Molecular and Cellular Biology Graduate Program, University of Massachusetts, Amherst, MA 01003, USA.
Proc Natl Acad Sci U S A. 2012 Dec 18;109(51):20814-9. doi: 10.1073/pnas.1209304109. Epub 2012 Dec 3.
Intracellular transport of cargo particles is performed by multiple motors working in concert. However, the mechanism of motor association to cargos is unknown. It is also unknown how long individual motors stay attached, how many are active, and how multimotor cargos would navigate a densely crowded filament with many other motors. Prior theoretical and experimental biophysical model systems of intracellular cargo have assumed fixed teams of motors transporting along bare microtubules or microtubules with fixed obstacles. Here, we investigate a regime of cargos transporting along microtubules crowded with free motors. Furthermore, we use cargos that are able to associate or dissociate motors as it translocates. We perform in vitro motility reconstitution experiments with high-resolution particle tracking. Our model system consists of a quantum dot cargo attached to kinesin motors, and additional free kinesin motors that act as traffic along the microtubule. Although high densities of kinesin motors hinder forward motion, resulting in a lower velocity, the ability to associate motors appears to enhance the run length and attachment time of the quantum dot, improving overall cargo transport. These results suggest that cargos that can associate new motors as they transport could overcome traffic jams.
货物颗粒的细胞内运输是由多个协同工作的马达完成的。然而，马达与货物结合的机制尚不清楚。也不知道单个马达附着的时间有多长，有多少个处于活跃状态，以及多马达货物如何在有许多其他马达的密集拥挤的纤维丝中导航。先前的细胞内货物的理论和实验生物物理模型系统假设固定的马达团队沿着裸露的微管或带有固定障碍物的微管运输。在这里，我们研究了沿着挤满自由马达的微管运输货物的状态。此外，我们使用在运输过程中能够与马达结合或解离的货物。我们使用高分辨率粒子跟踪进行了体外运动重建实验。我们的模型系统由一个连接在驱动蛋白马达上的量子点货物和额外的自由驱动蛋白马达组成，这些马达沿着微管充当交通。尽管高浓度的驱动蛋白马达阻碍了向前运动，导致速度降低，但与马达结合的能力似乎可以延长量子点的运行长度和附着时间，从而提高整体货物运输效率。这些结果表明，在运输过程中能够与新马达结合的货物可以克服交通堵塞。
