title: Delineation of the molecular mechanism for disulfide stress-induced aluminium toxicity.
abstract: Following our previous finding that the sulfhydryl-oxidising chemical diamide induced a marked elevation of cellular Al(3+) (Wu et al., Int J Mol Sci, 12:8119-8132, 2011), a further investigation into the underlying molecular mechanism was carried out, using the eukaryotic model organism Saccharomyces cerevisiae. The effects of non-toxic dose of diamide (0.8 mM) and a mild dose of aluminium sulphate (Al(3+)) (0.4 mM) were determined prior to the screening of gene deletion mutants. A total of 81 deletion mutants were selected for this study according to the available screening data against Al(3+) only (Kakimoto et al., BioMetals, 18: 467-474, 2005) and diamide only (Thorpe et al., Proc Natl Acad Sci USA, 101: 6564-6569, 2004). On the basis of our screening data and the cluster analysis, a cluster containing the gene deletions (rpe1∆, sec72∆, pdr5∆ and ric1∆) was found to be specifically sensitive to the mixture of diamide and Al(3+). However gnp1∆, mch5∆ and ccc1∆ mutants were resistant. Dithiothreitol (DTT) and ascorbate markedly reversed the diamide-induced Al(3+) toxicity. Inductively-coupled plasma optical emission spectrometry demonstrated that DTT reduced the intracellular Al(3+) content in diamide/Al(3+)-treated yeast cells six-fold compared to the non-DTT controls. These data together revealed that the pleiotropic drug resistance transporter (Pdr5p) and vacuolar/vesicular transport-related proteins (Ric1p and Sec72p) are the targets of diamide. A dysfunctional membrane-bound Pdr5p terminates the detoxification pathway for Al(3+) at the final step, leading to intracellular Al(3+) accumulation and hence toxicity. As Al(3+) toxicity has been a problem in agriculture and human health, this study has provided a significant step forward in understanding Al(3+) toxicity.
authors.affiliation: School of Science and Health, University of Western Sydney, Locked Bag 1797, Penrith, NSW, 2751, Australia. m.wu@uws.edu.au
authors.forename: Ming J
authors.initials: MJ
authors.lastname: Wu
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Murphy
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: O'Doherty
authors.forename: Stephen
authors.initials: S
authors.lastname: Mieruszynski
authors.forename: Mark
authors.initials: M
authors.lastname: Jones
authors.forename: Cindy
authors.initials: C
authors.lastname: Kersaitis
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Rogers
authors.forename: Trevor D
authors.initials: TD
authors.lastname: Bailey
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Higgins
mesh_terms: D000535:Aluminum / Q000494:pharmacology*; D003958:Diamide / Q000494:pharmacology; D004220:Disulfides / Q000494:pharmacology*; D004229:Dithiothreitol / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000378:metabolism
chemical_list: D004220:Disulfides; D003958:Diamide; D000535:Aluminum; D004229:Dithiothreitol