scholarly journals Molecular cloning and characterization of PTPπ, a novel receptor-like protein-tyrosine phosphatase

1996 ◽  
Vol 319 (1) ◽  
pp. 249-254 ◽  
Author(s):  
Susan CROSSLAND ◽  
Paul D SMITH ◽  
Mark R CROMPTON
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Catalytic Domain ◽  
Transmembrane Domain ◽  
Tyrosine Phosphatase ◽  
Growth Factor Receptor ◽  
Predicted Amino Acid Sequence ◽  
Phosphatase Domain ◽  
Protein Tyrosine ◽  
Foetal Brain

Novel cDNAs encoding a receptor-like protein-tyrosine phosphatase (rPTP) have been isolated from human breast tumour cells and foetal brain. The predicted protein of ∼160 kDa, called PTPπ, comprises an extracellular portion with a MAM (meprin-A5 antigen-PTPµ) domain, an IgG-like domain and four fibronectin III-like repeats, a hydrophobic transmembrane domain and an intracellular portion consisting of two PTP catalytic units. The predicted amino acid sequence shows high identity with those of the two homophilic binding rPTPs, PTPµ and PTPκ. A variant of PTPπ potentially encoding a protein lacking three amino acids within the N-terminal tyrosine phosphatase domain has been identified. Reverse transcription-PCR has been used to confirm the expression of the variant in human foetal brain tissue. Expression analysis has shown that PTPπ is expressed in a variety of tissue types. Both forms of the N-terminal catalytic domain, the C-terminal catalytic domain and both catalytic domains in tandem were expressed in bacteria as fusion proteins. Intrinsic phosphatase activity was detected for all protein products with an artificial substrate. The fusion protein comprising both domains in tandem was also shown to dephosphorylate purified autophosphorylated epidermal growth factor receptor in vitro.

scholarly journals Murine protein tyrosine phosphatase-PEST, a stable cytosolic protein tyrosine phosphatase

1995 ◽  
Vol 308 (2) ◽  
pp. 425-432 ◽  
Author(s):  
A Charest ◽  
J Wagner ◽  
S H Shen ◽  
M L Tremblay
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Northern Blot Analysis ◽  
Catalytic Domain ◽  
Tyrosine Phosphatase ◽  
Glutathione S Transferase ◽  
Epitope Tag ◽  
Reading Frame ◽  
Protein Tyrosine ◽  
Cytosolic Protein

We have isolated the murine cDNA homologue of the human protein tyrosine phosphatase PTP-PEST (MPTP-PEST) from an 18.5-day mouse embryonic kidney library. The cDNA isolated has a single open reading frame predicting a protein of 775 amino acids. When expressed in vitro as a glutathione S-transferase fusion protein, the catalytic domain (residues 1-453) shows intrinsic phosphatase activity. Reverse transcriptase PCR and Northern-blot analysis show that MPTP-PEST mRNA is expressed throughout murine development. Indirect immunofluorescence in COS-1 cells against a heterologous epitope tag attached to the N-terminus of MPTP-PEST, together with cellular fractionation and Western-blot experiments from different murine cell lines, indicate that MPTP-PEST is a free cytosolic protein of 112 kDa. Finally, sequence analysis indicates that the C-terminal portion of the protein contains four regions rich in proline, glutamate, serine and threonine, otherwise known as PEST sequences. These are characteristic of proteins that display very short intracellular half-lives. Despite the presence of these motifs, pulse-chase labelling experiments demonstrate that MPTP-PEST has a half-life of more than 4 h.

scholarly journals Receptor-Like Protein Tyrosine Phosphatase α Homodimerizes on the Cell Surface

2000 ◽  
Vol 20 (16) ◽  
pp. 5917-5929 ◽  
Author(s):  
Guoqiang Jiang ◽  
Jeroen den Hertog ◽  
Tony Hunter
Keyword(s):  
Biological Activity ◽  
Cell Surface ◽  
Protein Tyrosine Phosphatase ◽  
Intracellular Signaling ◽  
Catalytic Domain ◽  
Transmembrane Domain ◽  
Tyrosine Phosphatase ◽  
Receptor Protein ◽  
Dependent Manner ◽  
Protein Tyrosine

ABSTRACT We reported previously that the N-terminal D1 catalytic domain of receptor protein-tyrosine phosphatase α (RPTPα) forms a symmetrical, inhibited dimer in a crystal structure, in which a helix-turn-helix wedge element from one monomer is inserted into the catalytic cleft of the other monomer. Previous functional studies also suggested that dimerization inhibits the biological activity of a CD45 chimeric RPTP and the catalytic activity of an isolated RPTPς D1 catalytic domain. Most recently, we have also shown that enforced dimerization inhibits the biological activity of full-length RPTPα in a wedge-dependent manner. The physiological significance of such inhibition is unknown, due to a lack of understanding of how RPTPα dimerization is regulated in vivo. In this study, we show that transiently expressed cell surface RPTPα exists predominantly as homodimers, suggesting that dimerization-mediated inhibition of RPTPα biological activity is likely to be physiologically relevant. Consistent with our published and unpublished crystallographic data, we show that mutations in the wedge region of D1 catalytic domain and deletion of the entire D2 catalytic domain independently reduced but did not abolish RPTPα homodimerization, suggesting that both domains are critically involved but that neither is essential for homodimerization. Finally, we also provide evidence that both the RPTPα extracellular domain and the transmembrane domain were independently able to homodimerize. These results lead us to propose a zipper model in which inactive RPTPα dimers are stabilized by multiple, relatively weak dimerization interfaces. Dimerization in this manner would provide a potential mechanism for negative regulation of RPTPα. Such RPTPα dimers could be activated by extracellular ligands or intracellular binding proteins that induce monomerization or by intracellular signaling events that induce an open conformation of the dimer.

scholarly journals Protein Tyrosine Phosphatase φ Regulates Paxillin Tyrosine Phosphorylation and Mediates Colony-Stimulating Factor 1-Induced Morphological Changes in Macrophages

2001 ◽  
Vol 21 (5) ◽  
pp. 1795-1809 ◽  
Author(s):  
Fiona J. Pixley ◽  
Pierre S. W. Lee ◽  
John S. Condeelis ◽  
E. Richard Stanley
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Catalytic Domain ◽  
Morphological Changes ◽  
Tyrosine Phosphatase ◽  
Dominant Negative ◽  
Colony Stimulating Factor ◽  
Macrophage Cell ◽  
Protein Tyrosine ◽  
Stimulating Factor

ABSTRACT Removal of colony-stimulating factor 1 (CSF-1) causes macrophages to round up and to increase their expression of protein tyrosine phosphatase φ (PTPφ). This is accompanied by the disruption of focal complexes and the formation of ruffles. Here we have overexpressed wild-type (WT) PTPφ and a phosphatase-inactive (C325S) mutant in a macrophage cell line in the presence and absence of CSF-1. In the presence of CSF-1, WT PTPφ induces cell rounding and ruffle formation, while C325S PTPφ has no effect. In contrast, in CSF-1-starved cells, C325S PTPφ behaves in a dominant negative fashion, preventing rounding and ruffling. Furthermore, C325S PTPφ increases adhesion in cycling cells, while WT PTPφ enhances motility. In WT PTPφ-overexpressing cells, the focal contact protein paxillin is selectively depleted from focal complexes and specifically dephosphorylated on tyrosine. In contrast, paxillin is hyperphosphorylated in C325S PTPφ-expressing cells. Moreover, a complex containing PTPφ, paxillin, and a paxillin-associated tyrosine kinase, Pyk2, can be immunoprecipitated from macrophage lysates, and the catalytic domain of PTPφ selectively binds paxillin and Pyk2 in vitro. Although PTPφ and Pyk2 do not colocalize with paxillin in focal complexes, all three proteins are colocalized in dorsal ruffles. The results suggest that paxillin is dephosphorylated by PTPφ in dorsal ruffles, using Pyk2 as a bridging molecule, resulting in a reduced pool of tyrosine-phosphorylated paxillin available for incorporation into focal complexes, thereby mediating CSF-1 regulation of macrophage morphology, adhesion, and motility.

scholarly journals Dimerization In Vivo and Inhibition of the Nonreceptor Form of Protein Tyrosine Phosphatase Epsilon

2003 ◽  
Vol 23 (15) ◽  
pp. 5460-5471 ◽  
Author(s):  
Hila Toledano-Katchalski ◽  
Zohar Tiran ◽  
Tal Sines ◽  
Gidi Shani ◽  
Shira Granot-Attas ◽  
...  
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Direct Interaction ◽  
Receptor Type ◽  
Phosphatase Domain ◽  
Protein Tyrosine ◽  
Extracellular Domains ◽  
Type Protein

ABSTRACT cyt-PTPε is a naturally occurring nonreceptor form of the receptor-type protein tyrosine phosphatase (PTP) epsilon. As such, cyt-PTPε 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 (RPTPα) and CD45. Using immunoprecipitation and gel filtration, we show that cyt-PTPε forms dimers and higher-order associations in vivo, the first such demonstration among nonreceptor phosphatases. Although cyt-PTPε readily dimerizes in the absence of exogenous stabilization, dimerization is increased by oxidative stress. Epidermal growth factor receptor stimulation can affect cyt-PTPε dimerization and tyrosine phosphorylation in either direction, suggesting that cell surface receptors can relay extracellular signals to cyt-PTPε, which lacks extracellular domains of its own. The inactive, membrane-distal (D2) phosphatase domain of cyt-PTPε 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-PTPε activity. Intermolecular binding is inhibited by the extreme C and N termini of D2. cyt-PTPε 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-PTPε 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.

scholarly journals Protein tyrosine phosphatase 1B interacts with and is tyrosine phosphorylated by the epidermal growth factor receptor

1997 ◽  
Vol 327 (1) ◽  
pp. 139-145 ◽  
Author(s):  
Feng LIU ◽  
Jonathan CHERNOFF
Keyword(s):  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Growth Factor Receptor ◽  
Receptor Protein ◽  
Protein Tyrosine ◽  
Epidermal Growth

We used a substrate-trapping technique to search for substrates of protein tyrosine phosphatase (PTP) 1B. A catalytically inactive form of this enzyme forms a stable, phosphotyrosine-dependent complex with epidermal growth factor receptor (EGFR) both in vitro and in cells. PTP1B also interacts with activated platelet-derived growth factor receptor (PDGFR) but not with colony-stimulating factor 1 receptor (CSF-1R). After binding to EGFR, PTP1B becomes tyrosine-phosphorylated at Tyr-66, a site that conforms to the consensus binding sequence for the Src homology 2 (SH2) domains of the adapter protein Grb2. This tyrosine phosphorylation is correlated with a 3-fold increase in PTP catalytic activity. These findings suggest that PTP1B selectively regulates specific activated receptor protein tyrosine kinases (RPTKs) in vivoand might itself be regulated by such receptors.

Analysis of in vitro interactions of protein tyrosine phosphatase 1B with insulin receptors

2001 ◽  
Vol 173 (1-2) ◽  
pp. 109-120 ◽  
Author(s):  
Xin-Yuan Wang ◽  
Katrin Bergdahl ◽  
Anna Heijbel ◽  
Charlotta Liljebris ◽  
John E. Bleasdale
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
Insulin Receptors ◽  
Protein Tyrosine Phosphatase 1B ◽  
Protein Tyrosine ◽  
In Vitro Interactions

Protein-tyrosine phosphatase activity of CD45 is activated by sequential phosphorylation by two kinases

1994 ◽  
Vol 14 (8) ◽  
pp. 5523-5532
Author(s):  
D R Stover ◽  
K A Walsh
Keyword(s):  
T Cell Activation ◽  
Protein Tyrosine Phosphatase ◽  
Time Course ◽  
Cell Activation ◽  
Regulatory Mechanism ◽  
Transmembrane Protein ◽  
Tyrosine Phosphatase ◽  
Protein Tyrosine

We describe a potential regulatory mechanism for the transmembrane protein-tyrosine phosphatase CD45. Phosphorylation on both tyrosine and serine residues in vitro results in an activation of CD45 specifically toward one artificial substrate but not another. The activation of these kinases appears to be order dependent, as it is enhanced when phosphorylation of tyrosine precedes that of serine but phosphorylation in the reverse order yields no activation. Any of four protein-tyrosine kinases tested, in combination with the protein-serine/threonine kinase, casein kinase II, was capable of mediating this activation in vitro. The time course of phosphorylation of CD45 in response to T-cell activation is consistent with the possibility that this regulatory mechanism is utilized in vivo.

scholarly journals Six New 3,5-Dimethylcoumarins from Chelonopsis praecox, Chelonopsis odontochila and Chelonopsis pseudobracteata

2021 ◽  
Author(s):  
Chang-An Geng ◽  
Zhen-Tao Deng ◽  
Qian Huang ◽  
Chun-Lei Xiang ◽  
Ji-Jun Chen
Keyword(s):  
Protein Tyrosine Phosphatase ◽  
Tyrosine Phosphatase ◽  
2D Nmr ◽  
Cell Protein ◽  
Protein Tyrosine Phosphatase 1B ◽  
Protein Tyrosine ◽  
Aerial Parts ◽  
Spectroscopic Analyses ◽  
New Compounds

AbstractTen 3,5-dimethylcoumarins (1–6 and 8‒11) involving six new ones (1–6), together with a known 3-methylcoumarin (7), were isolated from the aerial parts of three Chelonopsis plants, C. praecox, C. odontochila, and C. pseudobracteata. The structures of the new compounds were determined by extensive HRESIMS, 1D and 2D NMR spectroscopic analyses. According to the substitution at C-5, these coumarins were classified into 5-methyl, 5-hydroxymethyl, 5-formyl, and 5-nor types. All the isolates were assayed for their inhibition on α-glucosidase, protein tyrosine phosphatase 1B, and T-cell protein tyrosine phosphatase in vitro. Graphic Abstract

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