The cell is a highly organized and dynamic structure. Most proteins are found exclusively in one compartment of the cell and are only transported to other locations as a result of intra- or extra-cellular signaling pathways. For the most part, proteins are synthesized in the cytoplasm and targeted either co- or post-translationally to their particular destination. Recently, an increasing number of human diseases have been attributed to mutations which result in the mistargeting of essential proteins. The signals responsible for the targeting membrane proteins in the biosynthetic and endocytic pathways are of particular interest to my laboratory. In addition to studying the basic cell biology of protein trafficking within the cell, we have begun to examine the trafficking and function of the protein implicated in hemochromatosis, the most common hereditary disease of people of European ancestry. Malfunctioning of this protein results in the abnormal accumulation of iron in the body. Iron uptake into the body is highly regulated. Although it is essential for life, too much iron is toxic and results in heart failure, adult onset diabetes, arthritis, and cirrhosis of the liver. We are examining the intracellular trafficking of this protein and how it participates in the control of iron uptake and egress.