title: Dimerization in vivo and inhibition of the nonreceptor form of protein tyrosine phosphatase epsilon.
abstract: cyt-PTP epsilon is a naturally occurring nonreceptor form of the receptor-type protein tyrosine phosphatase (PTP) epsilon. As such, cyt-PTP epsilon enables analysis of phosphatase regulation in the absence of extracellular domains, which participate in dimerization and inactivation of the receptor-type phosphatases receptor-type protein tyrosine phosphatase alpha (RPTPalpha) and CD45. Using immunoprecipitation and gel filtration, we show that cyt-PTP epsilon forms dimers and higher-order associations in vivo, the first such demonstration among nonreceptor phosphatases. Although cyt-PTP epsilon readily dimerizes in the absence of exogenous stabilization, dimerization is increased by oxidative stress. Epidermal growth factor receptor stimulation can affect cyt-PTP epsilon dimerization and tyrosine phosphorylation in either direction, suggesting that cell surface receptors can relay extracellular signals to cyt-PTP epsilon, which lacks extracellular domains of its own. The inactive, membrane-distal (D2) phosphatase domain of cyt-PTP epsilon is a major contributor to intermolecular binding and strongly interacts in a homotypic manner; the presence of D2 and the interactions that it mediates inhibit cyt-PTP epsilon activity. Intermolecular binding is inhibited by the extreme C and N termini of D2. cyt-PTP epsilon lacking these regions constitutively dimerizes, and its activities in vitro towards para-nitrophenylphosphate and in vivo towards the Kv2.1 potassium channel are markedly reduced. We conclude that physiological signals can regulate dimerization and phosphorylation of cyt-PTP epsilon in the absence of direct interaction between the PTP and extracellular molecules. Furthermore, dimerization can be mediated by the D2 domain and does not strictly require the presence of PTP extracellular domains.
authors.affiliation: Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Hila
authors.initials: H
authors.lastname: Toledano-Katchalski
authors.forename: Zohar
authors.initials: Z
authors.lastname: Tiran
authors.forename: Tal
authors.initials: T
authors.lastname: Sines
authors.forename: Gidi
authors.initials: G
authors.lastname: Shani
authors.forename: Shira
authors.initials: S
authors.lastname: Granot-Attas
authors.forename: Jeroen
authors.initials: J
authors.lastname: den Hertog
authors.forename: Ari
authors.initials: A
authors.lastname: Elson
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002850:Chromatography, Gel; D018076:DNA, Complementary / Q000378:metabolism; D051668:Delayed Rectifier Potassium Channels; D019281:Dimerization; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D051379:Mice; D008954:Models, Biological; D010766:Phosphorylation; D015221:Potassium Channels / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology*; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4; D051669:Shab Potassium Channels; D015398:Signal Transduction; D013696:Temperature; D013997:Time Factors; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D051668:Delayed Rectifier Potassium Channels; C496988:KCNB1 protein, human; C496990:Kcnb1 protein, mouse; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D051669:Shab Potassium Channels; D014443:Tyrosine; D006861:Hydrogen Peroxide; C490825:PTPRE protein, human; D017027:Protein Tyrosine Phosphatases; C098067:Ptpre protein, mouse; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4