Motor Coordination via a Tug-of-War Mechanism Drives Bidirectional Vesicle Transport

Abstract

Summary The microtubule motors kinesin and dynein function collectively to drive vesicular transport. High resolution tracking of vesicle motility in the cell indicates that transport is often bidirectional, characterized by frequent directional changes. However, the mechanisms coordinating the collective activities of oppositely-oriented motors bound to the same cargo are not well understood. To examine motor coordination, we purified neuronal transport vesicles and analyzed their motility using automated particle tracking with nanometer resolution. The motility of purified vesicles reconstituted in vitro closely models the movement of Lysotracker-positive vesicles in primary neurons, where processive bidirectional motility is interrupted with frequent directional switches, diffusional movement and pauses. Quantitative analysis indicates that vesicles co-purify with a low number of stably-bound motors: 1–5 dynein and 1–4 kinesin motors. These observations compare well to predictions from a stochastic tug-of-war model, where transport is driven by the force-dependent kinetics of teams of opposing motors in the absence of external regulation. Together, these observations indicate that vesicles move robustly with a small complement of tightly-bound motors, and suggest an efficient regulatory scheme for bidirectional motility where small changes in the number of engaged motors manifest in large changes in the motility of cargo.

Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

“…It has been shown that in general, the two types of opposite motors are attached at the same time on the cargo [388,156]. Then two scenarios can be considered [151,327,40] (Fig.…”

“…As a result, the cargo will go back and forth, possibly performing large (compared to the typical motor step size) excursions in each direction [156]. An experimental observation in favour of this scenario was made on endosomes which were found to be elongated when pausing [351].…”

“…In order to include these factors, one may not start from purified motors, but directly work with the whole complexes obtained from cell extracts, as done for example in [33,245] or [156] in semi in vitro experiments.…”

Segmentation of 3D Trajectories Acquired by TSUNAMI Microscope: An Application to EGFR Trafficking

“…4 F). The short-slow run represents motors engaged in a tug-of-war between oppositely directed molecular motors attached to the same cargo (87,88). The long-fast run (~4 mm displacement and 3 s duration, such as the movement within 305 to 308 s in phase III, Fig.…”

Multidirectional Activity Control of Cellular Processes by a Versatile Chemo‐optogenetic Approach

“…A model of a stochastic “tug‐of‐war” that describes the mechanical competition between antagonistic motors bound to the same cargo has been proposed 15. Small changes in the number of active motors lead to significant changes in the net direction of cargo motility 16. In our study, the extra force generated by the recruitment of additional kinesin or dynein motors outcompetes the force generated by the endogenous motors, thereby enforcing cargo transport toward the cell periphery or toward the cell center (Supporting Information, Figure S13).…”