Junctional protein MAGI-3 interacts with receptor tyrosine phosphatase beta (RPTP beta) and tyrosine-phosphorylated proteins.
Receptor protein tyrosine phosphatase beta (RPTP beta) mediates cell-cell and cell-matrix interactions. By searching for intracellular proteins that interact with the cytoplasmic region of this phosphatase using the two-hybrid method, we identified several proteins containing PDZ domains. One of these proteins, MAGI-3, contains a guanylate-kinase-like region, six PDZ and two ... WW domains. The interaction between RPTP beta and MAGI-3 was confirmed by co-immunoprecipitation and pulldown experiments in transfected cells. Immunofluorescence and immunoelectron microscopy revealed that MAGI-3 is concentrated in specific sites at the plasma membrane and in the nucleus. In epithelial cells, MAGI-3 was localized with ZO-1 and cingulin at tight junctions, whereas in primary cultured astrocytes it was found in E-cadherin-based cell-cell contacts and in focal adhesion sites. Although MAGI-3 itself was not phosphorylated on tyrosine residues, it became associated with tyrosine-phosphorylated proteins following a short treatment of the cells with vanadate. In glioblastoma SF763T cells MAGI-3 was associated with a tyrosine-phosphorylated protein with the apparent molecular weight of 130 kDa, whereas in Caco2 cells it was associated with a 90 kDa protein. Finally, we show that p130 served as a substrate for RPTP beta and that its dephosphorylation required the C-terminal sequence of the phosphatase, which mediated the interaction with MAGI-3. These findings suggest a possible role for MAGI-3 as a scaffolding molecule that links receptor tyrosine phosphatase with its substrates at the plasma membrane.
Mesh Terms:
Adherens Junctions, Amino Acid Sequence, Animals, Cadherins, Cell Communication, Cell Membrane, Cells, Cultured, Epithelial Cells, Guanylate Kinase, Humans, Immunohistochemistry, Intercellular Junctions, Membrane Proteins, Microfilament Proteins, Microscopy, Electron, Molecular Sequence Data, Nerve Tissue Proteins, Nucleoside-Phosphate Kinase, Phosphoproteins, Phosphorylation, Protein Structure, Tertiary, Protein Tyrosine Phosphatases, Rats, Receptor-Like Protein Tyrosine Phosphatases, Class 5, Tight Junctions, Tyrosine
Adherens Junctions, Amino Acid Sequence, Animals, Cadherins, Cell Communication, Cell Membrane, Cells, Cultured, Epithelial Cells, Guanylate Kinase, Humans, Immunohistochemistry, Intercellular Junctions, Membrane Proteins, Microfilament Proteins, Microscopy, Electron, Molecular Sequence Data, Nerve Tissue Proteins, Nucleoside-Phosphate Kinase, Phosphoproteins, Phosphorylation, Protein Structure, Tertiary, Protein Tyrosine Phosphatases, Rats, Receptor-Like Protein Tyrosine Phosphatases, Class 5, Tight Junctions, Tyrosine
J. Cell. Sci.
Date: Apr. 01, 2003
PubMed ID: 12615970
View in: Pubmed Google Scholar
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