Fig. 4.
Interaction of γc with the IL-2/15Rβ subunit demonstrated by confocal FRET microscopy. (A) FRET results measured between γc and IL-2/15Rβ subunits C-terminally tagged with EGFP (first column, green) and mCherry (second column, red) are shown for representative cells. Merged images are also presented (third column). TagBFP-Sac1 (ER marker) or giantin (Golgi marker) were also expressed (fifth column, blue). The fourth column displays the map of FRET efficiencies calculated only in pixels where the ER or Golgi marker was present. The first row shows data for the full-length IL-2/15Rβ (ER), whereas the second row displays data on the β-C7, a C-terminally truncated version of the β subunit having only 7 aa in its cytoplasmic tail (Golgi). FRET histograms are calculated for the selected cells. (B) FRET efficiencies (±SD) averaged for all measurements are shown for the ER/Golgi. The red arrow on the ordinate axis marks the range of the 3 negative control samples, E = 0.4 to 1.5%. Significant differences compared to negative control 1 (EGFP + mCherry) are indicated by the following: ***P < 0.001 (Student’s t test). FRET efficiencies and the numbers of cells measured for each sample are also summarized in Table 1.