Pyridines and pyrimidines mediating activity against an efflux-negative strain of Candida albicans through putative inhibition of lanosterol demethylase.
The first step in ergosterol biosynthesis in Saccharomyces cerevisiae consists of the condensation of two acetyl coenzyme A (acetyl-CoA) moieties by acetoacetyl-CoA thiolase, encoded by ERG10. The inhibition of the sterol pathway results in feedback activation of ERG10 transcription. A cell-based reporter assay, in which increased ERG10 transcription results in elevated specific beta-galactosidase activity, was used to find novel inhibitors of ergosterol biosynthesis that could serve as chemical starting points for the development of novel antifungal agents. A class of pyridines and pyrimidines identified in this way had no detectable activity against the major fungal pathogen Candida albicans (MICs > 64 micro g. ml(-1)). However, a strain of C. albicans lacking the Cdr1p and Cdr2p efflux pumps was sensitive to the compounds (with MICs ranging from 2 to 64 micro g. ml(-1)), suggesting that they are efficiently removed from wild-type cells. Quantitative analysis of sterol intermediates that accumulated during growth inhibition revealed the accumulation of lanosterol at the expense of ergosterol. Furthermore, a clear correlation was found between the 50% inhibitory concentration at which the sterol profile was altered and the antifungal activity, measured as the MIC. This finding strongly suggests that the inhibition of growth was caused by a reduction in ergosterol synthesis. The compounds described here are a novel class of antifungal pyridines and pyrimidines and the first pyri(mi)dines to be shown to putatively mediate their antifungal activity against C. albicans via lanosterol demethylase.
Buurman
Ed T
ET
Department of Microbiology. Department of Chemistry, AstraZeneca R&D Boston, Waltham, Massachusetts 02451, USA. ed.buurman@astrazeneca.com
Blodgett
April E
AE
Hull
Kenneth G
KG
Carcanague
Daniel
D
D000935:Antifungal Agents / Q000138:chemical synthesis / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects* / Q000201:enzymology*; D003470:Culture Media; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015725:Fluconazole / Q000494:pharmacology; D017930:Genes, Reporter / Q000235:genetics; D008826:Microbial Sensitivity Tests; D009281:Naphthalenes / Q000494:pharmacology; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D011725:Pyridines / Q000138:chemical synthesis / Q000494:pharmacology*; D011743:Pyrimidines / Q000138:chemical synthesis / Q000494:pharmacology*; D058886:Sterol 14-Demethylase; D013261:Sterols / Q000378:metabolism; D000077291:Terbinafine
D000935:Antifungal Agents; D003470:Culture Media; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D009281:Naphthalenes; D011725:Pyridines; D011743:Pyrimidines; D013261:Sterols; D015725:Fluconazole; D010088:Oxidoreductases; D058886:Sterol 14-Demethylase; D000077291:Terbinafine