Localization of the Lys, Asp, Glu, Leu tetrapeptide receptor to the Golgi complex and the intermediate compartment in mammalian cells

The nonclathrin COP vesicles are widely believed to facilitate transport between the ER and the Golgi complex, as well as intra-Golgi transport (Balch, 1990; Rothman and Orci, 1992) . When permeabilized cells or in vitro Golgi fractions are treated with GTPTS, a large increase can be seen in the number of COP-containing buds and/or vesicles (Rothman and Orci, 1992; Duden et al., 1991) . In our recent study, we could show that after GTP3,S treatment of SLO-permeabilized mouse L cells, many of the B-COP-containing vesicular buds were continuous with the membranes of the IC (Krijnse-Locker et al., 1994) . We therefore postulated that these COP vesicles are responsible for the first vesicular transport step in the biosynthetic pathway, a step that mediates transport from the IC to the Golgi compartment, where Man I is expected to be localized.