Protein kinases curb cell death

Networks of aspartic acid-directed caspases play a major role in the execution of programmed cell death. Studies have provided evidence that caspases or their substrates are subjected to phosphorylation, which suggests a potential convergence of protein kinase and caspase signaling pathways. Various caspase substrates, but also several procaspases, are protected from cleavage when they are phosphorylated at sites adjacent to caspase cleavage sites. Whereas many distinct protein kinases could potentially protect substrates from caspase-mediated cleavage, a study has identified protein kinase CK2 as the most prominent kinase that exerts a global inhibition of caspase signaling pathways. CK2 is a component of protein kinase networks that are involved in tumors derived from various tissues. Its dysregulation in many cancers, together with its dual function in promoting cell growth and in suppressing apoptosis, is particularly relevant to its oncogenic potential. Thus, this study suggests that the ability of CK2 to contribute to tumorigenesis resides, at least in part, in its ability to phosphorylate caspases or their targets.