Fig. 4.

Potency of ADP-ribosylation to induce calcium flux in HEK cells transiently transfected with P2X7 variants. HEK cells were co-transfected with expression constructs for mRFP, ART2.2, and wild-type or mutant P2X7 purinoceptors. Twenty hours post-transfection, cells were loaded with the calcium-sensitive fluorochrome Fura-2 before live cell imaging by fluorescence microscopy as in Fig. 2. At the indicated times, the perfusion buffer (37°C) was changed to subject cells to increasing doses of NAD. Gray lines show single cell tracings, red lines the calculated mean