Direct interaction of microtubule- and actin-based transport motors

The microtubule network is thought to be used for long-range transport of c ellular components in animal cells whereas the actin network is proposed to be used for short-range transport(1), although the mechanism(s) by which t his transport is coordinated is poorly understood. For example, in sea urch ins long-range Ca2+-regulated transport of exocytotic vesicles requires a m icrotubule-based motor, whereas an actin-based motor is used for short-rang e transport(2), In neurons, microtubule-based kinesin motor proteins are us ed for long-range vesicular transport(3) but microtubules do not extend int o the neuronal termini, where actin filaments form the cytoskeletal framewo rk(4), and kinesins are rapidly degraded upon their arrival in neuronal ter mini(5), indicating that vesicles may have to be transferred from microtubu les 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 the se complexes were functional, they also contain kinesin light chains and th e localization of MyoVA and KhcU overlaps in the cell, These results indica te that cellular transport is, in part, coordinated through the direct inte raction of different motor molecules.