Direct interaction of microtubule- and actin-based transport motors

The microtubule network is thought to be used for long-range transport of cellular components in animal cells whereas the actinnetwork is proposed to be used for short-range transport1, although the mechanism(s) by which this transport is coordinated is poorly understood. For example, in sea urchins long-range Ca2+-regulated transport of exocytotic vesicles requires a microtubule-based motor, whereas an actin-based motor is used for short-range transport2. In neurons, microtubule-based kinesin motor proteins are used for long-range vesicular transport3 but microtubules do not extend into the neuronal termini, where actin filaments form the cytoskeletal framework4, and kinesins are rapidly degraded upon their arrival in neuronal termini5, indicating that vesicles may have to be transferred from microtubules to actin tracks to reach their final destination. Here we show that an actin-based vesicle-transport motor, MyoVA (ref. 6), can interact directly with a microtubule-based transport motor, KhcU. As would be expected if these complexes were functional, they also contain kinesin light chains and the localization of MyoVA and KhcU overlaps in the cell. These results indicate that cellular transport is, in part, coordinated through the direct interaction of different motor molecules.