Kinesin and Dynein-Dynactin at Intersecting Microtubules: Motor Density Affects Dynein Function
Jennifer L Ross 1, Henry Shuman 2, Erika L.F. Holzbaur 2 and Yale E. Goldman 2*
1 University of Massachusetts - Amherst
2 University of Pennsylvania
* To whom correspondence should be addressed. E-mail: goldmany{at}mail.med.upenn.edu.
Submitted on August 17, 2007
Revised on September 17, 2007
Accepted on 18 October 2007
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Abstract |
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Kinesin and cytoplasmic dynein are microtubule-based motor proteins that actively transport material throughout the cell. Microtubules can intersect at a variety of angles both near the nucleus and at the cell periphery, and the behavior of molecular motors at these intersections has implications for long-range transport efficiency and accuracy. In order to test motor function at microtubule intersections, cross-overs were arranged in vitro using flow to orient successive layers of filaments. Single kinesin and cytoplasmic dynein-dynactin molecules fused with green-fluorescent protein, and artificial bead cargos decorated with multiple motors, were observed while encountering intersections. Single kinesins tend to cross intersecting microtubules, whereas single dynein-dynactins have a more varied response. For bead cargos, kinesin motion is independent of motor number. Dynein beads pause at high motor number, but their actions become more varied as the motor number is decreased. These results suggest that regulating the number of active dynein molecules could change a motile cargo into one that is anchored at an intersection, consistent with dynein's proposed transport and tethering functions in the cell.
Key Words:
Cytoskeletal Intersections, Cytoskeletal Organization, Golgi Tethering, Motor Regulation, Transport Obstacles
