Interactions between Casein Kinase Iε (CKIε) and Two Substrates from Disparate Signaling Pathways Reveal Mechanisms for Substrate-Kinase Specificity

Background Members of the Casein Kinase I (CKI) family of serine/threonine kinases regulate diverse biological pathways. The seven mammalian CKI isoforms contain a highly conserved kinase domain and divergent amino- and carboxy-termini. Although they share a preferred target recognition sequence and...

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Bibliographic Details
Published in:PloS one 2009-03, Vol.4 (3), p.e4766
Main Authors: Dahlberg, Caroline Lund, Nguyen, Elizabeth Z., Goodlett, David, Kimelman, David
Format: Article
Language:English
Subjects:
Binding
Biochemistry
Biochemistry/Protein Chemistry
C-Terminus
Casein
Casein kinase I
Cell Biology/Cell Signaling
Circadian rhythms
Crosslinking
Dishevelled protein
Experiments
Isoforms
Kinases
Mass spectrometry
Mass spectroscopy
Pathways
Pattern recognition
Pharmaceutical sciences
Phosphorylation
Polarity
Proteins
Rodents
Scientific imaging
Serine
Signal transduction
Substrates
Target recognition
Threonine
Transcription
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Summary:Background Members of the Casein Kinase I (CKI) family of serine/threonine kinases regulate diverse biological pathways. The seven mammalian CKI isoforms contain a highly conserved kinase domain and divergent amino- and carboxy-termini. Although they share a preferred target recognition sequence and have overlapping expression patterns, individual isoforms often have specific substrates. In an effort to determine how substrates recognize differences between CKI isoforms, we have examined the interaction between CKIε and two substrates from different signaling pathways. Methodology/Principal Findings CKIε, but not CKIα, binds to and phosphorylates two proteins: Period, a transcriptional regulator of the circadian rhythms pathway, and Disheveled, an activator of the planar cell polarity pathway. We use GST-pull-down assays data to show that two key residues in CKIα's kinase domain prevent Disheveled and Period from binding. We also show that the unique C-terminus of CKIε does not determine Dishevelled's and Period's preference for CKIε nor is it essential for binding, but instead plays an auxillary role in stabilizing the interactions of CKIε with its substrates. We demonstrate that autophosphorylation of CKIε's C-terminal tail prevents substrate binding, and use mass spectrometry and chemical crosslinking to reveal how a phosphorylation-dependent interaction between the C-terminal tail and the kinase domain prevents substrate phosphorylation and binding. Conclusions/Significance The biochemical interactions between CKIε and Disheveled, Period, and its own C-terminus lead to models that explain CKIε's specificity and regulation.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0004766