title: Determination of the catalytic activity of LEOPARD syndrome-associated SHP2 mutants toward parafibromin, a bona fide SHP2 substrate involved in Wnt signaling.
abstract: SHP2, encoded by the PTPN11 gene, is a protein tyrosine phosphatase that plays a key role in the proliferation of cells via RAS-ERK activation. SHP2 also promotes Wnt signaling by dephosphorylating parafibromin. Germline missense mutations of PTPN11 are found in more than half of patients with Noonan syndrome (NS) and LEOPARD syndrome (LS), both of which are congenital developmental disorders with multiple common symptoms. However, whereas NS-associated PTPN11 mutations give rise to gain-of-function SHP2 mutants, LS-associated SHP2 mutants are reportedly loss-of-function mutants. To determine the phosphatase activity of LS-associated SHP2 more appropriately, we performed an in vitro phosphatase assay using tyrosine-phosphorylated parafibromin, a biologically relevant substrate of SHP2 and the positive regulator of Wnt signaling that is activated through SHP2-mediated dephosphorylation. We found that LS-associated SHP2 mutants (Y279C, T468M, Q506P, and Q510E) exhibited a substantially reduced phosphatase activity toward parafibromin when compared with wild-type SHP2. Furthermore, each of the LS-associated mutants displayed a differential degree of decrease in phosphatase activity. Deviation of the SHP2 catalytic activity from a certain range, either too strong or too weak, may therefore lead to similar clinical outcomes in NS and LS, possibly through an imbalanced Wnt signal caused by inadequate dephosphorylation of parafibromin.
authors.affiliation: Division of Microbiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan; Department of Biochemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan.
authors.forename: Saori
authors.initials: S
authors.lastname: Noda
authors.affiliation: Division of Microbiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takahashi
authors.affiliation: Division of Microbiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Takeru
authors.initials: T
authors.lastname: Hayashi
authors.affiliation: Department of Biochemistry, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan.
authors.forename: Sei-ichi
authors.initials: S
authors.lastname: Tanuma
authors.affiliation: Division of Microbiology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan. Electronic address: mhata@m.u-tokyo.ac.jp.
authors.forename: Masanori
authors.initials: M
authors.lastname: Hatakeyama
mesh_terms: D000818:Animals; D019556:COS Cells; D002384:Catalysis; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D006801:Humans; D044542:LEOPARD Syndrome / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000235:genetics* / Q000378:metabolism*; D013379:Substrate Specificity; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D060449:Wnt Signaling Pathway
chemical_list: C454900:CDC73 protein, human; D025521:Tumor Suppressor Proteins; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11
keywords: LEOPARD syndrome; Noonan syndrome; Parafibromin/CDC73; Protein tyrosine phosphatase; SHP2/PTPN11; Wnt signal