Multidrug-resistance protein 5 is a multispecific organic anion transporter able to transport nucleotide analogs

Multidrug-resistance protein 5 is a multispecific organic anion transporter able to transport nucleotide analogs

^*Division of Molecular Biology and Center for Biomedical Genetics, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands; ^†Department of Pathology, University Hospital Free University, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands; ^‡Department of Neurology, Academic Medical Center, 1105 AZ Amsterdam, The Netherlands; ^§Department of Pharmacy, Slotervaart Hospital, Louwesweg 6, 1066 EC Amsterdam, The Netherlands; and ^¶Laboratory of Virology and Chemotherapy, Rega Institute for Medical Research, Katholieke Universiteit Leuven, Minderbroedersstraat 10, B-3000 Leuven, Belgium

Contributed by Piet Borst

Abstract

Two prominent members of the ATP-binding cassette superfamily of transmembrane proteins, multidrug resistance 1 (MDR1) P-glycoprotein and multidrug resistance protein 1 (MRP1), can mediate the cellular extrusion of xenobiotics and (anticancer) drugs from normal and tumor cells. The MRP subfamily consists of at least six members, and here we report the functional characterization of human MRP5. We found resistance against the thiopurine anticancer drugs, 6-mercaptopurine (6-MP) and thioguanine, and the anti-HIV drug 9-(2-phosphonylmethoxyethyl)adenine (PMEA) in MRP5-transfected cells. This resistance is due to an increased extrusion of PMEA and 6-thioinosine monophosphate from the cells that overproduce MRP5. In polarized Madin–Darby canine kidney II (MDCKII) cells transfected with an MRP5 cDNA construct, MRP5 is routed to the basolateral membrane and these cells transport S-(2,4-dinitrophenyl)glutathione and glutathione preferentially toward the basal compartment. Inhibitors of organic anion transport inhibit transport mediated by MRP5. We speculate that MRP5 might play a role in some cases of unexplained resistance to thiopurines in acute lymphoblastic leukemia and/or to antiretroviral nucleoside analogs in HIV-infected patients.

Footnotes

↵ ‖ To whom reprint requests should be addressed at: Division of Molecular Biology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. E-mail: pborst{at}nki.nl.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. U83661).
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.120159197.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.120159197
Abbreviations:

GSH,

glutathione;

GS-X,

GSH conjugate;

DNP-GS,

S-(2,4-dinitrophenyl)glutathione;

CDNB,

1-chloro-2,4-dinitrobenzene;

CMV,

cytomegalovirus;

HEK,

human embryonic kidney cells;

5-HP,

5-hydroxypyridine-2-carboxaldehyde thiosemicarbazone;

MDCKII cells,

Madin–Darby canine kidney II cells;

MDR,

multidrug resistance;

6-MP,

6-mercaptopurine;

MTX,

methotrexate;

MRP1,

MDR protein 1;

PMEA,

9-(2-phosphonylmethoxyethyl)adenine;

bis-POM-PMEA,

bis(pivaloyloxymethyl)-PMEA;

PMEAp,

PMEA monophosphate;

PMEApp,

PMEA diphosphate;

tIMP,

6-thioinosine monophosphate