The Effect of Tau on Dynamics of Kinesin Motor

Kinesin-1 is a motor protein that can perform cargo transport in cells by moving processively on microtubules towards the plus end. Tau, which is expressed at high levels in axons of neurons, is a microtubule-associated protein and can diffuse one-dimensionally on microtubules. It has been shown experimentally that tau can affect the motility of the kinesin motor. Here, an analytical theory is presented for the effect of the diffusive tau on the velocity and run length of the kinesin motor. With no or only one adjustable parameter, which depends on the experimental condition, the theoretical results are in good agreement with the available experimental data. It is found that at a large tau/tubulin ratio, tau has a large effect on the run length of the kinesin motor, with the run length depending sensitively on the diffusion constant of tau. This indicates that the kinesin-based axonal transport could be regulated by the variation of either the concentration or diffusion constant of tau, giving an explanation of why tau can diffuse on microtubules.