Cells were cultured in DME (Invitrogen) supplemented with 10% fetal bovine serum and 100 U/ml penicillin/streptomycin (Invitrogen) at 37°C in a humidified 5% CO2 incubator. Cells were serum-starved overnight, then fixed using 3.7% paraformaldehyde in PBS for 15 min, permeabilized using 0.2% Triton X-100 in PBS for 2 min, blocked with 2% BSA in PBS, and stained with the indicated primary antibodies at 4°C overnight, followed by incubation with a secondary Alexa Fluor 488–, 546– or 594–conjugated antibody. Images were captured by Leica TCS SP2 confocal microscope with HCX PL APO 63X objective.