Systematic Discovery of Short Linear Motifs Decodes Calcineurin Phosphatase Signaling

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Signaling

Background:

• Short linear motifs (SLiMs) mediate critical protein-protein interactions in cellular signaling pathways.
• Calcineurin (CN), a calcium-activated phosphatase, recognizes specific motifs like LxVP and PxIxIT.
• Identifying SLiM-driven interactions is challenging due to sequence degeneracy and low binding affinities.

Purpose of the Study:

• To elucidate the regulatory network of calcineurin (CN) by discovering its Short Linear Motif (SLiM)-based interactors.
• To investigate the role of CN in previously uncharacterized cellular compartments, such as the centrosome and nuclear pore complex (NPC).

Main Methods:

• In vitro proteome-wide detection of CN-binding peptides.
• In vivo SLiM-dependent proximity labeling.
• In silico modeling of motif determinants.
• Functional assays including dephosphorylation and nuclear transport reporter analysis.

Main Results:

• Uncovered novel CN interactors, including NOTCH1, which was validated as a CN substrate.
• Discovered SLiM-dependent proximity of CN to centrosomal and nuclear pore complex (NPC) proteins.
• Demonstrated that CN dephosphorylates NPC proteins in human and yeast cells, impacting nuclear transport.

Conclusions:

• The study establishes a comprehensive CN regulatory network, expanding our understanding of calcium and CN signaling.
• Reveals a conserved role for CN in regulating nuclear pore complex function.
• Highlights the synergy of experimental and computational methods for SLiM-based network discovery, providing a blueprint for future studies.