Structure-function relationships of protein kinase CK2

• Applicants: Professor Dr. Karsten Niefind; Professor Dr. Markus Pietsch
• Subject Area: Biochemistry ; Pharmacology ; Structural Biology
• Term: from 2010 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 173792144

Protein kinase CK2 (former name: 'casein kinase 2'), an essential and biomedically relevant enzyme ubiquitously expressed in eukaryotes, belongs to the superfamily of eukaryotic protein kinases. Depending on its localization and on the nature of its protein substrates, CK2-catalyzed phosphorylation leads to cell stabilization, e.g. by inhibition of apoptosis or stimulation of DNA repair, or to up-regulation of cell proliferation. In addition, CK2 affects several signal transduction pathways and the circadian rhythm. The so-called CK2 holoenzyme is the physiologically predominant entity with CK2 activity; it consists of two catalytically active subunits (CK2alpha) non-obligatory bound to a central dimer of regulatory subunits (CK2beta). By binding to the catalytic subunit CK2beta modifies the activity, the specificity and the stability of CK2alpha. CK2 is an attractive subject of basic research in the fields of biochemistry, cell biology and structural biology and of applied research with medical-pharmacological focus. While a first ATP-competitive CK2 inhibitor is currently investigated in clinical studies of cancer therapy, molecules interacting with CK2alpha sites outside the ATP binding cleft, such as at the CK2alpha/CK2beta interface, have drawn increased interest over the past years. The proposed project is intended to significantly contribute to both major fields, i.e. to basic as well as to applied research on CK2. Structural biology related basic research will be based on X-ray crystal structures of CK2 complexes, which will provide significant information on the substrate recognition by CK2 and the role of CK2beta during this process. Furthermore, such crystal structures will allow for obtaining insights into the dual substrate specificity of CK2 which catalyzes not only the phosphorylation of serine and threonine residues but has also been reported to accept tyrosine residues. Findings obtained in the first project phase, showing differences in the affinity of the two paralogous isoforms of human CK2alpha to CK2beta, will be further pursued, e.g. by structural studies in solution using small-angle X-ray scattering (SAXS). In addition to this, it is aimed to elucidate the structural basis of several phenomena published for non-human CK2. In the field of medical-pharmacological CK2 research, the cooperation of the two applicants during the first project phase has resulted in important outcomes that will now be further pursued: The three-dimensional structure of CK2alpha in complex with a CK2beta-competitive peptide has been the basis for the development of an assay suitable for high-throughput screening of potential CK2beta antagonists. This assay will be used in the search for new lead structures capable of inhibiting the CK2alpha/CK2beta subunit interaction. Both inhibitors found by screening and the few already known CK2beta antagonists will be optimized by rational and structure-based methods and eventually investigated in vivo.

• DFG Programme: Research Grants