The MAP kinase signal transduction network in Candida albicans.

MAP (mitogen-activated protein) kinase-mediated pathways are key elements in sensing and transmitting the response of cells to environmental conditions by the sequential action of phosphorylation events. In the fungal pathogen Candida albicans, different routes have been identified by genetic analysis, and especially by the phenotypic characterization of mutants altered in the Mkc1, Cek1/2 and Hog1 MAP kinases. The cell integrity (or MKC1-mediated) pathway is primarily involved in the biogenesis of the cell wall. The HOG pathway participates in the response to osmotic stress while the Cek1 pathway mediates mating and filamentation. Their actual functions are, however, much broader and Mkc1 senses several types of stress, while Hog1 is also responsive to other stress conditions and participates in two morphogenetic programmes: filamentation and chlamydospore formation. Furthermore, it has been recently shown that Cek1 participates in a putative pathway involved in the construction of the cell wall and which seems to be operative under basal conditions. As these stimuli are frequently encountered in the human host, they provide a reasonable explanation for the significant reduction in pathogenicity that several signal transduction mutants show in certain animal models of virulence. MAPK pathways therefore represent an attractive multienzymic system for which novel antifungal therapy could be designed.