Fig. 4. Electron micrographs of HeLa K44A cells incubated with a CTB-HRP conjugate. In A-D the cells were incubated for 30 minutes at 0°C before fixation and processing for EM. The CTB-HRP conjugate labeling is shown on the cell surface and both in caveolae (A,C) and clathrin-coated pits (B,D). Incubation of the cells with CTB-HRP for 30 minutes at 37°C also labels both caveolae (E) and clathrin-coated pits (F), whereas the labeling of the non-specialized cell surface is strongly reduced. In G-J the cells were induced for mutant dynamin expression before incubation with CTB-HRP for 30 minutes at 37°C. Both caveolae (G,I) and particularly clathrin-coated pits, which were frequent (two- to threefold increase compared with controls), were distinctly labeled (H-J). Bar, 100 nm.
