Cytocidal amino acid starvation of Saccharomyces cerevisiae and Candida albicans acetolactate synthase (ilv2{Delta}) mutants is influenced by the carbon source and rapamycin.
Abstract
The isoleucine and valine biosynthetic enzyme acetolactate synthase (Ilv2p) is an
attractive antifungal drug target, since the isoleucine and valine biosynthetic pathway
is not present in mammals, Saccharomyces cerevisiae ilv2Delta mutants do not survive
in vivo, Cryptococcus neoformans ilv2 mutants are avirulent, and both S. cerevisiae
and Cr. neoformans ilv2 mutants die upon isoleucine and valine starvation. To further
explore the potential of Ilv2p as an antifungal drug target, we disrupted Candida
albicans ILV2, and demonstrated that Ca. albicans ilv2Delta mutants were significantly
attenuated in virulence, and were also profoundly starvation-cidal, with a greater
than 100-fold reduction in viability after only 4 h of isoleucine and valine starvation.
As fungicidal starvation would be advantageous for drug design, we explored the basis
of the starvation-cidal phenotype in both S. cerevisiae and Ca. albicans ilv2Delta
mutants. Since the mutation of ILV1, required for the first step of isoleucine biosynthesis,
did not suppress the ilv2Delta starvation-cidal defects in either species, the cidal
phenotype was not due to alpha-ketobutyrate accumulation. We found that starvation
for isoleucine alone was more deleterious in Ca. albicans than in S. cerevisiae, and
starvation for valine was more deleterious than for isoleucine in both species. Interestingly,
while the target of rapamycin (TOR) pathway inhibitor rapamycin further reduced S.
cerevisiae ilv2Delta starvation viability, it increased Ca. albicans ilv1Delta and
ilv2Delta viability. Furthermore, the recovery from starvation was dependent on the
carbon source present during recovery for S. cerevisiae ilv2Delta mutants, reminiscent
of isoleucine and valine starvation inducing a viable but non-culturable-like state
in this species, while Ca. albicans ilv1Delta and ilv2 Delta viability was influenced
by the carbon source present during starvation, supporting a role for glucose wasting
in the Ca. albicans cidal phenotype.
Type
Journal articleSubject
Acetolactate SynthaseAnimals
Antifungal Agents
Candida albicans
Carbon
Fungal Proteins
Isoleucine
Male
Mice
Microbial Viability
Mutation
Phenotype
Saccharomyces cerevisiae
Sirolimus
Valine
Virulence
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https://hdl.handle.net/10161/4165Published Version (Please cite this version)
10.1099/mic.0.034348-0Publication Info
Kingsbury, Joanne M; & McCusker, John H (2010). Cytocidal amino acid starvation of Saccharomyces cerevisiae and Candida albicans acetolactate
synthase (ilv2{Delta}) mutants is influenced by the carbon source and rapamycin. Microbiology, 156(Pt 3). pp. 929-939. 10.1099/mic.0.034348-0. Retrieved from https://hdl.handle.net/10161/4165.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Show full item recordScholars@Duke
John Henry McCusker
Associate Professor Emeritus of Molecular Genetics and Microbiology
My research uses whole genome analysis as well as standard genetic and molecular
biological techniques in S. cerevisiae and, in particular, applies these techniques
to the following areas: The development of S. cerevisiae as a microbial model for
quantitative genetics. Quantitative traits are extremely important and have been
extensively studied in higher eukaryotes. Unfortunately, our understanding of quantitative
traits is poor because of: the polygenic and additive nature of qu

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