Biomedical subjects

Isabelle J Létourneau

Publications and source records attributed to Isabelle J Létourneau.

3 recordsLinked to original sources

PubMed2005

Limited modulation of the transport activity of the human multidrug resistance proteins MRP1, MRP2 and MRP3 by nicotine glucuronide metabolites.

The human ATP-binding cassette proteins MRP1 (ABCC1), MRP2 (ABCC2) and MRP3 (ABCC3) are active transporters of antineoplastic drugs as well as conjugated metabolites and other organic anions. In addition to being substrates, many glucuronide, glutathione and sulfate conjugates can also inhibit the transport activities of these MRP-related proteins, sometimes in a glutathione (GSH)-dependent manner. Nicotine is the major addictive component of cigarette smoke. Three glucuronide metabolites of this compound have been identified in vivo: nicotine-N-glucuronide, cotinine-N-glucuronide and trans-hydroxycotinine-O-glucuronide. In this study, we first chemically synthesized trans-hydroxycotinine-O-glucuronide and then tested the ability of this compound, nicotine-N-glucuronide and cotinine-N-glucuronide to modulate the vesicular transport of several organic anions by MRP1, MRP2 and MRP3. We observed that none of the three metabolites at concentrations up to 100muM significantly affected organic anion transport by MRP1 or MRP2, either in the absence or presence of GSH. MRP3-mediated transport of 17beta-estradiol 17-(beta-d-glucuronide) and methotrexate were partially inhibited by trans-hydroxycotinine-O-glucuronide (300 microM) (by 70% and 50%, respectively), whereas nicotine-N-glucuronide and cotinine-N-glucuronide had no effect. We conclude that the physiological functions of MRP1, MRP2 and MRP3 are not likely to be substantially affected by nicotine glucuronide metabolites at concentrations achievable in human serum.

ATP-Binding Cassette Transporters↗

PubMed2005

Functional characterization of non-synonymous single nucleotide polymorphisms in the gene encoding human multidrug resistance protein 1 (MRP1/ABCC1).

The 190-kDa ATP-binding cassette (ABC) multidrug resistance protein 1 (MRP1) encoded by the MRP1/ABCC1 gene mediates the active cellular efflux of glucuronide, glutathione and sulfate conjugates. It can also confer resistance to a diverse spectrum of chemotherapeutic agents and transport a variety of toxicants. In the present study, we examined 10 MRP1/ABCC1 missense genetic variants [non-synonymous single nucleotide polymorphisms (SNPs)] to determine whether or not they affect expression or function of the transporter. Variants 218C>T (Thr73Ile), 257C>T (Ser92Phe), 350C>T (Thr117Met), 689G>A (Arg230Gln), 1898G>A (Arg633Gln), 2168G>A (Arg723Gln), 2965G>A (Ala989Thr), 3140G>C (Cys1047Ser), 3173G>A (Arg1058Gln) and 4535C>T (Ser1512Leu) were recreated using site-directed mutagenesis and transfected into human embryonic kidney cells. Immunoblotting experiments showed that all mutant proteins were expressed at levels comparable to wild-type MRP1. Vesicular transport assays revealed that the Ala989Thr mutation caused a significant decrease in estradiol 17beta-glucuronide transport due to a decrease in apparent affinity (Km) for this organic anion. The transport properties of the other mutants were comparable to wild-type MRP1. When the MRP1/ABCC1 non-synonymous SNPs were evaluated by the SIFT algorithm using subsets of homologs and orthologs of MRP1/ABCC1, Arg230Gln, Val353Met, Arg433Ser, Gly671Val and Arg1058 mutations were predicted to be deleterious, whereas the PolyPhen algorithm predicted Ser92Phe and Gly671Val to be potentially damaging. Thus most predictions of these algorithms were not in accordance with our experimental results. In conclusion, our data suggest that none of the MRP1/ABCC1 variants studied are likely by themselves to have major deleterious effects in healthy individuals, and the SIFT and PolyPhen algorithms appear to be poor predictors of the phenotypic consequences of these MRP1 mutations at least in vitro.

Adenosine Triphosphate↗

PubMed2003

Functional and structural consequences of cysteine substitutions in the NH2 proximal region of the human multidrug resistance protein 1 (MRP1/ABCC1).

The 190 kDa multidrug resistance protein 1 (MRP1; ABCC1) is comprised of three membrane spanning domains (MSDs) and two nucleotide binding domains (NBDs) configured MSD1-MSD2-NBD1-MSD3-NBD2. MRP1 overexpression in tumor cells results in an ATP-dependent efflux of many oncolytic agents and arsenic and antimony oxyanions. MRP1 also transports GSSG and GSH as well as conjugated organic anions, including leukotriene C(4) and 17beta-estradiol 17-(beta-D-glucuronide) and certain xenobiotics in association with GSH. Previous studies have shown that portions of MSD1 and the cytoplasmic loop (CL3) connecting it to MSD2 are important for MRP1 transport function. In the present study, Cys residues at positions 43, 49, 85, 148, and 190 in MSD1 and positions 208 and 265 in CL3 were mutated to Ala and Ser, and the effects on protein expression, plasma membrane localization, trypsin sensitivity, organic anion transport, and drug resistance properties were investigated. Confocal microscopy showed that 11 of 14 mutants displayed significant levels of nonplasma membrane-associated MRP1. Most mutant proteins were also more resistant to trypsin proteolysis than wild-type MRP1. All Cys mutants transported organic anions (0.5-1.5-fold wild-type MRP1 activity), and cells expressing Ser-substituted but not Ala-substituted Cys43 and Cys265 MRP1 mutants exhibited a 2.5-fold decrease and a 3-fold increase in arsenite resistance, respectively; Cys43Ser MRP1 also conferred lower levels of vincristine resistance. These results indicate that certain Cys residues in the NH(2) proximal region of MRP1 can be important for its structure and selected transport activities.

Arsenites↗