Calmodulin Concentrates at Regions of Cell Growth in Saccharomyces cerevisiae

• Published in: The Journal of cell biology Vol. 118; no. 3; pp. 619 - 629
• Main Authors: Brockerhoff, Susan E., Davis, Trisha N.
• Format: Journal Article
• Language: English
• Published: New York, NY Rockefeller University Press 01.08.1992; The Rockefeller University Press
• Subjects: 3T3 cells; Actins; Actins - genetics; Actins - metabolism; Antibodies; Antibody Specificity; Biological and medical sciences; Calmodulin - immunology; Calmodulin - metabolism; Calmodulin - physiology; Cell cycle; Cell growth; Cell Polarity - physiology; Cells; Cellular biology; Daughter cells; Epithelial cells; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; Immunoblotting; Microbiology; Mother cells; Mutation; Mycology; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - growth & development; Saccharomyces cerevisiae - metabolism; Temperature; Yeast; Yeasts; Fungi; Binding protein; Yeast; Cell cycle; Ascomycetes; Localization; Saccharomyces cerevisiae; Calmodulin; Thallophyta
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.118.3.619

Calmodulin was localized in Saccharomyces cerevisiae by indirect immunofluorescence using affinity-purified polyclonal antibodies. Calmodulin displays an asymmetric distribution that changes during the cell cycle. In unbudded cells, calmodulin concentrates at the presumptive site of bud formation ∼10 min before bud emergence. In small budded cells, calmodulin accumulates throughout the bud. As the bud grows, calmodulin concentrates at the tip, then disperses, and finally concentrates in the neck region before cytokinesis. An identical staining pattern is observed when wild-type calmodulin is replaced with mutant forms of calmodulin impaired in binding Ca2+. Thus, the localization of calmodulin does not depend on its ability to bind Ca2+with a high affinity. Double labeling of yeast cells with affinity-purified anti-calmodulin antibody and rhodamine-conjugated phalloidin indicates that calmodulin and actin concentrate in overlapping regions during the cell cycle. Furthermore, disrupting calmodulin function using a temperature-sensitive calmodulin mutant delocalizes actin, and actl-4 mutants contain a random calmodulin distribution. Thus, calmodulin and actin distributions are interdependent. Finally, calmodulin localizes to the shmoo tip in cells treated with α-factor. This distribution, at sites of cell growth, implicates calmodulin in polarized cell growth in yeast.