Perturbation of the Vacuolar ATPase: A NOVEL CONSEQUENCE OF INOSITOL DEPLETION.
Depletion of inositol has profound effects on cell function and has been implicated in the therapeutic effects of drugs used to treat epilepsy and bipolar disorder. We have previously shown that the anticonvulsant drug valproate (VPA) depletes inositol by inhibiting myo-inositol-3-phosphate synthase, the enzyme that catalyzes the first and rate-limiting step of inositol biosynthesis. To elucidate the cellular consequences of inositol depletion, we screened the yeast deletion collection for VPA-sensitive mutants and identified mutants in vacuolar sorting and the vacuolar ATPase (V-ATPase). Inositol depletion caused by starvation of ino1Δ cells perturbed the vacuolar structure and decreased V-ATPase activity and proton pumping in isolated vacuolar vesicles. VPA compromised the dynamics of phosphatidylinositol 3,5-bisphosphate (PI3,5P2) and greatly reduced V-ATPase proton transport in inositol-deprived wild-type cells. Osmotic stress, known to increase PI3,5P2 levels, did not restore PI3,5P2 homeostasis nor did it induce vacuolar fragmentation in VPA-treated cells, suggesting that perturbation of the V-ATPase is a consequence of altered PI3,5P2 homeostasis under inositol-limiting conditions. This study is the first to demonstrate that inositol depletion caused by starvation of an inositol synthesis mutant or by the inositol-depleting drug VPA leads to perturbation of the V-ATPase.
From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202.
Rania M
RM
Deranieh
From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202.
Yihui
Y
Shi
the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, and.
Maureen
M
Tarsio
From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202.
Yan
Y
Chen
the Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
J Michael
JM
McCaffery
the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, and.
Patricia M
PM
Kane
From the Department of Biological Sciences, Wayne State University, Detroit, Michigan 48202, mlgreen@sun.science.wayne.edu.
Miriam L
ML
Greenberg
D000927:Anticonvulsants / Q000494:pharmacology*; D025141:Drug Resistance, Fungal / Q000235:genetics; D017353:Gene Deletion; D006706:Homeostasis; D007294:Inositol / Q000172:deficiency* / Q000235:genetics; D019753:Intramolecular Lyases / Q000037:antagonists & inhibitors*; D007296:Myo-Inositol-1-Phosphate Synthase / Q000235:genetics; D009997:Osmotic Pressure; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000201:enzymology*; D014635:Valproic Acid / Q000494:pharmacology*
D000927:Anticonvulsants; D018129:Phosphatidylinositol Phosphates; D029701:Saccharomyces cerevisiae Proteins; C106336:phosphatidylinositol 3,5-diphosphate; D007294:Inositol; D014635:Valproic Acid; D025262:Vacuolar Proton-Translocating ATPases; D019753:Intramolecular Lyases; C105497:D-myo-inositol-3-phosphate synthase; C519641:INO1 protein, S cerevisiae; D007296:Myo-Inositol-1-Phosphate Synthase
anticonvulsant; bipolar disorder; inositol; phosphoinositide; vacuolar ATPase; vacuole; valproate; yeast; yeast physiology