Altered Expression of Protein-tyrosine Phosphatase 2C in 293 Cells Affects Protein Tyrosine Phosphorylation and Mitogen-activated Protein Kinase Activation

• Published in: The Journal of biological chemistry 1995-05, Vol.270 (20), p.11765-11769
• Main Authors: Zhao, Zhizhuang, Tan, Zhongjia, Wright, Jocelyn H., Diltz, Curtis D., Shen, Shi-Hsiang, Krebs, Edwin G., Fischer, Edmond H.
• Format: Article
• Language: English
• Subjects: Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Cell Line; Cell Membrane - enzymology; Cytosol - enzymology; Enzyme Activation; Epidermal Growth Factor - pharmacology; Gene Expression Regulation, Enzymologic; Humans; Intracellular Signaling Peptides and Proteins; Kidney; Membrane Proteins - metabolism; Mitogen-Activated Protein Kinase Kinases; Mutagenesis, Site-Directed; Peptide Fragments - metabolism; Phosphorylation; Protein Kinases - metabolism; Protein Processing, Post-Translational; Protein Tyrosine Phosphatase, Non-Receptor Type 11; Protein Tyrosine Phosphatase, Non-Receptor Type 6; Protein Tyrosine Phosphatases - biosynthesis; Protein Tyrosine Phosphatases - genetics; Recombinant Fusion Proteins - metabolism; SH2 Domain-Containing Protein Tyrosine Phosphatases; Signal Transduction; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.270.20.11765

PTP2C, an SH2 domain-containing protein-tyrosine phosphatase, is recruited to the growth factor receptors upon stimulation of cells. To investigate its role in growth factor signaling, we have overexpressed by approximately 6-fold the native PTP2C and a catalytically inactive mutant of the enzyme in 293 human embryonic kidney cells. The native PTP2C was located entirely in the cytosol, while the inactive mutant was nearly equally distributed in cytosolic and membrane fractions. Expression of the latter caused hyperphosphorylation on tyrosine of a 43-kDa protein, which was co-immunoprecipitated and co-partitioned in the plasma membrane fraction with the inactive PTP2C mutant. This protein may represent a physiological substrate of PTP2C. Overexpression of the native PTP2C enhanced epidermal growth factor (EGF)-stimulated mitogen-activated protein (MAP) kinase kinase activity by 30%, whereas expression of the inactive mutant reduced the stimulated activity by 50%. Similar effects were observed for the activation of MAP kinase as determined by activity assay, gel mobility shift, and tyrosine phosphorylation. The data suggest that the phosphatase activity of PTP2C is partly required for MAP kinase activation by EGF and that PTP2C may function by dephosphorylating the 43-kDa membrane protein.