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

We first determined the localization of the KDEL-R in early spermatids of the mouse since the polarity of the Golgi complex, which is involved in secreting material for the developing acrosome, is very clearly defined in this cell (Fawcett, 1986) . Moreover, the TGN side of the stack, which is directly adjacent to the developing acrosome, has an extremely high concentration of clathrin (Grifliths et al., 1981) . We therefore prepared cryosections of pieces of the seminiferous tubules of the mouse and labeled these with anti-KDEL-R. In these sections, we searched for the early spermatid stages in which the acrosome is beginning to form around the tip of the nucleus of the developing sperm. During these stages, the Golgi complex is extremely pronounced and clearly polarized. The labeling of the Golgi stacks was extensive but essentially all the label was found on membranes at the cis side of the stack (Fig. 1) . The TGN had extremely low levels of labeling. However, in evaluating many Golgi stacks, it was clear that this low level of TGN labeling was much higher than that seen over the matrix of the nucleus, by definition, background.