title: Multidrug resistance mediated by the ATP-binding cassette transporter protein MRP.
abstract: Resistance to multiple natural product drugs associated with reduced drug accumulation in human tumor cells may be conferred by either the 170 kDa P-glycoprotein or the 190 kDa multidrug resistance protein, MRP. Both MRP and P-glycoprotein belong to the large and ancient ATP-binding cassette (ABC) superfamily of transport proteins but share only 15% amino acid identify. Unlike P-glycoprotein, MRP actively transports conjugated organic anions such as the cysteinyl leukotriene C4 and glutathione-conjugated aflatoxin B1. Transport of unconjugated chemotherapeutic agents appears to require cotransport of glutathione. MRP and several more recently discovered ABC proteins contain an additional NH2-proximal membrane-spanning domain not found in previously characterized ABC transporters. This domain, whose NH2-terminus is extracytosolic, is essential for MRP-mediated transport activity. This review summarizes current knowledge of the structural and transport characteristics of MRP which suggest that the physiologic functions of this protein could range from a protective role in chemical toxicity and oxidative stress to mediation of inflammatory responses involving cysteinyl leukotrienes.
authors.affiliation: Cancer Research Laboratories, Queen's University, Kingston, Ontario, Canada. coles@post.queensu.ca
authors.forename: S P
authors.initials: SP
authors.lastname: Cole
authors.forename: R G
authors.initials: RG
authors.lastname: Deeley
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000493:pharmacokinetics*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D018432:Drug Resistance, Multiple; D006801:Humans; D008958:Models, Molecular; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D017433:Protein Structure, Secondary; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D027425:ATP-Binding Cassette, Sub-Family C Proteins