title: Determination of the substrate specificity of protein-tyrosine phosphatase TULA-2 and identification of Syk as a TULA-2 substrate.
abstract: TULA-1 (UBASH3A/STS-2) and TULA-2 (p70/STS-1) represent a novel class of protein-tyrosine phosphatases. Previous studies suggest that TULA-2 is sequence-selective toward phosphotyrosyl (Tyr(P)) peptides. In this work the substrate specificity of TULA-1 and -2 was systematically evaluated by screening a combinatorial Tyr(P) peptide library. Although TULA-1 showed no detectable activity toward any of the Tyr(P) peptides in the library, TULA-2 recognizes two distinct classes of Tyr(P) substrates. On the N-terminal side of Tyr(P), the class I substrates contain a proline at the Tyr(P)-1 position, a hydrophilic residue at the Tyr(P)-2 position, and aromatic hydrophobic residues at positions Tyr(P)-3 and beyond. The class II substrates typically contain two or more acidic residues, especially at Tyr(P)-1 to Tyr(P)-3 positions, and aromatic hydrophobic residues at other positions. At the C-terminal side of Tyr(P), TULA-2 generally prefers acidic and aromatic residues. The library screening results were confirmed by kinetic analysis of representative peptides selected from the library as well as Tyr(P) peptides derived from various Tyr(P) proteins. TULA-2 is highly active toward peptides corresponding to the Tyr(P)-323 and Tyr(P)-352 sites of Syk, and the Tyr(P)-397 site of focal adhesion kinase and has lower activity toward other Tyr(P) sites in these proteins. In glycoprotein VI-stimulated platelets, knock-out of the TULA-2 gene significantly increased the phosphorylation level of Syk at Tyr-323 and Tyr-352 sites and to a lesser degree at the Tyr-525/526 sites. These results suggest that Syk is a bona fide TULA-2 substrate in platelets.
authors.affiliation: Department of Chemistry and Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Xianwen
authors.initials: X
authors.lastname: Chen
authors.forename: Lige
authors.initials: L
authors.lastname: Ren
authors.forename: Soochong
authors.initials: S
authors.lastname: Kim
authors.forename: Nicholas
authors.initials: N
authors.lastname: Carpino
authors.forename: James L
authors.initials: JL
authors.lastname: Daniel
authors.forename: Satya P
authors.initials: SP
authors.lastname: Kunapuli
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Tsygankov
authors.forename: Dehua
authors.initials: D
authors.lastname: Pei
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000201:enzymology*; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D019151:Peptide Library; D015539:Platelet Activation / Q000502:physiology*; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011948:Receptors, Antigen, T-Cell / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity / Q000502:physiology; D000072377:Syk Kinase
chemical_list: D018955:CD36 Antigens; D047908:Intracellular Signaling Peptides and Proteins; D019151:Peptide Library; D011948:Receptors, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D017027:Protein Tyrosine Phosphatases; C553497:TULA-2 protein, mouse