When present at intracellular concentrations above micromolar, vanadate becomes toxic to most organisms. However, the yeast Hansenula polymorpha is able to grow on vanadate concentrations in the millimolar range, showing at the same time modifications in cellular ultrastructure and polyphosphate metabolism. Here, the development of the ultrastructural changes, and of vacuolar and secretory activities, during exponential growth on vanadate and upon a return to vanadate-free conditions was investigated. External invertase secretion was inhibited by vanadate, as shown by a decrease in external invertase activity, an intracellular accumulation of small vesicles and a cytoplasmic accumulation of internal invertase. An aberrant appearance of the cell wall and defects in cellular surface growth, possibly linked to defects in secretion, were also observed. However, inhibition of the secretory pathway was not complete since the activity of another secreted enzyme, exoglucanase, increased in the presence of vanadate. Growth on vanadate was also accompanied by an enhancement of vacuolar proteolysis, as indicated by an increase in carboxypeptidase Y activity. However, these modifications were all reversible upon return to vanadate-free conditions, with the normalization process being complex and involving new and dramatic ultrastructural changes and activation of an autophagic mechanism. This mechanism is involved in the elimination/resorption of the observed vanadate-induced aberrant cell structures and/or sites involved in vanadate accumulation, a necessary prerequisite for restoration of conventional ultrastructure and metabolic functions.
BallouL,
HitzemanR. A.,
LewisM.S.,
BallouC.E.1991; Vanadate-resistant yeast mutants are defective in protein glycosyl-ation.. Proc Natl Acad Sci USA 88:3209–3212
BradfordM.M.1976; A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.. Anal Biochem 72:248–254
BrownD.,
GordonJ.1984; The stimulation of pp60v-src kinase activity by vanadate in intact cells accompanies a new phosphorylation state of the enzyme.. J Biol Chem 259:9580–9586
CatalanR.E.,
MartinezA.M.,
AragonesM.D.1980; Effects of vanadate on the cyclic AMP-protein kinase system in rat liver.. Biochem Biophys Res Commun 96:672–677
CransD.C.,
Mahroof-TahirM.,
KeramidasA.D.1995; Vanadium chemistry and biochemistry of relevance for use of vanadium compounds as antidiabetic agents.. Mol Cell Biochem 153:17–24
Kanik-EnnulatC.,
MontalvoE.,
NeffN.1995; Sodium orthovanadate-resistant mutants of Saccharomyces cerevisiae show defects in Golgi-mediated protein glycosylation, sporulation and detergent resistance.. Genetics 140:933–943
KarlishS.J.D.,
BeaugéL.A.,
GlynnI.M.1979; Vanadate inhibits (Na++ K+) ATPase by blocking a conformational change of the unphosphorylated form.. Nature 282:333–335
LindquistR.N.,
LynnJ.L.,
LienhardG.E.1973; Possible transition-state analogs for ribonuclease. The complexes of uridine with oxovanadium (IV) ion and vanadium (V) ion.. J Am Chem Soc 95:8762–8768
MulhollandJ.,
PreussD.,
MoonA.,
WongA.,
DrubinD.,
BotsteinD.1994; Ultrastructure of the yeast actin cytoskeleton and its association with the plasma membrane.. Cell Biol 125:381–391
NovickP.,
FieldC.,
SchekmanR.1980; Identification of 23 complementation groups required for post-translational events in the yeast secretory pathway.. Cell 21:205–215
PreussD.,
MulhollandJ.,
KaiserC.A.,
OrleanP.,
AlbrightC.,
RoseM.D.,
RobbinsP.W.,
BotsteinD.1991; Structure of the yeast endoplasmic reticulum: localization of ER proteins using immunofluorescence and immunoelectron microscopy.. Yeast 7:891–911
RambourgA.,
ClermontY.,
JacksonC.L.,
KepesF.1994; Ultrastructural modifications of vesicular and Golgi element in the Saccharomyces cerevisiae sec21 mutant at permissive and non-permissive temperatures.. Anat Rec 240:32–41
SullivanP.A.,
EmersonG.W.,
BroughtonM.J.,
StubbsH.J.1991; Transglucosylation catalysed by the exo-β-glucanase of Candida albicans.. In Candida and Candidamycosis pp. 35–38 Edited by TumbayE.,
SeeligerH. P. R.,
AngO.
New York: Plenum;
TakeshigeK.,
BabaM.,
TsuboiS.,
NodaT.,
OshumiY.1992; Autophagy in yeast demonstrated with proteinase-deficient mutants and condition for its induction.. J Cell Biol 119:301–311
WachA.,
GraberP.1991; The plasma membrane H+-ATPase from yeast. Effects of pH, vanadate and erythrosine B on ATP hydrolysis and ATP binding.. Eur J Biochem 201:91–97
WillskyG.R.,
WhiteD.A.,
McCabeB.C.1984; Metabolism of added orthovanadate to vanadyl and high-molecular-weight vanadate by Saccharomyces cerevisiae.. J Biol Chem 21:13273–13281
ZorodduM.A.,
BonomoR.P.,
Di BilioA.J.,
BerardiE.,
MeloniM.G.1991; EPR study on vanadyl and vanadate ion retention by a thermotolerant yeast.. J Inorg Biochem 43:731–738