Proteins synthesized in goldfish retinal ganglion cells and rapidly transported to the terminals of regenerating optic nerves were analyzed by two-dimensional (2-D) gel electrophoresis. Among the rapidly transported components, the most dramatic change observed during regeneration was for a family of polypeptides having molecular weights between 44,000 and 49,000 (44-49K) and isoelectric points of 4.6 to 4.9. Studies using [35S]methionine as a metabolic precursor in the eye showed that these proteins are present in both membranous and soluble fractions of the optic tectum, particularly during early stages of regeneration. Contralateral visual pathways, left intact to serve as controls, showed only very low levels of the proteins. These labeling changes were quantified in double-isotope studies, in which proteins from intact and regenerating sides were differentially labeled with [3H]proline and [14C]proline, comigrated on 2-D gels, and then counted for 3H/14C ratios. The labeling change for the 44-49K acidic proteins relative to the intact state was found to be over 100-fold in some day 19 regeneration samples and about 30-fold on day 40. Silver-stained gels of a tectal membrane fraction also revealed increased levels of the 44-49K acidic proteins during regeneration, indicating that the observed synthetic changes are accompanied by a net accumulation of the proteins.

Benowitz, L., & Lewis, E. (1983). Increased transport of 44,000- to 49,000-dalton acidic proteins during regeneration of the goldfish optic nerve: a two-dimensional gel analysis. The Journal of Neuroscience, 3(11), 2153–2163.