Tracking the pathogenicity of the yeast Candida albicans

Press release / January 24, 2000

Tracking the pathogenicity of the yeast Candida albicans (April 2000) Candida albicans is the most frequent fungal pathogen for humans. Scientists of the newly established research group "Automated Protein Screening Systems" at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have identified proteins, which are involved in the mechanisms responsible for pathogenicity of Candida and thus may represent specific targets for novel antimycotic drugs.

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Franz-Josef Johannes (right) and Steffen Rupp (left) and their team develop automated protein screening systems.
Proteomics
Among the 3,000 proteins the scienticst could detect from the Candida cells by 2D gel electrophoresis, they found until now about 20 which were present or absent only in the wildtype. Top: non-pathogenic Candida cells with protein pattern; bottom: pathogenic Candida cells with protein pattern.

In 1999 two research groups have been established at the Fraunhofer IGB which are founded by the German Ministery for Research and Education and the State of Baden-Württemberg. One group focuses on the development of automated protein screening systems, the other one works on biomimetic interfaces for applications in biotechnology. The researchers now present their first results: In the yeast Candida albicans, they have identified proteins which are involved in the mechanisms responsible for the yeast's pathogeniticity.

Candida albicans is the most frequent fungal pathogen for humans. Healthy individuals in general are not affected by Candida species. Usually only superficial infections of mucous membranes do occur. This is in general more an inconvenience than it is life threatening. However, for immunocompromized patients, especially after cancer treatment with chemotherapy, organ transplants or for AIDS patients there is a high risk to suffer from invasive, life threatening candidiasis. Until now there are only few treatments for invasive candidiasis, that also can give rise to severe side effects. Scientists of the newly established research group “Automated Protein Screening Systems“ at the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) in Stuttgart, Germany, now have identified proteins, which are involved in the mechanisms responsible for pathogenicity of Candida and thus may represent specific targets for novel antimycotic drugs.

The scientists carry out their investigations with both pathogenic and non-pathogenic Candida that have lost their virulence due to specific mutations. “We cultivate both variants under identical conditions and then compare the proteomes – the entity of all expressed proteins – of the virulent wildtype and the harmless mutant variant“, group leader Dr. Steffen Rupp explains. For this, the scientists optimized the two-dimensional gel electrophoresis, a method to analyze proteins according to charge and size much more efficiently than conventional methods. Among the 3,000 proteins the scienticst could detect from the Candida cells, they found until now about 20 which were present or absent only in the wildtype. Five of these proteins have already been isolated and characterized. These proteins do not exist in the related, non-pathogenic baker´s yeast Saccharomyces cerevisiae, indicating that they could be related to pathogenicity. A patent is pending.
In a second approach DNA microchip technology is applied to detect additional proteins that are important for the pathogenicity of Candida albicans. The genome of Candida albicans will be available for the public shortly, making a genome wide DNA microarray possible.

A second focus is concerned with the optimization of the two-hybrid system. This method allows the investigation of protein-protein interactions and thus is equally suited for drug screening. Dr. Franz-Josef Johannes detected a novel protein kinase termed PKCµ. The enzyme plays a key role in several intracellular signaling pathways. “As PKCµ is involved in the complex Tumor Necrosis Factor (TNF) intracellular signaling leading to programmed cell death (apoptosis), PKCµ leads to antiapoptotic effects pointing to a potential role for an important drug target“ says Johannes. Futhermore, PKCµ seems to be involved in other cellular functions such as the generation of immune response and inflammatory processes.

Optimizing of both methods for roboter-armed automated procedures together with micro-application will allow an effective high-throughput-screening. Both systems can easily be applied to other pharmaceutically relevant substances.