Figure 5.
In epithelial cells p27BBP/eIF6 distribution is similar to the one of β4 integrin and is present in hemidesmosomes and desmosomes. (A–E) The 804G clone A cell line that expresses human β4 integrin and forms hemidesmosomes in vitro was double-labeled for β4 integrin (A, A′, and D) and p27BBP/eIF6 (B, B′, and C), and the results were analyzed in the confocal microscope (E). In horizontal sections (x, y), β4 integrin staining is concentrated in the Swiss cheese pattern formed by hemidesmosome rosettes (A and D). The labeling generated by the p27BBP/eIF6 antiserum yields a pattern similar and superimposable to that of β4 (B and C). In vertical sections (x, z) part of p27BBP/ eIF6 is observed at the basal surface of epithelial cells, where β4 is localized. Note that both β4 and p27BBP/eIF6 stainings are excluded from the small circular areas characterizing the Swiss cheese pattern (A′ and B′). Bar, 10 μm. (F–I) Electron microscopy studies were performed on ultracryosections of human amnion immunolabeled with p27BBP/eIF6 antiserum (F and I) or double-immunolabeled with both anticytokeratins (15-nm gold beads) and p27BBP/eIF6 antiserum (5-nm gold beads) (G and H). The basal cytoplasm of amnion epithelial cells contains a large number of hemidesmosomes, especially in the distal portions of basal cell foot processes. As shown in F and H, p27BBP/eIF6 is localized in the innermost plaque of hemidesmosomes (arrowheads) in a region composed of a discrete network of thin filaments between the dense plaque and the intermediate filaments. p27BBP/eIF6 immunolabeling is also detected throughout the cytoplasm associated with thin filaments, which are adjacent to intermediate filaments, stained with anticytokeratin (G and H, arrows). p27BBP/eIF6 is also present in the cytoskeletal filament network that converges upon desmosomes (I). Bars, 0.125 μm (F); 0.1 μm (G and H); and 0.08 μm (I).