Voltar
Artigo Acesso aberto Revisado por pares
BIBTEX RIS

Regulation of the Low Molecular Weight Phosphotyrosine Phosphatase by Phosphorylation at Tyrosines 131 and 132

1997; Elsevier BV; Volume: 272; Issue: 9 Linguagem: Inglês

10.1074/jbc.272.9.5371

ISSN

1083-351X

Autores

Pankaj Tailor, Jennifer Gilman, Scott Williams, Clément Couture, Tomas Mustelin,

Tópico(s)

Glycosylation and Glycoproteins Research

Resumo

Activation of resting T lymphocytes is initiated by rapid but transient tyrosine phosphorylation of a number of cellular proteins. Several protein tyrosine kinases and protein tyrosine phosphatases are known to be important for this response. Here we report that normal T lymphocytes express the B isoform of low molecular weight protein tyrosine phosphatase B (LMPTP-B). The cDNA was cloned from Jurkat T cells, and an antiserum was raised against it. LMPTP immunoprecipitated from resting Jurkat T cells was found to be tyrosine phosphorylated. On stimulation of the cells through their T cell antigen receptor, the phosphotyrosine content of LMPTP-B declined rapidly. In co-transfected COS cells, Lck and Fyn caused phosphorylation of LMPTP, whereas Csk, Zap, and Jak2 did not. Most of the phosphate was located at Tyr-131, and some was also located at Tyr-132. Incubation of wild-type LMPTP with Lck and adenosine 5′-O-(thiotriphosphate) caused a 2-fold increase in the activity of LMPTP. Site-directed mutagenesis showed that Tyr-131 is important for the catalytic activity of LMPTP, and that thiophosphorylation of Tyr-131, and to a lesser degree Tyr-132, is responsible for the activation. Activation of resting T lymphocytes is initiated by rapid but transient tyrosine phosphorylation of a number of cellular proteins. Several protein tyrosine kinases and protein tyrosine phosphatases are known to be important for this response. Here we report that normal T lymphocytes express the B isoform of low molecular weight protein tyrosine phosphatase B (LMPTP-B). The cDNA was cloned from Jurkat T cells, and an antiserum was raised against it. LMPTP immunoprecipitated from resting Jurkat T cells was found to be tyrosine phosphorylated. On stimulation of the cells through their T cell antigen receptor, the phosphotyrosine content of LMPTP-B declined rapidly. In co-transfected COS cells, Lck and Fyn caused phosphorylation of LMPTP, whereas Csk, Zap, and Jak2 did not. Most of the phosphate was located at Tyr-131, and some was also located at Tyr-132. Incubation of wild-type LMPTP with Lck and adenosine 5′-O-(thiotriphosphate) caused a 2-fold increase in the activity of LMPTP. Site-directed mutagenesis showed that Tyr-131 is important for the catalytic activity of LMPTP, and that thiophosphorylation of Tyr-131, and to a lesser degree Tyr-132, is responsible for the activation. INTRODUCTIONOne of the earliest biochemical events seen in T lymphocytes triggered through the T cell antigen receptor complex is the enhanced phosphorylation of a number of cellular proteins on tyrosine residues (1Hsi E.D. Siegel J.N. Minami Y. Luong E.T. Klausner R.D. Samelson L.E. J. Biol. Chem. 1989; 264: 10836-10842Abstract Full Text PDF PubMed Google Scholar, 2June C.H. Fletcher M.C. Ledbetter J.A. Samelson L.E. J. Immunol. 1990; 144: 1591-1598PubMed Google Scholar). Inhibition of this event by pharmacological agents prevents T cell activation as measured by both functional readouts and biochemical assays (3Mustelin T. Coggeshall K.M. Isakov N. Altman A. Science. 1990; 247: 1584-1587Crossref PubMed Scopus (368) Google Scholar, 4June C.H. Fletcher M.C. Ledbetter J.A. Schieven G.L. Siegel J.N. Phillips A.F. Samelson L.E. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 7722-7727Crossref PubMed Scopus (432) Google Scholar). It has become evident that several protein tyrosine kinases (PTKs) 1The abbreviations used are: PTKprotein tyrosine kinasePTPaseprotein tyrosine phosphataseLMPTPlow molecular weight PTPasePTyrphosphotyrosineRT-PCRreverse transcription-polymerase chain reactionmAbmonoclonal antibodyHAhemagglutininGSTglutathione S-transferaseATPγSadenosine 5′-O-(thiotriphosphate). and the CD45 protein tyrosine phosphatase (PTPase) play crucial roles (reviewed in Refs. 5Altman A. Coggeshall K.M. Mustelin T. Adv. Immunol. 1990; 48: 277-360Google Scholar, 6Mustelin T. Src Family Tyrosine Kinases in Leukocytes. R. G. Landes Co., Austin, TX1994: 1-155Google Scholar, 7Mustelin T. Immunity. 1994; 1: 351-356Abstract Full Text PDF PubMed Scopus (82) Google Scholar), and that the T cell antigen receptor-induced cascade of transient tyrosine phosphorylation events depends on a dynamic interplay between these and, presumably, many additional PTKs and PTPases. In addition to CD45 (8Pingel J.T. Thomas M.L. Cell. 1989; 58: 1055-1065Abstract Full Text PDF PubMed Scopus (436) Google Scholar, 9Mustelin T. Coggeshall M.K. Altman A. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 6302-6306Crossref PubMed Scopus (406) Google Scholar, 10Koretzky G.A. Picus J. Thomas M.L. Weiss A. Nature. 1990; 346: 66-68Crossref PubMed Scopus (391) Google Scholar), only two other PTPases have been implicated in T cell activation, namely SHP1 (11Plas D.R. Johnson R. Pingel J.T. Matthews R.J. Dalton M. Roy G. Chan A.C. Thomas M.L. Science. 1996; 272: 1173-1176Crossref PubMed Scopus (329) Google Scholar) and SHP2 (12Tailor P. Jascur T. Williams S. von Willebrand M. Couture C. Mustelin T. Eur. J. Biochem. 1996; 237: 736-742Crossref PubMed Scopus (19) Google Scholar).The low molecular weight PTPases LMPTP-A and LMPTP-B constitute a class of PTPases with limited sequence homology to the other PTPases (13Ramponi G. Adv. Protein Phosphatases. 1994; 8: 1-25Google Scholar, 14Zhang M. Stauffacher C.V. Van Etten R.L. Adv. Protein Phosphatases. 1995; 9: 1-23Google Scholar, 15Cirri P. Chiarugi P. Camici G. Manao G. Raugie G. Cappugi G. Ramponi G. Eur. J. Biochem. 1993; 214: 647-657Crossref PubMed Scopus (99) Google Scholar, 16Su X.-D. Taddei N. Massimo S. Ramponi G. Nordlund P. Nature. 1994; 370: 575-578Crossref PubMed Scopus (203) Google Scholar). Nevertheless, these enzymes are highly specific for PTyr (14Zhang M. Stauffacher C.V. Van Etten R.L. Adv. Protein Phosphatases. 1995; 9: 1-23Google Scholar). Chemical modifications and mutagenesis experiments have shown that their catalytic mechanism involves a cysteine residue, Cys-12, which participates in phosphoenzyme intermediate formation (15Cirri P. Chiarugi P. Camici G. Manao G. Raugie G. Cappugi G. Ramponi G. Eur. J. Biochem. 1993; 214: 647-657Crossref PubMed Scopus (99) Google Scholar), as in other PTPases. The recent crystallization of LMPTP (16Su X.-D. Taddei N. Massimo S. Ramponi G. Nordlund P. Nature. 1994; 370: 575-578Crossref PubMed Scopus (203) Google Scholar) showed that the catalytic center is quite similar to that of "classical" PTPases, with Cys-12 residing in the bottom of the catalytic pocket.The physiological functions of LMPTP are unknown. Overexpression of LMPTP in cells transformed by PTK oncogenes leads to decreased proliferation and the ability to form colonies in soft agar (17Ramponi G. Ruggiero M. Raugei G. Berti A. Modesti A. Degl'Innocenti D. Magnelli L. Pazzagli C. Chiarugi V.P. Camici G. Int. J. Cancer. 1992; 51: 652-656Crossref PubMed Scopus (59) Google Scholar). Thus, a potential physiological function of the LMPTPs is to control normal cell growth by interacting directly or indirectly with the PTK signaling network. Reportedly, LMPTP can interact directly with the platelet-derived growth factor receptor PTK in NIH3T3 fibroblasts (18Berti A. Rigacci S. Raugei G. Degl'Innocenti D. Ramponi G. FEBS Lett. 1994; 349: 7-12Crossref PubMed Scopus (56) Google Scholar).We have examined the expression of LMPTP in T cells and have begun to investigate its potential role in T cell activation. We show that LMPTP is present in T cells, is tyrosine phosphorylated mainly at Tyr-131 presumably by Lck or Fyn, and becomes rapidly dephosphorylated on receptor ligation. As mutation or thiophosphorylation of Tyr-131 (and Tyr-132 to a lesser degree) affects the catalytic activity of LMPTP, it seems that LMPTP is regulated during T cell activation. INTRODUCTIONOne of the earliest biochemical events seen in T lymphocytes triggered through the T cell antigen receptor complex is the enhanced phosphorylation of a number of cellular proteins on tyrosine residues (1Hsi E.D. Siegel J.N. Minami Y. Luong E.T. Klausner R.D. Samelson L.E. J. Biol. Chem. 1989; 264: 10836-10842Abstract Full Text PDF PubMed Google Scholar, 2June C.H. Fletcher M.C. Ledbetter J.A. Samelson L.E. J. Immunol. 1990; 144: 1591-1598PubMed Google Scholar). Inhibition of this event by pharmacological agents prevents T cell activation as measured by both functional readouts and biochemical assays (3Mustelin T. Coggeshall K.M. Isakov N. Altman A. Science. 1990; 247: 1584-1587Crossref PubMed Scopus (368) Google Scholar, 4June C.H. Fletcher M.C. Ledbetter J.A. Schieven G.L. Siegel J.N. Phillips A.F. Samelson L.E. Proc. Natl. Acad. Sci. U. S. A. 1990; 87: 7722-7727Crossref PubMed Scopus (432) Google Scholar). It has become evident that several protein tyrosine kinases (PTKs) 1The abbreviations used are: PTKprotein tyrosine kinasePTPaseprotein tyrosine phosphataseLMPTPlow molecular weight PTPasePTyrphosphotyrosineRT-PCRreverse transcription-polymerase chain reactionmAbmonoclonal antibodyHAhemagglutininGSTglutathione S-transferaseATPγSadenosine 5′-O-(thiotriphosphate). and the CD45 protein tyrosine phosphatase (PTPase) play crucial roles (reviewed in Refs. 5Altman A. Coggeshall K.M. Mustelin T. Adv. Immunol. 1990; 48: 277-360Google Scholar, 6Mustelin T. Src Family Tyrosine Kinases in Leukocytes. R. G. Landes Co., Austin, TX1994: 1-155Google Scholar, 7Mustelin T. Immunity. 1994; 1: 351-356Abstract Full Text PDF PubMed Scopus (82) Google Scholar), and that the T cell antigen receptor-induced cascade of transient tyrosine phosphorylation events depends on a dynamic interplay between these and, presumably, many additional PTKs and PTPases. In addition to CD45 (8Pingel J.T. Thomas M.L. Cell. 1989; 58: 1055-1065Abstract Full Text PDF PubMed Scopus (436) Google Scholar, 9Mustelin T. Coggeshall M.K. Altman A. Proc. Natl. Acad. Sci. U. S. A. 1989; 86: 6302-6306Crossref PubMed Scopus (406) Google Scholar, 10Koretzky G.A. Picus J. Thomas M.L. Weiss A. Nature. 1990; 346: 66-68Crossref PubMed Scopus (391) Google Scholar), only two other PTPases have been implicated in T cell activation, namely SHP1 (11Plas D.R. Johnson R. Pingel J.T. Matthews R.J. Dalton M. Roy G. Chan A.C. Thomas M.L. Science. 1996; 272: 1173-1176Crossref PubMed Scopus (329) Google Scholar) and SHP2 (12Tailor P. Jascur T. Williams S. von Willebrand M. Couture C. Mustelin T. Eur. J. Biochem. 1996; 237: 736-742Crossref PubMed Scopus (19) Google Scholar).The low molecular weight PTPases LMPTP-A and LMPTP-B constitute a class of PTPases with limited sequence homology to the other PTPases (13Ramponi G. Adv. Protein Phosphatases. 1994; 8: 1-25Google Scholar, 14Zhang M. Stauffacher C.V. Van Etten R.L. Adv. Protein Phosphatases. 1995; 9: 1-23Google Scholar, 15Cirri P. Chiarugi P. Camici G. Manao G. Raugie G. Cappugi G. Ramponi G. Eur. J. Biochem. 1993; 214: 647-657Crossref PubMed Scopus (99) Google Scholar, 16Su X.-D. Taddei N. Massimo S. Ramponi G. Nordlund P. Nature. 1994; 370: 575-578Crossref PubMed Scopus (203) Google Scholar). Nevertheless, these enzymes are highly specific for PTyr (14Zhang M. Stauffacher C.V. Van Etten R.L. Adv. Protein Phosphatases. 1995; 9: 1-23Google Scholar). Chemical modifications and mutagenesis experiments have shown that their catalytic mechanism involves a cysteine residue, Cys-12, which participates in phosphoenzyme intermediate formation (15Cirri P. Chiarugi P. Camici G. Manao G. Raugie G. Cappugi G. Ramponi G. Eur. J. Biochem. 1993; 214: 647-657Crossref PubMed Scopus (99) Google Scholar), as in other PTPases. The recent crystallization of LMPTP (16Su X.-D. Taddei N. Massimo S. Ramponi G. Nordlund P. Nature. 1994; 370: 575-578Crossref PubMed Scopus (203) Google Scholar) showed that the catalytic center is quite similar to that of "classical" PTPases, with Cys-12 residing in the bottom of the catalytic pocket.The physiological functions of LMPTP are unknown. Overexpression of LMPTP in cells transformed by PTK oncogenes leads to decreased proliferation and the ability to form colonies in soft agar (17Ramponi G. Ruggiero M. Raugei G. Berti A. Modesti A. Degl'Innocenti D. Magnelli L. Pazzagli C. Chiarugi V.P. Camici G. Int. J. Cancer. 1992; 51: 652-656Crossref PubMed Scopus (59) Google Scholar). Thus, a potential physiological function of the LMPTPs is to control normal cell growth by interacting directly or indirectly with the PTK signaling network. Reportedly, LMPTP can interact directly with the platelet-derived growth factor receptor PTK in NIH3T3 fibroblasts (18Berti A. Rigacci S. Raugei G. Degl'Innocenti D. Ramponi G. FEBS Lett. 1994; 349: 7-12Crossref PubMed Scopus (56) Google Scholar).We have examined the expression of LMPTP in T cells and have begun to investigate its potential role in T cell activation. We show that LMPTP is present in T cells, is tyrosine phosphorylated mainly at Tyr-131 presumably by Lck or Fyn, and becomes rapidly dephosphorylated on receptor ligation. As mutation or thiophosphorylation of Tyr-131 (and Tyr-132 to a lesser degree) affects the catalytic activity of LMPTP, it seems that LMPTP is regulated during T cell activation.

Referência(s)