Kinesins in the nervous system

Both the development and the maintenance of neurons require a great deal of active cytoplasmic transport. Much of this transport is driven by microtub ule motor proteins. Membranous organelles and other macromolecular assembli es bind motor proteins that then use cycles of adenosine 5'-triphosphate hy drolysis to move these 'cargoes' along microtubules. Different sets of carg oes are transported to distinct locations in the cell. The resulting differ ential distribution of materials almost certainly plays an important part i n generating polarized neuronal morphologies and in maintaining their vecto rial signalling activities. A number of different microtubule motor protein s function in neurons; presumably they are specialized for accomplishing di fferent transport tasks. Questions about specific motor functions and the f unctional relationships between different motors present a great challenge. The answers will provide a much deeper understanding of fundamental transp ort mechanisms, as well as how these mechanisms are used to generate and su stain cellular asymmetries.