GSK3-mediated CLASP2 phosphorylation modulates kinetochore dynamics.

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Accurate chromosome segregation during mitosis relies on dynamic microtubule-kinetochore attachments.
• While the NDC80 complex is crucial, other microtubule-binding proteins like CLASP2 also localize to kinetochores.
• The precise regulation of kinetochore-microtubule interactions remains an active area of research.

Purpose of the Study:

• To investigate the role of GSK3-mediated phosphorylation of CLASP2α in regulating kinetochore-microtubule interactions.
• To determine how CLASP2α phosphorylation affects its localization and microtubule-binding activity.
• To understand the contribution of CLASP2α phosphorylation to chromosome segregation fidelity.

Main Methods:

• Utilized dominant phosphorylation-site variants of CLASP2α.
• Assessed CLASP2α-microtubule association and kinetochore localization.
• Measured sister kinetochore tension and chromosome segregation accuracy.
• Investigated the impact of GSK3-mediated phosphorylation on CLASP2α function.

Main Results:

• Global GSK3-mediated phosphorylation of CLASP2α abolished its microtubule association in metaphase but did not affect kinetochore localization.
• Phosphorylation of CLASP2α significantly weakened kinetochore-microtubule interactions, evidenced by reduced sister kinetochore tension.
• Expression of CLASP2α phosphorylation mutants led to increased chromosome segregation defects.

Conclusions:

• GSK3-mediated phosphorylation of CLASP2α plays a critical role in regulating kinetochore-microtubule dynamics.
• This phosphorylation event contributes to accurate chromosome segregation by modulating microtubule attachment stability.
• A model is proposed where kinetochore-bound CLASP2α is locally dephosphorylated to enable microtubule binding.