Substrate specificity of human ABCC4 (MRP4)-mediated cotransport of bile acids and reduced glutathione

2006 ◽  
Vol 290 (4) ◽  
pp. G640-G649 ◽  
Author(s):  
Maria Rius ◽  
Johanna Hummel-Eisenbeiss ◽  
Alan F. Hofmann ◽  
Dietrich Keppler
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Reduced Glutathione ◽  
Membrane Vesicles ◽  
Multidrug Resistance Protein ◽  
Bile Salt Export Pump ◽  
Physiological Conditions ◽  
Resistance Protein ◽  
The Common ◽  
Inside Out

The multidrug resistance protein ABCC4 (MRP4), a member of the ATP-binding cassette superfamily, mediates ATP-dependent unidirectional efflux of organic anions out of cells. Previous studies showed that human ABCC4 is localized to the sinusoidal membrane of hepatocytes and mediates, among other substrates, the cotransport of reduced glutathione (GSH) with bile acids. In the present study, using inside-out membrane vesicles, we demonstrated that human ABCC4 in the presence of physiological concentrations of GSH has a high affinity for the taurine and glycine conjugates of the common natural bile acids as well as the unconjugated bile acid cholate. Chenodeoxycholyltaurine and chenodeoxycholylglycine were the GSH cosubstrates with the highest affinities for ABCC4, with Km values of 3.6 and 5.9 μM, respectively. Ursodeoxycholyltaurine and ursodeoxycholylglycine were cotransported together with GSH by ABCC4 with Km values of 7.8 and 12.5 μM, respectively, but no transport of ursodeoxycholate and deoxycholate was observed. The simultaneous transport of labeled GSH and cholyltaurine or cholylglycine was demonstrated in double-labeled cotransport experiments with a bile acid-to-GSH ratio of ∼1:22. Km values of the bile acids for ABCC4 were in a range similar to those reported for the canalicular bile salt export pump ABCB11. Under physiological conditions, the sinusoidal ABCC4 may compete with canalicular ABCB11 for bile acids and thereby play a key role in determining the hepatocyte concentration of bile acids. In cholestatic conditions, ABCC4 may become a key pathway for efflux of bile acids from hepatocytes into blood.

scholarly journals Steroid and bile acid conjugates are substrates of human multidrug-resistance protein (MRP) 4 (ATP-binding cassette C4)

2003 ◽  
Vol 371 (2) ◽  
pp. 361-367 ◽  
Author(s):  
Noam ZELCER ◽  
Glen REID ◽  
Peter WIELINGA ◽  
Annemieke KUIL ◽  
Ingrid van der HEIJDEN ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Bile Acid ◽  
Bile Acids ◽  
Mammalian Cells ◽  
Physiological Role ◽  
Membrane Vesicles ◽  
Dependent Manner ◽  
Multidrug Resistance Protein ◽  
Resistance Protein ◽  
Dependent Transport

Human multidrug-resistance protein (MRP) 4 transports cyclic nucleotides and when overproduced in mammalian cells mediates resistance to some nucleoside analogues. Recently, it has been shown that Mrp4 is induced in the livers of Fxr(-/-) mice, which have increased levels of serum bile acids. Since MRP4, like MRP1–3, also mediates transport of a model steroid conjugate substrate, oestradiol 17-β-d-glucuronide (E217βG), we tested whether MRP4 may be involved in the transport of steroid and bile acid conjugates. Bile salts, especially sulphated derivatives, and cholestatic oestrogens inhibited the MRP4-mediated transport of E217βG. Inhibition by oestradiol 3,17-disulphate and taurolithocholate 3-sulphate was competitive, suggesting that these compounds are MRP4 substrates. Furthermore, we found that MRP4 transports dehydroepiandrosterone 3-sulphate (DHEAS), the most abundant circulating steroid in humans, which is made in the adrenal gland. The ATP-dependent transport of DHEAS by MRP4 showed saturable kinetics with Km and Vmax values of 2μM and 45pmol/mg per min, respectively (at 27°C). We further studied the possible involvement of other members of the MRP family of transporters in the transport of DHEAS. We found that MRP1 transports DHEAS in a glutathione-dependent manner and exhibits Km and Vmax values of 5μM and 73pmol/mg per min, respectively (at 27°C). No transport of DHEAS was observed in membrane vesicles containing MRP2 or MRP3. Our findings suggest a physiological role for MRP1 and MRP4 in DHEAS transport and an involvement of MRP4 in transport of conjugated steroids and bile acids.

scholarly journals Transport of bile acids in multidrug-resistance-protein 3-overexpressing cells co-transfected with the ileal Na+-dependent bile-acid transporter

2003 ◽  
Vol 369 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Noam ZELCER ◽  
Tohru SAEKI ◽  
Ilse BOT ◽  
Annemieke KUIL ◽  
Piet BORST
Keyword(s):  
Multidrug Resistance ◽  
Bile Acid ◽  
Bile Salt ◽  
Bile Acids ◽  
Multidrug Resistance Protein ◽  
High Affinity ◽  
Multidrug Resistance Protein 3 ◽  
Bile Acid Transporter ◽  
Resistance Protein ◽  
Acid Transporter

Many of the transporters involved in the transport of bile acids in the enterohepatic circulation have been characterized. The basolateral bile-acid transporter of ileocytes and cholangiocytes remains an exception. It has been suggested that rat multidrug resistance protein 3 (Mrp3) fulfills this function. Here we analyse bile-salt transport by human MRP3. Membrane vesicles from insect (Spodoptera frugiperda) cells expressing MRP3 show time-dependent uptake of glycocholate and taurocholate. Furthermore, sulphated bile salts were high-affinity competitive inhibitors of etoposide glucuronide transport by MRP3 (IC5010μM). Taurochenodeoxycholate, taurocholate and glycocholate inhibited transport at higher concentrations (IC50100, 250 and 500μM respectively). We used mouse fibroblast-like cell lines derived from mice with disrupted Mdr1a, Mdr1b and Mrp1 genes to generate transfectants that express the murine apical Na+-dependent bile-salt transporter (Asbt) and MRP3. Uptake of glycocholate by these cells is Na+-dependent, with a Km and Vmax of 29±7μM and 660±63pmol/min per mg of protein respectively and is inhibited by several organic-aniontransport inhibitors. Expression of MRP3 in these cells limits the accumulation of glycocholate and increases the efflux from cells preloaded with taurocholate or glycocholate. In conclusion, we find that MRP3 transports both taurocholate and glycocholate, albeit with low affinity, in contrast with the high-affinity transport by rat Mrp3. Our results suggest that MRP3 is unlikely to be the principal basolateral bile-acid transporter of ileocytes and cholangiocytes, but that it may have a role in the removal of bile acids from the liver in cholestasis.

Molecular aspects of hepatobiliary transport

1997 ◽  
Vol 272 (6) ◽  
pp. G1285-G1303 ◽  
Author(s):  
M. Muller ◽  
P. L. Jansen
Keyword(s):  
Multidrug Resistance ◽  
Bile Acid ◽  
Bile Acids ◽  
Bile Flow ◽  
Hepatic Uptake ◽  
Organic Anions ◽  
Transport Proteins ◽  
Organic Cations ◽  
Multidrug Resistance Protein ◽  
Resistance Protein

Generation of bile flow is a regulated, ATP-dependent process and depends on the coordinated action of a number of transporter proteins in the sinusoidal and canalicular domains of the hepatocyte. Dysfunction of any of these proteins leads to retention of substrates, with conjugated hyperbilirubinemia or cholestasis as a result. In recent years many of the transport proteins involved in bile formation have been identified, cloned, and functionally characterized. The hepatocyte sinusoidal membrane contains transport proteins for the hepatic uptake of organic anions and cations and for the uptake of bile acids. The multispecific organic anion transporting polypeptide (OATP) mediates the hepatic uptake of organic anions and a variety of organic amphiphilic compounds, including organic cations. The organic cation transporter OCT1 more specifically transports small organic cations. NTCP is the Na(+)-bile acid cotransporting protein that mediates the hepatic uptake of bile acids. The canalicular transport proteins are able to transport endogenous and exogenous metabolites into the bile against steep concentration gradients. Most of these transporters are members of the large ATP-binding cassette (ABC) superfamily, and their transport function directly depends on the hydrolysis of Mg2+/ATP. At least five ABC transporter proteins have been characterized so far: 1) the human multidrug resistance protein MDR1 mediates the excretion of hydrophobic, mostly cationic, metabolites; 2) MDR3 is involved in phosphatidylcholine secretion; 3) the canalicular bile acid transporter cBAT mediates secretion of monovalent bile salts and provides the molecular basis of bile acid-dependent bile flow; 4) SPGP, product of the P-glycoprotein sister gene, is exclusively expressed in the liver but its function is currently unknown; and 5) the human multidrug resistance protein MRP2 mediates the excretion of multivalent anionic conjugates.

scholarly journals Evaluating Hepatobiliary Transport with 18F-Labeled Bile Acids: The Effect of Radiolabel Position and Bile Acid Structure on Radiosynthesis and In Vitro and In Vivo Performance

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Stef De Lombaerde ◽  
Ken Kersemans ◽  
Sara Neyt ◽  
Jeroen Verhoeven ◽  
Christian Vanhove ◽  
...  
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Membrane Vesicles ◽  
Hepatic Uptake ◽  
Hepatobiliary Transport ◽  
Bile Acid Transporters ◽  
Significant Difference ◽  
The Impact

Introduction. An in vivo determination of bile acid hepatobiliary transport efficiency can be of use in liver disease and preclinical drug development. Given the increased interest in bile acid Positron Emission Tomography- (PET-) imaging, a further understanding of the impact of 18-fluorine substitution on bile acid handling in vitro and in vivo can be of significance. Methods. A number of bile acid analogues were conceived for nucleophilic substitution with [18F]fluoride: cholic acid analogues of which the 3-, 7-, or 12-OH function is substituted with a fluorine atom (3α-[18F]FCA; 7β-[18F]FCA; 12β-[18F]FCA); a glycocholic and chenodeoxycholic acid analogue, substituted on the 3-position (3β-[18F]FGCA and 3β-[18F]FCDCA, resp.). Uptake by the bile acid transporters NTCP and OATP1B1 was evaluated with competition assays in transfected CHO and HEK cell lines and efflux by BSEP in membrane vesicles. PET-scans with the tracers were performed in wild-type mice (n=3 per group): hepatobiliary transport was monitored and compared to a reference tracer, namely, 3β-[18F]FCA. Results. Compounds 3α-[18F]FCA, 3β-[18F]FGCA, and 3β-[18F]FCDCA were synthesized in moderate radiochemical yields (4–10% n.d.c.) and high radiochemical purity (>99%); 7β-[18F]FCA and 12β-[18F]FCA could not be synthesized and included further in this study. In vitro evaluation showed that 3α-FCA, 3β-FGCA, and 3β-FCDCA all had a low micromolar Ki-value for NTCP, OATP1B1, and BSEP. In vivo, 3α-[18F]FCA, 3β-[18F]FGCA, and 3β-[18F]FCDCA displayed hepatobiliary transport with varying efficiency. A slight yet significant difference in uptake and efflux rate was noticed between the 3α-[18F]FCA and 3β-[18F]FCA epimers. Conjugation of 3β-[18F]FCA with glycine had no significant effect in vivo. Compound 3β-[18F]FCDCA showed a significantly slower hepatic uptake and efflux towards gallbladder and intestines. Conclusion. A set of 18F labeled bile acids was synthesized that are substrates of the bile acid transporters in vitro and in vivo and can serve as PET-biomarkers for hepatobiliary transport of bile acids.

Characterization of the amino-terminal regions in the human multidrug resistance protein (MRP1)

2000 ◽  
Vol 113 (24) ◽  
pp. 4451-4461
Author(s):  
E. Bakos ◽  
R. Evers ◽  
G. Calenda ◽  
G.E. Tusnady ◽  
G. Szakacs ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Drug Transport ◽  
Cellular Localization ◽  
Membrane Vesicles ◽  
Sf9 Cells ◽  
Multidrug Resistance Protein ◽  
Hydrophobic Membrane ◽  
Amino Terminal ◽  
Mdckii Cells ◽  
Resistance Protein

The human multidrug resistance protein (MRP1) contributes to drug resistance in cancer cells. In addition to an MDR1-like core, MRP1 contains an N-terminal membrane-bound (TMD(0)) region and a cytoplasmic linker (L(0)), both characteristic of several members of the MRP family. In order to study the role of the TMD(0) and L(0) regions, we constructed various truncated and mutated MRP1, and chimeric MRP1-MDR1 molecules, which were expressed in insect (Sf9) and polarized mammalian (MDCKII) cells. The function of the various proteins was examined in isolated membrane vesicles by measuring the transport of leukotriene C(4) and other glutathione conjugates, and by vanadate-dependent nucleotide occlusion. Cellular localization, and glutathione-conjugate and drug transport, were also studied in MDCKII cells. We found that chimeric proteins consisting of N-terminal fragments of MRP1 fused to the N terminus of MDR1 preserved the transport, nucleotide occlusion and apical membrane routing of wild-type MDR1. As shown before, MRP1 without TMD(0)L(0) (Delta MRP1), was non-functional and localized intracellularly, so we investigated the coexpression of Delta MRP1 with the isolated L(0) region. Coexpression yielded a functional MRP1 molecule in Sf9 cells and routing to the lateral membrane in MDCKII cells. Interestingly, the L(0) peptide was found to be associated with membranes in Sf9 cells and could only be solubilized by urea or detergent. A 10-amino-acid deletion in a predicted amphipathic region of L(0) abolished its attachment to the membrane and eliminated MRP1 transport function, but did not affect membrane routing. Taken together, these experiments suggest that the L(0) region forms a distinct domain within MRP1, which interacts with hydrophobic membrane regions and with the core region of MRP1.

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