More is known about the neuromuscular synapse than any other synapse. Its geometrical simplicity and experimental accessibility have provided us with a relatively detailed account of what a synapse looks like and how a synapse functions. We remain, poorly informed about the biochemical events involved in the formation and maintenance of this highly specialized and organized region of cell-to-cell contact. An understanding of how synapses form both during development and during regeneration in the adult nervous system will provide important information not only for synapse formation in the peripheral nervous system, but also for the presently less tractable analysis of synapse formation in the central nervous system. This proposal is concerned with further characterization of two proteins which we have identified as components of the postsynaptic membrance at nerve-muscle synapses. The function of these proteins is unknown, but their location at the synapse suggests that they may have a role in the formation and/or maintenance of the synapse. We will use antibodies against one of these proteins (270kd) to determine whether it is restricted to synaptic sites, when it appears during synapse formation, its ultrastructural location, whether it interacts with other synaptic proteins and whether it is present at nerve-nerve synapses. We will continue to characterize cDNA clones encoding the other synaptic protein (43 kd) in order to study the structure of this protein, to further study its interaction with the postsynaptic membrane and to determine the function of this protein. We will develop methods of introducing anti-sense acetylcholine receptor RNA into developing Xenopus embryos to assess the feasibility the disrupting synapse formation by deleting synaptic proteins.
