Figure 5.

The ligated IL-5R complex is endocytosed and degraded in lysosomes. (a) TF1 cells that had been cytokine-starved for 24 hours were left untreated (lanes 1, 3, and 5) or were pretreated with 10 μM cytochalasin D (lanes 2, 4, and 6) for 1 hour prior to IL-5 stimulation (10 ng/ml) for the indicated times. Whole-cell lysates were prepared, and proteins were immunoprecipitated with anti-βc monoclonal antibody and immunoblotted with anti-βc polyclonal antibodies (top panel). The membrane was stripped and reprobed with anti–IL-5Rα antibodies (bottom panel). Note the accumulation of βc, β_IP, and IL-5Rα in the presence of the inhibitor in lane 6. (b) Same as in a, top panel, except that cells were pretreated with 200 nM bafilomycin A₁ in lanes 2, 4, and 6. Note the accumulation of β_IP in the presence of bafilomycin A₁ in lane 6 (bottom arrow).