Figure 7. Spongistatin 1 inhibits phosphorylation of PKC substrates and translocation of PKC without directly blocking PKC activity. A) Western blot analysis to investigate phosphorylation activity of PKC in spongistatin 1-treated cells (same stimulation as in PepChip), using an antibody against phosphorylated PKC substrates (serine residues). Kinase inhibitor staurosporine (stauro) abolished phosphorylation of PKC substrates. In contrast, spongistatin 1 reduced phosphorylation only of distinct PKC substrates (arrows). B) In PKC in vitro assay, spongistatin 1 did not significantly inhibit phosphorylation activity of PKC isoforms , I, II, , ε, or (P 0.05; rank-sum test).
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