Mechanisms of site-specific dephosphorylation and kinase opposition imposed by PP2A regulatory subunits

EMBO J. 2020 Jul 1;39(13):e103695. doi: 10.15252/embj.2019103695. Epub 2020 May 13.


PP2A is an essential protein phosphatase that regulates most cellular processes through the formation of holoenzymes containing distinct regulatory B-subunits. Only a limited number of PP2A-regulated phosphorylation sites are known. This hampers our understanding of the mechanisms of site-specific dephosphorylation and of its tumor suppressor functions. Here, we develop phosphoproteomic strategies for global substrate identification of PP2A-B56 and PP2A-B55 holoenzymes. Strikingly, we find that B-subunits directly affect the dephosphorylation site preference of the PP2A catalytic subunit, resulting in unique patterns of kinase opposition. For PP2A-B56, these patterns are further modulated by affinity and position of B56 binding motifs. Our screens identify phosphorylation sites in the cancer target ADAM17 that are regulated through a conserved B56 binding site. Binding of PP2A-B56 to ADAM17 protease decreases growth factor signaling and tumor development in mice. This work provides a roadmap for the identification of phosphatase substrates and reveals unexpected mechanisms governing PP2A dephosphorylation site specificity and tumor suppressor function.

Keywords: ADAM17; PP2A; phosphoproteomics; substrate specificity; tumor suppressor.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADAM17 Protein / genetics
  • ADAM17 Protein / metabolism*
  • Amino Acid Motifs
  • Animals
  • Binding Sites
  • HeLa Cells
  • Humans
  • Mice
  • Phosphorylation
  • Protein Phosphatase 2 / metabolism*


  • PP2A-B56alpha protein, human
  • Protein Phosphatase 2
  • ADAM17 Protein
  • ADAM17 protein, human
  • Adam17 protein, mouse