Cytokinesis in Tetrahymena: determination of division plane and organization of contractile ring.
A protein, Tetrahymena p85, is localized to the presumptive division plane before the formation of the contractile ring. p85 directly interacts with Tetrahymena calmodulin (CaM) in a Ca(2+)-dependent manner, and p85 and CaM colocalize in the division furrow. A Ca(2+)/CaM inhibitor N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide HCl (W7) inhibits the direct interaction between p85 and Ca(2+)/CaM. W7 also inhibits the localization of p85 and CaM to the division plane, and the formation of the contractile ring and division furrow. Tetrahymena fimbrin and elongation factor-1a (EF-1alpha), which induce bundling of Tetrahymena F-actin, are also localized to the division furrow during cytokinesis. The Tetrahymena fimbrin has two actin-binding domains, but lacks the EF-hand Ca(2+)-binding motif, suggesting that Tetrahymena fimbrin probably cross-links actin filaments in a Ca(2+)- insensitive manner during cytokinesis. The evidence also indicates that Ca(2+)/CaM inhibits the F-actin-bundling activity of EF-1alpha; and EF-1alpha and CaM colocalize in the division furrow. In this review, we propose that the Ca(2+)/CaM signal and its target protein p85 cooperatively regulate the determination of the division plane, and that a Ca(2+)-insensitive actin-bundling protein, Tetrahymena fimbrin, and a Ca(2+)/CaM-sensitive actin-bundling protein, EF-1alpha, play pivotal roles in regulating the organization of the contractile ring microfilaments.
Numata
O
O
Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan. numata@sakura.cc.tsukuba.ac.jp
Gonda
K
K
Watanabe
A
A
Kurasawa
Y
Y
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002147:Calmodulin / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D020648:Peptide Elongation Factor 1 / Q000378:metabolism; D015800:Protozoan Proteins; D013768:Tetrahymena / Q000166:cytology* / Q000502:physiology
D000199:Actins; D002147:Calmodulin; D018797:Cell Cycle Proteins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; D020648:Peptide Elongation Factor 1; D015800:Protozoan Proteins; C404904:p85 protein, Tetrahymena; C026742:plastin