Disease relevance of YCF1

• Mutagenesis of phenylalanine 713 in the YCF1 nucleotide binding fold 1, which correlates with the delta F508 mutation found in the most common form of cystic fibrosis, completely abolished YCF1 function in cadmium detoxification [1].
• On the basis of these results--the Cd2+ hypersensitivity of DTY167, versus DTY165, cells, the inducibility of YCF1-mediated transport, and the rapidity and spontaneity of Cd-GS2 formation--this new pathway is concluded to contribute substantially to Cd2+ detoxification [2].

High impact information on YCF1

• These results suggest that transgenic plants expressing YCF1 may be useful for phytoremediation of lead and cadmium [3].
• We have studied the utility of the yeast protein YCF1, which detoxifies cadmium by transporting it into vacuoles, for the remediation of lead and cadmium contamination [3].
• Disruption of either the ACR3 or YCF1 gene results in sensitivity to arsenite and disruption of both genes produces additive hypersensitivity [4].
• The substrate requirements, kinetics and Cd2+/glutathione stoichiometry of cadmium uptake and the molecular weight of the transport-active complex demonstrate that YCF1 selectively catalyzes the transport of bis(glutathionato)cadmium (Cd x +GS2) [2].
• The yeast cadmium factor (YCF1) gene encodes an MgATP-energized glutathione S-conjugate transporter responsible for the vacuolar sequestration of organic compounds after their S-conjugation with glutathione [2].

Chemical compound and disease context of YCF1

• Mutant strains of yeast that lack the YCF1 gene are hypersensitive to cadmium and this hypersensitivity is epistatic to yAP-1 overexpression [5].

Biological context of YCF1

• [3H]GSH transport was measured in vacuolar membrane vesicles isolated from a control strain of Saccharomyces cerevisiae (DTY165), the isogenic DTY167 strain that lacks a functional Ycf1p, and in DTY167 transformed with a 2-micrometer plasmid vector containing YCF1 [6].
• ATP-dependent transport of reduced glutathione on YCF1, the yeast orthologue of mammalian multidrug resistance associated proteins [6].
• In Saccharomyces cerevisiae, disruption of the YCF1 gene increases the sensitivity of cell growth to mercury [7].
• The energy requirements, kinetics, substrate specificity, and inhibitor profile of YCF1-mediated transport demonstrate that the vacuolar glutathione conjugate pump of yeast bears a strong mechanistic resemblance to the MRP1-encoded transporter of mammalian cells and the cognate, but as yet molecularly undefined, function of plant cells [8].
• These results suggest that YCF1 is composed of modular domains found in human proteins which function in drug and ion transport [1].

Anatomical context of YCF1

• Cadmium is compartmentalized in vacuoles through the Ycf1 transporter, in the form of a bis-glutathionato-cadmium complex [9].
• Whereas the mechanism of action of YCF1 is not known, MRP was recently found to transport glutathione S-conjugates across membranes [10].
• Growth of yeast strains, either deleted for the vacuolar ABC transporter Ycf1 or deleted for the plasma membrane ABC transporter Yor1p or overexpressing Yor1p, were compared for their sensitivity to cadmium [11].

Associations of YCF1 with chemical compounds

• Using a mutant strain deficient in YAP1, which codifies a transcription factor that controls the expression of both GSH1 and YCF1, we also observed a twofold increase in cadmium uptake, the same behavior shown by Deltagsh1 cells [9].
• Since YCF1 and YLL015w are rather homologous with multidrug resistant proteins (MRPs), they also suggest the involvement of this class of transporters in the ATP-dependent transport of unconjugated bilirubin [12].
• ATP-dependent [3H]GSH transport was cis-inhibited by substrates of the yeast YCF1 transporter, including sulphobromophthalein, glutathione S-conjugates and the alkaloid verapamil, and was competitively inhibited by S-(2, 4-dinitrophenyl)glutathione (DNP-SG) [13].
• Mutation of these residues to alanine severely impaired the Ycf1-dependent cadmium detoxification capacity and transport activity, while replacement by acidic residues (mimicking phosphorylation) significantly suppressed the cadmium resistance and transport defects [14].
• Ycf1 and Acr3 are transporters that have been previously shown to protect Saccharomyces cerevisiae cells from the toxic effects of arsenite [15].

Regulatory relationships of YCF1

• Genetic evidence suggests that Cka1p may regulate Ycf1p function through phosphorylation of Ser-251 either directly or indirectly [16].

Other interactions of YCF1

• Rather, the mechanism appears to be mediated via glutathione conjugation and removal from the cell because it is absent in strains lacking glutathione-S-transferases (GTT1, GTT2) or the GS-X pump (YCF1) [17].
• We propose that gsh1 cells are unable to form the Cd-GS(2) complex, while ycf1 cells would accumulate high levels of this complex in the cytoplasm [9].
• In addition, the expression patterns of YCF1 and BPT1 differ significantly [18].
• YCF1 mRNA levels and the expression of a YCF1-lacZ reporter construct positively correlates with changes in YAP1 gene dosage [5].
• We propose a model in which the glutathione peroxidase activity of glutaredoxins converts hydroperoxides to their corresponding alcohols; these can then be conjugated to GSH by glutathione-S-transferases and transported into the vacuole by Ycf1 [17].

Analytical, diagnostic and therapeutic context of YCF1

• We find in cell fractionation experiments that YCF1 is mainly localized in the vacuolar membrane in yeast, whereas MRP is associated both with the vacuolar membrane and with other internal membranes in the transformed yeast cells [10].
• In this work, the possibility of Ycf1 phosphorylation was examined using site-directed mutagenesis [14].

References