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A constitutively active GPCR governs morphogenic transitions in Cryptococcus neoformans.
Yen-Ping Hsueh1, Chaoyang Xue, Joseph Heitman
1Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27710, USA.
The EMBO Journal
|March 27, 2009
Summary
A novel constitutively active G protein-coupled receptor, CPR2, governs fungal morphogenesis in Cryptococcus neoformans. This discovery challenges existing paradigms of fungal reproduction and signaling pathways.
Area of Science:
- Mycology
- Molecular Biology
- Cell Biology
Background:
- Fungal sex relies on peptide pheromones and seven-transmembrane receptors.
- Cryptococcus neoformans exhibits both outcrossing (unisexual) and inbreeding (homothallic) mating.
- Mating-type locus (MAT) receptors are key for opposite-sex mating and contribute to unisexual mating.
Purpose of the Study:
- Investigate the role of the pheromone receptor-like gene, CPR2, outside the MAT locus.
- Determine CPR2's function in fungal sexual reproduction and morphogenesis.
- Characterize the mechanism of CPR2's activity and its signaling pathway.
Main Methods:
- Gene expression analysis of CPR2 during mating.
- Phenotypic analysis of cpr2 mutants and CPR2 overexpression strains.
- Heterologous expression of Cpr2 in Saccharomyces cerevisiae.
- Site-directed mutagenesis to identify key residues for activity.
Main Results:
- CPR2 expression is induced during a- mating and is not MAT-encoded.
- cpr2 mutants show fusion defects and abnormal hyphal structures.
- CPR2 overexpression induces unisexual reproduction.
- Heterologously expressed Cpr2 is constitutively active, independent of ligand, due to Leu(222) substitution.
- Cpr2(L222P) mutant loses constitutive activity.
- Cpr2 utilizes the same G-protein signaling cascade as Ste3a/alpha receptors.
Conclusions:
- CPR2 is a novel, constitutively active G protein-coupled receptor.
- This receptor governs fungal morphogenesis and reproduction.
- A naturally occurring constitutively active GPCR represents a new paradigm in fungal signaling.
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