In this project we will to apply various cellular imaging and molecular biological techniques (light and electron microcopy, live cell imaging, fluorescent protein constructs) to investigate the spatial and functional organization of endomembranes and tra ffic routes in mammalian cells. This joint project is based on recent findings showing that the intermediate compartment (IC) operating at the endoplasmic reticulum (ER)-Golgi boundary, and the endocytic recycling compartment (ERC) are both anchored next to the centrosome, raising the possibility that they functionally interact. Based on these results we intend to re-establish our collaboration to address our previous hypothesis (Saraste and Goud, 2007, Mol. Biol. Cell 18, 1430-36) stating that the biosyn thetic and endocytic membrane networks establish mirror compartments at the cell center, and that this symmetrical organization of endomembranes is a key to understand the membrane rearrangements that occur during cell division, polarization and different iation.