Fig. 4. Vault aggregation in normal normal human vascular endothelial cells (HUVECs) and the HeLa cancer cell line. HUVECs were incubated at 37°C for 30 min in the presence (A) or absence (B) of 0.5 mmol l^–1 K₂TeO₃ and subsequently stained with antibodies against MVP (red) and tubulin (green). MVP aggregates form at the cell periphery in HUVECs (arrows). In addition, HeLa cells were incubated at 37°C for 30 min in the presence or absence of 0.5 mmol l^–1 K₂TeO₃ and subsequently stained with tubulin and MVP antibodies (C–G). HeLa cells were subsequently washed three times in fresh medium without tellurite and incubated for an additional 24 h, fixed and processed for immunofluorescence. Accumulation of MVP at the cell periphery of HeLa cells is reversible. The MVP aggregates at the cell periphery (arrows, D) in the tellurite-treated cells are absent after a 24-h recovery period (E). In addition, the cell number has doubled in both the treated and untreated cultures. Occasionally, brightly-staining puncta form in response to tellurite treatment (asterisks). These bright MVP puncta are different from the MVP aggregates at the cell periphery in that these puncta stain with both MVP and tubulin. Bar, 20 µm.