Association of an axonally transported polypeptide (H) with 100-A filaments. Use of immunoaffinity electron microscope grids.

Abstract

Polypeptide H (MW 195,000) is axonally transported in rabbit retinal ganglion cells at a velocity of 0.7-1.1 mm/day, i.e., in the most slowly moving of the 5 transport groups described in these neurons. To identify the organelle associated with H, antibodies were prepared against H. The antibodies were adsorbed onto Formvar-coated EM grids. The immuno-affinity grids were incubated with extracts of spinal cord and examined by EM. They contained as many as 100 times more 100-.ANG. filaments than grids coated similarly with nonimmune IgG. The ability of the anti-H IgG to specifically adsorb filaments to grids was completely blocked by incubating the IgG with polypeptide H. The 100-.ANG. filaments adsorbed to anti-H immunoaffinity grids was specifically decorated by incubating them with anti-H IgG. H-antigens (and most likely H itself) apparently are associated with 100-.ANG. neurofilaments. The use of immunoaffinity grids may be a useful approach for determining the organelle associations of polypeptides.