FIGURE 9.

βc ubiquitination is partially dependent on the presence of JAK2 and JAK1. A, HEK293 cells expressing WT IL-5Rs were transfected with both JAK1 and JAK2 siRNAs, or scrambled -C siRNAs for 48 h as described under “Experimental Procedures.” Whole cell lysates from unstimulated cells were analyzed by IB with the indicated Abs to determine knockdown efficiencies (left panel). Whole cell lysates from A and IL-5 stimulated cells (10 ng/ml, 1 h) were IP with anti-βc antibodies and IB with indicated Abs (right panel). Note how the absence of JAK1/2 partially reduces βc-Ub. B, cells from A were labeled with anti-βc-activated protein C antibodies and analyzed by flow cytometry. Note how JAK1/2 gene silencing slightly reduced βc cell surface expression (hatched histogram).