Nerve growth factor (NGF) is necessary for the growth and maintenance of sympathetic and some sensory neurons. Its importance in development, as well as its potential use in wound healing and nerve regeneration, are due to its growth-promoting and chemotactic effects on neurons. NGF has also been implicated in several neurological diseases, for example, neurofibromatosis. The proposed research is aimed at understanding the biosynthesis, processing, and mechanism of action of nerve growth factor. NGF is found in significant quantities as a complex of subunits in both the mouse and in Mastomys natalensis, an African rat. The NGF complex from mouse has three subunits, while the NGF complex from Mastomys has only two. This difference presents a unique opportunity to study the functions and interactions of the components of the complexes. The two subunits of the Mastomys complex are similar to two of the mouse subunits. In mouse, the beta-NGF subunit is processed by the gamma-NGF subunit. However, Mastomys lacks the gamma subunit, containing only subunits similar to mouse alpha-and beta-NGF. The proposed experiments are designed to answer questions concerning the mechanism of beta subunit processing in the gamma-subunit-deficient Mastomys complex. The experiments will also answer questions regarding the lack of enzymatic activity exhibited by the alpha-NGF subunit of both mouse and Mastomys. Other specific results to be gained from this study are a description of possible processing pathways for both Mastomys subunits at both the RNA and protein levels, and production of subunit and processing enzyme precursors. This information will be necessary for future studies on the biosynthesis and assembly of the NGF complex. The methods described here propose to use existing mouse cDNA clones and synthetic oligonucleotides as hybridization probes to select Mastomys NGF subunit clones from a cDNA library. Selected Mastomys clones will be characterized by DNA sequencing, and the sequences compared with mouse sequences. The cDNA clones will also be used to isolate genomic clones and to synthesize NGF protein precursors. The materials and information generated by the this study will add to our knowledge of NGF structure, biosynthesis, and function and will facilitate future research on the mechanism of action of NGF.
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