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Vol. 16, Issue 7, 3334-3340, July 2005

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Pushing Forces Drive the Comet-like Motility of Microtubule Arrays in Dictyostelium

Daniela A. Brito ^* , Joshua Strauss ^* , Valentin Magidson ^*, Irina Tikhonenko ^*, Alexey Khodjakov ^* , and Michael P. Koonce ^* 

^* Division of Molecular Medicine, Wadsworth Center, Albany, NY 12201; Department of Biomedical Sciences, School of Public Health, University at Albany, Albany, NY 12201

Submitted January 21, 2005; Revised April 18, 2005; Accepted April 20, 2005
Monitoring Editor: J. Richard McIntosh

Overexpression of dynein fragments in Dictyostelium induces the movement of the entire interphase microtubule array. Centrosomes in these cells circulate through the cytoplasm at rates between 0.4 and 2.5 µm/s and are trailed by a comet-tail like arrangement of the microtubule array. Previous work suggested that these cells use a dynein-mediated pulling mechanism to generate this dramatic movement and that similar forces are at work to maintain the interphase MTOC position in wild-type cells. In the present study, we address the nature of the forces used to produce microtubule movement. We have used a laser microbeam to sever the connection between the motile centrosomes and trailing microtubules, demonstrating that the major force for such motility results from a pushing on the microtubules. We eliminate the possibility that microtubule assembly/disassembly reactions are significant contributors to this motility and suggest that the cell cortex figures prominently in locating force-producing molecules. Our findings indicate that interphase microtubules in Dictyostelium are subject to both dynein- and kinesin-like forces and that these act in concert to maintain centrosome position in the cell and to support the radial character of the microtubule network.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

Address correspondence to: Michael Koonce (Koonce{at}wadsworth.org).

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