Slow axonal transport

De Waegh, S. M., Lee, V. M.-Y. and Brady, S. T. Local modulation of neurofilament phosphorylation, axonal caliber, and slow axonal transport by myelinating Schwann cells. Cell 68 451-463,1992. 

DISCOVERY AND CONCEPTUAL DEVELOPMENT OF FAST AND SLOW AXONAL TRANSPORT 486... 

Axonal growth and regeneration are limited by rates of slow axonal transport 494... 

FIGURE 28-5 Schematic illustration of the movement of cytoskeletal elements in slow axonal transport. Slow axonal transport represents the movement of cytoplasmic constituents including cytoskeletal elements and soluble enzymes of intermediary metabolism at rates of 0.2-2 mm/day which are at least two orders of magnitude slower than those observed in fast axonal transport. As proposed in the structural hypothesis and supported by experimental evidence, cytoskeletal components are believed to be transported down the axon in their polymeric forms, not as individual subunit polypeptides. Cytoskeletal polypeptides are translated on cytoplasmic polysomes and then are assembled into polymers prior to transport down the axon in the anterograde direction. In contrast to fast axonal transport, no constituents of slow transport appear to be transported in the retrograde direction. Although the polypeptide composition of slow axonal transport has been extensively characterized, the motor molecule(s) responsible for the movement of these cytoplasmic constituents has not yet been identified. 

Cytoplasmic and cytoskeletal elements move coherently at slow transport rates. Two major rate components have been described for slow axonal transport, representing movement of cytoplasmic constituents including cytoskeletal elements and soluble enzymes of intermediary metabolism [3]. Cytoplasmic and cytoskeletal elements in axonal transport move with rates at least two orders of magnitude slower than fast transport. 

Axonal growth and regeneration are limited by rates of slow axonal transport. The rate of axonal growth during development and regeneration of a nerve is roughly... 

Properties of slow transport suggest molecular mechanisms. Information about mechanisms of slow axonal transport is relatively limited. They are energy-dependent and require an intact axonal cytoskeleton. Indirect evidence suggests that MTs play a critical role, because transport of NFs can be pharmacologically uncoupled from MT transport without eliminating slow transport [33]. In contrast, all agents that disrupt MTs appear to block slow transport of all components. While this does not rule out a role for the MF cytoskeleton in slow transport movements, MTs appear to provide motive force for other elements of the cytoskeleton. 

Baas, P. W. and Brown, A. Slow axonal transport the polymer transport model. Trends Cell Biol. 7 380-384,1997. 

Brown, A. Live-cell imaging of slow axonal transport in cultured neurons. Methods Cell Biol. 71 305-323,2003. 

Gold, B. G., Griffin, I. W. and Price, D. L. Slow axonal transport in acrylamide neuropathy different abnormalities produced by single-dose and continuous administration. /. Neurosci. 5 1755-1768,1985. 

Shah, J. V., Cleveland, D. W. Slow axonal transport fast motors in the slow lane. Curr. Opin.Cell Biol. 2002,14 58-62. 

Slow axonal transport involves primarily components of the cytoskeleton and its protein precursors. Slow transport can be resolved into two rates, one of less than lmm/day and one of several mm/day. Components traveling at the slower rate include tubulin and its associated proteins, along with a group of three other structural proteins known as the neurofilament triplet. Components traveling at the faster rate include some tubulin, as well as actin and various soluble enzymes. It has been noted that the rate of rapid transport is constant in an animal over a range of... 

Vallee RB, Bloom GS (1991) Mechanisms of fast and slow axonal transport. In Annu. Rev. Neurosci. 14 59-92... 

Terada, S., et al. Visualization of Slow Axonal Transport in Vivo. Science, 1996, 273, 784-788. 

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