Direct suppression of TCR-mediated activation of extracellular signal-regulated kinase by leukocyte protein tyrosine phosphatase, a tyrosine-specific phosphatase

J Immunol. 1999 Aug 1;163(3):1282-8.

Abstract

Leukocyte protein tyrosine phosphatase (LC-PTP)/hemopoietic PTP is a human cytoplasmic PTP that is predominantly expressed in the hemopoietic cells. Recently, it was reported that hemopoietic PTP inhibited TCR-mediated signal transduction. However, the precise mechanism of the inhibition was not identified. Here we report that extracellular signal-regulated kinase (ERK) is the direct target of LC-PTP. LC-PTP dephosphorylated ERK2 in vitro. Expression of wild-type LC-PTP in 293T cells suppressed the phosphorylation of ERK2 by a mutant MEK1, which was constitutively active regardless of upstream activation signals. No suppression of the phosphorylation was observed by LC-PTPCS, a catalytically inactive mutant. In Jurkat cells, LC-PTP suppressed the ERK and p38 mitogen-activated protein kinase cascades. LC-PTP and LC-PTPCS made complexes with ERK1, ERK2, and p38alpha, but not with the gain-of-function sevenmaker ERK2 mutant (D321N). A small deletion (aa 1-46) in the N-terminal portion of LC-PTP or Arg to Ala substitutions at aa 41 and 42 resulted in the loss of ERK binding activity. These LC-PTP mutants revealed little inhibition of the ERK cascade activated by TCR cross-linking. On the other hand, the wild-type LC-PTP did not suppress the phosphorylation of sevenmaker ERK2 mutant. Thus, the complex formation of LC-PTP with ERK is the essential mechanism for the suppression. Taken collectively, these results indicate that LC-PTP suppresses mitogen-activated protein kinase directly in vivo.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium-Calmodulin-Dependent Protein Kinases / antagonists & inhibitors*
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Cell Line
  • Enzyme Activation / immunology
  • Genetic Vectors / metabolism
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Jurkat Cells
  • Kidney
  • MAP Kinase Kinase 1
  • Macromolecular Substances
  • Mitogen-Activated Protein Kinase Kinases*
  • Mitogen-Activated Protein Kinases*
  • Phosphorylation
  • Protein Binding / immunology
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism
  • Protein Tyrosine Phosphatase, Non-Receptor Type 6
  • Protein Tyrosine Phosphatases / genetics
  • Protein Tyrosine Phosphatases / physiology*
  • Protein Tyrosine Phosphatases, Non-Receptor
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / metabolism
  • Receptors, Antigen, T-Cell / physiology*
  • Recombinant Fusion Proteins / biosynthesis
  • Recombinant Fusion Proteins / metabolism
  • Transfection
  • Tyrosine / metabolism*
  • p38 Mitogen-Activated Protein Kinases

Substances

  • Intracellular Signaling Peptides and Proteins
  • Macromolecular Substances
  • Receptors, Antigen, T-Cell
  • Recombinant Fusion Proteins
  • Tyrosine
  • Protein-Tyrosine Kinases
  • Protein Serine-Threonine Kinases
  • Calcium-Calmodulin-Dependent Protein Kinases
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 1
  • MAP2K1 protein, human
  • Mitogen-Activated Protein Kinase Kinases
  • PTPN6 protein, human
  • PTPN7 protein, human
  • Protein Tyrosine Phosphatase, Non-Receptor Type 6
  • Protein Tyrosine Phosphatases
  • Protein Tyrosine Phosphatases, Non-Receptor