Genomes and Genes
THE YEAST ERGOSTEROL PATHWAY
Principal Investigator: Martin Bard
Affiliation: Indiana University
Abstract: Serious fungal infections are rising due to the increased use of immunosuppressive agents (either employed to sustain organ transplants or as the result of cancer therapy). Membrane sterol and the sterol biosynthetic pathway have long been target sites for antifungal drugs. Two of the most widely used antifungal classes, the polyenes (amphotericin B) target plasma membrane-bound sterols and the azoles (fluconazole, and itraconazole) target the cytochrome P450-mediated step, lanosterol C-14 demethylation. Saccharomyces cerevisiae contains the best characterized sterol pathway at the genetic and molecular levels and is an excellent model system to study the topographical organization of sterol enzymes and the interactions between these enzymes within one or more sterol complexes. The post-squalene pathway leading to ergosterol in fungi or cholesterol in animal cells share eleven enzymatic reactions in addition to a scaffold protein required for efficient C-4 demethylation. In the post-squalene pathway only two enzymes in the cholesterol pathway and three in the ergosterol pathway account for the structural differences between these molecules. One goal of this proposal is to co-immunoprecipitate the sterol biosynthetic enzymes in order to determine whether there is a single enzymatic complex or several interacting complexes leading to end-product sterol. Specific pair wise enzymatic interactions will be evaluated using a membrane two-hybrid system. In addition interactions between sterol biosynthetic enzymes and sterol esterification enzymes will also be studied. A second major goal of this proposal is to investigate how loss of the ERG27 gene product leads to loss of the upstream enzymatic reaction, the oxidosqualene cyclase (Erg7p). This interaction will be studied at the transcriptional and post-translational levels. A number of transcriptional activators and repressors that affect several genes in the sterol pathway will be studied. Among these are the UPC2 and ECM22, YER064c and MOT3. A screen for novel transcriptional regulators of the C-4 demethylation genes will also be undertaken. Finally, we will complete our analysis of the ERG9 promoter which encodes the squalene synthase, the first enzyme in the mevalonate-sterol pathway dedicated to sterol synthesis.
Funding Period: 1995-06-01 - 2009-05-31
more information: NIH RePORT
- A systematic study of yeast sterol biosynthetic protein-protein interactions using the split-ubiquitin systemCaiqing Mo
Department of Biology, Indiana University Purdue University Indianapolis, 723 W Michigan St Indianapolis, IN 46202, USA
Biochim Biophys Acta 1737:152-60. 2005..Our results provide a working model as to how sterol biosynthetic enzymes are topologically organized not only in yeast but in plant and animal systems that share many of these biosynthetic reactions...
- Cumulative mutations affecting sterol biosynthesis in the yeast Saccharomyces cerevisiae result in synthetic lethality that is suppressed by alterations in sphingolipid profilesMartin Valachovic
Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, 40536
Genetics 173:1893-908. 2006..We show that deletion of YND1, like deletion of GDA1, alters the sphingolipid profiles, suggesting that changes in sphingolipids compensate for lethality produced by changes in sterol composition and abundance...
- Dap1p, a heme-binding protein that regulates the cytochrome P450 protein Erg11p/Cyp51p in Saccharomyces cerevisiaeJulia C Mallory
Department of Molecular and Biomedical Pharmacology, University of Kentucky, MS 305 UKMC, Lexington, KY 40536, USA
Mol Cell Biol 25:1669-79. 2005..Dap1p homologues have been identified in numerous eukaryotes, including mammals, suggesting that the Dap1p-cytochrome P450 protein pathway is broadly conserved in eukaryotic species...
- Genetic analyses involving interactions between the ergosterol biosynthetic enzymes, lanosterol synthase (Erg7p) and 3-ketoreductase (Erg27p), in the yeast Saccharomyces cerevisiaeB Teske
Indiana University Purdue University Indianapolis, Biology Department, Indianapolis, IN 46202, USA
Biochim Biophys Acta 1781:359-66. 2008..This study provides new insights into the role of Erg27p in sterol biosynthesis...
- Synthetically lethal interactions involving loss of the yeast ERG24: the sterol C-14 reductase geneM Shah Alam Bhuiyan
Biology Department, Indiana University Purdue University Indianapolis, 723 West Michigan Street, Indianapolis, IN 46202, USA
Lipids 42:69-76. 2007..These results suggest that novel sterol intermediates probably contribute to the synthetic lethality observed in this investigation...
- Dap1/PGRMC1 binds and regulates cytochrome P450 enzymesAdam L Hughes
Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
Cell Metab 5:143-9. 2007..These findings demonstrate that PGRMC1 is required for P450 activity and suggest that interindividual variation in PGRMC1 function may impact multiple biochemical pathways and drug metabolism...
- Molecular and enzymatic characterizations of novel bifunctional 3beta-hydroxysteroid dehydrogenases/C-4 decarboxylases from Arabidopsis thalianaAlain Rahier
Institut de Biologie Moleculaire des Plantes, CNRS UPR2357, 28 rue Goethe, 67083 Strasbourg Cedex, France
J Biol Chem 281:27264-77. 2006..These two novel oxidative decarboxylases constitute the first molecularly and functionally characterized HSDs from a short chain dehydrogenase/reductase family in plants...
- Endoplasmic reticulum-associated degradation is required for cold adaptation and regulation of sterol biosynthesis in the yeast Saccharomyces cerevisiaeJennifer Loertscher
Department of Chemistry, Seattle University, Seattle, WI 98122, USA
Eukaryot Cell 5:712-22. 2006..Cells lacking UBC7, CUE1, or DOA10 were cold sensitive, suggesting that these ERAD proteins have a role in cold adaptation, perhaps through effects on sterol biosynthesis...
- Erg28p is a key protein in the yeast sterol biosynthetic enzyme complexCaiqing Mo
Biology Department, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA
J Lipid Res 46:1991-8. 2005..Based on these results, we suggest that many if not all sterol biosynthetic proteins may be tethered as a large complex...
- Sterol uptake in Candida glabrata: rescue of sterol auxotrophic strainsMartin Bard
Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA
Diagn Microbiol Infect Dis 52:285-93. 2005..glabrata hem1 was able to grow indicating significant differences in exogenous sterol uptake between the 2 organisms. The ability of C. glabrata to replace ergosterol with host sterol may be responsible for its elevated azole resistance...
- A sterol-regulatory element binding protein is required for cell polarity, hypoxia adaptation, azole drug resistance, and virulence in Aspergillus fumigatusSven D Willger
Department of Veterinary Molecular Biology, Montana State University, Bozeman, MT, USA
PLoS Pathog 4:e1000200. 2008..Thus, these findings present a new function of SREBP proteins in filamentous fungi, and demonstrate for the first time that hypoxia adaptation is likely an important virulence attribute of pathogenic molds...