Figure 1.

MHCI and Tac enter cells in endosomes distinct from those carrying clathrin-derived cargo and then later merge. (A) Untransfected HeLa cells and those transfected with Tac were allowed to internalize surface-bound anti-MHCI or anti-Tac antibodies, respectively, along with soluble DiI-LDL (10 μg/ml) for 5 and 20 min at 37°C in complete media. Black and white inset at 20 min shows fluorescently labeled structures for each cargo with colocalized structures indicated by yellow arrows. (B) Untransfected and transfected cells expressing either Tac-LL or Tac were allowed to internalize soluble transferrin or DiI-LDL with antibodies to MHCI or Tac for 5 min at 37°C. For both A and B, at the end of the 37°C incubation, surface associated antibodies and DiI-LDL or transferrin were then removed with acid wash, cells were fixed, and internalized antibodies were labeled with fluorescently conjugated secondary antibodies. Bar, 10 μm