The plasma membrane of mammalian cells is composed of a great variety of different lipids which are laterally organized into lipid domains. The segregation of lipids into domains has been studied in great detail in vesicles but domain formation of lipids in the plasma membrane of live cells is still unclear. We have previously used fluorescence lifetime imaging microscopy to study the colocalization of the receptor for EGF with the ganglioside GM1 and the GPI-anchored green fluorescent protein. Here we have used this technology to study the effect of EGF on the organization of GM1 in the plasma membrane. Our data show that stimulation of the cell with EGF induces rapidly a strong increase in colocalization of GM1 molecules, suggesting the formation of large lipid domains. These results support the notion that activation of EGFR signaling may result in the formation of signaling platforms.
Keywords: EGF; FLIM; FRET; GM1; lipid rafts.