Direct suppression of TCR-mediated activation of extracellular signal-regulated kinase by leukocyte protein tyrosine phosphatase, a tyrosine-specific phosphatase.
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.
Biomedical Research Center, Osaka University Medical School, Japan.
M
M
Oh-hora
M
M
Ogata
Y
Y
Mori
M
M
Adachi
K
K
Imai
A
A
Kosugi
T
T
Hamaoka
D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation / Q000276:immunology; D005822:Genetic Vectors / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D007668:Kidney; D048369:MAP Kinase Kinase 1; D046911:Macromolecular Substances; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D010766:Phosphorylation; D011485:Protein Binding / Q000276:immunology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000502:physiology*; D054558:Protein Tyrosine Phosphatases, Non-Receptor; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases
D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D011948:Receptors, Antigen, T-Cell; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; C509249:PTPN6 protein, human; C502159:PTPN7 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D054558:Protein Tyrosine Phosphatases, Non-Receptor