A resident Golgi protein is excluded from peri-Golgi vesicles in NRK cells

To understand the structure and the function of the Golgi apparatus, it is essential to establish how resident Golgi enzymes are localized in only a few Golgi cisternae. In particular it is crucial to establish whether Golgi enzymes are retained specifically in cisternae, or if they are continuously transported from cisterna to cisterna. Here we report that a resident Golgi enzyme is largely excluded from peri-Golgi transport vesicles in normal rat kidney cells, a cell type in which conflicting results have been reported. Analysis of the lateral distribution of two markers within Golgi cisternae led to the same conclusion: a protein incorporated in vesicles (KDEL receptor) is concentrated at the rims of cisternae where vesicles form, while mannosidase II is not. These results suggest that localization of resident Golgi enzymes is achieved primarily by selective retention within cisternae and exclusion from transport vesicles. These observations cannot easily be reconciled with the vision of rapidly maturing Golgi cisternae as the principal means of intra-Golgi transport.