Figure 4.

Proteasome inhibitors stabilize IL-5Rα and βc protein/protein interaction. TF1 cells that were cytokine-starved for 48 hours were either left untreated (lanes 1, 3, and 5) or were pretreated with 50 μM LLnL (lanes 2, 4, and 6) or 0.01% (vol) DMSO (lane 7) for 1 hour prior to IL-5 stimulation (10 ng/ml) for the indicated times. Whole-cell lysates were prepared, and IP/IB analysis was performed with anti–IL-5Rα polyclonal antibody (top panel). The blot in the top panel was stripped and reprobed with anti-βc polyclonal antibodies (bottom panel). Note that both full-length βc receptor and β_IP coimmunoprecipitate with IL-5Rα antibodies (bottom panel).