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Updated: Sep 20, 2026
Identification of Novel CK2 Kinase Substrates Using a Versatile Biochemical Approach
Published on: February 21, 2019
Functional analysis of C-TAK1 substrate binding and identification of PKP2 as a new C-TAK1 substrate
Jürgen Müller1, Daniel A Ritt, Terry D Copeland
1Regulation of Cell Growth Laboratory, Center for Cancer Research, NCI-Frederick, PO Box B, Frederick, MD 21702, USA.
Abstract:
Cdc25C-associated kinase 1 (C-TAK1) has been implicated in cell cycle regulation and Ras signaling through its interactions with two putative substrates, the Cdc25C phosphatase and the MAPK scaffold KSR1. Here, we identify sequence motifs required for stable C-TAK1 association and substrate phosphorylation. Using a mutational approach to disrupt binding of C-TAK1 to KSR1 and Cdc25C, we demonstrate that C-TAK1 contributes to the regulation of these proteins in vivo through the generation of 14-3-3-binding sites. KSR1 proteins defective in C-TAK1 binding had severely reduced phosphorylation at the 14-3-3-binding site in vivo, were constitutively localized to the plasma membrane and had increased biological activity. Disruption of the Cdc25C-C-TAK1 interaction resulted in reduced 14-3-3-binding site phosphorylation and nuclear accumulation of Cdc25C in interphase cells. Finally, utilizing the acquired C-TAK1 binding and substrate phosphorylation data, we identify plakophilin 2 (PKP2) as a novel C-TAK1 substrate. Phosphorylation of PKP2 by C-TAK1 also generates a 14-3-3-binding site that influences PKP2 localization. These findings underscore the importance of C-TAK1 as a regulator of 14-3-3 binding and protein localization.
Insights
Cdc25C-associated kinase 1 (C-TAK1) regulates cell signaling by creating 14-3-3-binding sites on substrates like KSR1 and Cdc25C. This impacts protein localization and biological activity, highlighting C-TAK1
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Cdc25C-associated kinase 1 (C-TAK1) is involved in cell cycle regulation and Ras signaling.
- C-TAK1 interacts with Cdc25C phosphatase and KSR1, a MAPK scaffold protein.
Purpose of the Study:
- To identify sequence motifs essential for C-TAK1 binding and substrate phosphorylation.
- To investigate the role of C-TAK1 in regulating KSR1 and Cdc25C through 14-3-3-binding site generation.
- To identify novel C-TAK1 substrates and their regulation.
Main Methods:
- Mutational analysis to disrupt C-TAK1 binding to KSR1 and Cdc25C.
- In vivo phosphorylation assays to assess 14-3-3-binding site generation.
- Identification of plakophilin 2 (PKP2) as a novel C-TAK1 substrate.
Main Results:
- Disruption of C-TAK1 binding reduced 14-3-3-binding site phosphorylation in KSR1 and Cdc25C.
- KSR1 mutants showed constitutive plasma membrane localization and increased activity.
- Cdc25C mutants accumulated in the nucleus.
- PKP2 was identified as a novel substrate, with C-TAK1 phosphorylation creating a 14-3-3-binding site influencing its localization.
Conclusions:
- C-TAK1 is crucial for regulating 14-3-3 binding and protein localization.
- C-TAK1-mediated phosphorylation controls the cellular distribution and activity of key signaling proteins.
- The study identifies PKP2 as a new substrate, expanding the known functions of C-TAK1.
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