Actin bodies in yeast quiescent cells: an immediately available actin reserve?
Most eukaryotic cells spend most of their life in a quiescent state, poised to respond to specific signals to proliferate. In Saccharomyces cerevisiae, entry into and exit from quiescence are dependent only on the availability of nutrients in the environment. The transition from quiescence to proliferation requires not only drastic metabolic changes but also a complete remodeling of various cellular structures. Here, we describe an actin cytoskeleton organization specific of the yeast quiescent state. When cells cease to divide, actin is reorganized into structures that we named "actin bodies." We show that actin bodies contain F-actin and several actin-binding proteins such as fimbrin and capping protein. Furthermore, by contrast to actin patches or cables, actin bodies are mostly immobile, and we could not detect any actin filament turnover. Finally, we show that upon cells refeeding, actin bodies rapidly disappear and actin cables and patches can be assembled in the absence of de novo protein synthesis. This led us to propose that actin bodies are a reserve of actin that can be immediately mobilized for actin cables and patches formation upon reentry into a proliferation cycle.
Sagot
Isabelle
I
Institut de Biochimie et Génétique Cellulaires, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5095, Université Victor Segalen/Bordeaux II, F-33077 Bordeaux Cedex, France. isabelle.sagot@ibgc.u-bordeaux2.fr
Pinson
Benoît
B
Salin
Bénédicte
B
Daignan-Fornier
Bertrand
B
D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D008840:Microfilament Proteins / Q000378:metabolism; D014176:Protein Biosynthesis / Q000235:genetics; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000648:ultrastructure
D000199:Actins; D008840:Microfilament Proteins