CK2 constitutively associates with and phosphorylates chicken erythroid ankyrin and regulates its ability to bind to spectrin

Abstract

Previous analyses have shown that the phosphorylation state of chicken erythroid ankyrin regulates its association with the spectrin cytoskeleton in vivo. Treatment of erythroid cells with serine and threonine phosphatase inhibitors stimulates the hyperphosphorylation of ankyrin and its dissociation from spectrin. In this study, we demonstrate that a kinase that directs the phosphorylation of ankyrin in vivo coprecipitates with ankyrin-containing complexes and has properties identical to CK2. Studies using CK2-specific inhibitors have indicated that all of the phosphorylation events associated with erythroid ankyrin in vivo are CK2 dependent. Furthermore, inhibitor studies combined with in vitro binding analyses have indicated that the phosphorylation of erythroid ankyrin by CK2 regulates its ability to associate with spectrin. Additional analyses revealed that CK2 coprecipitates with ankyrin-3-containing complexes isolated from Madin Darby canine kidney epithelial cells and phosphorylates this epithelial ankyrin isoform in vivo. These results are the first demonstration of a kinase constitutively associating with the ankyrin-spectrin cytoskeleton in erythroid and kidney epithelial cells. This association provides a mechanism for rapidly reorganizing the membrane cytoskeleton in these cell types through the phosphorylation of ankyrin.