The novel role of the C-terminal region of SHP-2. Involvement of Gab1 and SHP-2 phosphatase activity in Elk-1 activation.
ABSTRACT SHP-2, a nontransmembrane-type protein-tyrosine phosphatase that contains two Src homology 2 (SH2) domains, is thought to participate in growth factor signal transduction pathways via SH2 domain interactions. To determine the role of each region of SHP-2 in platelet-derived growth factor signaling assayed by Elk-1 activation, we generated six deletion mutants of SHP-2. The large SH2 domain deletion SHP-2 mutant composed of amino acids 198-593 (SHP-2-(198-593)), but not the smaller SHP-2-(399-593), showed significantly higher SHP-2 phosphatase activity in vitro. In contrast, SHP-2-(198-593) mutant inhibited wild type SHP-2 phosphatase activity, whereas SHP-2-(399-593) mutant increased activity. To understand these functional changes, we focused on the docking protein Gab1 that assembles signaling complexes. Pull-down experiments with Gab1 suggested that the C-terminal region of SHP-2 as well as the SH2 domains (N-terminal region) associated with Gab1, but the SHP-2-(198-593) mutant did not associate with Gab1. SHP-2-(1-202) or SHP-2-(198-593) inhibited platelet-derived growth factorinduced Elk-1 activation, but SHP-2-(399-593) increased Elk-1 activation. Co-expression of SHP-2-(1-202) with SHP-2-(399-593) inhibited SHP-2-(399-593)/Gab1 interaction, and the SHP-2-(399-593) mutant induced SHP-2 phosphatase and Elk-1 activation, supporting the autoinhibitory effect of SH2 domains on the C-terminal region of SHP-2. These data suggest that both SHP-2/Gab1 interaction in the C-terminal region of SHP-2 and increased SHP-2 phosphatase activity are important for Elk-1 activation. Furthermore, we identified a novel sequence for SHP-2/Gab1 interactions in the C-terminal region of SHP-2.
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ABSTRACT: The signaling mechanisms by which neurotrophic receptors regulate neuronal survival and axonal growth are still incompletely understood. In the receptor tyrosine kinase RET, a receptor for GDNF (glial cell line-derived neurotrophic factor), the functions of the majority of tyrosine residues that become phosphorylated are still unknown. Here we have identified the protein-tyrosine phosphatase SHP2 as a novel direct interactor of RET and the first effector known to bind to phosphorylated Tyr(687) in the juxtamembrane region of the receptor. We show that SHP2 is recruited to RET upon ligand binding in a cooperative fashion, such that both interaction with Tyr(687) and association with components of the Tyr(1062) signaling complex are required for stable recruitment of SHP2 to the receptor. SHP2 recruitment contributes to the ability of RET to activate the PI3K/AKT pathway and promote survival and neurite outgrowth in primary neurons. Furthermore, we find that activation of protein kinase A (PKA) by forskolin reduces the recruitment of SHP2 to RET and negatively affects ligand-mediated neurite outgrowth. In agreement with this, mutation of Ser(696), a known PKA phosphorylation site in RET, enhances SHP2 binding to the receptor and eliminates the effect of forskolin on ligand-induced outgrowth. Together, these findings establish SHP2 as a novel positive regulator of the neurotrophic activities of RET and reveal Tyr(687) as a critical platform for integration of RET and PKA signals. We anticipate that several other phosphotyrosines of unknown function in neuronal receptor tyrosine kinases will also support similar regulatory functions.Journal of Biological Chemistry 10/2010; 285(41):31867-75. · 4.60 Impact Factor
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ABSTRACT: The SHP-2 tyrosine phosphatase plays key regulatory roles in the modulation of the cell response to growth factors and cytokines. Over the past decade, the integration of genetic, biochemical, and structural data has helped in interpreting the pathological consequences of altered SHP-2 function. Using complementary approaches, we provide evidence here that endogenous SHP-2 can dimerize through the formation of disulfide bonds that may also involve the catalytic cysteine. We show that the fraction of dimeric SHP-2 is modulated by growth factor stimulation and by the cell redox state. Comparison of the phosphatase activities of the monomeric self-inhibited and dimeric forms indicated that the latter is 3-fold less active, thus pointing to the dimerization process as an additional mechanism for controlling SHP-2 activity. Remarkably, dimers formed by different SHP-2 mutants displaying diverse biochemical properties were found to respond differently to epidermal growth factor (EGF) stimulation. Although this differential behavior cannot be rationalized mechanistically yet, these findings suggest a possible regulatory role of dimerization in SHP-2 function.Molecular and Cellular Biology 03/2012; 32(10):1998-2009. · 5.04 Impact Factor
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ABSTRACT: This study investigated the expression and prognostic value of SHP-2 in cervical cancer caused by human papillomavirus (HPV) infection. Forty-five specimens from patients with cervical cancer (stage I-III), 32 specimens from patients with cervical intraepithelial neoplasia (CIN) (I, II) and 20 normal cervical samples from patients with hysteromyoma were collected in Department of Pathology for comparison. The expression levels of SHP-2 and IFN-β proteins were detected by using immunohistochemistry. The mRNA expression level of SHP-2 was detected by using quantitative real-time polymerase chain reaction (PCR). HPVs were detected by HPV GenoArray Test. The Spearman correlation was used to compare the expression level of SHP-2 in HPV infected cervical cancer vs non-HPV infected normal cervix. The level of SHP-2 protein expression in the cancer tissues (88.8%) was significantly higher than in CIN tissues (62.5%) and normal cervixes (45%) (P<0.05 and P<0.05, respectively). The SHP-2 mRNA levels in the cancer tissues were upregulated as compared with those in the normal cervixes (P<0.05). Twenty-one (46.7%) cervical cancers, 25 (78.1%) CINs and 17 (85%) normal cervixes showed IFN-β positive staining in cytoplasm. There was statistically significant difference in the expression rate of IFN-β between cervical cancer and normal cervix (χ (2)=8.378, P<0.05) as well as between cervical cancer and CIN (χ (2)=7.695, P<0.05). HPV16/18 infections could be found in normal cervixs (15%), CINs (68.7%) and cervical cancers (84.4%). There was a correlation between HPV infection and SHP-2 expression in cervical cancer (r (s)=0.653, P<0.05). SHP-2 may be a useful prognostic and diagnostic indicator for HPV infected cervical cancer. In cervical cancers, SHP-2 mRNA and protein overexpression was associated with IFN-β lower-expression.Journal of Huazhong University of Science and Technology 04/2012; 32(2):247-51. · 0.78 Impact Factor