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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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Dynamics of surface receptors on a C3-injected cell.  Surface receptors were labeled with fluorescent latex beads.  Movements toward chromosomes initiated immediately upon the  injection of C3 (a and b, arrows). During anaphase (c), the cluster  of beads followed the top set of chromosomes and remained in  the vicinity of the chromosomes (d). Bar, 10 μm.
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Figure 6: Dynamics of surface receptors on a C3-injected cell. Surface receptors were labeled with fluorescent latex beads. Movements toward chromosomes initiated immediately upon the injection of C3 (a and b, arrows). During anaphase (c), the cluster of beads followed the top set of chromosomes and remained in the vicinity of the chromosomes (d). Bar, 10 μm.

Mentions: When cells were injected with C3 transferase at pro-metaphase or metaphase, surface-bound beads immediately started directional movement toward a central region of the cell, near the congregated chromosomes (Fig. 6, a and b). In addition, the movements were observed over most of the, if not the entire, top surface. During anaphase, the cluster of beads either followed the movement of one set of chromosomes (Fig. 6 c), or split into two and moved with each set (see Fig. 5 b′), as if they were tethered to the chromosomes. This cortical movement clearly accounts for the lack of concentration of actin filaments along the equator and the concentration over the segregated chromosomes/ spindle poles as described above.


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)

Dynamics of surface receptors on a C3-injected cell.  Surface receptors were labeled with fluorescent latex beads.  Movements toward chromosomes initiated immediately upon the  injection of C3 (a and b, arrows). During anaphase (c), the cluster  of beads followed the top set of chromosomes and remained in  the vicinity of the chromosomes (d). Bar, 10 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Dynamics of surface receptors on a C3-injected cell. Surface receptors were labeled with fluorescent latex beads. Movements toward chromosomes initiated immediately upon the injection of C3 (a and b, arrows). During anaphase (c), the cluster of beads followed the top set of chromosomes and remained in the vicinity of the chromosomes (d). Bar, 10 μm.
Mentions: When cells were injected with C3 transferase at pro-metaphase or metaphase, surface-bound beads immediately started directional movement toward a central region of the cell, near the congregated chromosomes (Fig. 6, a and b). In addition, the movements were observed over most of the, if not the entire, top surface. During anaphase, the cluster of beads either followed the movement of one set of chromosomes (Fig. 6 c), or split into two and moved with each set (see Fig. 5 b′), as if they were tethered to the chromosomes. This cortical movement clearly accounts for the lack of concentration of actin filaments along the equator and the concentration over the segregated chromosomes/ spindle poles as described above.

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