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Published on: November 8, 2006
Cyclin-dependent kinases control septin phosphorylation in Candida albicans hyphal development
Indrajit Sinha1, Yan-Ming Wang, Robin Philp
1Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673 Singapore.
Developmental Cell
|September 4, 2007
Summary
Candida albicans Cdc28 (a cyclin-dependent kinase) phosphorylates the septin Cdc11, controlling hyphal development. This phosphorylation is crucial for yeast morphogenesis and involves sequential kinase activity.
Area of Science:
- Cell Biology
- Molecular Biology
- Mycology
Background:
- Cyclin-dependent kinases (Cdks) regulate cell cycle processes, including cytoskeleton dynamics.
- Yeast morphogenesis, particularly hyphal development in Candida albicans, relies on precise cytoskeleton control.
- The specific targets and mechanisms by which Cdks influence the septin cytoskeleton during hyphal growth remain largely undefined.
Purpose of the Study:
- To elucidate the target and mechanism by which the Cdk Cdc28 controls cytoskeleton polarization during Candida albicans hyphal development.
- To investigate the role of specific phosphorylation events on the septin protein Cdc11 in regulating hyphal morphogenesis.
Main Methods:
- Investigated the interaction between Cdc28, cyclins (Ccn1, Hgc1), and the septin protein Cdc11 in Candida albicans.
- Utilized site-directed mutagenesis to examine the role of specific serine residues (Ser394, Ser395) on Cdc11 phosphorylation.
- Performed in vitro reconstitution experiments with purified proteins (Cdc28-Ccn1, Gin4, septins) to validate phosphorylation events.
- Observed transient septin-Cdc28 associations in Saccharomyces cerevisiae.
Main Results:
- Demonstrated that Cdc28, in complex with cyclins Ccn1 and Hgc1, phosphorylates Cdc11 on Ser394, a nonconsensus Cdk target, essential for hyphal development.
- Showed that phosphorylation of Ser394 by Cdc28 requires prior phosphorylation of Ser395 by the septin-associated kinase Gin4.
- Mutations at Ser394 or Ser395 abolished Cdc11 phosphorylation and impaired hyphal morphogenesis.
- Confirmed these phosphorylation events and protein interactions through reconstitution experiments.
Conclusions:
- Established a direct link between the cell-cycle regulator Cdc28 and the septin cytoskeleton in controlling polarized morphogenesis.
- Identified a sequential phosphorylation mechanism (Gin4 then Cdc28) on Cdc11 that is critical for hyphal development in Candida albicans.
- Suggests a conserved mechanism involving cell-cycle kinases and the septin cytoskeleton in polarized growth across different yeast species.
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