ABSTRACT
This chapter considers methods for studying receptors, endocytosis and the small transfer vesicles which shuttle between organelles. Receptors are concentrated into specialized areas of the plasma membrane, which invaginate to form vesicles which move into the cytosol taking with them molecules bound to the receptors. Receptor-mediated endocytosis has a number of important roles in internalizing molecules which cannot cross the plasma membrane through transport proteins or channels. Nonspecific binding can be determined by addition of an excess of the true ligand or an agonist, which will compete for binding. If the receptor is involved in endocytosis the principles are the same; however, the incubation must be carried out at 0–4°C to prevent internalization. Conventional biochemical methods has therefore been necessary to develop novel systems to investigate the organization of cells and vesicular transfer between organelles. The factors involved in vesicular tranport have been identified using a cell-free reconstituted system based on that developed by Rothman and co-workers.
