Fig. 1.

The insulin receptor (IR) is located in membrane microdomains enriched in cholesterol. A: representative confocal immunofluorescence of a single confocal slice of the IR, epidermal grwoth factor receptor (EGFR), and c-Met receptors (each receptor was labeled in green at left) and GM1 ganglioside labeled in red (middle) in HepG2 cells. Merged images show colocalization of IR and EGFR with GM1 but not c-Met with GM1 (right). B: quantification of fluorescence intensity on regions of interest, as represented by the tiny white squares in A. Superposition of the peaks indicates colocalization of green and red structures. (At least 20 slices from 30 cells of each group were individually analyzed). C: single confocal plane images of rat hepatocytes labeled for IR in green and GM1 in red (top) and z-stack images of the same cells (bottom). Merged images show colocalization of IR with GM1. D: high-resolution images of 3 regions of interest showing colocalization of green (IR) and red (GM1) structures. E: quantification of fluorescence intensity on delimited membrane regions of interest selected from several single slices of the merged images represented on D (representative small squares). Superposition of the peaks indicates colocalization of green and red structures. (At least 20 slices from 30 cells imaged of each group were individually analyzed). Scale bar = 10 µM.