Table 3.

Distribution of ErbB2 on Endosomes in Cells Treated with Geldanamycin Only or with Geldanamycin and Lactacystin

Distribution of Anti-ErbB2 Labeling (%)
A
B
Experimental Condition
Early EndosomeMVBLimiting MembraneInner Vesicles
AdditiveAntibody
Geldanamycine.c.*28.671.421.678.4
i.c.19.180.97.891.2
Lactacystin + geldanamycine.c.*55.944.161.138.9
i.c.56.443.670.828.2
  • NOTE: SKBr3 cells were preincubated with or without lactacystin (10 μmol/L) for 1 h before geldanamycin (3 μmol/L) was added for 6 h. The cells were then prepared for immunoelectron microscopy and labeled with antibodies e.c.* or i.c. directed against the extracellular or intracellular part of ErbB2, respectively. For each experimental condition, the labeling of ErbB2-positive endosomal compartments within 20 cell profiles was quantified with respect to both type of endosome and localization of ErbB2 within the endosome. A: The numbers of ErbB2-positive early endosome-like compartments and ErbB2-positive multivesicular bodies were counted and are presented as percentage of the total number or ErbB2-positive endosomes under each condition. B: The distribution of the labeling was quantified with respect to localization to the limiting membrane of endosomes or to vesicles within the endosomal lumen. The number of gold particles showing different localization is presented as percentage of the total number of gold particles.

  • Abbreviation: MVB, multivesicular body.