Pdr5-mediated multidrug resistance requires the CPY-vacuolar sorting protein Vps3: are xenobiotic compounds routed from the vacuole to plasma membrane transporters for efflux?
In Saccharomyces cerevisiae several members of the ATP-binding cassette transporter superfamily efflux a broad range of xenobiotic substrates from cells. The vacuole also plays a critical role in multidrug resistance. Mutations in genes such as VPS3 that are essential for vacuolar acidification and carboxypeptidase Y vacuolar protein-sorting are multidrug sensitive. A similar phenotype is also observed with deletions of VPS15, VPS34, and VPS38, which encode essential members of the carboxypeptidase Y vacuolar protein-sorting pathway. Prior to the work described herein, detoxification by transporters and the vacuole were presumed to function independently. We demonstrate that this is not the case. Significantly, Vps3 has an epistatic relationship with Pdr5, a major yeast multidrug transporter. Thus, a double pdr5, vps3 deletion mutant is no more multidrug sensitive than its isogenic single-mutant counterparts. Subcellular fractionation experiments and analysis of purified plasma membrane vesicles indicate, however, that a vps3 mutation does not affect the membrane-localization or ATPase activity of Pdr5 even though rhodamine 6G efflux is reduced significantly. This suggests that Vps3 and probably other members of the carboxypeptidase Y vacuolar protein-sorting pathway are required for relaying xenobiotic compounds to transporters in the membrane.
Rutledge
Robert M
RM
Department of Biology, The Catholic University of America, Washington, DC 20064, USA.
Ghislain
Michel
M
Mullins
J Michael
JM
de Thozée
Cedric Pety
CP
Golin
John
J
D018528:ATP-Binding Cassette Transporters / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D003022:Clotrimazole / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D026141:Drug Resistance, Multiple, Fungal / Q000235:genetics; D017353:Gene Deletion; D010641:Phenotype; D012235:Rhodamines / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D022161:Transport Vesicles; D014617:Vacuoles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000502:physiology; D015262:Xenobiotics / Q000378:metabolism*
D018528:ATP-Binding Cassette Transporters; C092438:PDR5 protein, S cerevisiae; D012235:Rhodamines; D029701:Saccharomyces cerevisiae Proteins; C065531:VPS3 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D015262:Xenobiotics; C026188:rhodamine 6G; D003513:Cycloheximide; D000251:Adenosine Triphosphatases; D003022:Clotrimazole