title: Functional genomics of monensin sensitivity in yeast: implications for post-Golgi traffic and vacuolar H+-ATPase function.
abstract: We have screened a complete collection of yeast knockout mutants for sensitivity to monensin, an ionophore that interferes with intracellular transport. A total of 63 sensitive strains were found. Most of the strains were deleted for genes involved in post-Golgi traffic, with an emphasis on vacuolar biogenesis. A high correlation was thus seen with VPS and VAM genes, but there were also significant differences between the three sets of genes. A weaker correlation was seen with sensitivity to NaCl, in particular rate of growth effects. Interestingly, all 14 genes encoding subunits of the vacuolar H(+)-ATPase (V-ATPase) were absent in our screen, even though they appeared in the VPS or VAM screens. All monensin-sensitive mutants that could be tested interact synthetically with a deletion of the A subunit of the V-ATPase, Vma1. Synthetic lethality was limited to mutations affecting endocytosis or retrograde transport to Golgi. In addition, vma1 was epistatic over the monensin sensitivity of vacuolar transport mutants, but not endocytosis mutants. Deletions of the two isoforms of the V-ATPase a subunit, Vph1 and Stv1 had opposite effects on the monensin sensitivity of a ypt7 mutant. These findings are consistent with a model where monensin inhibits growth by interfering with the maintenance of an acidic pH in the late secretory pathway. The synthetic lethality of vma1 with mutations affecting retrograde transport to the Golgi further suggests that it is in the late Golgi that a low pH must be maintained.
authors.affiliation: Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Gustavsson
authors.forename: Gunilla
authors.initials: G
authors.lastname: Barmark
authors.forename: Jimmy
authors.initials: J
authors.lastname: Larsson
authors.forename: Eva
authors.initials: E
authors.lastname: Murén
authors.forename: Hans
authors.initials: H
authors.lastname: Ronne
mesh_terms: D001692:Biological Transport / Q000187:drug effects; D043402:Cathepsin A / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects / Q000235:genetics; D004705:Endocytosis / Q000187:drug effects / Q000235:genetics; D011992:Endosomes / Q000187:drug effects / Q000235:genetics; D004843:Epistasis, Genetic; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal; D023281:Genomics; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism*; D008055:Lipids / Q000096:biosynthesis; D008954:Models, Biological; D008985:Monensin / Q000494:pharmacology*; D009154:Mutation / Q000235:genetics; D010716:Phosphatidylinositols / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology; D025262:Vacuolar Proton-Translocating ATPases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics
chemical_list: D008055:Lipids; D010716:Phosphatidylinositols; D012965:Sodium Chloride; D008985:Monensin; D043402:Cathepsin A; D025262:Vacuolar Proton-Translocating ATPases