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[Functional analysis of calcineurin-mediated signalling pathway using fission yeast as a model system]
1Division of Molecular Pharmacology and Pharmacogenomics, Department of Genome Sciences, Kobe University Graduate School of Medicine, Kobe city 650-0017, Japan.
Abstract:
Calcineurin (CN), a highly conserved Ca2+/calmodulin-regulated phosphatase, is a critical component of many calcium-regulated processes in mammalian cells, including T cell activation, cardiac hypertrophy, learning and memory. CN is specifically inhibited by the immunosuppressant drugs cyclosporin A and tacrolimus (FK506), and these drugs have served as valuable reagents in identifying the role of CN in a wide variety of cell types. CN may have additional functions in other cell types, and the loss of these functions may contribute to the side effects of these drugs, which include nephrotoxicity and neurotoxicity. A better understanding of the biological roles of CN in different cell types may promote the development of improved strategies for immunosuppression. We have been studying the CN signal transduction pathway in fission yeast because this system is amenable to genetics and has many advantages in terms of relevance to higher systems. Fission yeast has a single gene encoding the catalytic subunit of CN, ppb1+, that is essential for cytokinesis. We have shown that in fission yeast CN plays an essential role in maintaining chloride ion homeostasis and acts antagonistically with the Pmk1 MAP kinase pathway. We also carried out an isolation and a screening for several FK506-sensitive mutants in order to identify genes that share an essential function for viability with CN. Possible roles of these gene products in cellular functions in relation to calcineurin are discussed.
Insights
Calcineurin (CN) is vital for cell processes and is inhibited by immunosuppressants. Studying CN in fission yeast reveals its role in ion homeostasis and identifies new related genes.
Area of Science:
- Cell Biology
- Biochemistry
- Genetics
Background:
- Calcineurin (CN) is a Ca2+/calmodulin-dependent phosphatase crucial for mammalian cell functions like T cell activation and cardiac hypertrophy.
- Immunosuppressants like cyclosporin A and tacrolimus (FK506) inhibit CN, aiding research but causing side effects such as nephrotoxicity and neurotoxicity.
- Understanding CN's diverse roles is key to developing safer immunosuppression strategies.
Purpose of the Study:
- To investigate the biological roles of calcineurin (CN) in a model organism, fission yeast, due to its genetic tractability and relevance to higher eukaryotes.
- To identify genes that function with CN by screening for FK506-sensitive mutants in fission yeast.
- To elucidate the CN signaling pathway and its interactions within the cell.
Main Methods:
- Utilized fission yeast (Schizosaccharomyces pombe) as a model system for studying calcineurin signaling.
- Performed genetic screening to isolate FK506-sensitive mutants.
- Analyzed the essential role of the CN catalytic subunit gene (ppb1+) in fission yeast cytokinesis.
- Investigated the interaction between the CN pathway and the Pmk1 MAP kinase pathway.
Main Results:
- Demonstrated that CN, encoded by ppb1+, is essential for cytokinesis in fission yeast.
- Established that CN plays a critical role in maintaining chloride ion homeostasis in fission yeast.
- Showed that CN acts antagonistically with the Pmk1 MAP kinase pathway.
- Identified several FK506-sensitive mutants, suggesting genes that share essential functions with CN.
Conclusions:
- Fission yeast provides a valuable genetic system for understanding conserved calcineurin functions.
- CN is essential for chloride ion homeostasis and cytokinesis in fission yeast, highlighting its fundamental cellular roles.
- The identification of FK506-sensitive mutants opens avenues for discovering novel components and pathways interacting with calcineurin.