Dataset Information

Motor number controls cargo switching at actin-microtubule intersections in vitro.

ABSTRACT: Cellular activities such as endocytosis and secretion require that cargos actively switch between the microtubule (MT) and actin filament (AF) networks. Cellular studies suggest that switching may involve a tug of war or coordinate regulation of MT- and AF-based motor function.To test the hypothesis that motor number can be used to direct the outcome of a tug-of-war process, we reconstituted cargo switching at MT-AF intersections in a minimal system with purified myosin V and dynein-dynactin motors bound to beads. Beads containing both motors often paused at the intersections and rotated about an axis perpendicular to both filaments, suggesting that competing motors apply a torque on their cargo. Force measurements showed that motor forces scale with the number of engaged myosin V and dynein-dynactin motors. Whether beads remained on a MT or AF or switched to the alternate track was determined by which set of motors collectively produced greater force. Passing and switching probabilities were similar whether the bead approached an intersection on either a MT or an AF. Beads with a force ratio near unity had approximately equal probabilities of exiting on the MT, exiting on the AF, or remaining stalled at the intersection. A simple statistical model quantitatively describes the relationship between switching probability and motor number.Cargo switching can be tuned via combinations of 1-4 myosin V and 1-4 dynein-dynactin engaged motors through a simple force-mediated mechanism.

SUBMITTER: Schroeder HW

PROVIDER: S-EPMC2934746 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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Motor number controls cargo switching at actin-microtubule intersections in vitro.

Schroeder Harry W HW Mitchell Chris C Shuman Henry H Holzbaur Erika L F EL Goldman Yale E YE

Current biology : CB 20100415 8

<h4>Background</h4>Cellular activities such as endocytosis and secretion require that cargos actively switch between the microtubule (MT) and actin filament (AF) networks. Cellular studies suggest that switching may involve a tug of war or coordinate regulation of MT- and AF-based motor function.<h4>Results</h4>To test the hypothesis that motor number can be used to direct the outcome of a tug-of-war process, we reconstituted cargo switching at MT-AF intersections in a minimal system with purifi ...[more]

PMID: 20399098

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Project description:How intracellular transport controls the probability that cargos switch at intersections between filaments is not well understood. In one hypothesis some motors on the cargo attach to one filament while others attach to the intersecting filament, and the ensuing tug-of-war determines which filament is chosen. We investigate this hypothesis using 3D computer simulations, and discover that switching at intersections increases with the number of motors on the cargo, but is not strongly dependent on motor number when the filaments touch. Thus, simply controlling the number of active motors on the cargo cannot account for in vivo observations that found reduced switching with increasing motor number, suggesting additional mechanisms of regulation. We use simulations to show that one possible way to regulate switching is by simultaneously adjusting the separation between planes containing the crossing filaments and the total number of active motors on the cargo. Heretofore, the effect of filament-filament separation on switching has been unexplored. We find that the switching probability decreases with increasing filament separation. This effect is particularly strong for cargos with only a modest number of motors. As the filament separation increases past the maximum head-to-head distance of the motor, individual motors walking along a filament will be unable to reach the intersecting filament. Thus, any switching requires that other motors on the cargo attach to the intersecting filament and haul the cargo along it, while motor(s) engaged on the original filament detach. Further, if the filament separation is large enough, the cargo can have difficulty proceeding along the initial filament because the engaged motors can walk underneath the intersecting filament, but the cargo itself cannot fit between the filaments. Thus, the cargo either detaches entirely from the original filament, or must dip to the side of the initial filament and then pass below the crossing filament.

Dataset Information

Motor number controls cargo switching at actin-microtubule intersections in vitro.

Publications

Motor number controls cargo switching at actin-microtubule intersections in vitro.

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