Elongation factor-2 kinase: effective inhibition by the novel protein kinase inhibitor rottlerin and relative insensitivity towards staurosporine

The elongation factor-2 (eEF-2) is selectively phosphorylated by the eEF-2 kinase (calmodulin-dependent kinase III). This phosphorylation can be inhibited by calmodulin antagonists, such as CGS 9343B (IC 5o = 4 μM). The novel protein kinase inhibitor rottlerin is shown to suppress eEF-2 phosphorylation with an IC 50 of 5.3 μM. By contrast, the eEF-2 kinase is rather resistant towards the potent but non-selective protein kinase inhibitor staurosporine (IC 50> 50 μM) and thus can be differentiated from most other protein kinases that are suppressed by staurosporine in the nM range.