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Dictyostelium IQGAP-related protein specifically involved in the completion of cytokinesis.

Adachi H, Takahashi Y, Hasebe T, Shirouzu M, Yokoyama S, Sutoh K - J. Cell Biol. (1997)

Bottom Line: These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis.Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton.Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153. f37771@m-unix.cc.u-tokyo.ac.jp

ABSTRACT
The gapA gene encoding a novel RasGTPase-activating protein (RasGAP)-related protein was found to be disrupted in a cytokinesis mutant of Dictyostelium that grows as giant and multinucleate cells in a dish culture. The predicted sequence of the GAPA protein showed considerable homology to those of Gap1/Sar1 from fission yeast and the COOH-terminal half of mammalian IQGAPs, the similarity extending beyond the RasGAP-related domain. In suspension culture, gapA- cells showed normal growth in terms of the increase in cell mass, but cytokinesis inefficiently occurred to produce spherical giant cells. Time-lapse recording of the dynamics of cell division in a dish culture revealed that, in the case of gapA- cells, cytokinesis was very frequently reversed at the step in which the midbody connecting the daughter cells should be severed. Earlier steps of cytokinesis in the gapA- cells seemed to be normal, since myosin II was accumulated at the cleavage furrow. Upon starvation, gapA- cells developed and formed fruiting bodies with viable spores, like the wild-type cells. These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis. Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton. Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

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Development of Dictyostelium cells upon starvation.  (Left) AX2; (Right) D42-2. Vegetative cells were washed and  then plated onto phosphate agar. The developed phenotype was  observed after 24 h. Bar, 100 μm.
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Figure 10: Development of Dictyostelium cells upon starvation. (Left) AX2; (Right) D42-2. Vegetative cells were washed and then plated onto phosphate agar. The developed phenotype was observed after 24 h. Bar, 100 μm.

Mentions: When starved on phosphate agar, gapA− cells developed and formed normal fruiting bodies with viable spores at the same time as the wild-type cells (Fig. 10). The increase in size of the plaque on the bacterial lawn and the terminal phenotype were also unaffected by the mutation (data not shown). These results indicate that the GAPA protein is not required for Dictyostelium development and phagocytosis.


Dictyostelium IQGAP-related protein specifically involved in the completion of cytokinesis.

Adachi H, Takahashi Y, Hasebe T, Shirouzu M, Yokoyama S, Sutoh K - J. Cell Biol. (1997)

Development of Dictyostelium cells upon starvation.  (Left) AX2; (Right) D42-2. Vegetative cells were washed and  then plated onto phosphate agar. The developed phenotype was  observed after 24 h. Bar, 100 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2139833&req=5

Figure 10: Development of Dictyostelium cells upon starvation. (Left) AX2; (Right) D42-2. Vegetative cells were washed and then plated onto phosphate agar. The developed phenotype was observed after 24 h. Bar, 100 μm.
Mentions: When starved on phosphate agar, gapA− cells developed and formed normal fruiting bodies with viable spores at the same time as the wild-type cells (Fig. 10). The increase in size of the plaque on the bacterial lawn and the terminal phenotype were also unaffected by the mutation (data not shown). These results indicate that the GAPA protein is not required for Dictyostelium development and phagocytosis.

Bottom Line: These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis.Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton.Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

View Article: PubMed Central - PubMed

Affiliation: Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153. f37771@m-unix.cc.u-tokyo.ac.jp

ABSTRACT
The gapA gene encoding a novel RasGTPase-activating protein (RasGAP)-related protein was found to be disrupted in a cytokinesis mutant of Dictyostelium that grows as giant and multinucleate cells in a dish culture. The predicted sequence of the GAPA protein showed considerable homology to those of Gap1/Sar1 from fission yeast and the COOH-terminal half of mammalian IQGAPs, the similarity extending beyond the RasGAP-related domain. In suspension culture, gapA- cells showed normal growth in terms of the increase in cell mass, but cytokinesis inefficiently occurred to produce spherical giant cells. Time-lapse recording of the dynamics of cell division in a dish culture revealed that, in the case of gapA- cells, cytokinesis was very frequently reversed at the step in which the midbody connecting the daughter cells should be severed. Earlier steps of cytokinesis in the gapA- cells seemed to be normal, since myosin II was accumulated at the cleavage furrow. Upon starvation, gapA- cells developed and formed fruiting bodies with viable spores, like the wild-type cells. These results indicate that the GAPA protein is specifically involved in the completion of cytokinesis. Recently, it was reported that IQGAPs are putative effectors for Rac and CDC42, members of the Rho family of GTPases, and participate in reorganization of the actin cytoskeleton. Thus, it is possible that Dictyostelium GAPA participates in the severing of the midbody by regulating the actin cytoskeleton through an interaction with a member of small GTPases.

Show MeSH
Related in: MedlinePlus