Regulation of protein phosphatase 1I by Cdc25C-associated kinase 1 (C-TAK1) and PFTAIRE protein kinase

J Biol Chem. 2014 Aug 22;289(34):23893-900. doi: 10.1074/jbc.M114.557744. Epub 2014 Jul 15.


Protein phosphatase 1I (PP-1I) is a major endogenous form of protein phosphatase 1 (PP-1) that consists of the core catalytic subunit PP-1c and the regulatory subunit inhibitor 2 (I-2). Phosphorylation of the Thr-72 residue of I-2 is required for activation of PP-1I. We studied the effects of two protein kinases identified previously in purified brain PP-1I by mass spectrometry, Cdc25C-associated kinase 1 (C-TAK1) and PFTAIRE (PFTK1) kinase, for their ability to regulate PP-1I. Purified C-TAK1 phosphorylated I-2 in reconstituted PP-1I (PP-1c. I-2) on Ser-71, which resulted in partial inhibition of its ATP-dependent phosphatase activity and inhibited subsequent phosphorylation of Thr-72 by the exogenous activating kinase GSK-3. In contrast, purified PFTK1 phosphorylated I-2 at Ser-86, a site known to potentiate Thr-72 phosphorylation and activation of PP-1I phosphatase activity by GSK-3. These findings indicate that brain PP-1I associates with and is regulated by the associated protein kinases C-TAK1 and PFTK1. Multisite phosphorylation of the I-2 regulatory subunit of PP-1I leads to activation or inactivation of PP-1I through bidirectional modulation of Thr-72 phosphorylation, the critical activating residue of I-2.

Keywords: Cell Signaling; Enzyme; Enzyme Mechanism; Inhibitor 2; Ischemia; Protein Phosphorylation.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Cyclin-Dependent Kinases / metabolism*
  • Enzyme Activation
  • Humans
  • Molecular Sequence Data
  • Phosphorylation
  • Protein Phosphatase 1 / metabolism*
  • Protein-Serine-Threonine Kinases / chemistry
  • Protein-Serine-Threonine Kinases / metabolism*
  • Swine


  • MARK3 protein, human
  • Protein-Serine-Threonine Kinases
  • CDK14 protein, human
  • Cyclin-Dependent Kinases
  • Protein Phosphatase 1