Distinct dephosphorylation site signatures of PP1 and PP2A-B55 coordinate mitotic exit.

ABSTRACT: Mitotic exit requires extensive dephosphorylation of Ser/Thr residues by the PP1 and PP2A-B55 protein phosphatases in human cells. Several aspects of this are poorly understood including specific substrates and determinants of phosphatase specificity. Here we develop a novel in vitro assay, MRBLE-dephos, that allows multiplexing of dephosphorylation reactions to determine phosphatase specificity. Using MRBLE-dephos, we establish amino acid preferences of the residues surrounding the phosphorylation site for PP1 and PP2A-B55, which reveals common and unique preferences for the two phosphatases. We use specific inhibition of PP1 and PP2A-B55 in mitotic exit lysates coupled with quantitative phosphoproteomics to identify more than 2000 regulated phosphorylation sites and integrate this with mitotic interactomes to obtain a comprehensive map of mitotic dephosphorylation events. Importantly, the sites dephosphorylated during mitotic exit reveal key signatures that are consistent with the MRBLE-dephos results. We use these insights to specifically alter INCENP dephosphorylation kinetics at mitotic exit resulting in defective cytokinesis underscoring the biological relevance of our determined specificity principles. Finally, we provide a comprehensive characterization of PP1 binding motifs and show how these can shape dephosphorylation and how PP1 primes its own association with these motifs at mitotic exit. Collectively we provide a framework for understanding mitotic exit regulation by dephosphorylation and novel approaches to dissect protein phosphatase specificity.

INSTRUMENT(S): Orbitrap Fusion, Q Exactive Plus

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Arminja Kettenbach  

PROVIDER: MSV000091928 | MassIVE | Fri May 12 10:12:00 BST 2023

SECONDARY ACCESSION(S): PXD042194

REPOSITORIES: MassIVE