Neurite outgrowth factor (NOF) is a glycoprotein isolated from an extract of gizzard that induces neurite outgrowth from cultured retinal or ciliary ganglionic (CG) neurons. We have reported that a glycoprotein of approximately 82 kD solubilized from gizzard muscles binds to NOF (ligand blotting) and inhibits the neurite promoting activity of NOF (inhibition assay). The 82-kD protein (NOF binding protein) was purified from gizzard muscle membranes as a doublet band on SDS-PAGE and a polyclonal antibody was raised against it. An NOF binding protein in developing retina exhibited the same physicochemical properties as that of the gizzard muscle. Quantitative decrease in NOF binding protein in embryonic retinas was observed after day 11 by the inhibition assay, ligand blotting, and immunoblotting, its decrease being parallel with reduction of NOF-induced neurite outgrowth of embryonic retinas. In an immunohistochemical study, the antibody stained only the optic fiber layers of the retinas of 8-d embryos, and this staining was no longer detectable in retinas of 18-d embryos. These results suggest that the 82-kD protein is a novel membrane protein that behaves as an NOF receptor and that the loss of neuritic response of the retinal neurons to NOF reflects a decrease in NOF receptor molecules.

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