Intermediate filaments in nervous tissues

TLDR

Rabbit brain neurofilaments contain four major polypeptides of 200,000, 145,000, 68,000, and 51,000 daltons. Intermediate filaments were isolated from rabbit intradural spinal nerve roots using a modified axonal flotation method that avoids exposure to low ionic strength medium. The purified nerve root filaments are 75–80 % pure, show four major bands at 200,000, 145,000, 68,000, and 60,000 Da, correspond to a triplet of polypeptides (200,000, 145,000, 68,000 Da) with the 51,000‑Da band being glial, and antibodies against the triplet proteins localize to neurons while the 51,000‑Da antibody stains only glia.

Abstract

Intermediate filaments have been isolated from rabbit intradural spinal nerve roots by the axonal flotation method. This method was modified to avoid exposure of axons to low ionic strength medium. The purified filaments are morphologically 75-80 percent pure. The gel electrophoretogram shows four major bands migrating at 200,000, 145,000, 68,000, and 60,000 daltons, respectively. A similar preparation from rabbit brain shows four major polypeptides with mol wt of 200,000 145,000, 68,000, and 51,000 daltons. These results indicate that the neurofilament is composed of a triplet of polypepetides with mol wt of 200,000, 145,000, and 68,000 daltons. The 51,000-dalton band that appears in brain filament preparations as the major polypeptide seems to be of glial origin. The significance of the 60,000- dalton band in the nerve root filament preparation is unclear at this time. Antibodies raised against two of the triplet proteins isolated from calf brain localize by immunofluorescence to neurons in central and peripheral nerve. On the other hand, an antibody to the 51,000-dalton polypeptide gives only glial staining in the brain, and very weak peripheral nerve staining.