scholarly journals MOAT4, a novel multispecific organic-anion transporter for glucuronides and mercapturates in mouse L1210 cells and human erythrocytes

1996 ◽  
Vol 320 (1) ◽  
pp. 273-281 ◽  
Author(s):  
Manju SAXENA ◽  
Gary B HENDERSON
Keyword(s):  
Transport System ◽  
Organic Anion ◽  
High Sensitivity ◽  
Human Erythrocytes ◽  
Organic Anion Transporter ◽  
High Affinity ◽  
L1210 Cells ◽  
Anion Transporter ◽  
Dependent Transport ◽  
Inside Out

Glucuronides and mercapturates were examined as possible high-affinity substrates for a low-affinity ATP-dependent transport system for 2,4-dinitrophenyl S-glutathione (DNP-SG) in mouse L1210 cells. Initial inhibitor studies with inside-out vesicles revealed that the low-affinity transport of [3H]DNP-SG (Km 450 µM) exhibits a high sensitivity to N-acetyl 2,4-dinitrophenyl cysteine (NAc-DNP-Cys) (Ki 5.0 µM) and α-naphthyl β-D-glucuronide (naphthyl glucuronide) (Ki 8.5 µM). Direct transport measurements showed the presence of ATP-dependent uptake activities for NAc-DNP-[35S]Cys and naphthyl [14C] glucuronide, and Km values for half-maximal transport were comparable to the Ki values of these compounds for inhibition of [3H]DNP-SG transport. Transport of [3H]DNP-SG, NAc-DNP-[35S]Cys and naphthyl [14 C]glucuronide each showed the same sensitivity to various anions and anion conjugates. Inhibition was competitive and was most potent for bilirubin ditaurate, indoprofen, 4-biphenylacetic acid, 4-acridine 4β-D-glucuronide, N-acetyl leukotriene E4, 17β-oestradiol 3β-D-glucuronide and taurolithocholate 3-sulphate. Inside-out vesicles from human erythrocytes contain a comparable ATP-dependent transport system. These results show that NAc-DNP-Cys and naphthyl glucuronide are high-affinity substrates for a single system identified previously as a low-affinity transporter of DNP-SG. Substrate and inhibitor studies identify this system as a novel multispecific organic-anion transport system (MOAT4) that accommodates glucuronides and mercapturates and is distinct from other MOAT transporters. Human erythrocytes contain an additional ATP-dependent system for NAc-DNP-Cys (Km 33 µM) that does not transport monoglucuronides.

Rosuvastatin is a high affinity substrate of hepatic organic anion transporter OATP-C

2001 ◽  
Vol 2 (2) ◽  
pp. 90 ◽  
Author(s):  
C.D.A. Brown ◽  
A. Windass ◽  
K. Bleasby ◽  
B. Lauffart
Keyword(s):  
Organic Anion ◽  
Organic Anion Transporter ◽  
High Affinity ◽  
Anion Transporter

scholarly journals Olfactory mucosa-expressed organic anion transporter, Oat6, manifests high affinity interactions with odorant organic anions

2006 ◽  
Vol 351 (4) ◽  
pp. 872-876 ◽  
Author(s):  
Gregory Kaler ◽  
David M. Truong ◽  
Derina E. Sweeney ◽  
Darren W. Logan ◽  
Megha Nagle ◽  
...  
Keyword(s):  
Organic Anion ◽  
Organic Anions ◽  
Olfactory Mucosa ◽  
Organic Anion Transporter ◽  
High Affinity ◽  
Anion Transporter

scholarly journals The MRP4/ABCC4 Gene Encodes a Novel Apical Organic Anion Transporter in Human Kidney Proximal Tubules: Putative Efflux Pump for Urinary cAMP and cGMP

2002 ◽  
Vol 13 (3) ◽  
pp. 595-603 ◽  
Author(s):  
Rémon A. M. H. van Aubel ◽  
Pascal H. E. Smeets ◽  
Janny G. P. Peters ◽  
René J. M. Bindels ◽  
Frans G. M. Russel
Keyword(s):  
Efflux Pump ◽  
Organic Anion ◽  
Membrane Vesicles ◽  
Human Kidney ◽  
Proximal Tubules ◽  
Organic Anion Transporter ◽  
Anion Transporter ◽  
Dependent Transport ◽  
Camp And Cgmp ◽  
Kidney Proximal Tubules

ABSTRACT. The cyclic nucleotides cAMP and cGMP play key roles in cellular signaling and the extracellular regulation of fluid balance. In the kidney, cAMP is excreted across the apical proximal tubular membrane into urine, where it reduces phosphate reabsorption through a dipyridamole-sensitive mechanism that is not fully understood. It has long been known that this cAMP efflux pathway is dependent on ATP and is inhibited by probenecid. However, its identity and whether cGMP shares the same transporter have not been established. Here the expression, localization, and functional properties of human multidrug resistance protein 4 (MRP4) are reported. MRP4 is localized to the proximal tubule apical membrane of human kidney, and membrane vesicles from Sf9 cells expressing human MRP4 exhibit ATP-dependent transport of [3H]cAMP and [3H]cGMP. Both probenecid and dipyridamole are potent MRP4 inhibitors. ATP-dependent [3H]methotrexate and [3H]estradiol-17β-d-glucuronide transport by MRP4 and interactions with the anionic conjugates S-(2,4-dinitrophenyl)-glutathione, N-acetyl-(2,4-dinitrophenyl)-cysteine, α-naphthyl-β-d-glucuronide, and p-nitrophenyl-β-d-glucuronide are also demonstrated. In kidneys of rats deficient in the apical anionic conjugate efflux pump Mrp2, Mrp4 expression is maintained at the same level. It is concluded that MRP4 is a novel apical organic anion transporter and the putative efflux pump for cAMP and cGMP in human kidney proximal tubules.

scholarly journals Novel properties of hepatic canalicular reduced glutathione transport revealed by radiation inactivation

1998 ◽  
Vol 274 (5) ◽  
pp. G923-G930 ◽  
Author(s):  
Aravind V. Mittur ◽  
Neil Kaplowitz ◽  
Ellis S. Kempner ◽  
Murad Ookhtens
Keyword(s):  
Organic Anion ◽  
Membrane Vesicles ◽  
Organic Anion Transporter ◽  
Initial Increase ◽  
Radiation Inactivation ◽  
High Affinity ◽  
Anion Transporter ◽  
Sigmoidal Kinetics ◽  
Single Exponential Function ◽  
Functional Size

Transport of GSH at the canalicular pole of hepatocytes occurs by a facilitative carrier and can account for ∼50% of total hepatocyte GSH efflux. A low-affinity unit with sigmoidal kinetics accounts for 90% of canalicular transport at physiological GSH concentrations. A low-capacity transporter with high affinity for GSH has also been reported. It is not known whether the same or different proteins mediate low- and high-affinity GSH transport, although they do differ in inhibitor specificity. The bile of rats with a mutation in the canalicular multispecific organic anion transporter (cMOAT or MRP-2, a 170-kDa protein) is deficient in GSH, implying that cMOAT may transport GSH. However, transport of GSH in canalicular membrane vesicles (CMV) from these mutant rats remains intact. We examined the functional size of the two kinetic components of GSH transport by radiation inactivation of GSH uptake in rat hepatic CMV. High-affinity transport of GSH was inactivated as a single exponential function of radiation dose, yielding a functional size of ∼70 kDa. In contrast, low-affinity canalicular GSH transport exhibited a complex biexponential response to irradiation, characterized by an initial increase followed by a decrease in GSH transport. Inactivation analysis yielded a ∼76-kDa size for the low-affinity transporter. The complex inactivation indicated that the low-affinity transporter is associated with a larger protein of ∼141 kDa, which masked ∼80% of the potential transport activity in CMV. Additional studies, using inactivation of leukotriene C4 transport, yielded a functional size of ∼302 kDa for cMOAT, indicating that it functions as a dimer.

scholarly journals ATP-dependent transport of bilirubin glucuronides by the multidrug resistance protein MRP1 and its hepatocyte canalicular isoform MRP2

1997 ◽  
Vol 327 (1) ◽  
pp. 305-310 ◽  
Author(s):  
Gabriele JEDLITSCHKY ◽  
Inka LEIER ◽  
Ulrike BUCHHOLZ ◽  
Johanna HUMMEL-EISENBEISS ◽  
Brian BURCHELL ◽  
...  
Keyword(s):  
Multidrug Resistance ◽  
Membrane Vesicle ◽  
Organic Anion ◽  
Membrane Vesicles ◽  
Organic Anion Transporter ◽  
Multidrug Resistance Protein ◽  
Leukotriene C4 ◽  
Anion Transporter ◽  
Resistance Protein ◽  
Dependent Transport

Bilirubin is secreted from the liver into bile mainly as monoglucuronosyl and bisglucuronosyl conjugates. We demonstrate for the first time that ATP-dependent transport of both bilirubin glucuronides is mediated by the multidrug resistance protein (MRP1) as well as by the distinct canalicular (apical) isoform MRP2, also termed cMRP or cMOAT (canalicular multispecific organic anion transporter). In membrane vesicles from MRP1-transfected HeLa cells mono[3H]glucuronosylbilirubin and bis[3H]glucuronosylbilirubin (each at 0.5 μM) were transported with rates of 5.3 and 3.1 pmol/min per mg of protein respectively. Rat hepatocyte canalicular membrane vesicles, which contain Mrp2 (the rat equivalent of MRP2), transported mono[3H]glucuronosylbilirubin and bis[3H]glucuronosylbilirubin at rates of 8.9 and 8.5 pmol/min per mg of protein, whereas membrane vesicles from mutant liver lacking Mrp2 showed no transport of the conjugates. In membrane vesicles from human hepatoma Hep G2 cells, which predominantly expressed MRP2, transport rates were 8.3 and 4.4 pmol/min per mg of protein for monoglucuronosylbilirubin and bisglucuronosylbilirubin respectively. ATP-dependent transport of the glutathione S-conjugate [3H]leukotriene C4, an established high-affinity substrate for MRP1 and MRP2, was inhibited by both bilirubin glucuronides with IC50 values between 0.10 and 0.75 μM. The ratios of leukotriene C4 transport and bilirubin glucuronide transport, determined in the same membrane vesicle preparation, indicated substrate specificity differences between MRP1 and MRP2 with a preference of MRP2 for the glucuronides.

scholarly journals Cholate Resistance in Lactococcus lactisIs Mediated by an ATP-Dependent Multispecific Organic Anion Transporter

2000 ◽  
Vol 182 (18) ◽  
pp. 5196-5201 ◽  
Author(s):  
Atsushi Yokota ◽  
Marloes Veenstra ◽  
Peter Kurdi ◽  
Hendrik W. van Veen ◽  
Wil N. Konings
Keyword(s):  
Organic Anion ◽  
Membrane Vesicles ◽  
Organic Anion Transporter ◽  
Active Efflux ◽  
Multidrug Transporters ◽  
Ph Probe ◽  
Anion Transporter ◽  
P Type ◽  
Inside Out

ABSTRACT The cholate-resistant Lactococcus lactis strain C41-2, derived from wild-type L. lactis MG1363 through selection for growth on cholate-containing medium, displayed a reduced accumulation of cholate due to an enhanced active efflux. However,L. lactis C41-2 was not cross resistant to deoxycholate or cationic drugs, such as ethidium and rhodamine 6G, which are typical substrates of the multidrug transporters LmrP and LmrA in L. lactis MG1363. The cholate efflux activity in L. lactis C41-2 was not affected by the presence of valinomycin plus nigericin, which dissipated the proton motive force. In contrast, cholate efflux in L. lactis C41-2 was inhibited byortho-vanadate, an inhibitor of P-type ATPases and ATP-binding cassette transporters. Besides ATP-dependent drug extrusion by LmrA, two other ATP-dependent efflux activities have previously been detected in L. lactis, one for the artificial pH probe 2′,7′-bis-(2-carboxyethyl)-5(and 6)-carboxyfluorescein (BCECF) and the other for the artificial pH probe N-(fluorescein thio-ureanyl)-glutamate (FTUG). Surprisingly, the efflux rate of BCECF, but not that of FTUG, was significantly enhanced in L. lactis C41-2. Further experiments with L. lactisC41-2 cells and inside out membrane vesicles revealed that cholate and BCECF inhibit the transport of each other. These data demonstrate the role of an ATP-dependent multispecific organic anion transporter in cholate resistance in L. lactis.

scholarly journals ATP-dependent transport of unconjugated bilirubin by rat liver canalicular plasma membrane vesicles

1998 ◽  
Vol 331 (1) ◽  
pp. 99-103 ◽  
Author(s):  
Lorella PASCOLO ◽  
Enrique J. BAYON ◽  
Felicia CUPELLI ◽  
J. Donald OSTROW ◽  
Claudio TIRIBELLI
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Atp Hydrolysis ◽  
Organic Anion ◽  
Membrane Vesicles ◽  
Organic Anion Transporter ◽  
Unconjugated Bilirubin ◽  
Plasma Membrane Vesicles ◽  
Anion Transporter ◽  
Dependent Transport

The transport of highly purified 3H-labelled unconjugated bilirubin (UCB) was investigated in rat liver plasma membrane vesicles enriched in the canalicular domain and found to be stimulated (more than 5-fold) by the addition of ATP. Other nucleotides, such as AMP, ADP, GTP and a non-hydrolysable ATP analogue (adenosine 5´-[α,β-methylene] triphosphate), did not stimulate [3H]UCB transport, indicating that ATP hydrolysis was necessary for the stimulatory effect. [3H]UCB uptake occurred into an osmotically sensitive space. At an unbound bilirubin concentration ([Bf]) below saturation of the aqueous phase (no more than 70 nM UCB), the ATP-dependent transport followed saturation kinetics with respect to [Bf], with a Km of 26±8 nM and a Vmax of 117±11 pmol per 15 s per mg of protein. Unlabelled UCB inhibited the uptake of [3H]UCB, indicating that UCB was the transported species. Inhibitors of ATPase activity such as vanadate or diethyl pyrocarbonate decreased the ATP effect (59±11% and 100% respectively). Daunomycin, a known substrate for multidrug resistance protein-1, and taurocholate did not inhibit the ATP-dependent [3H]UCB transport, suggesting that neither mdr-1 nor the canalicular bile acid transporter is involved in the canalicular transport of UCB. [3H]UCB uptake (both with and without ATP) in canalicular vesicles obtained from TR- rats was comparable to that in vesicles obtained from Wistar rats, indicating that the canalicular multispecific organic anion transporter, cMOAT, does not account for UCB transport. These results indicate that UCB is transported across the canalicular membrane of the liver cell by an ATP-dependent mechanism involving an as yet unidentified transporter.

Characterization of hepatobiliary organic anion transporter regulation in the Zucker rat

2004 ◽  
Vol 42 (08) ◽  
Author(s):  
A Geier ◽  
CG Dietrich ◽  
C Gartung ◽  
F Lammert ◽  
HE Wasmuth ◽  
...  
Keyword(s):  
Organic Anion ◽  
Organic Anion Transporter ◽  
Zucker Rat ◽  
Anion Transporter
Sign in / Sign up

Export Citation Format

Share Document