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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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The distribution of TD60 (a and b) and γ-tubulin (c and  d) in Rho-inhibited NRK cells. Both control cells (a) and C3- injected cells (b) showed a localization of TD60 along the equator. Staining of γ-tubulin, used as a marker for centrosomes,  showed similar localizations at the spindle poles in a C3-injected  cell (d) and a control cell (c). Bar, 10 μm.
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Figure 9: The distribution of TD60 (a and b) and γ-tubulin (c and d) in Rho-inhibited NRK cells. Both control cells (a) and C3- injected cells (b) showed a localization of TD60 along the equator. Staining of γ-tubulin, used as a marker for centrosomes, showed similar localizations at the spindle poles in a C3-injected cell (d) and a control cell (c). Bar, 10 μm.

Mentions: TD60 antigen, a chromosomal passenger protein that relocates to the equatorial cortex during telophase, has been implicated in signaling cytokinesis (Andreassen et al., 1991; Margolis and Andreassen, 1993; Wheatley and Wang, 1996). The pattern of TD60 redistribution was unaffected by the microinjection of C3 (Fig. 9, a and b), and no concentration of TD60 was found near ectopic furrows. Similarly, there appeared to be no disruption to spindle poles, as visualized by staining with anti–γ-tubulin antibodies (Fig. 9, c and d).


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)

The distribution of TD60 (a and b) and γ-tubulin (c and  d) in Rho-inhibited NRK cells. Both control cells (a) and C3- injected cells (b) showed a localization of TD60 along the equator. Staining of γ-tubulin, used as a marker for centrosomes,  showed similar localizations at the spindle poles in a C3-injected  cell (d) and a control cell (c). Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 9: The distribution of TD60 (a and b) and γ-tubulin (c and d) in Rho-inhibited NRK cells. Both control cells (a) and C3- injected cells (b) showed a localization of TD60 along the equator. Staining of γ-tubulin, used as a marker for centrosomes, showed similar localizations at the spindle poles in a C3-injected cell (d) and a control cell (c). Bar, 10 μm.
Mentions: TD60 antigen, a chromosomal passenger protein that relocates to the equatorial cortex during telophase, has been implicated in signaling cytokinesis (Andreassen et al., 1991; Margolis and Andreassen, 1993; Wheatley and Wang, 1996). The pattern of TD60 redistribution was unaffected by the microinjection of C3 (Fig. 9, a and b), and no concentration of TD60 was found near ectopic furrows. Similarly, there appeared to be no disruption to spindle poles, as visualized by staining with anti–γ-tubulin antibodies (Fig. 9, c and d).

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