The axon is a slender projection of a neuron that conducts electrical impulses to synapses in muscles or other neurons. A number of cellular components such as mitochondria and vesicles are transported along the axon by microtubule-based molecular motors (kinesins and dyneins). The most important factors controlling the axonal transport are the structure and function of the motors involved and the condition of the rails (the microtubule, MT). In the last decade, a compelling evidence has been provided that MTs contain marks (posttranslational modifications, PTMs) that indicate what kind of activity should take place in a given MT segment. These cues are read and interpreted by molecular motors, MAPS and other proteins. Kinesin-1, the major motor that transports cargoes along MTs is a homodimer with a pair of MT-binding sites on each end of the molecule. In some conditions, kinesin-1, besides interacting with MT using its N-terminal motor domains, can also bind another MT by its tail site producing sliding of one MT relative to another. This type of pair sliding can be used to sort MTs in the same way it occurs in the mitotic spindle and also act as an efficient way to move large amounts of tubulin, in the form of short MTs. Both activities have been observed in Drosophila cultured neurons. The effects of PTMs on the interaction of the motor domain with MT are to some extent characterized, but the effects of PTMs in the cargo-MT on the MT pair sliding have never been examined. Currently, we are exploring the impact of two well-known PTMs (detyrosination and polyglutamylation) and one recently reported (polyamination) on MT-MT sliding. To that end, we have developed an assay in which the sliding is observed in vitro and quantified by kymographic analysis. Surprisingly, the velocity of the sliding was highly variable along the track indicating that its efficiency may be sensitive to many cellular and developmental mechanisms. FINANCIAL SUPPORT: Supported in part by NCN Grant 2014/13/B/NZ1/03995.
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