Aspects of the steroid response in fungi.

The number of fungal infections is increasing due to higher numbers of immunocompromised patients. Unfortunately, drug resistance represents a major additional problem in clinical praxis. Therefore factors contributing to infection by opportunistic pathogens, and to their growth and drug resistance are of major importance. It has been known for some time that mammalian steroid hormones are toxic to fungi. In this paper the response of fungi to the presence of steroid hormones will be discussed at different levels. First, the effect of steroid hormones on fungal growth, morphology and virulence will be considered. Processes affecting steroid intracellular concentration will be discussed; steroid uptake and, even more, steroid extrusion are currently of special interest. The role of biotransformation in the detoxification of active steroids will be taken into consideration and phases of steroid metabolism in fungal cells will be compared to phases of classical xenobiotic metabolism. Steroid signaling in fungi is presently not yet clear. It results in a global response of fungi to steroid hormones. Some of the genes differentially expressed in fungi as the result of exposure to steroid hormones may contribute to fungal drug resistance.