Concurrent knockdown of p85α and p85β diminishes receptor internalization. Receptor internalization was detected by flow cytometry in γ2A cells stably expressing EpoR and JAK2 and transfected with 100 nM siRNAs to SOCS3, p85α, p85β, or p85α and p85β together. Scrambled siRNA to GFP was used as a negative control. Immunoblots of each targeted protein demonstrate knockdown efficiency. Representative immunoblotting with actin was shown as a control. *P = .001 (unpaired t test) versus control.