title: The role of protein-tyrosine phosphatase 1B in integrin signaling.
abstract: Protein-tyrosine phosphatase 1B (PTP1B) is a key negative regulator of insulin and leptin signaling and a novel therapeutic target for the treatment of type 2 diabetes, obesity, and other associated metabolic syndromes. Because PTP1B regulates multiple signal pathways and it can both enhance and antagonize a cellular event, it is important to establish the physiological relevance of PTP1B in these processes. In this study, we utilize potent and selective PTP1B inhibitors to delineate the role of PTP1B in integrin signaling. We show that down-regulation of PTP1B activity with small molecule inhibitors suppresses cell spreading and migration to fibronectin, increases Tyr(527) phosphorylation in Src, and decreases phosphorylation of FAK, p130(Cas), and ERK1/2. In addition, PTP1B "substrate-trapping" mutants bind Tyr(527)-phosphorylated Src and protect it from dephosphorylation by endogenous PTP1B. These results establish that PTP1B promotes integrin-mediated responses in fibroblasts by dephosphorylating the inhibitory pTyr(527) and thereby activating the Src kinase. We also show that PTP1B forms a complex with Src and p130(Cas), and that the proline-rich motif PPRPPK (residues 309-314) in PTP1B is essential for the complex formation. We suggest that the specificity of PTP1B for Src pTyr(527) is mediated by protein-protein interactions involving the docking protein p130(Cas) with both Src and PTP1B in addition to the interactions between the PTP1B active site and the pTyr(527) motif.
authors.affiliation: Departments of Molecular Pharmacology and Biochemistry, Albert Einstein College of Medicine, Bronx, New York 10461.
authors.forename: Fubo
authors.initials: F
authors.lastname: Liang
authors.forename: Seung-Yub
authors.initials: SY
authors.lastname: Lee
authors.forename: Jiao
authors.initials: J
authors.lastname: Liang
authors.forename: David S
authors.initials: DS
authors.lastname: Lawrence
authors.forename: Zhong-Yin
authors.initials: ZY
authors.lastname: Zhang
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D002460:Cell Line; D002465:Cell Movement; D050719:Crk-Associated Substrate Protein; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000737:chemistry; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D016023:Integrins / Q000378:metabolism*; D007700:Kinetics; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D008954:Models, Biological; D008956:Models, Chemical; D009154:Mutation; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000737:chemistry; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D050717:Retinoblastoma-Like Protein p130; D015398:Signal Transduction; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: C493841:BCAR1 protein, human; D050719:Crk-Associated Substrate Protein; D004791:Enzyme Inhibitors; D005353:Fibronectins; D016023:Integrins; D011506:Proteins; D050717:Retinoblastoma-Like Protein p130; D019000:Phosphotyrosine; D014443:Tyrosine; D011392:Proline; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C516607:PTPN1 protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases