DUR inhibits IL2R:Dsg2 chimera internalization. (A) Schematic representation of IL2R:Dsg2 chimeras. Ecto, ectodomain; TM, transmembrane domain. (B) Lysates from SCC68 cells expressing IL2R:Dsg2 chimeras were immunoblotted with the indicated antibodies. (C) Biotinylation assay of cells grown in medium with 0.25 mM Ca²⁺. The graph shows the results from five independent experiments. n ≥ 3 per mutant. Paired t test. L, surface pool of the Dsg2 mutants. 30’, cytoplasmic pool of the Dsg2 mutants after 30 min of internalization. S, residual Dsg2 mutant protein left on the cell surface after stripping. The bottom and top of the box are the 25th and 75th percentile (the lower and upper quartiles), respectively. The horizontal line near the middle of the box is the 50th percentile (the median). The ends of the whisker are the minimum and maximum of all the data. (D) Cells were labeled with anti-IL2R antibody at 4°C and then incubated at 37°C for 0 or 30 min. Residual surface antibodies were subsequently stripped. Internalized IL2R:ICS (top) and IL2R:RUDI (bottom) chimeras were visualized using indirect immunofluorescence. Bar, 20 µm. Graph, from one representative experiment, shows the ratio of mean cytoplasmic intensity per cell/mean surface label intensity per cell for each mutant. Number of cells quantified are as follows: IL2R:ICS (n = 63) and IL2R:RUDI (n = 66). Error bars are SEM.