Pten regulates spindle pole movement through Dlg1-mediated recruitment of Eg5 to centrosomes

Phosphatase and tensin homologue (Pten) suppresses neoplastic growth by negatively regulating PI(3)K signalling through its phosphatase activity. To gain insight into the actions of non-catalytic Pten domains in normal physiological processes and tumorigenesis, we engineered mice lacking the PDZ-binding domain (PDZ-BD). Here, we show that the PDZ-BD regulates centrosome movement and that its heterozygous or homozygous deletion promotes aneuploidy and tumour formation. We found that Pten is recruited to pre-mitotic centrosomes in a Plk1-dependent fashion to create a docking site for protein complexes containing the PDZ-domain-containing protein Dlg1 (also known as Sap97) and Eg5 (also known as Kif11), a kinesin essential for centrosome movement and bipolar spindle formation. Docking of Dlg1-Eg5 complexes to Pten depended on Eg5 phosphorylation by the Nek9-Nek6 mitotic kinase cascade and Cdk1. PDZ-BD deletion or Dlg1 ablation impaired loading of Eg5 onto centrosomes and spindle pole motility, yielding asymmetrical spindles that are prone to chromosome missegregation. Collectively, these data demonstrate that Pten, through the Dlg1-binding ability of its PDZ-BD, accumulates phosphorylated Eg5 at duplicated centrosomes to establish symmetrical bipolar spindles that properly segregate chromosomes, and suggest that this function contributes to tumour suppression.