(A) PKC- and PKC-δ inhibit IL-3–induced tyrosine phosphorylation of Jak2.

32D-wt, 32D-α, 32D-δ, and 32D-ε cells, and Ba/F3 cells were pretreated with vehicle alone or with 100 ng/mL TPA for 30 minutes and then stimulated with IL-3 (10 ng/mL) for 15 minutes, as indicated. Jak2 was immunoprecipitated and subjected to anti-phosphotyrosine and anti-Jak2 immunoblotting. (B) The effect of TPA concentration (left panel) and kinetics (right panel) on Jak2 tyrosine phosphorylation in 32D-δ cells. 32D-δ cells were treated with vehicle alone or with TPA (30 minutes) before IL-3 stimulation, and Jak2 was immunoprecipitated and subjected to anti-phosphotyrosine immunoblotting. (C) PKC-δ inhibits IL-3–induced tyrosine phosphorylation of IL-3Rβ. 32D-wt and 32D-δ cells were treated with TPA (30 minutes) and IL-3 (15 minutes), as indicated. IL-3Rβ was immunoprecipitated and immunoblotted with anti-phosphotyrosine antibody and reprobed with anti–IL-3Rβ antibody.