Angiostatin internalization and its migration to mitochondria. (A) Endothelial cells were incubated with hFcAS (10 μg/mL) for 30 minutes and 120 minutes, then fixed and permeabilized, and probed by Alexa 488 anti–human IgG. hFcAS, not plasminogen or hFc, could be internalized. Internalization was achieved at the indicated intervals after siRNA treatment for 72 hours. Internalization of hFcAS was decreased in ATP synthase α or β subunit–interfering RNA-treated cells. Confirming that ATP synthase expression has been decreased after siRNA-treated cells, (B) Western blot and (C) immunostaining of β subunit after 72-hour treatment with siRNA. Bar represents 20 μm. (D) HUVECs were subjected to FACS analysis using angiostatin concentration of 10 μg/mL and probed by Alexa 488 anti–human IgG. The red area represents the control Fc binding.