Figure 4.

Monensin induced down-regulation of T200V chimeric receptor. Down-regulation assays were performed on AKR-2B clones containing wild-type type I and II chimeric receptors (□) or a wild-type type II and T200V type I mutant (▵) in the presence of 100 μM monensin and 10 ng/ml GM-CSF. The data represent the mean (± SE) of three separate experiments done in duplicate on two independent mutant clones (T200V-10 and -12) and wild-type (A105) control cells. The ligand-induced down-regulation of the T200V clones in the absence of monensin reported in Figure 2 is shown for comparison (▴). Preliminary experiments demonstrated that monensin had no effect on ligand binding and decreased wild-type cell surface receptor binding in a dose-dependant manner, with 100 μM being maximally effective (our unpublished data).