Destinations of Some Fast‐Transported Proteins in Sensory Neurons of Bullfrog Sciatic Nerve

Abstract

Many characteristics of proteins that are fast axonally transported have been described, but the destinations of most within the neuron remain unknown. We have studied the destinations of some fast-transported proteins in sensory neurons of the bullfrog sciatic nerve, specifically to determine which may be deposited in axons and which may be destined for more distal, possibly terminal, areas. Dorsal root ganglia were pulse-labeled with [35S]methionine in vitro, following which they were separated from the sciatic nerve. After additional periods of transport, radioactive proteins from two areas of the nerve were separated by two-dimensional polyacrylamide gel electrophoresis and used to develop x-ray film. The first area contained the wavefront of transported radioactivity (wavefront region), whereas the second area was taken from nerve through which the wavefront had already passed (plateau region). The amount of radioactivity in certain fast-transported protein species from each area was determined by computer analysis of digitized video images of fluorographs. Certain proteins were preferentially left behind the wavefront and, therefore, may supply axon and possibly other nerve components, whereas other proteins were found almost exclusively in the wavefront and, hence, may supply more distal, possibly terminal, areas.

A Fast Axonally Transported Protein of the Frog Sciatic Sensory Axons Undergoes Similar Qualitative Changes During Regeneration In Vitro and In Vivo

“…Several previous studies have dealt with quantitative alterations in fast transported proteins after amphibian sciatic nerve injury (Perry and Wilson, 198 1;Tedeschi and Wilson, 1983;Perry eta]., 1987b;Rulli and Wilson, 1987;Edbladh et al, 1990;Edstrom et al, 1990). In common with these, the present results suggest the absence of dramatic quantitative changes of proteins in such nerves.…”

Acrylamide‐Induced Increases in Deposition of Axonally Transported Glycoproteins in Rat Sciatic Nerve

“…The first two possible explanations relate to the fact that axonally transported macromolecules must be unloaded from the transport vector when they reach their appropriate destinations. It is known that different axonally transported proteins have different sites of deposition within neurons (e.g., Goodrum and Morell, 1982;Toews et al, 1982;Stone et al, 1984;Rulli and Wilson, 1987) and differences in the degree of unloading of different classes of transported lipids have also been demonstrated (Blaker et al, 1981;Toews et al, 1983Toews et al, , 1988Droz et al, 1985). Our present findings of attenuation of the crest of rapidly transported glycoproteins and a decrease in the amount of labeled glycoproteins cleared from the axons, suggest that acrylamide treatment brings about an increase in the unloading or deposition of axonally transported glycoproteins.…”

Three subpopulations of fast axonally transported retinal ganglion cell proteins are differentially trafficked in the rat optic pathway

“…We have designated these as class III FT proteins. Quantitative analyses have shown that the longer the length of axon, the greater the percentage of fasttransported proteins destined for axon deposition (Grafstein, 1967;Rulli and Wilson, 1987;Cancalon andBeidler, 1975, 1977). How do members of the class III FT proteins localize predominantly to axons?…”

“…This presumption has been supported by experimental investigations demonstrating selective localization of some rapid axonally transported proteins to axons or terminals (for review see Smith and Snyder, 1992). Specifically, some rapidly transported proteins have been found to translocate preferentially as moving phase species (presumably destined for terminals) while other rapidly transported proteins have been found to enter a relatively stationary phase (presumably destined for deposition in axons) (Cancalon andBeidler, 1975, 1977;Stone et al, 1984;Rulli and Wilson, 1987;Li et al, 1996a,b). Quantitative analyses have suggested that the longer the length of the axon, the greater the percentage of fast-transported proteins destined for axon deposition (Grafstein, 1967;Rulli and Wilson, 1987;Cancalon andBeidler, 1975, 1977).…”

“…Specifically, some rapidly transported proteins have been found to translocate preferentially as moving phase species (presumably destined for terminals) while other rapidly transported proteins have been found to enter a relatively stationary phase (presumably destined for deposition in axons) (Cancalon andBeidler, 1975, 1977;Stone et al, 1984;Rulli and Wilson, 1987;Li et al, 1996a,b). Quantitative analyses have suggested that the longer the length of the axon, the greater the percentage of fast-transported proteins destined for axon deposition (Grafstein, 1967;Rulli and Wilson, 1987;Cancalon andBeidler, 1975, 1977). Since the majority of these studies employed long-axon systems with diffuse terminals, moving-phase axonally transported proteins could only be inferred as terminal-directed species (Cancalon andBeidler, 1975, 1977;Stone et al, 1984).…”