Reversible Inactivation of Protein-tyrosine Phosphatase 1B in A431 Cells Stimulated with Epidermal Growth Factor

Abstract

Stimulation of various cells with growth factors results in a transient increase in the intracellular concentration of H2O2 that is required for growth factor-induced protein tyrosine phosphorylation. The effect of H2O2 produced in response to epidermal growth factor (EGF) on the activity of protein-tyrosine phosphatase 1B (PTP1B) was investigated in A431 human epidermoid carcinoma cells. H2O2 inactivated recombinant PTP1B in vitro by oxidizing its catalytic site cysteine, most likely to sulfenic acid. The oxidized enzyme was reactivated more effectively by thioredoxin than by glutaredoxin or glutathione at their physiological concentrations. Oxidation by H2O2 prevented modification of the catalytic cysteine of PTP1B by iodoacetic acid, suggesting that it should be possible to monitor the oxidation state of PTP1B in cells by measuring the incorporation of radioactivity into the enzyme after lysis of the cells in the presence of radiolabeled iodoacetic acid. The amount of such radioactivity associated with PTP1B immunoprecipitated from A431 cells that had been stimulated with EGF for 10 min was 27% less than that associated with PTP1B from unstimulated cells. The amount of iodoacetic acid-derived radioactivity associated with PTP1B reached a minimum 10 min after stimulation of cells with EGF and returned to base line values by 40 min, suggesting that the oxidation of PTP1B is reversible in cells. These results indicate that the activation of a receptor tyrosine kinase by binding of the corresponding growth factor may not be sufficient to increase the steady state level of protein tyrosine phosphorylation in cells and that concurrent inhibition of protein-tyrosine phosphatases by H2O2 might also be required. Stimulation of various cells with growth factors results in a transient increase in the intracellular concentration of H2O2 that is required for growth factor-induced protein tyrosine phosphorylation. The effect of H2O2 produced in response to epidermal growth factor (EGF) on the activity of protein-tyrosine phosphatase 1B (PTP1B) was investigated in A431 human epidermoid carcinoma cells. H2O2 inactivated recombinant PTP1B in vitro by oxidizing its catalytic site cysteine, most likely to sulfenic acid. The oxidized enzyme was reactivated more effectively by thioredoxin than by glutaredoxin or glutathione at their physiological concentrations. Oxidation by H2O2 prevented modification of the catalytic cysteine of PTP1B by iodoacetic acid, suggesting that it should be possible to monitor the oxidation state of PTP1B in cells by measuring the incorporation of radioactivity into the enzyme after lysis of the cells in the presence of radiolabeled iodoacetic acid. The amount of such radioactivity associated with PTP1B immunoprecipitated from A431 cells that had been stimulated with EGF for 10 min was 27% less than that associated with PTP1B from unstimulated cells. The amount of iodoacetic acid-derived radioactivity associated with PTP1B reached a minimum 10 min after stimulation of cells with EGF and returned to base line values by 40 min, suggesting that the oxidation of PTP1B is reversible in cells. These results indicate that the activation of a receptor tyrosine kinase by binding of the corresponding growth factor may not be sufficient to increase the steady state level of protein tyrosine phosphorylation in cells and that concurrent inhibition of protein-tyrosine phosphatases by H2O2 might also be required. Ligation of a variety of cell surface receptors, including those for growth factors and cytokines, induces a transient increase in the intracellular concentration of H2O2 in mammalian cells (1Lo Y.Y.C. Cruz T.F. J. Biol. Chem. 1995; 270: 11727-11730Abstract Full Text Full Text PDF PubMed Scopus (468) Google Scholar, 2Sundaresan M. Yu Z.-X. Ferrans V.J. Irani K. Finkel T. Science. 1996; 270: 296-299Crossref Scopus (2285) Google Scholar, 3Bae Y.S. Kang S.W. Seo M.S. Baines I.C. Tekle E. Chock P.B. Rhee S.G. J. Biol. Chem. 1997; 272: 217-221Abstract Full Text Full Text PDF PubMed Scopus (1085) Google Scholar). Inhibition of this effect blocks receptor-mediated signal transduction. For example, inhibition of the accumulation of H2O2 by introducing catalase into NIH 3T3 or A431 cells prevented the induction of tyrosine phosphorylation by platelet-derived growth factor or epidermal growth factor (EGF) 1The abbreviations used are: EGF, epidermal growth factor; PTK, protein-tyrosine kinase; PTP, protein-tyrosine phosphatase; PTP1, protein-tyrosine phosphatase 1; PTP1B, protein-tyrosine phosphatase 1B; DTT, dithiothreitol; GR, glutathione reductase; PAGE, polyacrylamide gel electrophoresis; Trx, thioredoxin; Grx, glutaredoxin; TR, Trx reductase; HPLC, high performance liquid chromatography; pNPP, p-nitrophenyl phosphate; Bis-Tris, [bis(2-hydroxyethyl)imino]-tris(hydroxymethyl) methane; DTNB, 5,5′-dithiobis-(2-nitrobenzoic acid). 1The abbreviations used are: EGF, epidermal growth factor; PTK, protein-tyrosine kinase; PTP, protein-tyrosine phosphatase; PTP1, protein-tyrosine phosphatase 1; PTP1B, protein-tyrosine phosphatase 1B; DTT, dithiothreitol; GR, glutathione reductase; PAGE, polyacrylamide gel electrophoresis; Trx, thioredoxin; Grx, glutaredoxin; TR, Trx reductase; HPLC, high performance liquid chromatography; pNPP, p-nitrophenyl phosphate; Bis-Tris, [bis(2-hydroxyethyl)imino]-tris(hydroxymethyl) methane; DTNB, 5,5′-dithiobis-(2-nitrobenzoic acid). (2Sundaresan M. Yu Z.-X. Ferrans V.J. Irani K. Finkel T. Science. 1996; 270: 296-299Crossref Scopus (2285) Google Scholar, 3Bae Y.S. Kang S.W. Seo M.S. Baines I.C. Tekle E. Chock P.B. Rhee S.G. J. Biol. Chem. 1997; 272: 217-221Abstract Full Text Full Text PDF PubMed Scopus (1085) Google Scholar). Direct exposure of cells to H2O2 also increases protein tyrosine phosphorylation and activates signal transduction pathways (2Sundaresan M. Yu Z.-X. Ferrans V.J. Irani K. Finkel T. Science. 1996; 270: 296-299Crossref Scopus (2285) Google Scholar, 3Bae Y.S. Kang S.W. Seo M.S. Baines I.C. Tekle E. Chock P.B. Rhee S.G. J. Biol. Chem. 1997; 272: 217-221Abstract Full Text Full Text PDF PubMed Scopus (1085) Google Scholar, 4Heffetz D. Bushkin I. Dror R. Zick Y. J. Biol. Chem. 1990; 265: 2896-2902Abstract Full Text PDF PubMed Google Scholar, 5Irani K. Xia Y. Zweier J.L. Sollott S.J. Der C.J. Fearon E.R. Sundaresan M. Finkel T. Goldschmidt-Clermont P.J. Science. 1997; 275: 1649-1652Crossref PubMed Scopus (1418) Google Scholar). Because the extent of protein tyrosine phosphorylation in a cell reflects an equilibrium between the actions of protein-tyrosine kinases (PTKs) and protein-tyrosine phosphatases (PTPs), either stimulation of PTKs or inhibition of PTPs would be expected to shift the equilibrium toward phosphorylation. PTP activity in crude cell extracts can be inactivated by various oxidants, including H2O2, and this inactivation can be reversed by incubation with thiol compounds such as dithiothreitol (DTT) and GSH (6Hecht D. Zick Y. Biochem. Biophys. Res. Commun. 1992; 188: 773-779Crossref PubMed Scopus (247) Google Scholar, 7Sullivan S.G. Chiu D.T.-Y. Errasfa M. Wang J.M. Qi J.-S. Stern A. Free Radical Biol. Med. 1994; 16: 399-403Crossref PubMed Scopus (104) Google Scholar). These observations suggest that PTPs might undergo H2O2-dependent inactivation in cells, resulting in a shift in the equilibrium with PTKs toward phosphorylation. PTPs constitute a diverse family of enzymes that can be divided into several subgroups, including receptor PTPs and nonreceptor PTPs (8Fischer E.H. Charbonneau H. Tonks N.K. Science. 1991; 253: 401-406Crossref PubMed Scopus (862) Google Scholar, 9Stone R.L. Dixon J.E. J. Biol. Chem. 1994; 269: 31323-31326Abstract Full Text PDF PubMed Google Scholar, 10Denu J.M. Stuckey J.A. Saper M.A. Dixon J.E. Cell. 1996; 87: 361-364Abstract Full Text Full Text PDF PubMed Scopus (299) Google Scholar, 11Tonks N.K. Neel B.G. Cell. 1996; 87: 365-368Abstract Full Text Full Text PDF PubMed Scopus (488) Google Scholar). All PTPs contain an essential cysteine residue in the signature active site motif, HCXXGXXR(S/T). The PTP active site cysteines exhibit low pK a values (5.4 for mammalian PTP1 (12Lohse D.L. Denu J.M. Santoro N. Dixon J.E. Biochemistry. 1997; 36: 4568-4575Crossref PubMed Scopus (156) Google Scholar), 5.6 for human dual specific PTP (13Denu J.M. Zhou G. Guo Y. Dixon J.E. Biochemistry. 1995; 34: 3396-3403Crossref PubMed Scopus (121) Google Scholar), and 4.7 for Yersinia PTP (14Zhang Z.-Y. Dixon J.E. Biochemistry. 1993; 32: 9340-9345Crossref PubMed Scopus (238) Google Scholar)) and are readily ionized at neutral pH, whereas the pK a of a typical cysteine residue is 8.5. The ionized essential sulfhydryl group (thiolate anion) contributes to the formation of a thiol-phosphate intermediate in the catalytic mechanism of PTPs (15Guan K. Dixon J.E. J. Biol. Chem. 1991; 266: 17026-17030Abstract Full Text PDF PubMed Google Scholar). In addition, the essential cysteine is the target of specific modification by various sulfhydryl-alkylating reagents (12Lohse D.L. Denu J.M. Santoro N. Dixon J.E. Biochemistry. 1997; 36: 4568-4575Crossref PubMed Scopus (156) Google Scholar, 13Denu J.M. Zhou G. Guo Y. Dixon J.E. Biochemistry. 1995; 34: 3396-3403Crossref PubMed Scopus (121) Google Scholar, 14Zhang Z.-Y. Dixon J.E. Biochemistry. 1993; 32: 9340-9345Crossref PubMed Scopus (238) Google Scholar, 16Pot D.A. Woodford T.A. Remboutsika E. Haun R.S. Dixon J.E. J. Biol. Chem. 1991; 266: 19688-19696Abstract Full Text PDF PubMed Google Scholar, 17Zhou G. Denu J.M. Wu L. Dixon J.E. J. Biol. Chem. 1994; 269: 28084-28090Abstract Full Text PDF PubMed Google Scholar). We now demonstrate that H2O2, either added extracellularly or generated intracellularly in response to EGF, can cause reversible inactivation of PTPs in cells, and we identify the most plausible electron donor responsible for the reactivation of such inactivated PTPs. PTP1B, the widely expressed cytosolic enzyme originally purified from human placenta (18Tonks N.K. Diltz C.D. Fischer E.H. J. Biol. Chem. 1988; 263: 6722-6730Abstract Full Text PDF PubMed Google Scholar), was chosen as the target enzyme and was studied in A431 human epidermoid carcinoma cells. Dulbecco's modified Eagle's medium, fetal bovine serum, penicillin, and streptomycin were from Life Technologies, Inc. Rabbit polyclonal antibodies to PTP1B were kindly provided by B. G. Neel (Harvard University). A monoclonal antibody to PTP1B was obtained from Oncogene Science. Horseradish peroxidase-conjugated antibodies to mouse or to rabbit immunoglobulin G were from Amersham Pharmacia Biotech. Yeast glutathione reductase (GR) and bovine catalase were from Boehringer Mannheim. The synthetic peptide Raytide and the kinase p43v-abl were from Oncogene Science. [γ-33P]ATP was from Amersham Pharmacia Biotech, and14C- or 3H-labeled iodoacetic acid was from NEN Life Science Products. Complementary DNA corresponding to the 37-kDa form (NH2-terminal 321 residues) of PTP1B was obtained by the polymerase chain of the polymerase at the site of a to the of PTP1B by a and expressed in by The PTP1B protein was purified from with the of an The of the PTP1B as by gel was A of the purified PTP1B was with to the and was on a the purified and enzymes were in the presence of 10 for and in an at a and of the enzyme were in an at PTP1B was used this Trx Res. PubMed Scopus Google was obtained by the polymerase chain into the and expressed in E. by Trx was purified to from the cytosolic of E. by at by on gel Pharmacia and high performance liquid and were purified from as M. A. Biochemistry. PubMed Scopus Google Scholar, J.L. J.A. Biochemistry. 1993; Scopus Google Scholar, A. 1996; PubMed Scopus Google Scholar). The of recombinant PTP1B and Trx were and the A values of were and The of were with the protein with bovine as a were used to PTP1B The activity of recombinant PTP1B was with p-nitrophenyl as a in a 40 and 10 (13Denu J.M. Zhou G. Guo Y. Dixon J.E. Biochemistry. 1995; 34: 3396-3403Crossref PubMed Scopus (121) Google Scholar). The formation was by the in A of PTP1B activity in was with Raytide as a Neel B.G. Cell. 1992; Full Text PDF PubMed Scopus Google Scholar). the bovine 10 DTT, and Raytide were at for min, after the was by the of 10 of acid, and the radioactivity associated with the peptide was as Biochem. 87: PubMed Scopus Google Scholar). PTP1B that had been with and a was at with H2O2 in a of 40 and min, the oxidation was by of The resulting oxidized and enzymes in were with of a 5,5′-dithiobis-(2-nitrobenzoic and The concentration of acid was with a of at Biochem. Biophys. PubMed Scopus Google Scholar). PTP1B that had been with H2O2 for 10 min and with catalase as was with acid in a of of 40 a PTP1B was with acid. 10 min at the was by and the were to gel on a to iodoacetic acid. The were and at with of in a of The resulting were by on a with a of in acid at a of corresponding to peptide were and a of was for A431 cells, in Dulbecco's modified Eagle's with fetal bovine serum, and streptomycin were to in The cells were of for and stimulated with EGF or H2O2 or The cells were and in an to of lysis and acid and a cells that were not stimulated with EGF or H2O2 were and min at in the the was by of iodoacetic acid in and by the of of The were at for The resulting were to a gel to were and protein were The were by for at with 40 of and at for 40 of immunoglobulin that had been with an of monoclonal antibody to PTP1B were added to the resulting and incubation was for an The were in lysis in and in and either to in to the amount of radioactivity into PTP1B or to the amount of PTP activity by with PTP1B was originally from human placenta as a 37-kDa protein (18Tonks N.K. Diltz C.D. Fischer E.H. J. Biol. Chem. 1988; 263: 6722-6730Abstract Full Text PDF PubMed Google Scholar). was that the PTP1B protein and that the 37-kDa protein to the 321 J. R.L. Neel B.G. A. 1990; 87: PubMed Scopus Google Scholar). The of the protein contain a responsible for of PTP1B in the Neel B.G. Cell. 1992; Full Text PDF PubMed Scopus Google Scholar). The 37-kDa PTP1B cysteine not to form on the of the of the protein D. Tonks N.K. Science. 1994; 263: PubMed Scopus Google Scholar). and of PTP1B are of the PTP family H. Tonks N.K. Diltz C.D. M. E.H. A. PubMed Scopus Google Scholar). a pK of is the essential cysteine residue at the active of in PTP1, the of PTP1B, PTP activity (15Guan K. Dixon J.E. J. Biol. Chem. 1991; 266: 17026-17030Abstract Full Text PDF PubMed Google Scholar). The active site cysteines of various including of PTP1B, are by the iodoacetic acid (12Lohse D.L. Denu J.M. Santoro N. Dixon J.E. Biochemistry. 1997; 36: 4568-4575Crossref PubMed Scopus (156) Google Scholar, 13Denu J.M. Zhou G. Guo Y. Dixon J.E. Biochemistry. 1995; 34: 3396-3403Crossref PubMed Scopus (121) Google Scholar, 14Zhang Z.-Y. Dixon J.E. Biochemistry. 1993; 32: 9340-9345Crossref PubMed Scopus (238) Google Scholar, 16Pot D.A. Woodford T.A. Remboutsika E. Haun R.S. Dixon J.E. J. Biol. Chem. 1991; 266: 19688-19696Abstract Full Text PDF PubMed Google Scholar, 17Zhou G. Denu J.M. Wu L. Dixon J.E. J. Biol. Chem. 1994; 269: 28084-28090Abstract Full Text PDF PubMed Google Scholar). The active site cysteine also been as the site of oxidation by various (2Sundaresan M. Yu Z.-X. Ferrans V.J. Irani K. Finkel T. Science. 1996; 270: 296-299Crossref Scopus (2285) Google Scholar, 3Bae Y.S. Kang S.W. Seo M.S. Baines I.C. Tekle E. Chock P.B. Rhee S.G. J. Biol. Chem. 1997; 272: 217-221Abstract Full Text Full Text PDF PubMed Scopus (1085) Google Scholar, D. Zick Y. Biochem. Biophys. Res. Commun. 1992; 188: 773-779Crossref PubMed Scopus (247) Google Scholar, 7Sullivan S.G. Chiu D.T.-Y. Errasfa M. Wang J.M. Qi J.-S. Stern A. Free Radical Biol. Med. 1994; 16: 399-403Crossref PubMed Scopus (104) Google Scholar, A. A. J. 1996; PubMed Scopus Google Scholar), in should be to monitor the extent of inactivation of PTPs in cells by measuring the amount of radioactivity into the enzyme after cell lysis in the presence of radiolabeled iodoacetic acid. this we expressed the 37-kDa PTP1B in E. purified the recombinant and it to modification by H2O2 and iodoacetic acid. with in the inactivation of the purified recombinant 37-kDa PTP1B in a on and A the enzyme from the in had been inactivated to various by incubation with of were to with iodoacetic acid at the extent of in to the extent of inactivation that the site of oxidation by H2O2 is the as the site of by iodoacetic acid. The in were obtained with results were obtained with PTP1B the We the of sulfhydryl in PTP1B and after oxidation by H2O2 for with the of from the presence of and sulfhydryl PTP1B for the and suggesting that cysteine residue is by identify the cysteine, we PTP1B oxidized with H2O2 for 10 min to as as enzyme to acid. The enzymes were with the resulting were by on a to and the amount of radioactivity associated with was not The from oxidized and PTP1B enzymes produced For PTP1B, of radioactivity was associated with a that at min, whereas the of radioactivity was several for the the that at min the most this amount was of that associated with the corresponding for the of the peptide from the enzyme a of the of of PTP1B with the that the residue corresponding to was as cysteine and the corresponding to and were The PTP1B between and cysteines at and the after were and for most of the was at the with also for the several radioactivity was at the corresponding to and results suggest that the active site is the site of by iodoacetic acid as as the site of oxidation by it should be possible to monitor the extent of PTP1B inactivation by H2O2 by measuring the amount of iodoacetic acid into the enzyme at A431 cells were for various with EGF and in an by exposure to a and acid. PTP1B was immunoprecipitated from the cell with a specific monoclonal and the radioactivity associated with the PTP1B protein was after The extent of incorporation of acid into PTP1B with of incubation of the cells with EGF, a minimum at 10 min, and returned to the by 40 min from that the extent of the in acid incorporation into the PTP1B after stimulation of cells for 10 min with EGF was Stimulation of A431 cells for 10 min with H2O2 at of or the extent of radioactivity into the PTP1B by and These results suggest that PTP1B is oxidized at the active site cysteine in response to stimulation of cells with EGF or for the oxidation of the active site cysteine of PTP1B was provided by reactivation of PTP1B is likely oxidized to sulfenic acid by H2O2 Because sulfenic acid is readily by a incubation of the from the in would be expected to the PTP1B oxidized by H2O2 not those modified by iodoacetic acid. this we the iodoacetic from the and cells to and for PTP the PTP activity of from or and min for and cells was than that for from unstimulated cells These results the that PTP1B is oxidized by H2O2 and that the modified enzyme can be to its state by the activity of PTP1B, were from A431 cell and to and of PTP activity as in the of with the that iodoacetic acid was from the lysis The PTP activity was min and was not by stimulation of cells with EGF or H2O2, suggesting that the amount of PTP1B was not by EGF or The PTP of from iodoacetic were expressed as a of the PTP activity The that such from unstimulated cells PTP activity of that PTP1B was not by iodoacetic acid or that a of PTP1B in unstimulated cells in an oxidized The of the activity by for the stimulated cells for and for cells with or were than the corresponding in iodoacetic acid and The for this is not is possible that exposure of to might in oxidation of sulfenic acid to acid be by PTP1B that had been inactivated by exposure to H2O2 was in the presence of various electron and reactivation was In to and the Trx of Trx, TR, and and the of Grx, GR, and were used as electron In the Trx oxidized Trx is by with the of by In the oxidized is by in from the of The most reactivation was by whereas GSH was the electron The Trx was less than DTT, and the was less than the Trx The of the and was by measuring M. A. J. Biol. Chem. Full Text PDF PubMed Google and glutathione M. J. B. A. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google of the Trx and was used at a their not increase the of reactivation not The of oxidized PTP1B by the Trx and the was also by the to the oxidation of PTP1B by GSH was also to oxidation by including and in the In with the in the for the of oxidation was Trx GSH the concentration of used in the is expected to be of oxidized PTP1B by the Trx required TR, and reactivation in the of of the was not The concentration of Trx required for reactivation was the that H2O2 is required for the growth factor-induced tyrosine phosphorylation of we investigated in response to EGF is of PTP1B in A431 cells. with the of the recombinant 37-kDa form of PTP1B, we that the essential residue is the site of oxidation by The oxidized of cysteine sulfenic acid, acid, and acid The intermediate can be as the form of PTP1B on the of that of was after H2O2 and the and acid can be on the of the that the oxidized PTP1B can be to its state by PTP1B was to form and acid oxidized in the presence of G. J. J. B. G. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google and K. J. M. Wang J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar), sulfenic acid is and readily with a the sulfenic acid intermediate of PTP1B is by the to the of the 37-kDa form of PTP1B D. Tonks N.K. Science. 1994; 263: PubMed Scopus Google Scholar), cysteine are the is also by a to was to the of and to its pK we the amount of radiolabeled iodoacetic acid into PTP1B as a of in the oxidation state of the protein in A431 cells stimulated with was on observations that iodoacetic acid with of PTP1B at and that the oxidation of this cysteine residue by H2O2 its with iodoacetic acid. of A431 cells to EGF in a in the extent of iodoacetic acid of PTP1B, with the 10 min after stimulation and the to values by 40 is to the oxidation of PTP1B by H2O2, that EGF H2O2 and that inhibition of H2O2 accumulation protein tyrosine phosphorylation in A431 cells Y.S. Kang S.W. Seo M.S. Baines I.C. Tekle E. Chock P.B. Rhee S.G. J. Biol. Chem. 1997; 272: 217-221Abstract Full Text Full Text PDF PubMed Scopus (1085) Google Scholar). exposure of recombinant PTP1B to H2O2 also in a in by iodoacetic acid. A in of PTP1B with a was also PTP1B was immunoprecipitated from or A431 cells. Wu and G. is with that PTP activity in crude extracts of cells was by as a of of cells with H2O2 S.G. Chiu D.T.-Y. Errasfa M. Wang J.M. Qi J.-S. Stern A. Free Radical Biol. Med. 1994; 16: 399-403Crossref PubMed Scopus (104) Google Scholar). we the of Trx, Grx, and GSH to oxidized recombinant PTP1B in Trx at was more than or The of Trx and GSH are and A. M. Biochemistry. PubMed Scopus Google Scholar, Science. 1992; PubMed Scopus Google Scholar). Trx is to be a electron donor for PTP1B in cells. Trx was to be the electron donor for the of an active site cysteine sulfenic acid, whereas was for the of the enzyme a Chem. Res. Scopus Google Scholar, H. J. Biochem. 1994; PubMed Scopus Google Scholar, H. K. J. Biochem. 1992; PubMed Scopus Google Scholar). we the of PTP1B to H2O2 in response to of cells with EGF, PTP enzymes are also to such it is possible that the concentration of H2O2 is high to PTPs in of the cell in the are and that H2O2 that from such are readily by various a inactivation of PTP1B is possible for that 27% of this enzyme was oxidized in A431 cells. the mechanism of H2O2 the site of the concentration of H2O2 generated in response to growth factors and is the of the that growth factor-induced protein tyrosine phosphorylation and that growth factor-induced of H2O2 is sufficient to cause inactivation of PTP1B, we that the activation of a receptor by with a growth factor may not be sufficient to increase the steady state level of protein tyrosine phosphorylation in a concurrent inhibition of PTPs by also be required for this The extent of tyrosine phosphorylation of receptor PTKs and their would to values after of H2O2 and the reactivation of PTPs by electron in vitro suggest that Trx might be a physiological electron donor for to be PTPs also form a sulfenic acid intermediate on oxidation with H2O2 and Trx such oxidized The low PTP, to PTPs several in active site R.L. Dixon J.E. J. Biol. Chem. 1994; 269: 31323-31326Abstract Full Text PDF PubMed Google Scholar, N. M. G. 1994; PubMed Scopus Google Scholar), a on oxidation with A. G. G. G. L. G. G. J. Biol. Chem. 1994; 269: Full Text PDF PubMed Google Scholar). A the of Trx in growth factor-induced protein tyrosine phosphorylation is in is with the of H2O2 results in inhibition of the PTP activity of in the H2O2 by or an of its PTP activity L. J. Biol. Chem. 1993; Full Text PDF PubMed Google Scholar, L. J. 1997; Google Scholar), and of intracellular by protein tyrosine phosphorylation S.G. J.M. J.A. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). The is also with the that the activity of receptor PTKs might be sufficient to increase the extent of protein tyrosine phosphorylation in cells with such as iodoacetic acid and or oxidants, such as that cause the inactivation of PTPs A. A. J. 1996; PubMed Scopus Google Scholar). for the of nonreceptor PTP activity phosphorylation at and tyrosine Neel B.G. Cell. 1992; Full Text PDF PubMed Scopus Google Tonks N.K. J. 1993; PubMed Scopus Google Scholar, Neel B.G. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, D. A. J. T.A. J. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar, T. D. Tonks N.K. A. 1997; PubMed Scopus Google Scholar, J. Biochem. J. 1997; PubMed Scopus Google Scholar), R. D. Biochemistry. 1993; 32: PubMed Scopus Google Scholar, D. Neel B.G. Biochemistry. 1994; PubMed Scopus Google Scholar), and A. M. Neel B.G. J. 1993; PubMed Scopus Google Scholar, J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). In to of PTP oxidation by H2O2 a for of PTP by also been for the receptor PTP R. T. A. Science. PubMed Scopus Google Scholar). We H. for G. Neel for antibodies to PTP1B and R. and M. for peptide