58,000 Dalton Intermediate Filament Proteins of Neuronal and Nonneuronal Origin in the Goldfish Visual Pathway

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Abstract
A group of proteins in the goldfish optic nerve with a MW of 58 k Daltons (K) was analyzed by two-dimensional gel electrophoresis. Results show the proteins are differentially phosphorylated and found exclusively in a cytoskeletal-enriched fraction. The proteins from this fraction can be reconstituted into typical intermediate filament structures, as shown by EM. Two components which are of neuronal origin are transported within the slow phase of transport. The 58K proteins are the most abundant proteins in the optic nerve, and they are distinct from actin and tubulin. They are intermediate filament proteins. Cytoskeletal preparations of rat spinal cord, rat optic nerve and goldfish optic nerve were compared by one-dimensional gel electrophoresis. The rat spinal cord contains glial fibrillary acidic protein (GFAP), and the rat optic nerve contains vimentin and GFAP, in addition to the neurofilament triplet. A typical mammalian neurofilament triplet is not detected in the goldfish optic nerve, while the major cytoskeletal constituent is a 58K band which coelectrophoreses with vimentin in the rat optic nerve by 1-dimensional gel electrophoresis.