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Centrosome positioning in interphase cells.

Burakov A, Nadezhdina E, Slepchenko B, Rodionov V - J. Cell Biol. (2003)

Bottom Line: It is known that centrosome positioning requires a radial array of cytoplasmic microtubules (MTs) that can exert pushing or pulling forces involving MT dynamics and the activity of cortical MT motors.It has also been suggested that actomyosin can play a direct or indirect role in this process.Using this approach in combination with microinjection of function-blocking probes, we found that a MT-dependent dynein pulling force plays a key role in the positioning of the centrosome at the cell center, and that other forces applied to the centrosomal MTs, including actomyosin contractility, can contribute to this process.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Center for Biomedical Imaging, University of Connecticut Health Center, Technology, Farmington, CT 06032-1507, USA.

ABSTRACT
The position of the centrosome is actively maintained at the cell center, but the mechanisms of the centering force remain largely unknown. It is known that centrosome positioning requires a radial array of cytoplasmic microtubules (MTs) that can exert pushing or pulling forces involving MT dynamics and the activity of cortical MT motors. It has also been suggested that actomyosin can play a direct or indirect role in this process. To examine the centering mechanisms, we introduced an imbalance of forces acting on the centrosome by local application of an inhibitor of MT assembly (nocodazole), and studied the resulting centrosome displacement. Using this approach in combination with microinjection of function-blocking probes, we found that a MT-dependent dynein pulling force plays a key role in the positioning of the centrosome at the cell center, and that other forces applied to the centrosomal MTs, including actomyosin contractility, can contribute to this process.

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Forces involved in the positioning of the centrosome. Pulling forces applied to the MTs at the cell cortex by dynein act to position the centrosome at the cell center. Pushing forces, including actin centripetal flow and MT dynamics, are directed toward the cell center.
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fig5: Forces involved in the positioning of the centrosome. Pulling forces applied to the MTs at the cell cortex by dynein act to position the centrosome at the cell center. Pushing forces, including actin centripetal flow and MT dynamics, are directed toward the cell center.

Mentions: The results of our study demonstrate that the centrosome in mammalian cells is positioned at the cell center predominantly by the MT pulling mechanisms. Furthermore, our results show that this pulling force in nonpolarized mammalian cells is exerted by cytoplasmic dynein (Fig. 5). Other forces that act on the centrosomal MTs can also contribute to the centrosome positioning. One such force is exerted by actomyosin contractility. It has been shown that actomyosin centripetal flow can move the anchored MTs toward the cell center with considerable force (Wittmann and Waterman-Storer, 2001) and can therefore contribute to the centering mechanisms. Our data that locally induced contractility can misplace the centrosome from its central position are consistent with these results. Another force that has been suggested to have a role in centrosome positioning is MT dynamics. However, as evident from experiments with dynein inhibition, actomyosin contractility and MT dynamics working separately or in combination with each other are not sufficient to position the centrosome at the cell center in the absence of dynein activity. Therefore, in stationary nonpolarized cells dynein pulling force appears to be a predominant centering mechanism.


Centrosome positioning in interphase cells.

Burakov A, Nadezhdina E, Slepchenko B, Rodionov V - J. Cell Biol. (2003)

Forces involved in the positioning of the centrosome. Pulling forces applied to the MTs at the cell cortex by dynein act to position the centrosome at the cell center. Pushing forces, including actin centripetal flow and MT dynamics, are directed toward the cell center.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172857&req=5

fig5: Forces involved in the positioning of the centrosome. Pulling forces applied to the MTs at the cell cortex by dynein act to position the centrosome at the cell center. Pushing forces, including actin centripetal flow and MT dynamics, are directed toward the cell center.
Mentions: The results of our study demonstrate that the centrosome in mammalian cells is positioned at the cell center predominantly by the MT pulling mechanisms. Furthermore, our results show that this pulling force in nonpolarized mammalian cells is exerted by cytoplasmic dynein (Fig. 5). Other forces that act on the centrosomal MTs can also contribute to the centrosome positioning. One such force is exerted by actomyosin contractility. It has been shown that actomyosin centripetal flow can move the anchored MTs toward the cell center with considerable force (Wittmann and Waterman-Storer, 2001) and can therefore contribute to the centering mechanisms. Our data that locally induced contractility can misplace the centrosome from its central position are consistent with these results. Another force that has been suggested to have a role in centrosome positioning is MT dynamics. However, as evident from experiments with dynein inhibition, actomyosin contractility and MT dynamics working separately or in combination with each other are not sufficient to position the centrosome at the cell center in the absence of dynein activity. Therefore, in stationary nonpolarized cells dynein pulling force appears to be a predominant centering mechanism.

Bottom Line: It is known that centrosome positioning requires a radial array of cytoplasmic microtubules (MTs) that can exert pushing or pulling forces involving MT dynamics and the activity of cortical MT motors.It has also been suggested that actomyosin can play a direct or indirect role in this process.Using this approach in combination with microinjection of function-blocking probes, we found that a MT-dependent dynein pulling force plays a key role in the positioning of the centrosome at the cell center, and that other forces applied to the centrosomal MTs, including actomyosin contractility, can contribute to this process.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology and Center for Biomedical Imaging, University of Connecticut Health Center, Technology, Farmington, CT 06032-1507, USA.

ABSTRACT
The position of the centrosome is actively maintained at the cell center, but the mechanisms of the centering force remain largely unknown. It is known that centrosome positioning requires a radial array of cytoplasmic microtubules (MTs) that can exert pushing or pulling forces involving MT dynamics and the activity of cortical MT motors. It has also been suggested that actomyosin can play a direct or indirect role in this process. To examine the centering mechanisms, we introduced an imbalance of forces acting on the centrosome by local application of an inhibitor of MT assembly (nocodazole), and studied the resulting centrosome displacement. Using this approach in combination with microinjection of function-blocking probes, we found that a MT-dependent dynein pulling force plays a key role in the positioning of the centrosome at the cell center, and that other forces applied to the centrosomal MTs, including actomyosin contractility, can contribute to this process.

Show MeSH
Related in: MedlinePlus