Figure 2

Pitstop 2 and genistein exhibit specificity toward inhibition of clathrin- and caveolin-mediated endocytosis. The specificity of the inhibitory effects of pitstop 2 and genistein were monitored by measuring the endocytosis of specific markers for caveolin- and clathrin-mediated endocytosis, respectively. Panel (a) shows representative confocal microscopic images of the internalization of cholera toxin B Alexa Fluor 594 (red) into macrophages (DIC images) upon treatment with increasing concentrations of pitstop 2. The macrophage nucleus is stained with DAPI (blue). The extent of internalization of cholera toxin B quantified as cholera toxin B positive puncta per unit area, normalized to untreated cells, is shown in panel (b). Data represent means ± S.E. of at least 5 independent experiments. Panel (c) shows representative confocal microscopic images of the internalization of transferrin Alexa Fluor 568 into macrophages upon treatment with increasing concentrations of genistein. Panel (d) shows the extent of internalization of transferrin quantified as the number of transferrin positive puncta per unit area, normalized to untreated cells. Data represent means ± S.E. of at least 5 independent measurements. The scale bar represents 10 μm. See Materials and Methods for more details.