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. 2017 Nov 22;8:860. doi: 10.3389/fphar.2017.00860

FIGURE 4.

FIGURE 4

Functional testing of fluorescence-labeled P2X4 and P2X7 constructs by two-electrode voltage clamp measurements. (A) Examples of current traces in oocytes expressing wildtype P2X4 (P2X4wt) of P2X7 (P2X7wt) or different fluorescence-labeled P2X4 and P2X7 constructs, as indicated. The colors of the construct names relate to the colors of the bars in (B,C). (B) Maximal current amplitudes obtained during the application of 1 mM ATP for 6 s. (C) Kinetics of ion channel currents in oocytes expressing different labeled P2X constructs. The relative inactivation (Iinact,rel) was calculated as the amplitude of the current between 2 and 6 s after the application of 1 mM ATP normalized to the current amplitude at the 2 s time point. A decay in the current amplitude (Iinact,rel > 0) indicates desensitization (seen for all P2X4 constructs); an increase in current amplitude during this period (Iinact,rel < 0) was usually seen for P2X7 constructs and is of unknown origin. Bar colors: light blue = P2X4wt or C-terminally labeled constructs, dark blue = P2X4 constructs labeled within the extracelllar domain, red = P2X7wt or C-terminally labeled constructs, rosy = C-terminally truncated and labeled P2X7 constructs, dark red = P2X7 constructs labeled within the extracelllar domain. Data are the means ± SEM from 5–20 oocytes.