Elsevier

Toxicology

Volume 167, Issue 1, 5 October 2001, Pages 3-23
Toxicology

Review
Toxicological relevance of the multidrug resistance protein 1, MRP1 (ABCC1) and related transporters

https://doi.org/10.1016/S0300-483X(01)00454-1Get rights and content

Abstract

The 190 kDa multidrug resistance protein 1 (MRP1/ABCC1) is a founding member of a subfamily of the ATP binding cassette (ABC) superfamily of transport proteins and was originally identified on the basis of its elevated expression in multidrug resistant lung cancer cells. In addition to its ability to confer resistance in tumour cells, MRP1 is ubiquitously expressed in normal tissues and is a primary active transporter of GSH, glucuronate and sulfate conjugated and unconjugated organic anions of toxicological relevance. Substrates include lipid peroxidation products, herbicides, tobacco specific nitrosamines, mycotoxins, heavy metals, and natural product and antifolate anti-cancer agents. MRP1 also transports unmodified xenobiotics but often requires GSH to do so. Active efflux is generally an important aspect of cellular detoxification since it prevents the accumulation of conjugated and unconjugated compounds that have the potential to be directly toxic. The related transporters MRP2 and MRP3 have overlapping substrate specificities with MRP1 but different tissue distributions, and evidence that they also have chemoprotective functions are discussed. Finally, MRP homologues have been described in other species including yeast and nematodes. Those isolated from the vascular plant Arabidopsis thaliana (AtMRPs) decrease the cytoplasmic concentration of conjugated toxins through sequestration in vacuoles and are implicated in providing herbicide resistance to plants.

Introduction

The multidrug resistance protein 1 (MRP1) and related transporters are members of the ATP binding cassette (ABC) superfamily of transport proteins. This superfamily is among the largest and most widespread protein superfamilies known and its members are responsible for the active transport of a wide variety of compounds across biological membranes including phospholipids, ions, peptides, steroids, polysaccharides, amino acids, organic anions, drugs and other xenobiotics (Borst et al., 1999, Cole and Deeley, 1998, Hipfner et al., 1999, Higgins, 1992, Klein et al., 1999). Typical eukaryotic ABC transporters contain two hydrophobic, polytopic membrane spanning domains (MSD) and two hydrophilic, cytosolic nucleotide binding domains (NBD) organized in pairs (MSD–NBD or NBD–MSD) expressed either as one continuous unit or two separate polypeptides (Decottignies and Goffeau, 1997, Hipfner et al., 1999). In most ABC transporters, the binding and subsequent hydrolysis of ATP at their NBDs is believed to provide energy for the movement of substrates across the membrane. Two sequence motifs located in each NBD, designated ‘Walker A’ and ‘Walker B’, are conserved among all ABC transporter superfamily members as well as several other ATP-binding proteins (Walker et al., 1982). The lysine residue in the Walker A motif is involved in the binding of the β-phosphate of ATP while the aspartic acid residue in the Walker B motif interacts with Mg2+ (Sharom et al., 1999, Hung et al., 1998). In addition, there is a highly conserved 14 amino acid sequence located between the Walker A and B sequences referred to as the ‘active transporter signature’ (or C motif) but its precise function is not yet well understood (Higgins, 1992).

The multidrug resistance protein 1 (MRP1/ABCC1) is a founding member of a subfamily in the ABC superfamily designated ‘C’, and was originally cloned from a multidrug resistant human small cell lung cancer cell line (Cole et al., 1992). Increased expression of the 190 kDa MRP1 in drug selected tumour cell lines and transfected cells results in an ATP-dependent efflux of several natural product type drugs (e.g. anthracyclines, epipodophyllotoxins and the Vinca alkaloids) as well as the folic acid analogue, methotrexate, and certain arsenic and antimonial centered oxyanions (Cole et al., 1994, Hooijberg et al., 1999a, Zaman et al., 1994, Hipfner et al., 1999). In addition to its ability to confer resistance, MRP1 is a primary active transporter of GSH, glucuronate and sulfate conjugated organic anions such as the inflammatory mediator leukotriene C4 (LTC4), the cholestatic conjugated estrogen 17β-estradiol 17-(β-d-glucuronide) (E217βG) and the sulfated bile salt sulfatolithocholate (Leier et al., 1994, Leier et al., 1996, Loe et al., 1996a, Loe et al., 1996b, Jedlitschky et al., 1996, Muller et al., 1994). MRP1 also mediates transport of glutathione disulfide (GSSG) (Leier et al., 1996). Most of the anticancer drugs to which MRP1 confers resistance are not conjugated to a significant extent in vivo. Instead, it appears that at least some of them are effluxed from cells by MRP1 via a co-transport mechanism with reduced glutathione (GSH) (Loe et al., 1998, Zaman et al., 1995, Lorico et al., 1996, Rappa et al., 1997). Native and recombinant MRP1 have been purified to 85–90% homogeneity and their ATPase activity characterized (Chang et al., 1997, Mao et al., 1999). We have also shown that the purified protein reconstituted in phospholipid vesicles is capable of organic anion transport and GSH-dependent vincristine transport, suggesting it does not require additional cellular components for its basal activity (Mao et al., 2000). In addition, Rosenberg et al. (2001) have recently reported the structural characterization of the purified protein to approximately 22 Å resolution by electron microscopy of single particles and two-dimensional crystal/lipid arrays and obtained some evidence for a dimeric association of the protein.

The murine orthologue of MRP1, mrp1, has been cloned and the two protein share 88% amino acid identity (Stride et al., 1996). Despite the high level of identity between MRP1/mrp1, some remarkable differences in substrate specificity exist. Murine mrp1 transports E217βG with approximately 10-fold lower efficiency than human MRP1, and in contrast to human MRP1, confers negligible resistance to anthracycline antibiotics such as doxorubicin, daunorubicin and epirubicin (Stride et al., 1997). By examining the properties of various MRP1/mrp1 hybrid molecules, the region of MRP1 that is essential for these differences in substrate specificity was localized to the COOH-terminal region of the protein (Stride et al., 1999). Two amino acid residues have recently been identified in this region of human MRP1 that are essential for specific substrate interactions. Thus substitution of a glutamate at position 1089 with glutamine as found in the murine protein results in a marked decrease in anthracycline resistance, while transport of LTC4 and E217βG remain unchanged (Zhang et al., 2001). In addition, substitution of a tryptophan at position 1246 which is present in both the human and murine proteins with both conserved and non-conserved amino acids eliminates E217βG transport and drug resistance while leaving LTC4 and GSH transport intact (Ito et al., 2001). Consistant with these latter findings, Daoud et al. (2001) have shown that four transmembrane segments are labeled with photoaffinity substrate analogues, one of which is the transmembrane segment of MRP1 that contains Trp1246.

Subsequent to the identification of MRP1, six additional MRP-related genes (MRP2–7) belonging to the ABC subfamily C have been cloned and five (MRP2–6) have been functionally characterized to varying degrees over the last 5 years (Paulusma et al., 1996, Kool et al., 1997, Kool et al., 1999a, Hopper et al., 2001, Lee et al., 1998; Suzuki et al., 1997; McAleer et al., 1999, Schuetz et al., 1999). Other members of subfamily C that are of clinical, but not apparent toxicological, relevance are the sulfonylurea receptors SUR1 and SUR2, and the cystic fibrosis transmembrane conductance regulator (CFTR). The lung disease cystic fibrosis is caused by mutations in CFTR (Welsh and Smith, 1993) while persistent hyperinsulinemic hypoglycemia of infancy is caused by mutations in SUR1 (Bryan and Aguilar-Bryan, 1997). MRP2 (ABCC2), MRP3 (ABCC3) and MRP6 (ABCC6) are the most closely related subfamily C proteins to MRP1 sharing 49, 58 and 45% amino acid identity, respectively (Fig. 1A). One of the major characteristics of proteins belonging to subfamily C is the relatively low sequence homology between their NH2- and COOH-terminal NBDs. In addition, these proteins lack thirteen amino acids between the Walker A and Walker B motifs in NBD1 that are present in NBD2 and in both NBDs of most other eukaryotic ABC transporters (Cole et al., 1992, Hipfner et al., 1999). Considerable evidence now exists that the two NBDs of proteins within this subfamily are functionally non-equivalent (Gao et al., 2000, Hou et al., 2000, Nagata et al., 2000, Matsuo et al., 1999, Nagel, 1999). Five of the MRP-related proteins, MRP1, 2, 3, 6 and 7 (ABCC10), have an atypical structure with five, rather than four, domains. The fifth domain (MSD1 or TMD0) of approximately 200 amino acids has an extracytosolic NH2-terminus and consists of five transmembrane segments connected to a typical four domain transporter core by an intracellular loop (CL3 or L0) of approximately 130 amino acids (Fig. 1B) (Cole et al., 1992, Hipfner et al., 1997, Bakos et al., 1996, Stride et al., 1996). The more distantly related MRP4 (ABCC4) and MRP5 (ABCC5) lack MSD1 and share just 39% and 34% amino acid identity with MRP1, respectively. The transport properties and involvement of MRP6 in protection of tissues from xenobiotics has not been studied extensively (Madon et al., 2000, Borst et al., 1999). Although its elevated expression has been observed in several drug resistant cell lines, this has been attributed to co-amplification with MRP1 which is a neighbouring gene on chromosome 16 (Kool et al., 1999a). Mutations in MRP6 are thought to be responsible for the connective tissue disorder Pseudoxanthoma elasticum; however, the precise physiological function of this transported is currently unknown (Ringpgeil et al., 2000). The recently reported MRP7 appears to be the most divergent family member identified and nothing is yet known of its physiological function or potential role in xenotoxin disposition. Thus MRP6 and MRP7 will not be considered further in this review.

In addition to the mammalian MRPs described above, MRP-related proteins have also been identified in a wide variety of non-mammalian organisms including insects, yeast, protozoa, nematodes and plants. To date, 15 MRP-related coding sequences have been identified in the vascular plant Arabidopsis thaliana (Sánchez-Fernández et al., 2001), a member of the mustard plant family that is frequently used for genetic studies because of its small genome, lack of repetitive DNA and the technical ease with which it can be grown. Five AtMRP genes have been isolated as full-length cDNAs and shown to encode functional GS-conjugate pumps (Liu et al., 2001). These proteins share approximately 35% amino acid identity with human MRP1 (Lu et al., 1997, Lu et al., 1998, Tommasini et al., 1997, Tommasini et al., 1998, Sanchez-Fernandez et al., 1998). Hydropathy analyses of AtMRP1-5 indicate that they contain the third NH2-proximal MSD that is present in MRP1, 2, 3, 6 and 7 (Rea et al., 1998). These proteins also contain the characteristic thirteen amino acid deletion between the Walker A and B motifs in NBD1.

AtMRP1–5 are associated with vacuolar membranes and, like the MRP-related proteins in mammalian cells, they have been shown to transport various GSH conjugates including S-(2,4-dinitrophenyl)-SG, GSSG, as well as GSH conjugates of herbicides (e.g. metolachlor-SG) and plant pigments or anthocyanins, a subclass of flavonoids (e.g. cyanidin 3-glucoside-SG) (Lu et al., 1997). At present, AtMRP2 appears to be the highest capacity transporter of these substrates. In addition to GSH conjugates, AtMRP2 and AtMRP3 also transport the negatively charged malonyl ester of one of the tetrapyrrole metabolites of chlorophyll isolated from rape (Brassica napus), Bn-NCC-1 (Brassica napus-non-fluorescent chlorophyll catabolite-1) (Rea et al., 1998). Thus, like members of the human MRP subfamily, these plant MRP-like transporters have a broad spectrum of substrates of remarkable structural diversity. Plant transporters are potential targets for modifying responses to herbicides and other xenobiotics (Rea et al., 1998), bearing in mind that although they may serve to protect the plant, their toxic substrates are in intracellular vacuoles and thus may pass directly up the food chain.

Section snippets

Role in detoxification

Considerable evidence from in vitro and in vivo investigations indicate that MRP1 has a role in protecting tissues from toxin induced damage. Though less well characterized, this is true of MRP2 and possibly other MRPs as well. Compounds of toxicological relevance that are presently known to be substrates and modulators of MRP1 are listed in Table 1 and the chemical structures of some of these are illustrated in Fig. 2. Most of the in vitro evidence has been acquired through transport assays

Conclusions

In addition to being of major relevance in clinical resistance to anticancer drugs, MRP1 has an important and overlapping role in protecting normal mammalian tissues from a wide range of xenobiotic-induced damage. There is also compelling evidence that MRP-related ABC transporters contribute significantly to the removal of toxins in many other species, including plants (A. thaliana), nematodes (C. elegans), yeast (S. cerevisiae), and other non-vertebrates. It is conceivable that these versatile

Acknowledgements

The authors would like to thank Drs P.A. Rea and Z.S. Li for the kind gift of [14C]metolachlor-SG. We thank Dr Jim Gerlach for providing valuable advice and assistance with sequence alignments and analyses, and Maureen Rogers for assistance in the preparation of the manuscript and figures. Supported by grant MT-10519 from the Medical Research Council of Canada (MRCC)/ Canadian Institutes of Health Research. E.M. Leslie is the recipient of an MRCC Doctoral Award.

References (150)

  • M.F. Fromm et al.

    Human MRP3 transporter: identification of the 5′-flanking region, genomic organization and alternative splice variants

    Biochim. Biophys. Acta

    (1999)
  • M. Gao et al.

    Comparison of the functional characteristics of the nucleotide binding domains of multidrug resistance protein 1

    J. Biol. Chem.

    (2000)
  • H. Glatt

    Sulfotransferases in the bioactivation of xenobiotics

    Chem. Biol. Interact.

    (2000)
  • M. Heijn et al.

    Anthracyclines modulate multidrug resistance protein (MRP) mediated organic anion transport

    Biochim. Biophys. Acta

    (1997)
  • A.B. Hill et al.

    Dialkylquinoneimine metabolites of chloroacetanilide herbicides induce sister chromatid exchanges in culture human lymphocytes

    Mutat. Res.

    (1997)
  • D.R. Hipfner et al.

    Membrane topology of the multidrug resistance protein, MRP: a study of glycosylation-site mutants reveals an extracytosolic NH2-terminus

    J. Biol. Chem.

    (1997)
  • T. Hirohashi et al.

    Characterization of the transport properties of cloned rat multidrug resistance-associated protein 3 (MRP3)

    J. Biol. Chem.

    (1999)
  • J.H. Hooijberg et al.

    Modulation by (iso)flavonoids of the ATPase activity of the multidrug resistance protein

    FEBS Lett.

    (1997)
  • J.H. Hooijberg et al.

    The effect of glutathione on the ATPase activity of MRP1 in its natural membranes

    FEBS Lett.

    (2000)
  • E. Hopper et al.

    Analysis of the structure and expression pattern of MRP7 (ABCC10), a new member of the MRP subfamily

    Cancer Lett.

    (2001)
  • Y.-X. Hou et al.

    Allosteric interactions between the two non-equivalent nucleotide binding domains of multidrug resistance protein MRP1

    J. Biol. Chem.

    (2000)
  • K. Ito et al.

    Mutation of a single conserved tryptophan in multidrug resistance protein 1 (MRP1/ABCC1) results in loss of drug resistance and selective loss of organic anion transport

    J. Biol. Chem.

    (2001)
  • G. Jedlitschky et al.

    The multidrug resistance resistance protein 5 functions as an ATP-dependent export pump for cyclic nucleotides

    J. Biol. Chem.

    (2000)
  • S.V. Kala et al.

    The MRP2/cMOAT transporter and arsenic–glutathione complex formation are required for biliary excretion of arsenic

    J. Biol. Chem.

    (2000)
  • J. Kartenbeck et al.

    Absence of the canalicular isoform of the MRP gene-encoded conjugate export pump from the hepatocytes in Dubin–Johnson syndrome

    Hepatology

    (1996)
  • Y. Kiuchi et al.

    cDNA cloning and inducible expression of human multidrug resistance associated protein 3 (MRP3)

    FEBS Lett.

    (1998)
  • I. Klein et al.

    An inventory of the human ABC proteins

    Biochim. Biophys. Acta

    (1999)
  • J. Konig et al.

    Conjugate export pumps of the multidrug resistance protein (MRP) family: localization, substrate specificity and MRP2-mediated drug resistance

    Biochim. Biophys. Acta

    (1999)
  • I. Leier et al.

    The MRP gene encodes an ATP-dependent export pump for leukotriene C4 and structurally related conjugates

    J. Biol. Chem.

    (1994)
  • E.M. Leslie et al.

    Transport of the β-O-Glucuronide conjugate of the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) by the Multidrug Resistance Protein 1 (MRP1). Requirement for glutathione or a non-sulfur-containing analog

    J. Biol. Chem.

    (2001)
  • G. Liu et al.

    Enhanced multispecificity of Arabidopsis vacuolar MRP-type ABC transporter, AtMRP2

    J. Biol. Chem.

    (2001)
  • D.W. Loe et al.

    Multidrug resistance protein (MRP)-mediated transport of leukotriene C4 and chemotherapeutic agents in membrane vesicles: demonstration of glutathione-dependent vincristine transport

    J. Biol. Chem.

    (1996)
  • D.W. Loe et al.

    ATP-dependent 17β-estradiol 17-(β-D-glucuronide) transport by multidrug resistance protein: inhibition by cholestatic steroids

    J. Biol. Chem.

    (1996)
  • D.W. Loe et al.

    Structure-activity studies of verapamil analogs that modulate transport of leukotriene C4 and reduced glutathione by multidrug resistance protein MRP1

    Biochem. Biophys. Res. Commun.

    (2000)
  • S.C. Lu et al.

    Alterations in glutathione homeostasis in mutant Eisai hyperbilirubinemic rats

    Hepatology

    (1996)
  • Q. Mao et al.

    ATPase activity of purified and reconstituted multidrug resistance protein MRP1 from drug-selected H69AR cells

    Biochim. Biophys. Acta

    (1999)
  • M. Matsuo et al.

    ATP binding properties of the nucleotide-binding folds of SUR1

    J. Biol. Chem.

    (1999)
  • C.S. Morrow et al.

    Coordinated action of glutathione S-transferases (GSTs) and multidrug resistance protein 1 (MRP1) in antineoplastic drug detoxification. Mechanism of GST A1-1- and MRP1-associated resistance to chlorambucil in MCF7 breast carcinoma cells

    J. Biol. Chem.

    (1998)
  • K. Nagata et al.

    Nonequivalent nucleotide trapping in the two nucleotide binding folds of the human multidrug resistance protein MRP1

    J. Biol. Chem.

    (2000)
  • G. Nagel

    Differential function of the two nucleotide binding domains on cystic fibrosis transmembrane conductance regulator

    Biochim. Biophys. Acta

    (1999)
  • B. Papadopoulou et al.

    Contribution of the Leishmania P-glycoprotein-related gene ltpgpA to oxyanion resistance

    J. Biol. Chem.

    (1994)
  • C.M. Paumi et al.

    Role of the multidrug resistance protein 1 (MRP1) and glutathione S-transferase A1-1 in alkylating agent resistance: kinetics of gluathione conjugate formation and efflux govern differential cellular sensitivitiy to chlorambucil versus melphalan toxicity

    J. Biol. Chem.

    (2001)
  • J.D. Allen et al.

    Extensive contribution of the multidrug transporters P-glycoprotein and Mrp1 to basal drug resistance

    Cancer Res.

    (2000)
  • E. Bakos et al.

    Interactions of the human multidrug resistance proteins MRP1 and MRP2 with organic anions

    Mol. Pharmacol.

    (2000)
  • K. Barnouin et al.

    Multidrug resistance protein-mediated transport of chlorambucil and melphalan conjugated to glutathione

    Br. J. Cancer

    (1998)
  • M.G. Belinsky et al.

    Characterization of MOAT-C and MOAT-D, new members of the MRP/cMOAT subfamily of transporter proteins

    J. Natl. Cancer Inst.

    (1998)
  • M.L. Blackburn et al.

    Characterization of the enzymatic and nonenzymatic reaction of 13-oxooctadecadienoic acid with glutathione

    Chem. Res. Toxicol.

    (1997)
  • P. Borst et al.

    A family of drug transporters: the multidrug resistance-associated proteins

    J. Natl. Cancer Inst.

    (2000)
  • J.-M. Brechot et al.

    Different pattern of MRP localization in ciliated and basal cells from human bronchial epithelium

    J. Histochem. Cytochem.

    (1998)
  • A. Broeks et al.

    Homologues of the human multidrug resistance genes MRP and MDR contribute to heavy metal resistance in the soil nematode Caenorhabditis elegans

    EMBO J.

    (1996)
  • Cited by (354)

    • Cadmium induced Fak -mediated anoikis activation in kidney via nuclear receptors (AHR/CAR/PXR)-mediated xenobiotic detoxification pathway

      2022, Journal of Inorganic Biochemistry
      Citation Excerpt :

      ABC transporters as a protein family of the phase III detoxification system, ABC transporters prevent the accumulation of Cd and inhibit adverse effects on growth and survival [77]. ABC transporter family includes P-GP and MRP1 [78], MRP1 is associated with the detoxification system of heavy metals [79] and heavy metals include Cd as substrates of MRP1 [80]. Callaghan et al. suggested that P-GP can play a role in eliminating Cd from cells to reduce toxicity [81].

    View all citing articles on Scopus
    View full text