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The small GTP-binding protein rho regulates cortical activities in cultured cells during division.

O'Connell CB, Wheatley SP, Ahmed S, Wang YL - J. Cell Biol. (1999)

Bottom Line: All treated, well-adherent cells underwent cleavage-like activities and most of them divided successfully.The effects of C3 appeared to be dependent on cell adhesion; less adherent 3T3 fibroblasts exhibited irregular cortical ingression only when cells started to increase attachment during respreading, but managed to complete cytokinesis.Our results indicate that Rho does not simply activate actin-myosin II interactions during cytokinesis, but regulates the spatial pattern of cortical activities and completion of cytokinesis possibly through modulating the mechanical strength of the cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.

ABSTRACT
We have investigated the role of the small GTP-binding protein Rho in cytokinesis by microinjecting an inhibitor, C3 ribosyltransferase, into cultured cells. Microinjection of C3 into prometaphase or metaphase normal rat kidney epithelial cells induced immediate and global cortical movement of actin toward the metaphase plate, without an apparent effect on the mitotic spindle. During anaphase, concentrated cortical actin filaments migrated with separating chromosomes, leaving no apparent concentration of actin filaments along the equator. Myosin II in injected epithelial cells showed a diffuse distribution throughout cell division. All treated, well-adherent cells underwent cleavage-like activities and most of them divided successfully. However, cytokinesis became abnormal, generating irregular ingressions and ectopic cleavage sites even when mitosis was blocked with nocodazole. The effects of C3 appeared to be dependent on cell adhesion; less adherent 3T3 fibroblasts exhibited irregular cortical ingression only when cells started to increase attachment during respreading, but managed to complete cytokinesis. Poorly adherent HeLa cells showed neither ectopic cleavage nor completion of cytokinesis. Our results indicate that Rho does not simply activate actin-myosin II interactions during cytokinesis, but regulates the spatial pattern of cortical activities and completion of cytokinesis possibly through modulating the mechanical strength of the cortex.

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Time lapse images of NRK cells microinjected with C3 transferase after the initiation of cytokinesis. Time in minutes after microinjection is shown in the upper right corner. Roughly half of the cells injected after the initiation of furrowing proceeded through cytokinesis without any apparent effects (compare a–d with Fig. 1, c–e). The remaining cells showed increased cortical activities outside the equatorial region (f–h). All the injected cells completed cytokinesis with a normal-looking furrow and midbody (d and h). Bar, 20 μm.
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Figure 2: Time lapse images of NRK cells microinjected with C3 transferase after the initiation of cytokinesis. Time in minutes after microinjection is shown in the upper right corner. Roughly half of the cells injected after the initiation of furrowing proceeded through cytokinesis without any apparent effects (compare a–d with Fig. 1, c–e). The remaining cells showed increased cortical activities outside the equatorial region (f–h). All the injected cells completed cytokinesis with a normal-looking furrow and midbody (d and h). Bar, 20 μm.

Mentions: The effects of C3 were dependent on the timing of microinjection. When C3 was microinjected into NRK cells already undergoing cytokinesis (Fig. 2, n = 15), the cleavage continued to completion 100% of the time (Fig. 2, d and h). In 53% of these cells cytokinesis showed no detectable abnormalities (compare Fig. 2, a–d with Fig. 1, c–e). The remaining cells showed some abnormal cortical activities outside the equator (Fig. 2, g and h), without impairing the morphology or progression of the cleavage furrow.


The small GTP-binding protein rho regulates cortical activities in cultured cells during division.

O'Connell CB, Wheatley SP, Ahmed S, Wang YL - J. Cell Biol. (1999)

Time lapse images of NRK cells microinjected with C3 transferase after the initiation of cytokinesis. Time in minutes after microinjection is shown in the upper right corner. Roughly half of the cells injected after the initiation of furrowing proceeded through cytokinesis without any apparent effects (compare a–d with Fig. 1, c–e). The remaining cells showed increased cortical activities outside the equatorial region (f–h). All the injected cells completed cytokinesis with a normal-looking furrow and midbody (d and h). Bar, 20 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132903&req=5

Figure 2: Time lapse images of NRK cells microinjected with C3 transferase after the initiation of cytokinesis. Time in minutes after microinjection is shown in the upper right corner. Roughly half of the cells injected after the initiation of furrowing proceeded through cytokinesis without any apparent effects (compare a–d with Fig. 1, c–e). The remaining cells showed increased cortical activities outside the equatorial region (f–h). All the injected cells completed cytokinesis with a normal-looking furrow and midbody (d and h). Bar, 20 μm.
Mentions: The effects of C3 were dependent on the timing of microinjection. When C3 was microinjected into NRK cells already undergoing cytokinesis (Fig. 2, n = 15), the cleavage continued to completion 100% of the time (Fig. 2, d and h). In 53% of these cells cytokinesis showed no detectable abnormalities (compare Fig. 2, a–d with Fig. 1, c–e). The remaining cells showed some abnormal cortical activities outside the equator (Fig. 2, g and h), without impairing the morphology or progression of the cleavage furrow.

Bottom Line: All treated, well-adherent cells underwent cleavage-like activities and most of them divided successfully.The effects of C3 appeared to be dependent on cell adhesion; less adherent 3T3 fibroblasts exhibited irregular cortical ingression only when cells started to increase attachment during respreading, but managed to complete cytokinesis.Our results indicate that Rho does not simply activate actin-myosin II interactions during cytokinesis, but regulates the spatial pattern of cortical activities and completion of cytokinesis possibly through modulating the mechanical strength of the cortex.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA.

ABSTRACT
We have investigated the role of the small GTP-binding protein Rho in cytokinesis by microinjecting an inhibitor, C3 ribosyltransferase, into cultured cells. Microinjection of C3 into prometaphase or metaphase normal rat kidney epithelial cells induced immediate and global cortical movement of actin toward the metaphase plate, without an apparent effect on the mitotic spindle. During anaphase, concentrated cortical actin filaments migrated with separating chromosomes, leaving no apparent concentration of actin filaments along the equator. Myosin II in injected epithelial cells showed a diffuse distribution throughout cell division. All treated, well-adherent cells underwent cleavage-like activities and most of them divided successfully. However, cytokinesis became abnormal, generating irregular ingressions and ectopic cleavage sites even when mitosis was blocked with nocodazole. The effects of C3 appeared to be dependent on cell adhesion; less adherent 3T3 fibroblasts exhibited irregular cortical ingression only when cells started to increase attachment during respreading, but managed to complete cytokinesis. Poorly adherent HeLa cells showed neither ectopic cleavage nor completion of cytokinesis. Our results indicate that Rho does not simply activate actin-myosin II interactions during cytokinesis, but regulates the spatial pattern of cortical activities and completion of cytokinesis possibly through modulating the mechanical strength of the cortex.

Show MeSH
Related in: MedlinePlus