Drug resistance mechanisms and their regulation in non-albicans Candida species.

Fungal pathogens use various mechanisms to survive exposure to drugs. Prolonged treatment very often leads to the stepwise acquisition of resistance. The limited number of antifungal therapeutics and their mostly fungistatic rather than fungicidal character facilitates selection of resistant strains.

Differential expression of the Candida glabrata CgRTA1 and CgRSB1 genes in response to various stress conditions.

Candida glabrata, a human opportunistic pathogen is characterized by intrinsic, low susceptibility to fluconazole and a high capacity for acquiring high-level azole resistance. This is related to the elevated expression of genes belonging to the CgPdr1-governed regulon, comprising numerous genes, of which the multidrug ABC transporter-encoding CgCDR1, CgCDR2, CgSNQ2 are the best characterized. The function of certain PDR loci, such as CgRTA1 and CgRSB1 is poorly understood.

A conserved interdomain communication pathway of pseudosymmetrically distributed residues affects substrate specificity of the fungal multidrug transporter Cdr1p.

Understanding the communication pathways between remote sites in proteins is of key importance for understanding their function and mechanism of action. These remain largely unexplored among the pleiotropic drug resistance (PDR) representatives of the ubiquitous superfamily of ATP-binding cassette (ABC) transporters. To identify functionally coupled residues important for the polyspecific transport by the fungal ABC multidrug transporter Cdr1p a new selection strategy, towards increased resistance to a preferred substrate of the homologous Snq2p, was applied to a library of randomly generated mutants.

The regulatory inputs controlling pleiotropic drug resistance and hypoxic response in yeast converge at the promoter of the aminocholesterol resistance gene RTA1.

Aminosterols possessing potent fungicidal activity are attractive alternatives to currently available antifungals. Although their precise mechanism of action is not fully understood, the effect of 7-aminocholesterol (7-ACH) involves a partial block of Δ8-Δ7 isomerase and C-14 reductase. The function of RTA1 encoding the 7-transmembrane helix protein, cloned as the multicopy suppressor of 7-ACH toxicity in yeast, remains unclear.

The antifungal properties of chicken egg cystatin against Candida yeast isolates showing different levels of azole resistance.

The increasing incidence of fungal infections together with the emergence of strains resistant to currently available antifungal drugs calls for the development of new classes of antimycotics. Naturally occurring antifungal proteins and peptides are of interest because of low toxicity, immunomodulatory potential and mechanisms of action distinct from those of currently available drugs. In this study, the potent antifungal activity of cystatin, affinity-purified from chicken egg white (CEWC), against the most frequent human fungal pathogens of the genus Candida was identified and characterised.

Substrates and modulators of the multidrug transporter Cdr1p of Candida albicans in antifungal extracts of medicinal plants.

The effective treatment of infections caused by the most frequent human fungal pathogens Candida albicans and Candida glabrata is hindered by a limited number of available antifungals and development of resistance. In this study, we identified new extracts of medicinal plants inhibiting the growth of C. glabrata, a species generally showing low sensitivity to azoles.

Modulation of the antifungal activity of new medicinal plant extracts active on Candida glabrata by the major transporters and regulators of the pleiotropic drug-resistance network in Saccharomyces cerevisiae.

The increased incidence of drug-resistant fungal infections, a process in which active efflux plays an important role, calls for the development of new treatments. Candida albicans and Candida glabrata are the most frequent human fungal pathogens. The latter, in spite of its increased azole tolerance, is rarely used in medicinal plant screening.

New high-throughput screening assay to reveal similarities and differences in inhibitory sensitivities of multidrug ATP-binding cassette transporters.

Cdr1p is the major ATP-binding cassette multidrug transporter conferring resistance to azoles and other antifungals in Candida albicans. In this study, the identification of new Cdr1p inhibitors by use of a newly developed high-throughput fluorescence-based assay is reported. The assay also allowed monitoring of the activity and inhibition of the related transporters Pdr5p and Snq2p of Saccharomyces cerevisiae, which made it possible to compare its performance with those of previously established procedures.

Compensatory activation of the multidrug transporters Pdr5p, Snq2p, and Yor1p by Pdr1p in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the transcription factors Pdr1p and Pdr3p activate the expression of several genes, including PDR5, SNQ2, and YOR1, which encode ATP-binding cassette transporters that extrude dozens of antifungals with overlapping but distinct specificity. In this study, it was observed that growth resistance to specific Pdr5p substrates rose upon disruption of the YOR1 or SNQ2 coding region and was accompanied by increased efflux. Similarly, resistance to Yor1p- and Snq2p-specific substrates increased upon deletion of PDR5.

LTCI, a novel chymotrypsin inhibitor of the potato I family from the earthworm Lumbricus terrestris. Purification, cDNA cloning, and expression.

A novel chymotrypsin inhibitor of the potato I protease inhibitor family from the earthworm Lumbricus terrestris was purified. The inhibitor, named LTCI, was isolated by methanol extraction, affinity chromatography on immobilized methylchymotrypsin, and ion exchange chromatography followed by RP-HPLC. The 7076 Da inhibitor consists of a single polypeptide chain of 64-amino-acid residues without disulfide bridges.

Differential regulation of ceramide synthase components LAC1 and LAG1 in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the essential ceramide synthase reaction requires the presence of one of a homologous pair of genes, LAG1 and LAC1. Mutants that lack both of these genes cannot produce ceramide and exhibit a striking synthetic growth defect. While the regulation of ceramide production is critical for the control of proliferation and for stress tolerance, little is known of the mechanisms that ensure proper control of this process.

A higher plant mitochondrial homologue of the yeast m-AAA protease. Molecular cloning, localization, and putative function.

Mitochondrial AAA metalloproteases play a fundamental role in mitochondrial biogenesis and function. They have been identified in yeast and animals but not yet in plants. This work describes the isolation and sequence analysis of the full-length cDNA from the pea (Pisum sativum) with significant homology to the yeast matrix AAA (m-AAA) protease.

Regulation of pleiotropic drug resistance in yeast.

This review focuses on the molecular mechanisms involved in the regulation of multiple drug resistance in the model yeast Saccharomyces cerevisiae and the pathogenic fungus Candida albicans. Recent developments in the study of the transcription factors Pdr1p, Pdr3p and Yap1p are reported. Understanding the molecular basis leading to multiple drug resistance is a prerequisite for the development of new antifungal therapeutics.