Fig. 2. The C-terminus of P2X4 alone can mediate internalization from the plasma membrane. (A) Representative confocal images of NRK cells transfected with either CD8-reporter or CD8-4C-reporter constructs, P2X4(AU5) wild-type, or Y378S-mutant receptors. Cells were live-labeled with anti-CD8 or anti-AU5 for 30 minutes at 37°C. Cell surface (red) and internalized (green) receptors were visualized using Cy3- and FITC-conjugated secondary antibodies, before and after permeabilization, respectively. Bars, 10 µm. (B) Histogram, showing the proportion of protein detected at the cell surface (red) or in internal compartments (green) after labeling (n=18-54). **, P<0.01.