Functional expression of the Candida albicans alpha-factor receptor in Saccharomyces cerevisiae.

Candida albicans genes involved in mating have been identified previously by homology to Saccharomyces cerevisiae mating pathway components. The C. albicans genome encodes CaSte2p, a homolog of the S. cerevisiae alpha-mating pheromone receptor Ste2p, and two potential pheromones, alpha-F13 (GFRLTNFGYFEPG) and alpha-F14 (GFRLTNFGYFEPGK). The response of several C. albicans strains to the synthesized peptides was determined. The alpha-F13 was degraded by a C. albicans MTLa strain but not by S. cerevisiae MATa cells. The CaSTE2 gene was cloned and expressed in a ste2-deleted strain of S. cerevisiae. Growth arrest and beta-galactosidase activity induced from a FUS1-lacZ reporter construct increased in a dose-dependent manner upon exposure of transgenic S. cerevisiae to alpha-F13. Mating between the strain expressing CaSTE2 and an opposite mating type was mediated by alpha-F13 and not by the S. cerevisiae alpha-factor. The results indicated that CaSte2p effectively coupled to the S. cerevisiae signal transduction pathway. Functional expression of CaSte2p in S. cerevisiae provides a well-defined system for studying the biochemistry and molecular biology of the C. albicans pheromone and its receptor.