This project seeks to analyze the molecular leading to the formation of synaptic structures in muscle cells. The approach we have taken to this problem is to construct a simplified system in a non-muscle cell line. We transfected CHO cells with all four cDNA's for mouse muscle acetylcholine receptor (AChR), and have isolated clonal CHO lines which appear to express surface AChR. We intend to use these cells to investigate four broad questions. 1. What are the differences between AChR synthesis, assembly and transport in C2 muscle cells and in non-muscle cell line? Is all necessary information for the normal occurrence of these processes contained within the structural genes of the AChR? 2. Do these processes occur when only one, two, or three subunits are present? 3. Can AChRs in a non-muscle cell be made to cluster by exogenous factors added directly or secreted by nerve cells in co-culture? 4. How are assembly, transport, and clustering affected by the introduction of the 43 kDa protein, which is normally associated with the AChR in muscle cells? These questions are of interest from three perspectives. First, they will lead to a better general understanding of the assembly and behavior of oligomeric membrane proteins. Second, because the AChR is a member of a superfamily of ligand-gated receptors that includes receptors for the major receptors of the CNS, these experiments will have particular significance for the expression of oligomeric receptors in neuronal cells. Finally, because the AChR is the primary site of attack in the disease, myasthenia gravis, it is important to know how the amount and distribution of this protein is regulated.
