Abstract
Purpose: :
Protein kinase CK2 (CK2) is an important regulator of cell migration, proliferation, and tumor growth. CK2 is abundant in retinal vascular endothelial cells and astrocytes, and its inhibition blocks retinal neovascularization in a mouse model. In human cultured astrocytic and vascular endothelial cells, CK2 inhibition caused dramatic cell shape change leading to cell rounding. The purpose was to study the effects of CK2 inhibition on activation of some signaling mediators during cell shape changes in human cultured vascular endothelial cells.
Methods: :
Cultured human brain microvascular endothelial cells (HBMVEC) were used. Specific CK2 inhibitor TBB, and p38 activity inhibitor SB 202190 (both from Calbiochem) were added at 0.02-0.10 mM in medium with 0.5% serum. Western analysis was used to examine phosphorylated forms of signaling molecules ERK and p38MAPK after the inhibitor treatment.
Results: :
After TBB treatment of HBMVEC, an increase in phospho-p38 (p-p38) was observed, whereas no such effect was found for SB 202190. When the cells were treated with both TBB and SB 202190, we observed a decrease in p38 phosphorylation suggesting an important role of autophosphorylation of p38 that may be down-regulated by CK2. Surprisingly, SB 202190 (that did not induce cell shape changes) enhanced the rounding effect caused by suboptimal concentration of TBB on the cells cultured with serum that suggests p38 may be involved in serum-mediated cell spreading. We observed also that TBB and SB 202190 each increased pERK1/2 levels, whereas their combined action had an additive effect leading to a higher phosphorylation of ERK1/2. Thus, there is a correlation between the Western blot and morphological data on combined action of TBB and SB 202190: p38 inhibitor enhanced both TBB-induced cell rounding and phosphorylation of ERK1/2.
Conclusions: :
Our data suggest possible important roles of signaling molecules in mediating the CK2 inhibitor-induced cell shape changes that may underlie the anti-angiogenic effect of CK2 inhibition in vivo, and may allow for the development of novel anti-angiogenic therapeutic approaches.
Keywords: retinal neovascularization • phosphorylation • enzymes/enzyme inhibitors