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Septin Stability and Recycling during Dynamic Structural Transitions in Cell Division and Development

2008; Elsevier BV; Volume: 18; Issue: 16 Linguagem: Inglês

10.1016/j.cub.2008.07.020

1879-0445

Michael A. McMurray, Jeremy Thorner,

Microtubule and mitosis dynamics

Septins are conserved proteins found in hetero-oligomeric complexes that are incorporated into distinct structures during cell division and differentiation; yeast septins Cdc3, Cdc10, Cdc11, and Cdc12 form hetero-octamers and polymerize into filaments, which form a "collar" at the mother-bud neck [1Versele M. Thorner J. Some assembly required: Yeast septins provide the instruction manual.Trends Cell Biol. 2005; 15: 414-424Abstract Full Text Full Text PDF PubMed Scopus (157) Google Scholar]. Posttranslational modifications, nucleotide binding, and protein-protein and protein-lipid interactions influence assembly and disassembly of septin structures [2Weirich C.S. Erzberger J.P. Barral Y. The septin family of GTPases: Architecture and dynamics.Nat. Rev. Mol. Cell Biol. 2008; 9: 478-489Crossref PubMed Scopus (243) Google Scholar], but whether individual septins are used repeatedly to build higher-order assemblies was not known. We used fluorescence-based pulse-chase methods to visualize the fate of pre-existing (old) and newly synthesized (new) molecules of two septins, Cdc10 and Cdc12. They were recycled through multiple mitotic divisions, and old and new molecules were incorporated indistinguishably into the collar. Likewise, old and new subunits intermixed within hetero-octamers, indicating that exchange occurs at this organizational level. Remarkably, in meiosis, Cdc10 made during vegetative growth was reutilized to build sporulation-specific structures and reused again during spore germination for budding and during subsequent mitotic divisions. Although Cdc12 also persisted during sporulation, it was excluded from septin structures and replaced by another subunit, Spr3; only new Cdc12 populated the collar of germinating spores. Thus, mechanisms governing septin incorporation are specific to each subunit and to the developmental state of the cell.