors.forename: Susan P C
authors.initials: SP
authors.lastname: Cole
authors.affiliation: Department of Physiology and Membrane Protein Disease Research Group, University of Alberta, Edmonton, AB T6G 2H7, Canada; Department of Laboratory Medicine and Pathology, Faculty of Medicine and Dentistry, 10-102 Clinical Sciences Building, University of Alberta, Edmonton, AB T6G 2G3, Canada. Electronic address: eleslie@ualberta.ca.
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Leslie
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001152:Arsenicals / Q000378:metabolism*; D001711:Biotransformation; D002101:Cacodylic Acid / Q000378:metabolism; D002460:Cell Line; D015232:Dinoprostone / Q000378:metabolism*; D004785:Environmental Pollutants / Q000378:metabolism*; D004958:Estradiol / Q000031:analogs & derivatives* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009942:Organometallic Compounds / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D021381:Protein Transport; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D034421:Sus scrofa
chemical_list: D001152:Arsenicals; D002101:Cacodylic Acid; D015232:Dinoprostone; D004785:Environmental Pollutants; D004958:Estradiol; D005978:Glutathione; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009942:Organometallic Compounds; D011994:Recombinant Proteins; C073492:ABCC4 protein, human; C406082:monomethylarsonous acid; C025483:estradiol-17 beta-glucuronide
keywords: 17β-estradiol 17-(β-d-glucuronide) (PubChem CID: 443090); ATP-binding cassette transporter; Arsenic; Glutathione; MRP4/ABCC4; Non-synonymous single nucleotide polymorphism; Prostaglandin E(2); dimethylarsinic acid (PubChem CID: 2513); glutathione (PubChem CID: 124886); monomethylarsonous acid (PubChem CID: 161491); prostaglandin E(2) (PubChem CID: 5280360)