Fig. 5.

The effect of ATP on trafficking of P2X receptors in neurons. A–C, ATP-dependent P2X4(AU5) and P2X2(FLAG) receptor internalization was measured by live-labeling neurons for 30 min at 37°C with anti-AU5 and anti-FLAG, respectively. Cell surface and internalized receptors were stained after 15 min incubation in control or Ca²⁺-free solution with or without ATP (100 μm) (A). B, C, Quantification of P2X4(AU5) and P2X2(FLAG) receptor internalization. Histograms show the internalized fluorescence as a fraction of total labeled (surface plus internalized) fluorescence, normalized to control cells (n = 7–29 neurons for each condition). ATP-dependent (100 μm) internalization of P2X4(AU5) receptors is independent of extracellular Ca²⁺(B). D, E, Neurons expressing P2X2-GFP receptors were stained with anti-MAP-2. Application of ATP (100 μm) causes dendritic injury in P2X2-GFP transfected neurons.