Open AccessPP2A-B55γ counteracts Cdk1 and regulates proper spindle orientation through cortical dynein adaptor NuMA
Author(s) -
Riya Keshri,
Ashwathi Rajeevan,
Sachin Kotak
Publication year - 2020
Publication title -
journal of cell science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.384
H-Index - 278
eISSN - 1477-9137
pISSN - 0021-9533
DOI - 10.1242/jcs.243857
Subject(s) - biology , microbiology and biotechnology , dephosphorylation , dynein , mitosis , phosphorylation , spindle apparatus , cyclin dependent kinase 1 , protein phosphatase 2 , microtubule , cell division , phosphatase , cell cycle , cell , genetics
Proper orientation of the mitotic spindle is critical for accurate development and morphogenesis. In human cells, spindle orientation is regulated by the evolutionarily conserved protein NuMA that interacts with dynein and enriches it at the cell cortex. Pulling forces generated by cortical dynein orient the mitotic spindle. Cdk1-mediated NuMA phosphorylation at Threonine 2055 negatively regulates its cortical localization. Thus, only non-phosphorylated NuMA at T2055 localizes at the cell cortex. However, the identity and the mechanism of action of phosphatase complex involved in T2055 dephosphorylation remains elusive. Here, we characterized the PPP2CA-B55γ-PPP2R1B complex that counteracts Cdk1 to orchestrate cortical NuMA for proper spindle orientation. In vitro reconstitution experiments revealed that this complex is sufficient for T2055 dephosphorylation. Importantly, we identified polybasic residues in NuMA that are critical for T2055 dephosphorylation, and for maintaining appropriate cortical NuMA levels for accurate spindle elongation. Furthermore, we found that Cdk1 and PP2A-B55γ-mediated phosphorylation and dephosphorylation at T2055 are reversible events. Altogether, this study uncovers a novel mechanism by which Cdk1 and its counteracting B55γ-PP2A complex orchestrate spatiotemporal levels of cortical force generators for flawless mitosis.