Novel NGF‐induced proteins in PC12 cells: Immunological evidence for their presence in brain nerve endings using a single monoclonal antibody

A monoclonal antibody, S‐11D9, detected a group of novel polypeptides whose expression was induced 6 hr after incubation of PC12 cells with nerve growth factor. The antigens also were visualized by immune precipitation and Western blotting in synaptic vesicles, clathrin‐coated vesicles, and synaptic plasma membrane prepared from bovine brain. A large polypeptide was detected on the synaptic plasma membrane; an intermediate size protein was visualized on the plasma membrane and on both synaptic and clathrin‐coated vesicles, while a smaller molecule was found only on brain Golgi‐enriched membrane preparations. Immunofluorescence labeling with S‐11D9 on nerve growth factor‐stimulated PC12 cells showed the antigens distributed in the cytoplasm and concentrated in discrete areas on the tip of most neurites. The particular distribution of these proteins in vesicles and synaptic plasma membrane and the finding that the different antigens share a common epitope recognized by a single monoclonal antibody open the possibility that these molecules are related markers for organelle transport pathways in nerve cells.