Modulation of transcriptional mineralocorticoid receptor activity by casein kinase 2

The pathogenesis of cardiovascular diseases is a multifunctional process in which the mineralocorticoid receptor (MR), a ligand-dependent transcription factor, is involved as proven by numerous clinical studies. The development of pathophysiological MR actions depends on the existence of additional factors e.g. inflammatory cytokines and seems to involve posttranslational MR modifications e.g. phosphorylation. Casein kinase 2 (CK2) is a ubiquitously expressed multifunctional serine/threonine kinase that can be activated under inflammatory conditions as the MR. Sequence analysis and inhibitor experiments revealed that CK2 acts as a positive modulator of MR activity by facilitating MR-DNA interaction with subsequent rapid MR degradation. Peptide microarrays and site-directed mutagenesis experiments identified the highly conserved S459 as a functionally relevant CK2 phosphorylation site of the MR. Moreover, MR-CK2 protein-protein interaction mediated by HSP90 was shown by co-immunoprecipitation. During inflammation, cytokine stimulation led to a CK2-dependent increased expression of proinflammatory genes. The additional MR activation by aldosterone during cytokine stimulation augmented CK2-dependent NFκB signaling which enhanced the expression of proinflammatory genes further. Overall, in an inflammatory environment the bidirectional CK2-MR interaction aggravate the existing pathophysiological cellular situation.