Gangliosideshavebeen found toreside inglycosphingolipid-enriched microdomains (GEM) of the plasma membrane and to be involved in the regulation of epidermal growth factor receptor (EGFr or ErbB1) gain further insight into the mechanisms involved in EGFr modulation by gangliosides, we investigated the distribution of EGFr family members in the plasma membrane of CHO-K1 cells, which were genetically modified to express different gan-glioside molecules or depleted of glycolipids.