Pim-1 negatively regulates the activity of PTP-U2S phosphatase and influences terminal differentiation and apoptosis of monoblastoid leukemia cells

Arch Biochem Biophys. 2001 Jun 1;390(1):9-18. doi: 10.1006/abbi.2001.2370.


The levels of Pim-1, a serine/threonine kinase, increase during phorbol myristate acetate (PMA)-induced myeloid cell differentiation. The tyrosine phosphatase PTP-U2S is also associated with PMA-induced differentiation of myeloid cells and has been shown to enhance differentiation and the onset of apoptosis. PTP-U2S contains a Pim-1 phosphorylation consensus sequence, KKRKLTN, which is efficiently phosphorylated by Pim-1. Immunoprecipitated PTP-U2S from U937 cells was phosphorylated by recombinant Pim-1, resulting in a decrease in its phosphatase activity. During PMA-induced differentiation, U937 cells transfected with the dominant negative Pim-1 underwent rapid differentiation and accelerated apoptosis. The opposite effect was observed for wild-type Pim-1. Our results, therefore, provide compelling evidence that Pim-1 functions to negatively regulate PMA-induced differentiation in part through the phosphorylation of PTP-U2S. Together these data suggest that Pim-1 phosphorylates PTP-U2S in vivo to decrease the phosphatase activity that may be necessary to prevent the premature onset of apoptosis following differentiation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Apoptosis
  • Base Sequence
  • Binding Sites / genetics
  • Cell Differentiation
  • DNA Primers / genetics
  • Humans
  • Kinetics
  • Protein Tyrosine Phosphatases / metabolism*
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-pim-1
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Subcellular Fractions / metabolism
  • U937 Cells


  • DNA Primers
  • Proto-Oncogene Proteins
  • Recombinant Fusion Proteins
  • PIM1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-pim-1
  • Protein Tyrosine Phosphatases