title: Dimerization inhibits the activity of receptor-like protein-tyrosine phosphatase-alpha.
abstract: Protein-tyrosine phosphatases (PTPs) are vital for regulating tryosine phosphorylation in many processes, including growth and differentiation. The regulation of receptor-like PTP (RPTP) activity remains poorly understood, but based on the crystal structure of RPTPalpha domain 1 we have proposed that dimerization can negatively regulate activity, through the interaction of an inhibitory 'wedge' on one monomer with the catalytic cleft of domain 1 in the other monomer. Here we show that dimerization inhibits the activity of a full-length RPTP in vivo. We generated stable disulphide-bonded full-length RPTPalpha homodimers by expressing mutants with single cysteines at different positions in the ectodomain juxtamembrane region. Expression of wild-type RPTPalpha and Phe135Cys and Thr141Cys mutants in RPTPalpha-null mouse embryo cells increased dephosphorylation and activity of Tyr 529 in the protein tyrosine kinase c-Src; in contrast, expression of a Pro137Cys mutant did not. Mutation of Pro 210/211 to leucine in the inhibitory wedge of the Pro137Cys mutant restored its ability to activate c-Src, indicating that dimerization may inhibit full-length RPTPalpha activity in a manner stereochemically consistent with RPTPalpha crystal structures. Our results suggest that RPTPalpha activity can in principle be negatively regulated by dimerization in vivo.
authors.affiliation: Molecular Biology and Virology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA. gjiang@aim.salk.edu
authors.forename: G
authors.initials: G
authors.lastname: Jiang
authors.forename: J
authors.initials: J
authors.lastname: den Hertog
authors.forename: J
authors.initials: J
authors.lastname: Su
authors.forename: J
authors.initials: J
authors.lastname: Noel
authors.forename: J
authors.initials: J
authors.lastname: Sap
authors.forename: T
authors.initials: T
authors.lastname: Hunter
mesh_terms: D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002384:Catalysis; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D019281:Dimerization; D004220:Disulfides / Q000378:metabolism; D051379:Mice; D016297:Mutagenesis, Site-Directed; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4; D011956:Receptors, Cell Surface; D014162:Transfection; D019061:src-Family Kinases
chemical_list: D004220:Disulfides; D011956:Receptors, Cell Surface; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D017027:Protein Tyrosine Phosphatases; C516843:Ptpra protein, mouse; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4