Ca²⁺/Calmodulin-dependent Protein Kinase IV Stimulates Nuclear Factor-κB Transactivation via Phosphorylation of the p65 Subunit

Calmodulin-dependent protein kinase IV (CaMKIV) is a key mediator of Ca²⁺-induced gene expression. In this study, CaMKIV was found to directly associate with and phosphorylate the nuclear factor-κB (NFκB) component p65 both in vitro and in vivo. The phosphorylation of p65 by CaMKIV resulted in recruitment of transcription coactivator cAMP-response element-binding protein-binding protein and concomitant release of corepressor silencing mediator for retinoid and thyroid hormone receptors, as demonstrated by the glutathione S-transferase pull down and mammalian two hybrid assays. In addition, cotransfection of CaMKIV resulted in cytosolic translocation of the silencing mediator for retinoid and thyroid hormone receptors. Consistent with these results, cotransfected CaMKIV dramatically stimulated the NFκB transactivation in mammalian cells. From these results, NFκB is suggested to be a novel downstream effector molecule of CaMKIV.