Cell Structure and Function
Online ISSN : 1347-3700
Print ISSN : 0386-7196
ISSN-L : 0386-7196
REGULAR ARTICLES
Calmodulin and Ca2+/Calmodulin-Binding Proteins are Involved in Tetrahymena thermophila Phagocytosis
Kohsuke GondaMie KomatsuOsamu Numata
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2000 Volume 25 Issue 4 Pages 243-251

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Abstract

The ciliated protist, Tetrahymena thermophila, possesses one oral apparatus for phagocytosis, one of the most important cell functions, in the anterior cell cortex. The apparatus comprises four membrane structures which consist of ciliated and unciliated basal bodies, a cytostome where food is collected by oral ciliary motility, and a cytopharynx where food vacuoles are formed. The food vacuole is thought to be transported into the cytoplasm by a deep fiber which connects with the oral apparatus. Although a large number of studies have been done on the structure of the oral apparatus, the molecular mechanisms of phagocytosis in Tetrahymena thermophila are not well understood. In this study, using indirect immunofluorescence, we demonstrated that the deep fiber consisted of actin, CaM, and Ca2+/CaM-binding proteins, p85 and EF-1α, which are closely involved in cytokinesis. Moreover, we showed that CaM, p85, and EF-1α are colocalized in the cytostome and the cytopharynx of the oral apparatus. Next, we examined whether Ca2+/CaM signal regulates Tetrahymena thermophila phagocytosis, using Ca2+/CaM inhibitors chlorpromazine, trifluoperazine, N-(6-aminohexyl)-1-naphthalenesulfonamide, and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide HCl. In Tetrahymena, it is known that Ca2+/CaM signal is closely involved in ciliary motility and cytokinesis. The results showed that one of the inhibitors, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide HCl, inhibited the food vacuole formation rather than the ciliary motility, while the other three inhibitors effectively prevented the ciliary motility. Considering the colocalization of CaM, p85, and EF-1α to the cytopharynx, these results suggest that the Ca2+/CaM signal plays a pivotal role in Tetrahymena thermophila food vacuole formation.

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© 2000 by Japan Society for Cell Biology
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