Insights into secretory and endocytic membrane traffic using green fluorescent protein chimeras.

Green fluorescent fusion proteins, which can be visualized in the unperturbed environment of a living cell, have become important reporter molecules for studying protein localization and trafficking within secretory and endocytic membranes of living cells. They have been used in a wide variety of applications, including time-lapse imaging, double-labeling and photobleach experiments. Results from such work are clarifying the steps involved in the formation, translocation and fusion of transport intermediates, are defining the roles for microtubules in membrane transport, and are providing insights into the mechanisms of protein retention and localization within organelles. In so doing, they have changed our thinking about the temporal and spatial relationships between subcellular membrane structures and the morphogenesis of secretory and endocytic organelles.