Chapter 9 Fast axonal transport: recent developments

Publisher Summary Fast axonal transport carries membranous organelles inside axons, both away from (anterograde transport) and toward (retrograde transport) the cell body. This chapter describes recent progress made in understanding the molecular mechanisms of fast axonal transport. It also discusses some properties of fast axonal transport that have received relatively little attention, but that may be important for fully understanding the mechanisms of transport. There are at least five waves of materials that move by axonal transport in the anterograde direction. These waves differ in their velocity and have different protein compositions. They apparently reflect the movement of different types of organelles. Whereas cytoplasmic materials move in the slowest components of transport, membranous organelles all move in the fastest two components. The very fastest component contains vesicular precursors of plasma membrane, synaptic vesicles, and smooth endoplasmic reticulum and moves with a maximum velocity of 410 mm/day. In most radiolabeling experiments, this component has been studied as fast axonal transport. Fast axonal transport can be detected by radioactively labeling the transported materials, by observing the accumulation of transported materials at an injury, or by trapping endogenous materials at a cold block and then observing their movement upon rewarming.