A Cytosolic Protein-tyrosine Phosphatase PTP1B Specifically Dephosphorylates and Deactivates Prolactin-activated STAT5a and STAT5b

Abstract

Prolactin (PRL) plays a central and crucial role in the regulation of milk protein gene expression in mammary epithelial cells. PRL binding to its cognate receptor leads to receptor dimerization and activation of the tyrosine kinase Janus kinase 2 (JAK2), associated with the membrane-proximal, intracellular domain of the receptor. In turn, JAK2 phosphorylates and activates STAT5, a member of the signal transducers and activators of transcription (STAT) family. We have recently reported that 16 different protein-tyrosine phosphatases (PTP) were expressed in lactating mouse mammary gland and mammary epithelial cells (Aoki, N., Kawamura, M., Yamaguchi-Aoki, Y., Ohira, S., and Matsuda, T. (1999) J. Biochem.(Tokyo) 125, 669–675). We investigated the involvement of each PTP in PRL signaling. Among the 12 phosphatases including SHP-2 examined, a cytosolic phosphatase PTP1B was found to specifically dephosphorylate STAT5a and STAT5b in transfected COS7 and in vitro. Nuclear translocation of STAT5a and STAT5b was largely inhibited upon overexpression of PTP1B. The PRL-dependent transcriptional activation of the β-casein gene promoter was also inhibited by PTP1B. Furthermore, retrovirus-mediated overexpression of PTP1B resulted in dephosphorylation of endogenous STAT5 and down-regulation of β-casein gene expression in mammary epithelial COMMA-1D cells when the cells were treated with lactogenic hormones. Endogenous tyrosine-phosphorylated STAT5 proteins in mammary epithelial COMMA-1D cells as well as tyrosine-phosphorylated STAT5a and STAT5b expressed in COS7 cells were co-precipitated by substrate-trapping mutants of recombinant PTP1B. These results strongly suggest that PTP1B dephosphorylates PRL-activated STAT5a and STAT5b, thereby negatively regulating PRL-mediated signaling pathway. Prolactin (PRL) plays a central and crucial role in the regulation of milk protein gene expression in mammary epithelial cells. PRL binding to its cognate receptor leads to receptor dimerization and activation of the tyrosine kinase Janus kinase 2 (JAK2), associated with the membrane-proximal, intracellular domain of the receptor. In turn, JAK2 phosphorylates and activates STAT5, a member of the signal transducers and activators of transcription (STAT) family. We have recently reported that 16 different protein-tyrosine phosphatases (PTP) were expressed in lactating mouse mammary gland and mammary epithelial cells (Aoki, N., Kawamura, M., Yamaguchi-Aoki, Y., Ohira, S., and Matsuda, T. (1999) J. Biochem.(Tokyo) 125, 669–675). We investigated the involvement of each PTP in PRL signaling. Among the 12 phosphatases including SHP-2 examined, a cytosolic phosphatase PTP1B was found to specifically dephosphorylate STAT5a and STAT5b in transfected COS7 and in vitro. Nuclear translocation of STAT5a and STAT5b was largely inhibited upon overexpression of PTP1B. The PRL-dependent transcriptional activation of the β-casein gene promoter was also inhibited by PTP1B. Furthermore, retrovirus-mediated overexpression of PTP1B resulted in dephosphorylation of endogenous STAT5 and down-regulation of β-casein gene expression in mammary epithelial COMMA-1D cells when the cells were treated with lactogenic hormones. Endogenous tyrosine-phosphorylated STAT5 proteins in mammary epithelial COMMA-1D cells as well as tyrosine-phosphorylated STAT5a and STAT5b expressed in COS7 cells were co-precipitated by substrate-trapping mutants of recombinant PTP1B. These results strongly suggest that PTP1B dephosphorylates PRL-activated STAT5a and STAT5b, thereby negatively regulating PRL-mediated signaling pathway. Janus kinase signal transducers and activators of transcription protein-tyrosine phosphatase prolactin glutathioneS-transferase enhanced chemiluminescence hemagglutinin polyacrylamide gel electrophoresis polymerase chain reaction Dulbecco's modified Eagle's medium fetal calf serum interleukin The polypeptide hormone prolactin is produced in the anterior pituitary, regulates the activity of milk protein gene promoters in mammary epithelial cells, and plays an important role in the growth and differentiation of lymphocytes (1DeVlaming V.L. Barrington E.J.W. Hormones and Evolution. Academic Press, New York1979: 561-642Google Scholar). It exhibits its activity via its cognate receptor and the activation of intracellular signaling molecules such as the Janus kinase (JAK)1 signal transducers and activators of transcription (STAT) pathway. The prolactin (PRL) receptor, belonging to the hematopoietin receptor superfamily (2Bazan F Biochem. Cell Biol. 1989; 164: 788-795Google Scholar), does not possess intrinsic tyrosine kinase activity but is associated with the cytoplasmic tyrosine kinase JAK2 (3Dusanter-Fourt I. Muller O. Ziemiecki A. Mayeux P. Drucker B. Djiane J. Wilks A. Harpur A.G. Fisher S. Gisselbrecht S. EMBO J. 1994; 13: 2583-2591Crossref PubMed Scopus (134) Google Scholar, 4Rui H. Kirken R.A. Farrar W.L. J. Biol. Chem. 1994; 269: 5364-5368Abstract Full Text PDF PubMed Google Scholar, 5Lebrun J.-J. Ali S. Sofer L. Ullrich A. Kelly P.A. J. Biol. Chem. 1994; 269: 14021-14026Abstract Full Text PDF PubMed Google Scholar). Ligand binding leads to dimerization of the receptor and activation of JAK2 (5Lebrun J.-J. Ali S. Sofer L. Ullrich A. Kelly P.A. J. Biol. Chem. 1994; 269: 14021-14026Abstract Full Text PDF PubMed Google Scholar). JAK2 phosphorylates not only the prolactin receptor but also the transcription factor STAT5. Upon phosphorylation, STAT5 forms homodimers, translocates to the nucleus, and specifically binds to the promoter regions of target genes, thus activating transcription (6Ihle J.N. Cell. 1996; 84: 331-334Abstract Full Text Full Text PDF PubMed Scopus (1262) Google Scholar, 7Heim M.H. J. Clin. Invest. 1996; 26: 1-12Google Scholar).Two closely related STAT5a and STAT5b have been identified and were shown to be encoded by similar but different genes (8Azam M. Erdjument-Bromege H. Kreider M. P. J.N. EMBO J. PubMed Scopus Google Scholar, B. L. S. A. PubMed Scopus Google Scholar, S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, B. M. PubMed Google Scholar). STAT5a and STAT5b the with the found B. L. S. A. PubMed Scopus Google Scholar, S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, B. M. PubMed Google Scholar). STAT5a was identified as a of PRL in mammary epithelial cells M. B. Cell. Biol. PubMed Google Scholar, H. B. EMBO J. 1994; 13: PubMed Scopus Google Scholar). STAT5b was cells, mammary and (8Azam M. Erdjument-Bromege H. Kreider M. P. J.N. EMBO J. PubMed Scopus Google Scholar, B. L. S. A. PubMed Scopus Google Scholar, S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, H. A. A. EMBO J. PubMed Scopus Google Scholar). It is that STAT5a and STAT5b expressed in and with a S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and STAT5b also by including growth factor H. A. A. EMBO J. PubMed Scopus Google Scholar, I. H. B. EMBO J. PubMed Scopus Google Scholar), L. L. M. B. Gisselbrecht S. I. EMBO J. PubMed Scopus Google Scholar), interleukin M. S. B. PubMed Scopus Google Scholar, J. T. M. M. J. L. A. J. S. Full Text PDF PubMed Scopus Google Scholar), (8Azam M. Erdjument-Bromege H. Kreider M. P. J.N. EMBO J. PubMed Scopus Google Scholar, H. A. A. EMBO J. PubMed Scopus Google Scholar), H. A. A. EMBO J. PubMed Scopus Google Scholar), J. T. M. M. J. L. A. J. S. Full Text PDF PubMed Scopus Google Scholar), as well as growth factor its receptor tyrosine kinase and by tyrosine and S. S. S. A. PubMed Scopus (134) Google Scholar, L. 1996; Google Scholar, J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). These that STAT5a and STAT5b in different signaling of genes in that STAT5a and STAT5b but in the associated with PRL S. M. S. J.N. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). is also reported that STAT5a and STAT5b be A. S. T. Cell. Biol. 1996; PubMed Scopus Google and with S. L. Gisselbrecht S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google a and activation and tyrosine upon J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). It is that phosphatases tyrosine and a the that dephosphorylation of leads to the activation PubMed Scopus Google Scholar), is that the phosphatases also a role in signaling of the protein-tyrosine phosphatases was shown to be gene transcription M. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar), and have shown that SHP-2 to β-casein promoter activation in a S. A. Kelly P.A. Ullrich A. EMBO J. 1996; PubMed Scopus Google Scholar, S. S. M. B. PubMed Google Scholar). dephosphorylation of the JAK2 and STAT5 the PRL receptor and the involvement of the in a regulation have been found that 16 different including and SHP-2 were expressed in mammary and mammary epithelial cells and that of were in lactating mammary M. S. T. J. Biochem. PubMed Scopus Google Scholar). in investigated the involvement of each PTP in PRL signaling by expression prolactin receptor, and each and found that of the tyrosine of STAT5a and STAT5b and promoter activation of β-casein gene were in COS7 cells when cytosolic PTP1B was Nuclear translocation of STAT5 was also inhibited by PTP1B. of PTP1B in mammary epithelial COMMA-1D cells also resulted in dephosphorylation of PRL-activated STAT5 and down-regulation of β-casein gene expression upon lactogenic hormone STAT5a and STAT5b were by recombinant PTP1B in and were co-precipitated by substrate-trapping mutants of PTP1B. These results strongly suggest that STAT5a and STAT5b of PTP1B and by the phosphatase in PRL-mediated signaling the proteins have been well is have the regulation of and have been of STAT5. of protein protein been shown to STAT5 by kinase activity of STAT5 to A. M. A. A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. A. Cell. Biol. PubMed Scopus Google Scholar, S. Ali S. Cell. PubMed Scopus Google Scholar, A. H. Kelly P.A. M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. A. S. A. PubMed Scopus Google Scholar, S. Muller O. P. A. Gisselbrecht S. Mayeux P. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). It also been that the of STAT5 be by the J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. M. M. M. H. A. A. PubMed Google Scholar, B. PubMed Google Scholar, S. J. J.N. EMBO J. PubMed Google Scholar). tyrosine of STAT5 is the its H. M. B. EMBO J. 1994; 13: PubMed Scopus Google Scholar), dephosphorylation of STAT5 been largely and related have been shown to be in involvement of SHP-2 in PRL signaling been shown by S. A. Kelly P.A. Ullrich A. EMBO J. 1996; PubMed Scopus Google Scholar, S. S. M. B. PubMed Google Scholar). Upon PRL SHP-2 forms a with PRL receptor and and SHP-2 mutants of SHP-2 inhibited the signaling in a that the phosphatase activity of SHP-2 is tyrosine JAK2 its activation S. S. M. B. PubMed Google Scholar). SHP-2 also been shown to be in signaling in cells M. J. Google Scholar), plays a role in signaling A. T. T. T. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). It is also reported that is upon growth hormone and dephosphorylate STAT5b in cells P.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). SHP-2 and a role the cells and the that a cytosolic phosphatase PTP1B PRL-activated STAT5a and STAT5b in transfected COS7 cells as well as in vitro. In cytoplasmic and and receptor the tyrosine of STAT5a and STAT5b not that activity of PTP1B is the dephosphorylation of STAT5a and STAT5b and that PTP1B STAT5a and STAT5b but not of STAT5 2 and tyrosine-phosphorylated STAT5a and STAT5b were co-precipitated with the substrate-trapping mutants of PTP1B and transcriptional activation of STAT5a and STAT5b was when PTP1B was PTP1B was shown to be a in PRL signaling to of β-casein gene expression in mammary epithelial COMMA-1D cells These results strongly and suggest that PTP1B is a PTP specifically and PRL-activated STAT5a and of tyrosine-phosphorylated proteins tyrosine dephosphorylation and to the a of activation and M. EMBO J. 1996; PubMed Scopus Google Scholar). that translocation of STAT5a and STAT5b was largely inhibited when PTP1B was tyrosine of STAT5 is its and binding to its target genes, that PTP1B in the translocation by and tyrosine-phosphorylated that expression of PTP1B was largely in lactating mammary gland a of milk proteins the of PRL and that the expression to that in mammary gland and of M. S. T. J. Biochem. PubMed Scopus Google Scholar). a role of PTP1B in regulation of the to β-casein promoter of the identified in mammary gland and mammary epithelial cells were also in lactating mammary the that cytoplasmic as well as phosphatases in the dephosphorylate and the PRL-activated STAT5 was the cytosolic of as a protein J. Biol. Chem. Full Text PDF PubMed Google and is to be and expressed in cells and be associated with its Cell. Full Text PDF PubMed Scopus Google Scholar), is also its with the J. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). We that of expressed PTP1B was in and its and were PRL of endogenous PTP1B in tyrosine dephosphorylation of STAT5. It been reported that PTP1B is upon the of protein kinase A. EMBO J. PubMed Scopus Google and and J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and that PTP1B tyrosine upon growth factor J. Biochem. J. PubMed Scopus Google Scholar). In of tyrosine and was by and not of PTP1B PRL to be Ali and Ali S. Ali S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google have reported that STAT5 tyrosine and translocation by by a of mutants of the PRL receptor S. Ali S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of tyrosine with the receptor not tyrosine of STAT5, but translocation and binding to the target were involvement of dephosphorylate the tyrosine the PRL receptor, in PRL-mediated target gene have a phosphatase inhibited PRL-mediated β-casein promoter activation the of STAT5. and T. Matsuda, in the the tyrosine dephosphorylation of STAT5 by cytoplasmic PTP1B. We reported that translocation and transcriptional of STAT5 were largely In to STAT5, been shown that the PRL signaling also results in tyrosine of and L. H. R.A. Kirken R.A. Farrar W.L. Cell. 1996; PubMed Scopus Google Scholar). PTP1B is also in regulation in is in in The polypeptide hormone prolactin is produced in the anterior pituitary, regulates the activity of milk protein gene promoters in mammary epithelial cells, and plays an important role in the growth and differentiation of lymphocytes (1DeVlaming V.L. Barrington E.J.W. Hormones and Evolution. Academic Press, New York1979: 561-642Google Scholar). It exhibits its activity via its cognate receptor and the activation of intracellular signaling molecules such as the Janus kinase (JAK)1 signal transducers and activators of transcription (STAT) pathway. The prolactin (PRL) receptor, belonging to the hematopoietin receptor superfamily (2Bazan F Biochem. Cell Biol. 1989; 164: 788-795Google Scholar), does not possess intrinsic tyrosine kinase activity but is associated with the cytoplasmic tyrosine kinase JAK2 (3Dusanter-Fourt I. Muller O. Ziemiecki A. Mayeux P. Drucker B. Djiane J. Wilks A. Harpur A.G. Fisher S. Gisselbrecht S. EMBO J. 1994; 13: 2583-2591Crossref PubMed Scopus (134) Google Scholar, 4Rui H. Kirken R.A. Farrar W.L. J. Biol. Chem. 1994; 269: 5364-5368Abstract Full Text PDF PubMed Google Scholar, 5Lebrun J.-J. Ali S. Sofer L. Ullrich A. Kelly P.A. J. Biol. Chem. 1994; 269: 14021-14026Abstract Full Text PDF PubMed Google Scholar). Ligand binding leads to dimerization of the receptor and activation of JAK2 (5Lebrun J.-J. Ali S. Sofer L. Ullrich A. Kelly P.A. J. Biol. Chem. 1994; 269: 14021-14026Abstract Full Text PDF PubMed Google Scholar). JAK2 phosphorylates not only the prolactin receptor but also the transcription factor STAT5. Upon phosphorylation, STAT5 forms homodimers, translocates to the nucleus, and specifically binds to the promoter regions of target genes, thus activating transcription (6Ihle J.N. Cell. 1996; 84: 331-334Abstract Full Text Full Text PDF PubMed Scopus (1262) Google Scholar, 7Heim M.H. J. Clin. Invest. 1996; 26: 1-12Google Scholar). closely related STAT5a and STAT5b have been identified and were shown to be encoded by similar but different genes (8Azam M. Erdjument-Bromege H. Kreider M. P. J.N. EMBO J. PubMed Scopus Google Scholar, B. L. S. A. PubMed Scopus Google Scholar, S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, B. M. PubMed Google Scholar). STAT5a and STAT5b the with the found B. L. S. A. PubMed Scopus Google Scholar, S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, B. M. PubMed Google Scholar). STAT5a was identified as a of PRL in mammary epithelial cells M. B. Cell. Biol. PubMed Google Scholar, H. B. EMBO J. 1994; 13: PubMed Scopus Google Scholar). STAT5b was cells, mammary and (8Azam M. Erdjument-Bromege H. Kreider M. P. J.N. EMBO J. PubMed Scopus Google Scholar, B. L. S. A. PubMed Scopus Google Scholar, S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, H. A. A. EMBO J. PubMed Scopus Google Scholar). It is that STAT5a and STAT5b expressed in and with a S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). STAT5a and STAT5b also by including growth factor H. A. A. EMBO J. PubMed Scopus Google Scholar, I. H. B. EMBO J. PubMed Scopus Google Scholar), L. L. M. B. Gisselbrecht S. I. EMBO J. PubMed Scopus Google Scholar), interleukin M. S. B. PubMed Scopus Google Scholar, J. T. M. M. J. L. A. J. S. Full Text PDF PubMed Scopus Google Scholar), (8Azam M. Erdjument-Bromege H. Kreider M. P. J.N. EMBO J. PubMed Scopus Google Scholar, H. A. A. EMBO J. PubMed Scopus Google Scholar), H. A. A. EMBO J. PubMed Scopus Google Scholar), J. T. M. M. J. L. A. J. S. Full Text PDF PubMed Scopus Google Scholar), as well as growth factor its receptor tyrosine kinase and by tyrosine and S. S. S. A. PubMed Scopus (134) Google Scholar, L. 1996; Google Scholar, J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). These that STAT5a and STAT5b in different signaling of genes in that STAT5a and STAT5b but in the associated with PRL S. M. S. J.N. Cell. Full Text Full Text PDF PubMed Scopus Google Scholar). is also reported that STAT5a and STAT5b be A. S. T. Cell. Biol. 1996; PubMed Scopus Google and with S. L. Gisselbrecht S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google STAT5 a and activation and tyrosine upon J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). It is that phosphatases tyrosine and a the that dephosphorylation of leads to the activation PubMed Scopus Google Scholar), is that the phosphatases also a role in signaling of the protein-tyrosine phosphatases was shown to be gene transcription M. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar), and have shown that SHP-2 to β-casein promoter activation in a S. A. Kelly P.A. Ullrich A. EMBO J. 1996; PubMed Scopus Google Scholar, S. S. M. B. PubMed Google Scholar). dephosphorylation of the JAK2 and STAT5 the PRL receptor and the involvement of the in a regulation have been found that 16 different including and SHP-2 were expressed in mammary and mammary epithelial cells and that of were in lactating mammary M. S. T. J. Biochem. PubMed Scopus Google Scholar). in investigated the involvement of each PTP in PRL signaling by expression prolactin receptor, and each and found that of the tyrosine of STAT5a and STAT5b and promoter activation of β-casein gene were in COS7 cells when cytosolic PTP1B was Nuclear translocation of STAT5 was also inhibited by PTP1B. of PTP1B in mammary epithelial COMMA-1D cells also resulted in dephosphorylation of PRL-activated STAT5 and down-regulation of β-casein gene expression upon lactogenic hormone STAT5a and STAT5b were by recombinant PTP1B in and were co-precipitated by substrate-trapping mutants of PTP1B. These results strongly suggest that STAT5a and STAT5b of PTP1B and by the phosphatase in PRL-mediated signaling pathway. the proteins have been well is have the regulation of and have been of STAT5. of protein protein been shown to STAT5 by kinase activity of STAT5 to A. M. A. A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. A. Cell. Biol. PubMed Scopus Google Scholar, S. Ali S. Cell. PubMed Scopus Google Scholar, A. H. Kelly P.A. M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. A. S. A. PubMed Scopus Google Scholar, S. Muller O. P. A. Gisselbrecht S. Mayeux P. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). It also been that the of STAT5 be by the J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. M. M. M. H. A. A. PubMed Google Scholar, B. PubMed Google Scholar, S. J. J.N. EMBO J. PubMed Google Scholar). tyrosine of STAT5 is the its H. M. B. EMBO J. 1994; 13: PubMed Scopus Google Scholar), dephosphorylation of STAT5 been largely and related have been shown to be in involvement of SHP-2 in PRL signaling been shown by S. A. Kelly P.A. Ullrich A. EMBO J. 1996; PubMed Scopus Google Scholar, S. S. M. B. PubMed Google Scholar). Upon PRL SHP-2 forms a with PRL receptor and and SHP-2 mutants of SHP-2 inhibited the signaling in a that the phosphatase activity of SHP-2 is tyrosine JAK2 its activation S. S. M. B. PubMed Google Scholar). SHP-2 also been shown to be in signaling in cells M. J. Google Scholar), plays a role in signaling A. T. T. T. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). It is also reported that is upon growth hormone and dephosphorylate STAT5b in cells P.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). SHP-2 and a role the cells and the that a cytosolic phosphatase PTP1B PRL-activated STAT5a and STAT5b in transfected COS7 cells as well as in vitro. In cytoplasmic and and receptor the tyrosine of STAT5a and STAT5b not that activity of PTP1B is the dephosphorylation of STAT5a and STAT5b and that PTP1B STAT5a and STAT5b but not of STAT5 2 and tyrosine-phosphorylated STAT5a and STAT5b were co-precipitated with the substrate-trapping mutants of PTP1B and transcriptional activation of STAT5a and STAT5b was when PTP1B was PTP1B was shown to be a in PRL signaling to of β-casein gene expression in mammary epithelial COMMA-1D cells These results strongly and suggest that PTP1B is a PTP specifically and PRL-activated STAT5a and of tyrosine-phosphorylated proteins tyrosine dephosphorylation and to the a of activation and M. EMBO J. 1996; PubMed Scopus Google Scholar). that translocation of STAT5a and STAT5b was largely inhibited when PTP1B was tyrosine of STAT5 is its and binding to its target genes, that PTP1B in the translocation by and tyrosine-phosphorylated that expression of PTP1B was largely in lactating mammary gland a of milk proteins the of PRL and that the expression to that in mammary gland and of M. S. T. J. Biochem. PubMed Scopus Google Scholar). a role of PTP1B in regulation of the to β-casein promoter of the identified in mammary gland and mammary epithelial cells were also in lactating mammary the that cytoplasmic as well as phosphatases in the dephosphorylate and the PRL-activated STAT5 was the cytosolic of as a protein J. Biol. Chem. Full Text PDF PubMed Google and is to be and expressed in cells and be associated with its Cell. Full Text PDF PubMed Scopus Google Scholar), is also its with the J. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). We that of expressed PTP1B was in and its and were PRL of endogenous PTP1B in tyrosine dephosphorylation of STAT5. It been reported that PTP1B is upon the of protein kinase A. EMBO J. PubMed Scopus Google and and J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and that PTP1B tyrosine upon growth factor J. Biochem. J. PubMed Scopus Google Scholar). In of tyrosine and was by and not of PTP1B PRL to be Ali and Ali S. Ali S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google have reported that STAT5 tyrosine and translocation by by a of mutants of the PRL receptor S. Ali S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of tyrosine with the receptor not tyrosine of STAT5, but translocation and binding to the target were involvement of dephosphorylate the tyrosine the PRL receptor, in PRL-mediated target gene have a phosphatase inhibited PRL-mediated β-casein promoter activation the of STAT5. and T. Matsuda, in the the tyrosine dephosphorylation of STAT5 by cytoplasmic PTP1B. We reported that translocation and transcriptional of STAT5 were largely In to STAT5, been shown that the PRL signaling also results in tyrosine of and L. H. R.A. Kirken R.A. Farrar W.L. Cell. 1996; PubMed Scopus Google Scholar). PTP1B is also in regulation in is in in the proteins have been well is have the regulation of and have been of STAT5. of protein protein been shown to STAT5 by kinase activity of STAT5 to A. M. A. A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. A. Cell. Biol. PubMed Scopus Google Scholar, S. Ali S. Cell. PubMed Scopus Google Scholar, A. H. Kelly P.A. M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. A. S. A. PubMed Scopus Google Scholar, S. Muller O. P. A. Gisselbrecht S. Mayeux P. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). It also been that the of STAT5 be by the J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, A. M. M. M. H. A. A. PubMed Google Scholar, B. PubMed Google Scholar, S. J. J.N. EMBO J. PubMed Google Scholar). tyrosine of STAT5 is the its H. M. B. EMBO J. 1994; 13: PubMed Scopus Google Scholar), dephosphorylation of STAT5 been largely SHP-2 and related have been shown to be in involvement of SHP-2 in PRL signaling been shown by S. A. Kelly P.A. Ullrich A. EMBO J. 1996; PubMed Scopus Google Scholar, S. S. M. B. PubMed Google Scholar). Upon PRL SHP-2 forms a with PRL receptor and and SHP-2 mutants of SHP-2 inhibited the signaling in a that the phosphatase activity of SHP-2 is tyrosine JAK2 its activation S. S. M. B. PubMed Google Scholar). SHP-2 also been shown to be in signaling in cells M. J. Google Scholar), plays a role in signaling A. T. T. T. Biol. Full Text Full Text PDF PubMed Scopus Google Scholar). It is also reported that is upon growth hormone and dephosphorylate STAT5b in cells P.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). SHP-2 and a role the cells and In the that a cytosolic phosphatase PTP1B PRL-activated STAT5a and STAT5b in transfected COS7 cells as well as in vitro. In cytoplasmic and and receptor the tyrosine of STAT5a and STAT5b not that activity of PTP1B is the dephosphorylation of STAT5a and STAT5b and that PTP1B STAT5a and STAT5b but not of STAT5 2 and tyrosine-phosphorylated STAT5a and STAT5b were co-precipitated with the substrate-trapping mutants of PTP1B and transcriptional activation of STAT5a and STAT5b was when PTP1B was PTP1B was shown to be a in PRL signaling to of β-casein gene expression in mammary epithelial COMMA-1D cells These results strongly and suggest that PTP1B is a PTP specifically and PRL-activated STAT5a and of tyrosine-phosphorylated proteins tyrosine dephosphorylation and to the a of activation and M. EMBO J. 1996; PubMed Scopus Google Scholar). that translocation of STAT5a and STAT5b was largely inhibited when PTP1B was tyrosine of STAT5 is its and binding to its target genes, that PTP1B in the translocation by and tyrosine-phosphorylated STAT5. that expression of PTP1B was largely in lactating mammary gland a of milk proteins the of PRL and that the expression to that in mammary gland and of M. S. T. J. Biochem. PubMed Scopus Google Scholar). a role of PTP1B in regulation of the to β-casein promoter of the identified in mammary gland and mammary epithelial cells were also in lactating mammary the that cytoplasmic as well as phosphatases in the dephosphorylate and the PRL-activated STAT5 PTP1B was the cytosolic of as a protein J. Biol. Chem. Full Text PDF PubMed Google and is to be and expressed in cells and be associated with its Cell. Full Text PDF PubMed Scopus Google Scholar), is also its with the J. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). We that of expressed PTP1B was in and its and were PRL of endogenous PTP1B in tyrosine dephosphorylation of STAT5. It been reported that PTP1B is upon the of protein kinase A. EMBO J. PubMed Scopus Google and and J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google and that PTP1B tyrosine upon growth factor J. Biochem. J. PubMed Scopus Google Scholar). In of tyrosine and was by and not of PTP1B PRL to be Ali and Ali S. Ali S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google have reported that STAT5 tyrosine and translocation by by a of mutants of the PRL receptor S. Ali S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of tyrosine with the receptor not tyrosine of STAT5, but translocation and binding to the target were involvement of dephosphorylate the tyrosine the PRL receptor, in PRL-mediated target gene have a phosphatase inhibited PRL-mediated β-casein promoter activation the of STAT5. and T. Matsuda, In in the the tyrosine dephosphorylation of STAT5 by cytoplasmic PTP1B. We reported that translocation and transcriptional of STAT5 were largely In to STAT5, been shown that the PRL signaling also results in tyrosine of and L. H. R.A. Kirken R.A. Farrar W.L. Cell. 1996; PubMed Scopus Google Scholar). PTP1B is also in regulation in is in in We and of expression and We also P. of cells. cytosolic protein-tyrosine phosphatase PTP1B specifically dephosphorylates and STAT5a and of PDF