Browsing by Subject "Protein Tyrosine Phosphatase, Non-Receptor Type 11"

Now showing 1 - 9 of 9
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    Inhibition of SHP2-mediated dephosphorylation of Ras suppresses oncogenesis
    (Nature Publishing Group, 2015-11-30) Bunda, Severa; Burrell, Kelly; Heir, Pardeep; Zeng, Lifan; Alamsahebpour, Amir; Kano, Yoshihito; Raught, Brian; Zhang, Zhong-Yin; Zadeh, Gelareh; Ohh, Michael; Department of Biochemistry and Molecular Biology, IU School of Medicine
    Ras is phosphorylated on a conserved tyrosine at position 32 within the switch I region via Src kinase. This phosphorylation inhibits the binding of effector Raf while promoting the engagement of GTPase-activating protein (GAP) and GTP hydrolysis. Here we identify SHP2 as the ubiquitously expressed tyrosine phosphatase that preferentially binds to and dephosphorylates Ras to increase its association with Raf and activate downstream proliferative Ras/ERK/MAPK signalling. In comparison to normal astrocytes, SHP2 activity is elevated in astrocytes isolated from glioblastoma multiforme (GBM)-prone H-Ras(12V) knock-in mice as well as in glioma cell lines and patient-derived GBM specimens exhibiting hyperactive Ras. Pharmacologic inhibition of SHP2 activity attenuates cell proliferation, soft-agar colony formation and orthotopic GBM growth in NOD/SCID mice and decelerates the progression of low-grade astrocytoma to GBM in a spontaneous transgenic glioma mouse model. These results identify SHP2 as a direct activator of Ras and a potential therapeutic target for cancers driven by a previously 'undruggable' oncogenic or hyperactive Ras.
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    Leukaemogenic effects of Ptpn11 activating mutations in the stem cell microenvironment
    (SpringerNature, 2016-11-10) Dong, Lei; Yu, Wen-Mei; Zheng, Hong; Loh, Mignon L.; Bunting, Silvia T.; Pauly, Melinda; Huang, Gang; Zhou, Muxiang; Broxmeyer, Hal E.; Scadden, David T.; Qu, Kui; Department of Microbiology & Immunology, IU School of Medicine
    Germline activating mutations of the protein tyrosine phosphatase SHP2 (encoded by PTPN11), a positive regulator of the RAS signalling pathway, are found in 50% of patients with Noonan syndrome. These patients have an increased risk of developing leukaemia, especially juvenile myelomonocytic leukaemia (JMML), a childhood myeloproliferative neoplasm (MPN). Previous studies have demonstrated that mutations in Ptpn11 induce a JMML-like MPN through cell-autonomous mechanisms that are dependent on Shp2 catalytic activity. However, the effect of these mutations in the bone marrow microenvironment remains unclear. Here we report that Ptpn11 activating mutations in the mouse bone marrow microenvironment promote the development and progression of MPN through profound detrimental effects on haematopoietic stem cells (HSCs). Ptpn11 mutations in mesenchymal stem/progenitor cells and osteoprogenitors, but not in differentiated osteoblasts or endothelial cells, cause excessive production of the CC chemokine CCL3 (also known as MIP-1α), which recruits monocytes to the area in which HSCs also reside. Consequently, HSCs are hyperactivated by interleukin-1β and possibly other proinflammatory cytokines produced by monocytes, leading to exacerbated MPN and to donor-cell-derived MPN following stem cell transplantation. Remarkably, administration of CCL3 receptor antagonists effectively reverses MPN development induced by the Ptpn11-mutated bone marrow microenvironment. This study reveals the critical contribution of Ptpn11 mutations in the bone marrow microenvironment to leukaemogenesis and identifies CCL3 as a potential therapeutic target for controlling leukaemic progression in Noonan syndrome and for improving stem cell transplantation therapy in Noonan-syndrome-associated leukaemias.
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    Molecular Basis of Gain-of-Function LEOPARD Syndrome-Associated SHP2 Mutations
    (American Chemical Society, 2014-07-01) Yu, Zhi-Hong; Zhang, Ruo-Yu; Walls, Chad D.; Chen, Lan; Zhang, Sheng; Wu, Li; Liu, Sijiu; Zhang, Zhong-Yin; Department of Biochemistry & Molecular Biology, IU School of Medicine
    The Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 2 (SHP2) is a critical signal transducer downstream of growth factors that promotes the activation of the RAS-ERK1/2 cascade. In its basal state, SHP2 exists in an autoinhibited closed conformation because of an intramolecular interaction between its N-SH2 and protein tyrosine phosphatase (PTP) domains. Binding to pTyr ligands present on growth factor receptors and adaptor proteins with its N-SH2 domain localizes SHP2 to its substrates and frees the active site from allosteric inhibition. Germline mutations in SHP2 are known to cause both Noonan syndrome (NS) and LEOPARD syndrome (LS), two clinically similar autosomal dominant developmental disorders. NS-associated SHP2 mutants display elevated phosphatase activity, while LS-associated SHP2 mutants exhibit reduced catalytic activity. A conundrum in how clinically similar diseases result from mutations to SHP2 that have opposite effects on this enzyme’s catalytic functionality exists. Here we report a comprehensive investigation of the kinetic, structural, dynamic, and biochemical signaling properties of the wild type as well as all reported LS-associated SHP2 mutants. The results reveal that LS-causing mutations not only affect SHP2 phosphatase activity but also induce a weakening of the intramolecular interaction between the N-SH2 and PTP domains, leading to mutants that are more readily activated by competing pTyr ligands. Our data also indicate that the residual phosphatase activity associated with the LS SHP2 mutant is required for enhanced ERK1/2 activation. Consequently, catalytically impaired SHP2 mutants could display gain-of-function properties because of their ability to localize to the vicinity of substrates for longer periods of time, thereby affording the opportunity for prolonged substrate turnover and sustained RAS-ERK1/2 activation.
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    Mutated Ptpn11 alters leukemic stem cell frequency and reduces the sensitivity of acute myeloid leukemia cells to Mcl1 inhibition
    (Nature Publishing Group, 2015-06) Chen, Lili; Chen, Wei; Mysliwski, Maria; Serio, Justin; Ropa, James; Abulwerdi, Fardokht A.; Chan, Rebecca J.; Patel, Jay P.; Tallman, Martin S.; Paietta, Elisabeth; Melnick, Ari; Levine, Ross L.; Abdel-Wahab, Omar; Nikolovska-Coleska, Zaneta; Muntean, Andrew G.; Department of Pediatrics, IU School of Medicine
    PTPN11 encodes the Shp2 non-receptor protein-tyrosine phosphatase implicated in several signaling pathways. Activating mutations in Shp2 are commonly associated with juvenile myelomonocytic leukemia but are not as well defined in other neoplasms. Here we report that Shp2 mutations occur in human acute myeloid leukemia (AML) at a rate of 6.6% (6/91) in the ECOG E1900 data set. We examined the role of mutated Shp2 in leukemias harboring MLL translocations, which co-occur in human AML. The hyperactive Shp2E76K mutant, commonly observed in leukemia patients, significantly accelerated MLL-AF9-mediated leukemogenesis in vivo. Shp2E76K increased leukemic stem cell frequency and affords MLL-AF9 leukemic cells IL3 cytokine hypersensitivity. As Shp2 is reported to regulate anti-apoptotic genes, we investigated Bcl2, Bcl-xL and Mcl1 expression in MLL-AF9 leukemic cells with and without Shp2E76K. Although the Bcl2 family of genes was upregulated in Shp2E76K cells, Mcl1 showed the highest upregulation in MLL-AF9 cells in response to Shp2E76K. Indeed, expression of Mcl1 in MLL-AF9 cells phenocopies expression of Shp2E76K, suggesting Shp2 mutations cooperate through activation of anti-apoptotic genes. Finally, we show Shp2E76K mutations reduce sensitivity of AML cells to small-molecule-mediated Mcl1 inhibition, suggesting reduced efficacy of drugs targeting MCL1 in patients with hyperactive Shp2.
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    PI3K p110δ uniquely promotes gain-of-function Shp2-induced GM-CSF hypersensitivity in a model of JMML
    (American Society of Hematology, 2014-05-01) Goodwin, Charles B.; Li, Xing Jun; Mali, Raghuveer S.; Chan, Gordon; Kang, Michelle; Liu, Ziyue; Vanhaesebroeck, Bart; Neel, Benjamin G.; Loh, Mignon L.; Lannutti, Brian J.; Kapur, Reuben; Chan, Rebecca J.; Department of Pediatrics, IU School of Medicine
    Although hyperactivation of the Ras-Erk signaling pathway is known to underlie the pathogenesis of juvenile myelomonocytic leukemia (JMML), a fatal childhood disease, the PI3K-Akt signaling pathway is also dysregulated in this disease. Using genetic models, we demonstrate that inactivation of phosphatidylinositol-3-kinase (PI3K) catalytic subunit p110δ, but not PI3K p110α, corrects gain-of-function (GOF) Shp2-induced granulocyte macrophage-colony-stimulating factor (GM-CSF) hypersensitivity, Akt and Erk hyperactivation, and skewed hematopoietic progenitor distribution. Likewise, potent p110δ-specific inhibitors curtail the proliferation of GOF Shp2-expressing hematopoietic cells and cooperate with mitogen-activated or extracellular signal-regulated protein kinase kinase (MEK) inhibition to reduce proliferation further and maximally block Erk and Akt activation. Furthermore, the PI3K p110δ-specific inhibitor, idelalisib, also demonstrates activity against primary leukemia cells from individuals with JMML. These findings suggest that selective inhibition of the PI3K catalytic subunit p110δ could provide an innovative approach for treatment of JMML, with the potential for limiting toxicity resulting from the hematopoietic-restricted expression of p110δ.
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    Shp2 function in hematopoietic stem cell biology and leukemogenesis
    (Ovid Technologies (Wolters Kluwer) - Lippincott Williams & Wilkins, 2012-07) Nabinger, Sarah C.; Chan, Rebecca J.; Department of Pediatrics, IU School of Medicine
    PURPOSE OF REVIEW: The protein tyrosine phosphatase Shp2 is encoded by PTPN11 and positively regulates physiologic hematopoiesis. Mutations of PTPN11 cause the congenital disorder Noonan syndrome and pathologically promote human leukemias. Given the high frequency of PTPN11 mutations in human disease, several animal models have been generated to investigate Shp2 in hematopoietic stem cell (HSC) function and leukemic transformation. RECENT FINDINGS: Two independent animal models bearing knockout of Shp2 in hematopoietic tissues clearly demonstrate the necessity of Shp2 in HSC repopulating capacity. Reduced HSC quiescence and increased apoptosis accounts for diminished HSC function in the absence of Shp2. The germline mutation Shp2D61G enhances HSC activity and induces myeloproliferative disease (MPD) in vivo by HSC transformation. The somatic mutation Shp2D61Y produces MPD in vivo but fails to induce acute leukemia, whereas somatic Shp2E76K produces MPD in vivo that transforms into full-blown leukemia. HSCs expressing Shp2D61Y do not generate MPD in recipient animals upon transplantation, whereas Shp2E76K-expressing HSCs yield MPD as well as acute leukemia in recipient animals. The mechanisms underlying the unique functions of Shp2D61Y and Shp2E76K in HSC transformation and leukemogenesis continue to be under investigation. SUMMARY: Further understanding of the physiologic and pathologic role of Shp2 in hematopoiesis and leukemogenesis, respectively, will yield information needed to develop therapeutic strategies targeted to Shp2 in human disease.
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    SHP2 phosphatase promotes mast cell chemotaxis toward stem cell factor via enhancing activation of the Lyn/Vav/Rac signaling axis
    (The American Association of Immunologists, 2014-05-15) Sharma, Namit; Everingham, Stephanie; Ramdas, Baskar; Kapur, Reuben; Craig, Andrew W.B.; Department of Pediatrics, IU School of Medicine
    SHP2 protein-tyrosine phosphatase (encoded by Ptpn11) positively regulates KIT (CD117) signaling in mast cells and is required for mast cell survival and homeostasis in mice. In this study, we uncover a role of SHP2 in promoting chemotaxis of mast cells toward stem cell factor (SCF), the ligand for KIT receptor. Using an inducible SHP2 knockout (KO) bone marrow-derived mast cell (BMMC) model, we observed defects in SCF-induced cell spreading, polarization, and chemotaxis. To address the mechanisms involved, we tested whether SHP2 promotes activation of Lyn kinase that was previously shown to promote mast cell chemotaxis. In SHP2 KO BMMCs, SCF-induced phosphorylation of the inhibitory C-terminal residue (pY507) was elevated compared with control cells, and phosphorylation of activation loop (pY396) was diminished. Because Lyn also was detected by substrate trapping assays, these results are consistent with SHP2 activating Lyn directly by dephosphorylation of pY507. Further analyses revealed a SHP2- and Lyn-dependent pathway leading to phosphorylation of Vav1, Rac activation, and F-actin polymerization in SCF-treated BMMCs. Treatment of BMMCs with a SHP2 inhibitor also led to impaired chemotaxis, consistent with SHP2 promoting SCF-induced chemotaxis of mast cells via a phosphatase-dependent mechanism. Thus, SHP2 inhibitors may be useful to limit SCF/KIT-induced mast cell recruitment to inflamed tissues or the tumor microenvironment.
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    Therapeutic Potential of Targeting the Oncogenic SHP2 Phosphatase
    (American Chemical Society, 2014-08-14) Zeng, Li-Fan; Zhang, Ruo-Yu; Yu, Zhi-Hong; Li, Sijiu; Wu, Li; Gunawan, Andrea M.; Lane, Brandon S.; Mali, Raghuveer S.; Li, Xingjun; Chan, Rebecca J.; Kapur, Reuben; Wells, Clark D.; Zhang, Zhong-Yin; Department of Biochemistry & Molecular Biology, IU School of Medicine
    , The Src homology 2 domain containing protein tyrosine phosphatase-2 (SHP2) is an oncogenic phosphatase associated with various kinds of leukemia and solid tumors. Thus, there is substantial interest in developing SHP2 inhibitors as potential anticancer and antileukemia agents. Using a structure-guided and fragment-based library approach, we identified a novel hydroxyindole carboxylic acid-based SHP2 inhibitor 11a-1, with an IC50 value of 200 nM and greater than 5-fold selectivity against 20 mammalian PTPs. Structural and modeling studies reveal that the hydroxyindole carboxylic acid anchors the inhibitor to the SHP2 active site, while interactions of the oxalamide linker and the phenylthiophene tail with residues in the β5–β6 loop contribute to 11a-1’s binding potency and selectivity. Evidence suggests that 11a-1 specifically attenuates the SHP2-dependent signaling inside the cell. Moreover, 11a-1 blocks growth factor mediated Erk1/2 and Akt activation and exhibits excellent antiproliferative activity in lung cancer and breast cancer as well as leukemia cell lines.