FIGURE 8:

CABII is necessary to mediate increased water flux through AQP1 by CAII. AQP1 Water transport activity was measured by confocal fluorescence microscopy of HEK293 cells transfected with AQP1 CAB mutants in the presence and absence of CAII. (A) Cells were perfused initially with isotonic (dark blue bar) and then hypotonic (light blue bar) medium, and eGFP fluorescence was recorded. eGFP concentration as assessed by fluorescence in a representative ROI normalized to initial fluorescence in that ROI (F/F₀) is plotted vs. time. The constructs transfected are indicated on the left side of the curves. (B) Rate of fluorescence change corrected for activity of vector-transfected cells and normalized to AQP1 amount at the cell surface. Cell surface expression was determined by biotinylation and is presented in Supplemental Figure S7. Asterisk represents a statistically significant difference (p < 0.05) compared with AQP1, and number sign (#) represents a statistically significant difference from AQP1 + CAII.