title: Human 70-kDa SHP-1L differs from 68-kDa SHP-1 in its C-terminal structure and catalytic activity.
abstract: The tyrosine phosphatase SHP-1 functions as a negative regulator in hematopoietic cell development, proliferation, and receptor-mediated cellular activation. In Jurkat T cells, a major 68-kDa band and a minor 70-kDa band were immunoprecipitated by a monoclonal antibody against the SHP-1 protein-tyrosine phosphatase domain, while an antibody against the SHP-1 C-terminal 19 amino acids recognized only the 68-kDa SHP-1. The SDS-gel-purified 70-kDa protein was subjected to tryptic mapping and microsequencing, which was followed by molecular cloning. It revealed that the 70-kDa protein, termed SHP-1L, is a C-terminal alternatively spliced form of SHP-1. SHP-1L is 29 amino acids longer than SHP-1, and its 66 C-terminal amino acids are different from SHP-1. The C terminus of SHP-1L contains a proline-rich motif PVPGPPVLSP, a potential Src homology 3 domain-binding site. In contrast to SHP-1, tyrosine phosphorylation of SHP-1L is not detected upon stimulation in Jurkat T cells. This is apparently due to the lack of a single in vivo tyrosine phosphorylation site, which only exists in the C terminus of SHP-1 (Y564). COS cell-expressed glutathione S-transferase-SHP-1L can dephosphorylate tyrosine-phosphorylated ZAP70. At pH 7.4, SHP-1L was shown to be more active than SHP-1 in the dephosphorylation of ZAP70. At pH 5.4, SHP-1L and SHP-1 exhibited similar catalytic activity. It is likely that these two isoforms play different roles in the regulation of hematopoietic cell signal transduction.
authors.affiliation: Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA. yong-jiu_jin@dfci.harvard.edu
authors.forename: Y J
authors.initials: YJ
authors.lastname: Jin
authors.forename: C L
authors.initials: CL
authors.lastname: Yu
authors.forename: S J
authors.initials: SJ
authors.lastname: Burakoff
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D002384:Catalysis; D003001:Cloning, Molecular; D006801:Humans; D006863:Hydrogen-Ion Concentration; D047908:Intracellular Signaling Peptides and Proteins; D019169:Jurkat Cells; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010766:Phosphorylation; D011233:Precipitin Tests; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D014638:Vanadates / Q000494:pharmacology; D051746:ZAP-70 Protein-Tyrosine Kinase
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D020033:Protein Isoforms; C076715:pervanadate; D014638:Vanadates; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; C497261:ZAP70 protein, human; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases