CK1δ kinase activity is modulated by protein kinase C α (PKCα)-mediated site-specific phosphorylation

Abstract

Cellular signal transduction components are usually regulated not only on transcriptional or translational level, but also by posttranslational modifications. Among these, reversible phosphorylation represents the most abundant modification. In general, phosphorylation events are essential for regulating the activity of central signal transduction proteins, also including kinases itself. Members of the CK1 family can be found as central signal transduction proteins in numerous cellular pathways. Due to its wide variety of cellular functions the activity of CK1 family members has to be tightly regulated. We previously reported that PKA and Chk1 are able to phosphorylate CK1δ within its C-terminal regulatory domain, consequently resulting in altered CK1 kinase activity. In the present study, we show by several methods that protein kinase C α (PKCα) as well is able to phosphorylate CK1δ at its C-terminally located residues S328, T329, and S370. Furthermore, we analyze the functional consequences of PKCα-mediated phosphorylation on CK1δ kinase activity. Mutation of S328, T329, or S370 to alanine dramatically alters the kinetic parameters of CK1δ. By using the PKCα-specific inhibitor Go-6983 in a selected cell culture model, we finally show that the in vitro detected regulatory connection between PKCα and CK1δ is also relevant in the cellular context. Taken together, these data contribute to a deeper understanding of cellular signal transduction networks thereby helping to form a basis for the development of future therapeutic concepts.

Characterization of the ERG-regulated Kinome in Prostate Cancer Identifies TNIK as a Potential Therapeutic Target

“…CSNK1D phosphorylates AXIN and APC, thus contributing to the negative regulation of β-catenin. Interestingly, in our screen, an increase in the phosphorylation of S328 and S331 on CSNK1D was detected (Figure 1, Figure 2), and these phosphorylation events all act to reduce the activity of CSNK1D [26]. In addition, we identified ERG-mediated upregulation of PKCα expression, and this kinase phosphorylates and negatively regulates CSNK1D (S328) in vitro [26].…”

Newly Developed CK1-Specific Inhibitors Show Specifically Stronger Effects on CK1 Mutants and Colon Cancer Cell Lines

“…While increased activity was determined for GST-CK1δ R299Q and GST-CK1δ Q399* , decreased activity was observed for GST-CK1δ R316G and GST-CK1δ H414Y . In general, several C-terminal residues of CK1δ are involved in regulation of kinase activity, mostly by phosphorylation events mediated by intramolecular autophosphorylation or by phosphorylation by upstream kinases [21,[34][35][36]. Consequently, if this domain is affected by conformational changes due to amino acid exchanges also regulation of kinase activity might be affected.…”

A CK1 FRET biosensor reveals that DDX3X is an essential activator of CK1ε

“…Also, reactions without addition of kinase were performed and analyzed in order to correct for false-positive results. Mass spectrometry data acquisition and analysis of trypsin-digested samples were performed at the Core Unit Mass Spectrometry and Proteomics (Ulm University) essentially as described in Meng et al (2016) .…”