title: Junctional protein MAGI-3 interacts with receptor tyrosine phosphatase beta (RPTP beta) and tyrosine-phosphorylated proteins.
abstract: 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.
authors.affiliation: Department of Molecular Cell Biology, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Adamsky
authors.forename: Katya
authors.initials: K
authors.lastname: Arnold
authors.forename: Helena
authors.initials: H
authors.lastname: Sabanay
authors.forename: Elior
authors.initials: E
authors.lastname: Peles
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism / Q000648:ultrastructure; D000595:Amino Acid Sequence / Q000502:physiology; D000818:Animals; D015820:Cadherins / Q000378:metabolism / Q000648:ultrastructure; D002450:Cell Communication / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000378:metabolism / Q000648:ultrastructure; D051528:Guanylate Kinases; D006801:Humans; D007150:Immunohistochemistry; D007365:Intercellular Junctions / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000378:metabolism / Q000648:ultrastructure; D008840:Microfilament Proteins; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000648:ultrastructure; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism / Q000648:ultrastructure; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000502:physiology; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5; D019108:Tight Junctions / Q000378:metabolism / Q000648:ultrastructure; D014443:Tyrosine / Q000378:metabolism; D062826:Zonula Occludens-1 Protein
chemical_list: C061407:CGN protein, human; D015820:Cadherins; C496469:MAGI3 protein, human; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; C569042:TJP1 protein, human; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; D014443:Tyrosine; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases; C516895:PTPRZ1 protein, human; D017027:Protein Tyrosine Phosphatases; C516897:Ptprz1 protein, rat; D054633:Receptor-Like Protein Tyrosine Phosphatases, Class 5