Candida albicans is the fungus most often causing invasive disease in humans. The number of susceptible individuals to this infection, which carries a high risk of serious sequelae and death, continues to rise, in parallel with the advances in treatment of serious illnesses that compromise patients' immune defenses. In bloodstream infections with this fungus, attributable mortality is close to 40%. One reason for the high mortality of invasive Candida infection is the limited choice of antifungal drugs available for its treatment. Echinocandins have been a recent addition to the clinically available antifungals, with several important advantages. In order to preserve the utility of the echinocandins during potential future widespread use, early identification of mutations which give rise to echinocandin resistance will be useful. The target of echinocandins is the enzyme that produces the major component of Candida's cell wall. An intact wall is critical for the fungal cell's survival. In the model fungus Saccharomyces cerevisiae, numerous regulatory circuits have been identified which govern the activity of cell wall synthesis. Saccharomyces mutants which are resistant or hypersensitive to echinocandins have provided an entry point for the analysis of these regulatory circuits. Though much can be learned from the insights gained in S. cerevisiae, the physiology and the genome of C. albicans show important differences from Saccharomyces, because it has evolved to maintain its cell wall against the host's immune system. We propose a genomic survey of resistance and hypersensitivity to echinocandins in C. albicans itself. A collection of heterozygous C. albicans mutants will be screened for their growth in the presence of an echinocandin. The mutants are generated using a transposon which inserts in a maximally random fashion, using only a dinucleotide as a recognition sequence. By a protocol we developed in a pilot screen, resistant and hypersensitive mutants will be collected. Their phenotypes will be confirmed and the locus of the transposon insertion will be identified. Linkage of the transposon insertion to the echinocandin-related phenotype will be determined by recreating a mutation in the same locus, in the wild type strain. The resulting overview of genes involved in Candida's echinocandin response will provide probes to dissect the networks that regulate this pathogen's ability to maintain the integrity of its cell wall. ? ?
| Cowen, Leah E; Singh, Sheena D; Köhler, Julia R et al. (2009) Harnessing Hsp90 function as a powerful, broadly effective therapeutic strategy for fungal infectious disease. Proc Natl Acad Sci U S A 106:2818-23 |
