Figure 8.

Effect of β-truncated constructs on TSHR internalization. HEK-293 cells transfected with the expression vectors encoding the β-constructs and WT receptors were incubated with biotinylated TSHR-monoclonal antibody (9F4), which recognizes the TSHR ectodomain. After removal of the unbound Ig, cells were incubated at 37 C as indicated. Surface-bound antibody was quantified by measuring the fluorescent intensity of the bound Streptavidin-PE by the flow cytometry. Specific binding at each time point was normalized to the biotinylated TSHR monoclonal antibody (9F4) at 0 min. The inset illustrates the internalization rate of the WT TSHR and the truncated subunits alone. The main figure demonstrates that the subunit constructs markedly increased the internalization rate of the WT TSHR when cotransfected.