Fig. 4. The CT and C2A of synaptotagmin VII are taken up into an internal compartment in PC12 cells. A morphological uptake assay was used to verify the results seen with the radioactive internalization assays. In this case, PC12 cells stably expressing Syt 7 (A,B), CT 7 (C,D) and C2A 7 (E,F) were plated on eight-well slides, surface stained with anti-CD4 antibody at 4°C (A,C,E) and moved to 37°C for 10 minutes (B,D,F). Cells were fixed, and immunofluorescence microscopy was carried out.