Kinase domain autophosphorylation rewires the activity and substrate specificity of CK1 enzymes

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Signaling

Background:

• Casein kinase 1 (CK1) enzymes are serine/threonine kinases crucial for various cellular functions.
• Misregulation of CK1 activity is implicated in diseases such as cancer, neurodegenerative disorders, and sleep phase disorders.

Purpose of the Study:

• To elucidate the conserved mechanism of CK1 activity regulation through autophosphorylation.
• To investigate the structural and functional consequences of T220 autophosphorylation in CK1.

Main Methods:

• X-ray crystallography to determine structures of CK1 with and without T220 phosphorylation.
• Molecular dynamics simulations to analyze protein plasticity and conformational changes.
• In vitro kinase assays to assess substrate specificity and activity.
• Quantitative phosphoproteomics to identify global signaling changes in response to T220 phosphorylation disruption.

Main Results:

• Autophosphorylation of threonine 220 (T220) in CK1δ, located near the substrate binding cleft, was identified as an evolutionarily conserved regulatory mechanism.
• T220 phosphorylation increases the plasticity of helix αG, leading to significant conformational changes in the substrate binding cleft.
• Phosphorylation at T220 generally decreases CK1 activity toward many substrates but enhances activity toward a specific high-affinity substrate.
• Disruption of T220 autophosphorylation was shown to rewire CK1 signaling networks in *Schizosaccharomyces pombe*.

Conclusions:

• T220 autophosphorylation represents a unique regulatory mechanism specific to the CK1 family.
• This mechanism provides a novel way to modulate CK1 substrate specificity and cellular signaling.
• Understanding T220 regulation offers potential therapeutic targets for CK1-associated diseases.