Selective targeting of individual isoforms to investigate the role of CK2 in cell survival

Abstract

CK2 is a highly conserved protein serine/threonine kinase that is represented by two catalytic isozymes, CK2α and CK2α’, that have similar catalytic activity but appear to exhibit functional specialization in cells. Evidence suggests that CK2 has a general anti-apoptotic role in cells, via the protection of pro-apoptotic proteins from caspase-mediated cleavage. In the present study, CK2α and/or CK2α’ were specifically knocked down using RNA interference or chemical inhibition to elucidate the role of specific CK2 isoforms in the maintenance of cell viability. HeLa cells were treated with selective CK2 inhibitors or transfected with CK2α-shRNA, CK2α’-shRNA or a control scramble-shRNA. Examination of various apoptotic indicators was carried out using microscopic examination and western blot analysis. Knockdown of either CK2αor CK2α’ or treatment with CK2 inhibitors resulted in the induction of apoptosis as indicated by the cleavage of PARP. Interestingly, the addition of z-VAD a general caspase inhibitor to CK2-inhibitor-treated cells resulted in a reduction of cleaved PARP, suggesting that a proportion of these cells undergo caspase-dependent apoptosis. The results of this study indicate definitively that both CK2α and CK2α’ participate in the protection of cells from apoptosis, and that the protection may be caspase dependent. This work was supported by an operating grant and a strategic training program grant from the Canadian Institutes of Health Research.