Journal of Neuroscience, Vol 7, 792-806, Copyright © 1987 by Society for Neuroscience
Fast axonally transported proteins in regenerating goldfish optic axons
GW Perry, DW Burmeister and B Grafstein
Fast axonal transport of protein was examined in regenerating goldfish
optic axons after a lesion of either the optic tract or optic nerve, which
revealed changes in the original intact optic axon segments or in the newly
regenerated axon segments, respectively. In animals killed either 6 or 24
hr after injection of 3H-proline into the eye, labeling of total
fast-transported protein in the original axon segments was increased by 2 d
after the lesion, reached a peak of nearly 20 X normal at 2 weeks, and then
declined to a level somewhat above normal at 12 weeks. When the labeling of
individual transported proteins was examined by 2-dimensional gel
electrophoresis, it was found that no new labeled proteins appeared during
regeneration, but all proteins examined showed an increase in labeling.
Among the various proteins, there was great variation in the magnitude and
time course of the labeling increase. The largest increase, to nearly 200 X
normal with 6 hr labeling, was seen in a protein with a molecular weight of
45 kDa and a pl of about 4.5, resembling a protein that has previously been
designated a "growth-associated protein" (GAP-43; Skene and Willard,
1981a). The proteins showing increased labeling included a small fraction
of cytoskeletal proteins (alpha-tubulin, beta-tubulin, and actin) that was
apparently transported at a much faster rate than is usually expected of
these constituents. In the new axon segments, the total protein labeling
was increased by 1 week after the lesion, remained elevated at a nearly
constant level of about 7 X normal from about 2 to 5 weeks, and then
declined to levels somewhat above normal by 12 weeks. The 45 kDa protein
again showed the largest increase, and became the single most prominently
labeled constituent in the new axons. On the basis of the time course of
labeling in both original and new axon segments during regeneration, the
fast-transported proteins were tentatively separated into 5 classes that
may represent groups of proteins that are coregulated during regeneration.
They may conceivably correspond to different functional or structural
entities within the neuron.
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