Nerve growth factor, NGF, is a protein which is involved in the development and maintenance of the sensory and sympathetic nervous systems. Most of our information concerning the biochemical and biological properties of this important protein is derived from studies on NGF found in the mouse salivary gland, and high concentration source for NGF. Although NGF is believed to play a role in many species, including humans, the salivary gland is unlikely to be the source of NGF since NGF is not found in the glands of most animals. No universal source of NGF has been identified and the possibility exists that numerous tissues in vivo synthesize NGF in low concentrations. Since the mouse salivary gland is unique in having such high concentrations of NGF, are the properties of NGF produced in this gland applicable to NGF produced elsewhere? To answer this question, NGF synthesized by several non-salivary gland sources will be studied. Numerous types of cells synthesize NGF in vitro and cell culture systems will be used to study non-salivary gland NGF. Our recent results indicate that fibroblast cells produce two new forms of NGF. The biochemical and biological properties of these new fibroblast NGF molecules will be studied using biochemical techniques (column chromatography, immunoaffinity columns, polyacrylamide gel electrophoresis) coupled with specific NGF radioimmunoassays. Several types of cells in culture (fibroblast, glial, muscle) synthesize NGF and this project will determine if they all produce similar molecules. Cells from different species will be studied in order to establish similarities or differences among NGF molecules seen in various animals. Human NGF will be examined in normal fibroblasts and in fibroblasts taken from patients with neurofibromatosis, a disease in which changes in NGF have been reported. This project will therefore compare NGF from different cell types, different animals, and in normal versus diseased situations. The properties of NGF precursor molecules will be examined using a cell-free translation system directed with fibroblast cell RNA. NGF precursor molecules may be more readily studied in this system since fibroblasts lack a protein believed to be involved in cleaving an NGF precursor molecule. Immunocytochemical studies on the mouse salivary gland will establish the cellular location for each of the subunits of the NGF molecule. Results from this study will provide additional insight into the possible functional role of this molecule.
