MRP8, ATP-binding cassette C11 (ABCC11), is a cyclic nucleotide efflux pump and a resistance factor for fluoropyrimidines 2',3'-dideoxycytidine and 9'-(2'-phosphonylmethoxyethyl)adenine.
MRP8 (ABCC11) is a recently identified cDNA that has been assigned to the multidrug resistance-associated protein (MRP) family of ATP-binding cassette transporters, but its functional characteristics have not been determined. Here we examine the functional properties of the protein using transfected LLC-PK1 cells. It is shown that ectopic expression of MRP8 reduces basal intracellular levels of cAMP and cGMP and enhances cellular extrusion of cyclic nucleotides in the presence or absence of stimulation with forskolin or SIN-1A. Analysis of the sensitivity of MRP8-overexpressing cells revealed that they are resistant to a range of clinically relevant nucleotide analogs, including the anticancer fluoropyrimidines 5'-fluorouracil (approximately 3-fold), 5'-fluoro-2'-deoxyuridine (approximately 5-fold), and 5'-fluoro-5'-deoxyuridine (approximately 3-fold), the anti-human immunodeficiency virus agent 2',3'-dideoxycytidine (approximately 6-fold) and the anti-hepatitis B agent 9'-(2'-phosphonylmethoxynyl)adenine (PMEA) (approximately 5-fold). By contrast, increased resistance was not observed for several natural product chemotherapeutic agents. In accord with the notion that MRP8 functions as a drug efflux pump for nucleotide analogs, MRP8-transfected cells exhibited reduced accumulation and increased efflux of radiolabeled PMEA. In addition, it is shown by the use of in vitro transport assays that MRP8 is able to confer resistance to fluoropyrimidines by mediating the MgATP-dependent transport of 5'-fluoro-2'-deoxyuridine monophosphate, the cytotoxic intracellular metabolite of this class of agents, but not of 5'-fluorouracil or 5'-fluoro-2'-deoxyuridine. We conclude that MRP8 is an amphipathic anion transporter that is able to efflux cAMP and cGMP and to function as a resistance factor for commonly employed purine and pyrimidine nucleotide analogs.
Guo
Yanping
Y
Medical Science Division, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Kotova
Elena
E
Chen
Zhe-Sheng
ZS
Lee
Kun
K
Hopper-Borge
Elizabeth
E
Belinsky
Martin G
MG
Kruh
Gary D
GD
D018528:ATP-Binding Cassette Transporters / Q000378:metabolism / Q000502:physiology*; D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D000998:Antiviral Agents / Q000494:pharmacology; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D004396:Coloring Agents / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D005467:Floxuridine / Q000737:chemistry; D005472:Fluorouracil / Q000494:pharmacology; D005822:Genetic Vectors; D006131:Growth Inhibitors / Q000494:pharmacology; D015151:Immunoblotting; D020128:Inhibitory Concentration 50; D007313:Insecta; D008954:Models, Biological; D009602:Nitrosamines / Q000494:pharmacology; D009711:Nucleotides / Q000378:metabolism; D063065:Organophosphonates; D013552:Swine; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D014162:Transfection; D016047:Zalcitabine / Q000494:pharmacology*
C435500:ABCC11 protein, human; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D000998:Antiviral Agents; D004396:Coloring Agents; D018076:DNA, Complementary; D006131:Growth Inhibitors; D009602:Nitrosamines; D009711:Nucleotides; D063065:Organophosphonates; D013778:Tetrazolium Salts; D013844:Thiazoles; D005467:Floxuridine; D005576:Colforsin; C006006:N-nitrosomorpholinoaminoacetonitrile; C053001:adefovir; D016047:Zalcitabine; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; C022616:thiazolyl blue; D006152:Cyclic GMP; D000225:Adenine; D005472:Fluorouracil