Kinesin-2's Neck-Linker is Critical to Navigating Obstacles on the Microtubule Surface More Efficiently Than Kinesin-1

Abstract

A number of cargo during intracellular transport are known to be bound to both kinesin-1 and kinesin-2, but the advantage of having two similarly plus-end directed motors on a single cargo is not clear. Kinesin-1 is known to be sensitive to alterations in the microtubule track, including those arising from post-translational modifications, changes in nucleotide state, and the presence of microtubule associated proteins (MAPs) such as Tau. Less is known about effects of microtubule lattice modifications on kinesin-2 motility. Kinesin-2, which contains three additional amino acids in its neck-linker compared with kinesin-1, has reduced stepping coordination between motor domains, which decreases its processivity on paclitaxel-stabilized microtubules. We hypothesize these differences in kinesin-2's structure and function allows it to more easily navigate obstacles on the microtubule surface, such as Tau, compared to kinesin-1. To directly test this hypothesis, we used single molecule imaging with TIRF microscopy to measure motility from different kinesin-1 and kinesin-2 neck-linker chimeras stepping along microtubules in the absence or presence of two isoforms of Tau known to differentially affect kinesin-1 motility. Our results demonstrate that kinesin-2, unlike kinesin-1, is insensitive in the presence of either Tau isoform on paclitaxel-stabilized microtubules. Swapping the neck-linkers between kinesin-1 and kinesin-2 resulted in a switch in the sensitivity to Tau between the two motors: the kinesin-1 construct containing a kinesin-2 neck-linker became insensitive to Tau, while the kinesin-2 construct containing a kinesin-1 neck-linker became sensitized to the presence of Tau. Thus, while kinesin-2 is less processive than kinesin-1, it is better optimized through its longer neck-linker to navigate obstacles on the microtubule surface, such as Tau, allowing the two motors to work together for the efficient delivery of cargo in the complex intracellular environment.