Signal transduction pathways regulating differentiation and pathogenicity of Cryptococcus neoformans

The basidiomycetous yeast Cryptococcus neoformans is a human pathogen, Several phenotypes of this organism are defined as virulence traits including the polysaccharide capsule, melanin, and the ability to grow at 37 degrees C. The signaling pathways regulating the expression of these phenotypes and other important cellular processes are being defined on a molecular level. For example, the highly conserved signaling molecule calcineurin regulates high temperature growth in C. neoformans. A cryptococcal homolog of Saccharomyces cerevisiae STE12, the gene for a transcriptional regulator activated by the MAP kinase cascade, has also been identified. Additionally, the C. neoformans G alpha protein GPA1 and cAMP regulate mating, melanin production, encapsulation, and pathogenicity. This fungus is an excellent model to further dissect virulence-associated signaling pathways. The conserved role of G alpha proteins and cAMP-associated signaling pathways in fungal differentiation and pathogenicity is also reviewed. (C) 1998 Academic Press.