Heterologous desensitization of EGF receptors and PDGF receptors by sequestration in caveolae

Epidermal growth factor(EGF) and platelet-derived growth factor (PDGF) receptors have beenreported to signal via caveolin-containing membranes called caveolae.In contrast, others report that EGF and PDGF receptors are exclusivelyassociated with caveolin-devoid membranes called rafts. Our subcellularfractionation and coimmunoprecipitation studies demonstrate that, inthe absence of ligand, EGF and PDGF receptors are associated withrafts. However, in the presence of ligand, EGF and PDGF receptorstransiently associate with caveolae. Surprisingly, pretreatment ofcells with EGF prevents PDGF-dependent phosphorylation of PDGFreceptors and extracellular signal-regulated kinase (ERK) 1/2 kinaseactivation. Furthermore, cells pretreated with PDGF preventEGF-dependent phosphorylation of EGF receptors and ERK1/2 kinaseactivation. Radioligand binding studies demonstrate that incubation ofcells with EGF or PDGF causes both EGF and PDGF receptors to bereversibly sequestered from the extracellular space. Experiments withmethyl--cyclodextrin, filipin, and antisense caveolin-1 demonstratethat sequestration of the receptors is dependent on cholesterol andcaveolin-1. We conclude that ligand-induced stimulation of EGF or PDGFreceptors can cause the heterologous desensitization of the otherreceptor by sequestration in cholesterol-rich, caveolin-containingmembranes or caveolae.