We will carry out several projects: 1) the high resolution immunoelectron microscopic localization of a number of recently discovered junctional proteins at a variety of membrane - microfilament attachment sites; 2) continued search for integral membrane proteins at these sites, using a monoclonal antibody approach combined with selection by immunocytochemical localization; 3) continued studies of the immunolocalization of phosphotyrosine residues of proteins inside intact cells, using specific monoclonal antibodies generated to phosphotyrosine; 4) the extension of our immunoelectron microscopic studies of the intracellular pathways of serum protein secretion in cultured hepatocytes; and 5) the exploration of the molecular basis for the association which we have demonstrated between the Golgi apparatus and the microtubule organizing center in cells.