Wilson, J. O. | bioRxiv Science

bioRxiv2022

Cholesterol in the cargo membrane reduces kinesin-1 binding to microtubules in the presence of tau

Intracellular cargos are often membrane-bound and transported by microtubule-based motors in the presence of microtubule-associated proteins (MAPs). Whereas increasing evidence reveals how MAPs impact the interactions between motors and microtubules, critical questions remain about the impact of the cargo membrane on transport. Here we combined in vitro optical trapping with theoretical approaches to determine the effect of a lipid cargo membrane on kinesin-based transport in the presence of MAP tau. Attaching kinesins to a fluid lipid membrane decreases the inhibitory effect of tau in comparison to membrane-free cargos. Adding cholesterol, which reduces kinesin diffusion in the cargo membrane, amplifies the inhibitory effect of tau on kinesin in a dosage-dependent manner. Our findings can be understood in a framework in which kinesin diffusion in the cargo membrane counteracts binding-site occlusion by tau. Our study establishes a direct link between the physical properties of cargo membrane and MAP-based regulation of kinesin-1.

biophysics↗

bioRxiv2018

Cargo diffusion shortens single-kinesin runs at low viscous drag

Molecular motors are mechanoenzymes that actively drive long-range transport in cells. Thermal diffusion of the cargo can result in mechanical load on the motor carrying the cargo; the direction of this diffusion-based load is not correlated with motor motion. Recent single molecule-based experiments highlighted a strong asymmetric dependence of the run length of the single kinesin-1 motor on load direction, raising the intriguing possibility that thermal diffusion of the cargo may non-trivially influence the run length of the motor carrying the cargo. To test this possibility, here we employed Monte Carlo-based stochastic simulations to evaluate the transport of single-kinesin cargos over a large parameter space of physiologically relevant solution viscosities, cargo sizes, and motor velocities. Our simulations uncovered a previously unexplored, significant shortening effect of cargo diffusion on single-kinesin run length. This effect is non-monotonically influenced by viscous drag force on the cargo, which biases the effect of cargo diffusion toward the hindering direction. The non-monotonic variation of cargo run length with drag force is the direct result of the asymmetric response of kinesins run length to load direction. Our findings may be important for understanding the diverse characteristics of cargo transport, including run length, observed in living cells.

biophysics↗