Specificity of PKC isoforms on inhibition of Jak2.
(A) Jak2-induced tyrosine phosphorylation of Stat5 is specifically inhibited by PKC-α and PKC-δ. COS7 cells were transfected with Stat5a, Jak2, and equal amounts of different PKC isoform expression plasmids, as indicated. Forty-eight hours after transfection, the cells were lysed and Stat5a was immunoprecipitated and subjected to anti-phosphotyrosine and anti-Stat5a immunoblotting. (B) COS7 cells were transfected with Stat1, Jak2, and equal amounts of different PKC isoform expression plasmids, as indicated. After 48 hours the cells were lysed for electrophoretic mobility shift assay. 8 μg protein from each lysate was incubated with 32P-labeled GAS oligonucleotide and separated on 4.5% TBE-PAGE, followed by autoradiography.
