SH2-containing phosphotyrosine phosphatase as a target of protein-tyrosine kinases

SHP2 promotes proliferation of breast cancer cells through regulating Cyclin D1 stability via the PI3K/AKT/GSK3β signaling pathway

Objective: The tyrosine phosphatase SHP2 has a dual role in cancer initiation and progression in a tissue type-dependent manner. Several studies have linked SHP2 to the aggressive behavior of breast cancer cells and poorer outcomes in people with cancer. Nevertheless, the mechanistic details of how SHP2 promotes breast cancer progression remain largely undefined. Methods: The relationship between SHP2 expression and the prognosis of patients with breast cancer was investigated by using the TCGA and GEO databases. The expression of SHP2 in breast cancer tissues was analyzed by immunohistochemistry. CRISPR/Cas9 technology was used to generate SHP2-knockout breast cancer cells. Cell-counting kit-8, colony formation, cell cycle, and EdU incorporation assays, as well as a tumor xenograft model were used to examine the function of SHP2 in breast cancer proliferation. Quantitative RT-PCR, western blotting, immunofluorescence staining, and ubiquitination assays were used to explore the molecular mechanism through which SHP2 regulates breast cancer proliferation. Results: High SHP2 expression is correlated with poor prognosis in patients with breast cancer. SHP2 is required for the proliferation of breast cancer cells in vitro and tumor growth in vivo through regulation of Cyclin D1 abundance, thereby accelerating cell cycle progression. Notably, SHP2 modulates the ubiquitin-proteasome-dependent degradation of Cyclin D1 via the PI3K/AKT/GSK3β signaling pathway. SHP2 knockout attenuates the activation of PI3K/AKT signaling and causes the dephosphorylation and resultant activation of GSK3β. GSK3β then mediates phosphorylation of Cyclin D1 at threonine 286, thereby promoting the translocation of Cyclin D1 from the nucleus to the cytoplasm and facilitating Cyclin D1 degradation through the ubiquitin-proteasome system. Conclusions: Our study uncovered the mechanism through which SHP2 regulates breast cancer proliferation. SHP2 may therefore potentially serve as a therapeutic target for breast cancer.

Genetic diversity and virulence characteristics of Helicobacter pylori isolates in different human ethnic groups

Helicobacter pylori is the most predominant bacterium in almost 50% of the world's population and colonization causes a persistent inflammatory response leading to chronic gastritis. It shows high genetic diversity and individuals generally harbour a distinct bacterial population. With the advancement of whole-genome sequencing technology, new H. pylori subpopulations have been identified that show admixture between various H. pylori strains. Genotypic variation of H. pylori may be related to the presence of virulence factors among strains and is associated with different outcomes of infection in different individuals. This review summarizes the genetic diversity in H. pylori strain populations and its virulence characteristics responsible for variable outcomes in different ethnic groups.

Analysis of EYA3 Phosphorylation by Src Kinase Identifies Residues Involved in Cell Proliferation

Eyes absent (EYA) are non-thiol-based protein tyrosine phosphatases (PTPs) that also have transcriptional co-activator functions. Their PTP activity is involved in various pathologies. Recently, we demonstrated that Src tyrosine kinase phosphorylates human EYA3 by controlling its subcellular localization. We also found EYA3′s ability to autodephosphorylate, while raising the question if the two opposing processes could be involved in maintaining a physiologically adequate level of phosphorylation. Using native and bottom-up mass spectrometry, we performed detailed mapping and characterization of human EYA3 Src-phosphorylation sites. Thirteen tyrosine residues with different phosphorylation and autodephosphorylation kinetics were detected. Among these, Y77, 96, 237, and 508 displayed an increased resistance to autodephosphorylation. Y77 and Y96 were found to have the highest impact on the overall EYA3 phosphorylation. Using cell cycle analysis, we showed that Y77, Y96, and Y237 are involved in HEK293T proliferation. Mutation of the three tyrosine residues abolished the pro-proliferative effect of EYA3 overexpression. We have also identified a Src-induced phosphorylation pattern of EYA3 in these cells. These findings suggest that EYA3′s tyrosine phosphorylation sites are non-equivalent with their phosphorylation levels being under the control of Src-kinase activity and of EYA3′s autodephosphorylation.

Targeting SHP2 as a promising strategy for cancer immunotherapy

Src homology-2-containing protein tyrosine phosphatase 2 (SHP2) is a major phosphatase involved in several cellular processes. In recent years, SHP2 has been the focus of significant attention in human diseases, particular in cancer. Several studies have shown that SHP2 plays an important role in regulating immune cell functions in tumor microenvironment. A few clinical trials conducted using SHP2 allosteric inhibitors have shown remarkable anti-tumor benefits and good safety profiles. This review focuses on the current understanding of the regulation of SHP2 and highlights the vital roles of SHP2 in T lymphocytes, macrophages and cancer cells. It also summarizes the current development of SHP2 inhibitors as a promising strategy for cancer immunotherapy.

SHP2 deficiency promotes Staphylococcus aureus pneumonia following influenza infection

Objectives

Secondary bacterial pneumonia is common following influenza infection. However, it remains unclear about the underlying molecular mechanisms.

Materials and methods

We established a mouse model of post‐influenza S aureus pneumonia using conditional Shp2 knockout mice (LysM^Cre/+:Shp2^flox/flox). The survival, bacterial clearance, pulmonary histology, phenotype of macrophages, and expression of type I interferons and chemokines were assessed between SHP2 deletion and control mice (Shp2^flox/flox). We infused additional KC and MIP‐2 to examine the reconstitution of antibacterial immune response in LysM^Cre/+:Shp2^flox/flox mice. The effect of SHP2 on signal molecules including MAPKs (JNK, p38 and Erk1/2), NF‐κB p65 and IRF3 was further detected.

Results

LysM^Cre/+:Shp2^flox/flox mice displayed impaired antibacterial immunity and high mortality compared with control mice in post‐influenza S aureus pneumonia. The attenuated antibacterial ability was associated with the induction of type I interferon and suppression of chemo‐attractants KC and MIP‐2, which reduced the infiltration of neutrophils into the lung upon secondary bacterial invasion. In additional, Shp2 knockout mice displayed enhanced polarization to alternatively activated macrophages (M2 phenotype). Further in vitro analyses consistently demonstrated that SHP2‐deficient macrophages were skewed towards an M2 phenotype and had a decreased antibacterial capacity. Moreover, SHP2 modulated the inflammatory response to secondary bacterial infection via interfering with NF‐κB and IRF3 signalling in macrophages.

Conclusions

Our findings reveal that the SHP2 expression enhances the host immune response and prompts bacterial clearance in post‐influenza S aureus pneumonia.

SHP-2 in Lymphocytes' Cytokine and Inhibitory Receptor Signaling

Somewhat counterintuitively, the tyrosine phosphatase SHP-2 (SH2 domain-containing protein tyrosine phosphatase-2) is crucial for the activation of extracellular signal-regulated kinase (ERK) downstream of various growth factor receptors, thereby exerting essential developmental functions. This phosphatase also deploys proto-oncogenic functions and specific inhibitors have recently been developed. With respect to the immune system, the role of SHP-2 in the signaling of cytokines relevant for myelopoiesis and myeloid malignancies has been intensively studied. The function of this phosphatase downstream of cytokines important for lymphocytes is less understood, though multiple lines of evidence suggest its importance. In addition, SHP-2 has been proposed to mediate the suppressive effects of inhibitory receptors (IRs) that sustain a dysfunctional state in anticancer T cells. Molecules involved in IR signaling are of potential pharmaceutical interest as blockade of these inhibitory circuits leads to remarkable clinical benefit. Here, we discuss the dichotomy in the functions ascribed to SHP-2 downstream of cytokine receptors and IRs, with a focus on T and NK lymphocytes. Further, we highlight the importance of broadening our understanding of SHP-2′s relevance in lymphocytes, an essential step to inform on side effects and unanticipated benefits of its therapeutic blockade.

Tumor immunology and immunotherapy: a journey I started from Hangzhou

This short article is dedicated to the 90th Anniversary of the School of Life Sciences at Zhejiang University, China. Immunotherapy of cancer is currently a hot topic in the biomedical field, and a re-search focus of my laboratory is on developing new and effective combinatorial immunotherapeutic strategies for liver cancer. Of note, my interest in immunotherapy of cancer stems from the training as an undergraduate student at Hangzhou University, China, almost 40 years ago.

SHP2 inhibition triggers anti-tumor immunity and synergizes with PD-1 blockade

Tyrosine phosphatase SHP2 is a promising drug target in cancer immunotherapy due to its bidirectional role in both tumor growth promotion and T-cell inactivation. Its allosteric inhibitor SHP099 is known to inhibit cancer cell growth both in vitro and in vivo. However, whether SHP099-mediated SHP2 inhibition retards tumor growth in vivo via anti-tumor immunity remains elusive. To address this, a CT-26 colon cancer xenograft model was established in mice since this cell line is insensitive to SHP099. Consequently, SHP099 minimally affected CT-26 tumor growth in immuno-deficient nude mice, but significantly decreased the tumor burden in CT-26 tumor-bearing mice with intact immune system. SHP099 augmented anti-tumor immunity, as shown by the elevated proportion of CD8⁺IFN-γ⁺ T cells and the upregulation of cytotoxic T-cell related genes including Granzyme B andPerforin, which decreased the tumor load. In addition, tumor growth in mice with SHP2-deficient T-cells was markedly slowed down because of enhanced anti-tumor responses. Finally, the combination of SHP099 and anti-PD-1 antibody showed a higher therapeutic efficacy than either monotherapy in controlling tumor growth in two colon cancer xenograft models, indicating that these agents complement each other. Our study suggests that SHP2 inhibitor SHP099 is a promising candidate drug for cancer immunotherapy.

Emerging Targeted Therapies for the Treatment of Non-small Cell Lung Cancer

PURPOSE OF REVIEW

Lung cancer remains the leading cause of cancer-related mortality worldwide. Genetic and molecular profiling of non-small cell lung cancer (NSCLC) has led to the discovery of actionable oncogenic driver alterations, which has revolutionized treatment for this disease. This review will move beyond traditional mutational drivers such as EGFR and ALK and will instead focus on emerging targets and the efficacy of new precision therapies.

RECENT FINDINGS

Here, we discuss both established and emerging targeted therapy approaches, as well as ongoing challenges for the treatment of NSCLC patients harboring oncogenic alterations of the following types-gene fusions (ROS1, RET, NTRK), receptor tyrosine kinases (MET amplification and exon 14 mutations and EGFR/HER2 exon 20 insertion mutations), and MAPK signaling (SHP2 and altered BRAF and NF1). The treatment of lung cancer is increasingly biomarker-driven, as patients are selected for targeted agents based on the identification of genetic alterations amenable to inhibition. Our ability to further improve patient outcomes with this precision medicine approach will require continued efforts to identify, characterize, and target lesions driving lung cancer tumorigenesis and progression.

Targeting liver cancer stem cells for the treatment of hepatocellular carcinoma

Liver cancer is one of the most common malignant tumors and prognosis remains poor. It has been increasingly recognized that liver cancer stem cells (LCSCs) are responsible for the carcinogenesis, recurrence, metastasis and chemoresistance of hepatocellular carcinoma (HCC). Targeting LCSCs is promising to be a new direction for the treatment of HCC. Herein, we summarize the potentially therapeutic targets in LCSCs at the level of genes, molecules and cells, such as knockout of oncogenes or oncoproteins, restoring the silent tumor suppressor genes, inhibition of the transcription factors and regulation of noncoding RNAs (including microRNAs and long noncoding RNAs) in LCSCs at the genetic level; inhibition of markers and blockade of the key signaling pathways of LCSCs at the molecular level; and inhibiting autophagy and application of oncolytic adenoviruses in LCSCs at the cellular level. Moreover, we analyze the potential targets in LCSCs to eliminate chemoresistance of HCC. Thereinto, the suppression of autophagy and Nanog by chloroquine and shRNA respectively may be the most promising targeting approaches. These targets may provide novel therapeutic strategies for the treatment of HCC by targeting LCSCs.

Clinical significance and biological function of WD repeat domain 54 as an oncogene in colorectal cancer

In recent years, protein-protein interactions have become an attractive candidate for identifying biomarkers and drug targets for various diseases. However, WD40 repeat (WDR) domain proteins, some of the most abundant mediators of protein interactions, are largely unexplored. In our study, 57 of 361 known WDR proteins were identified as hub nodes, and a hub (WDR54) with elevated mRNA in colorectal cancer (CRC) was selected for further study. Immunohistochemistry of specimens from 945 patients confirmed the elevated expression of WDR54 in CRC, and we found that patients with WDR54-high tumors typically had a shorter disease-specific survival (DSS) than those with WDR54-low tumors, especially for the subgroup without well-differentiated tumors. Multivariate analysis showed that WDR54-high tumors were an independent risk factor for DSS, with a hazard ratio of 2.981 (95% confidence interval, 1.425-6.234; p = 0.004). Knockdown of WDR54 significantly inhibited the growth and aggressiveness of CRC cells and reduced tumor growth in a xenograft model. Each WDR54 isoform (a, b, and c) was found to reverse the inhibitory effect of WDR54 knockdown; however, only isoform c, which exhibited the highest expression, was increased in CRC cells. Sensitization of WDR54 knockdown to an SHP2 inhibitor was consistently found in CRC cells, and the underlying mechanism involved their common function in regulating AKT and ERK signaling. In conclusion, the present study is the first to investigate the significance of WDR54 in cancer and to conclude that WDR54 serves as an oncogene in CRC and may be a potential prognostic marker and therapeutic target.

Protein Tyrosine Phosphatases: Regulators of CD4 T Cells in Inflammatory Bowel Disease

Protein tyrosine phosphatases (PTPs) play a critical role in co-ordinating the signaling networks that maintain lymphocyte homeostasis and direct lymphocyte activation. By dephosphorylating tyrosine residues, PTPs have been shown to modulate enzyme activity and both mediate and disrupt protein-protein interactions. Through these molecular mechanisms, PTPs ultimately impact lymphocyte responses to environmental cues such as inflammatory cytokines and chemokines, as well as antigenic stimulation. Mouse models of acute and chronic intestinal inflammation have been shown to be exacerbated in the absence of PTPs such as PTPN2 and PTPN22. This increase in disease severity is due in part to hyper-activation of lymphocytes in the absence of PTP activity. In accordance, human PTPs have been linked to intestinal inflammation. Genome wide association studies (GWAS) identified several PTPs within risk loci for inflammatory bowel disease (IBD). Therapeutically targeting PTP substrates and their associated signaling pathways, such as those implicated in CD4⁺ T cell responses, has demonstrated clinical efficacy. The current review focuses on the role of PTPs in controlling CD4⁺ T cell activity in the intestinal mucosa and how disruption of PTP activity in CD4⁺ T cells can contribute to intestinal inflammation.

SHP2 inhibition restores sensitivity in ALK-rearranged non-small-cell lung cancer resistant to ALK inhibitors

Most anaplastic lymphoma kinase (ALK)-rearranged non-small-cell lung tumors initially respond to small-molecule ALK inhibitors, but drug resistance often develops. Of tumors that develop resistance to highly potent second-generation ALK inhibitors, approximately half harbor resistance mutations in ALK, while the other half have other mechanisms underlying resistance. Members of the latter group often have activation of at least one of several different tyrosine kinases driving resistance. Such tumors are not expected to respond to lorlatinib-a third-generation inhibitor targeting ALK that is able to overcome all clinically identified resistant mutations in ALK-and further therapeutic options are limited. Herein, we deployed a shRNA screen of 1,000 genes in multiple ALK-inhibitor-resistant patient-derived cells (PDCs) to discover those that confer sensitivity to ALK inhibition. This approach identified SHP2, a nonreceptor protein tyrosine phosphatase, as a common targetable resistance node in multiple PDCs. SHP2 provides a parallel survival input downstream of multiple tyrosine kinases that promote resistance to ALK inhibitors. Treatment with SHP099, the recently discovered small-molecule inhibitor of SHP2, in combination with the ALK tyrosine kinase inhibitor (TKI) ceritinib halted the growth of resistant PDCs through preventing compensatory RAS and ERK1 and ERK2 (ERK1/2) reactivation. These findings suggest that combined ALK and SHP2 inhibition may be a promising therapeutic strategy for resistant cancers driven by several different ALK-independent mechanisms underlying resistance.

Tyrosine phosphatase SHP2 negatively regulates NLRP3 inflammasome activation via ANT1-dependent mitochondrial homeostasis

Aberrant activation of NLRP3 inflammasome has an important function in the pathogenesis of various inflammatory diseases. Although many components and mediators of inflammasome activation have been identified, how NLRP3 inflammasome is regulated to prevent excessive inflammation is unclear. Here we show NLRP3 inflammasome stimulators trigger Src homology-2 domain containing protein tyrosine phosphatase-2 (SHP2) translocation to the mitochondria, to interact with and dephosphorylate adenine nucleotide translocase 1 (ANT1), a central molecule controlling mitochondrial permeability transition. This mechanism prevents collapse of mitochondrial membrane potential and the subsequent release of mitochondrial DNA and reactive oxygen species, thus preventing hyperactivation of NLRP3 inflammasome. Ablation or inhibition of SHP2 in macrophages causes intensified NLRP3 activation, overproduction of proinflammatory cytokines IL-1β and IL-18, and increased sensitivity to peritonitis. Collectively, our data highlight that, by inhibiting ANT1 and mitochondrial dysfunction, SHP2 orchestrates an intrinsic regulatory loop to limit excessive NLRP3 inflammasome activation.

Macrophage-Restricted Shp2 Tyrosine Phosphatase Acts as a Rheostat for MMP12 through TGF-β Activation in the Prevention of Age-Related Emphysema in Mice

Persistent activation of macrophages in lungs plays a critical role in the production of matrix metalloproteinases (MMPs) that contributes to the destruction of alveolar walls, a hallmark for pulmonary emphysema. Dysregulated TGF-β1 signaling has been an essential determinant in the elevation of MMPs during the development of emphysema. Nevertheless, the mechanism for this MMP-dependent pathogenesis has yet to be clearly investigated. Recently, we identified an important role for tyrosine phosphatase Src homology domain-containing protein tyrosine phosphatase 2 (Shp2) in regulating the activation of alveolar macrophages. Over a long-term observation period, mice with Shp2 deletion in macrophages (LysMCre:Shp2^fl/fl ) develop spontaneous, progressive emphysema-like injury in the lungs, characterized by massive destruction of alveolar morphology, interstitial extracellular matrix degradation, and elevated levels of MMPs, particularly, significant increases of macrophage elastase (MMP12) in aged mice. Further analysis demonstrated that MMP12 suppression by TGF-β1 activation was apparently abrogated in LysMCre:Shp2^fl/fl mice, whereas the TGF-β1 concentration in the lungs was relatively the same. Mechanistically, we found that loss of Shp2 resulted in attenuated SMAD2/3 phosphorylation and nuclear translocation in response to TGF-β activation, thereby upregulating MMP12 expression in macrophages. Together, our findings define a novel physiological function of Shp2 in TGF-β1/MMP12-dependent emphysema, adding insights into potential etiologies for this chronic lung disorder.

SHP2 negatively regulates HLA-ABC and PD-L1 expression via STAT1 phosphorylation in prostate cancer cells

Src homology region 2-containing protein tyrosine phosphatase 2 (SHP2) is a ubiquitous protein tyrosine phosphatase that activates the signal transduction pathways of several growth factors and cytokines. In our study, SHP2 expression was very high in prostate cancer (PCa) cell lines, and the expression of phospho-signal transducer and activator of transcription 1 (p-STAT1) and STAT1 was very low. SHP2 knockdown upregulated the expression of p-STAT1 and downregulated phospho-extracellular signal regulated kinase (p-ERK). SHP2 depletion also increased the expression of human leukocyte antigen (HLA)-ABC and programmed death ligand 1 (PD-L1). When tumor cells were pretreated with Janus kinase 2 (JAK2) inhibitor, SHP2 depletion failed to induce HLA-ABC and PD-L1 expression. Furthermore, treating tumor cells with the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK) inhibitor PD0325901 did not upregulate HLA-ABC and PD-L1. SHP2 depletion was associated with increased T-cell activation (CD25 MFI of CD8⁺) by coculture of allogeneic healthy donor peripheral blood monocytes (PBMC) with SHP2 siRNA pretreated PCa cell lines. These results show that SHP2 targeting upregulates HLA-ABC and PD-L1 expression via STAT1 phosphorylation in PCa cells and SHP2 depletion could increase T-cell activation.

Genetically encoding phosphotyrosine and its nonhydrolyzable analog in bacteria

Tyrosine phosphorylation is a common protein posttranslational modification, which plays a critical role in signal transduction and the regulation of many cellular processes. Using a pro-peptide strategy to increase cellular uptake of O-phosphotyrosine (pTyr) and its nonhydrolyzable analog 4-phosphomethyl-L-phenylalanine (Pmp), we identified an orthogonal aminoacyl-tRNA synthetase/tRNA pair that allows the site-specific incorporation of both pTyr and Pmp into recombinant proteins in response to the amber stop codon in Escherichia coli in good yields. The X-ray crystal structure of the synthetase reveals a reconfigured substrate binding site formed by non-conservative mutations and substantial local structural perturbations. We demonstrate the utility of this method by introducing Pmp into a putative phosphorylation site whose corresponding kinase is unknown and determined the affinities of the individual variants for the substrate 3BP2. In summary, this work provides a useful recombinant tool to dissect the biological functions of tyrosine phosphorylation at specific sites in the proteome.

Loss of Ptpn11 (Shp2) drives satellite cells into quiescence

The equilibrium between proliferation and quiescence of myogenic progenitor and stem cells is tightly regulated to ensure appropriate skeletal muscle growth and repair. The non-receptor tyrosine phosphatase Ptpn11 (Shp2) is an important transducer of growth factor and cytokine signals. Here we combined complex genetic analyses, biochemical studies and pharmacological interference to demonstrate a central role of Ptpn11 in postnatal myogenesis of mice. Loss of Ptpn11 drove muscle stem cells out of the proliferative and into a resting state during muscle growth. This Ptpn11 function was observed in postnatal but not fetal myogenic stem cells. Furthermore, muscle repair was severely perturbed when Ptpn11 was ablated in stem cells due to a deficit in stem cell proliferation and survival. Our data demonstrate a molecular difference in the control of cell cycle withdrawal in fetal and postnatal myogenic stem cells, and assign to Ptpn11 signaling a key function in satellite cell activity.

DOI:http://dx.doi.org/10.7554/eLife.21552.001

Shp2 promotes liver cancer stem cell expansion by augmenting β-catenin signaling and predicts chemotherapeutic response of patients

Src-homology 2 domain-containing phosphatase 2 (Shp2) has been reported to play an important role in the maintenance and self-renewal of embryonic and adult stem cells, but its role in cancer stem cells (CSCs) remains obscure. Herein, we observed high expression of Shp2 in both chemoresistant hepatocellular carcinomas (HCCs) and recurrent HCCs from patients. A remarkable increase of Shp2 was detected in sorted epithelial cell adhesion molecule-positive or cluster of differentiation 133-positive liver CSCs and in CSC-enriched hepatoma spheroids from patients. Up-regulated Shp2 facilitated liver CSC expansion by promoting the dedifferentiation of hepatoma cells and enhancing the self-renewal of liver CSCs. Mechanistically, Shp2 dephosphorylated cell division cycle 73 in the cytosol of hepatoma cells, and the dephosphorylated cell division cycle 73 bound β-catenin and facilitated the nuclear translocation of β-catenin, which promoted the dedifferentiation of hepatoma cells. Shp2 increased β-catenin accumulation by inhibiting glycogen synthase kinase 3β-mediated β-catenin degradation in liver CSCs, thereby enhancing the self-renewal of liver CSCs. Blockage of β-catenin abolished the discrepancy in liver CSC proportion and the self-renewal capacity between Shp2-depleted hepatoma cells and control cells, which further confirmed that β-catenin is required in Shp2-promoted liver CSC expansion. More importantly, HCC patients with low Shp2 levels benefited from transcatheter arterial chemoembolization or sorafenib treatment, but patients with high Shp2 expression did not, indicating the significance of Shp2 in personalized HCC therapy.

CONCLUSION

Shp2 could promote HCC cell dedifferentiation and liver CSC expansion by amplifying β-catenin signaling and may be useful in predicting patient response to chemotherapeutics. (Hepatology 2017;65:1566-1580).

Shp2 Inhibits Proliferation of Esophageal Squamous Cell Cancer via Dephosphorylation of Stat3

Shp2 (Src-homology 2 domain-containing phosphatase 2) was originally reported as an oncogene in kinds of solid tumors and hematologic malignancies. However, recent studies indicated that Shp2 may act as tumor suppressors in several tumor types. We investigated the function of Shp2 in esophageal squamous cell cancer (ESCC). The expression level of Shp2 was analyzed in tumor tissues in comparison with adjacent normal tissues of ESCC patients by immunohistochemistry and Western blot. Shp2 was knocked down by Short hairpin RNA to evaluate its function in ESCC cell lines. The relationship between Shp2 and p-Stat3 (signal transducer and activator of transcription 3) in human ESCC tissues was statistically examined. A significant low expression of Shp2 was found in ESCC tissues. Low expression of Shp2 was related to poorer overall survival in patients from The Cancer Genome Atlas (TCGA) dataset. Knockdown of Shp2 increased the growth of ESCC cell lines both in vivo and vitro. Activation of Stat3 (p-Stat3) was induced by Shp2 depletion. Expression of p-Stat3 was negatively correlated with Shp2 expression in ESCC tissues. Furthermore, knockdown of Shp2 attenuated cisplatin-sensitivity of ESCC cells. Shp2 might suppress the proliferation of ESCC by dephosphorylation of p-Stat3 and represents a novel research field for targeted therapy.

Eosinophil differentiation in the bone marrow is promoted by protein tyrosine phosphatase SHP2

SHP2 participates in multiple signaling events by mediating T-cell development and function, and regulates cytokine-dependent granulopoiesis. To explore whether and how SHP2 can regulate bone-marrow eosinophil differentiation, we investigate the contribution of SHP2 in the bone-marrow eosinophil development in allergic mice. Blockade of SHP2 function by SHP2 inhibitor PHPS-1 or conditional shp2 knockdown by adenovirus-inhibited bone-marrow-derived eosinophil differentiation in vitro, with no detectable effects on the apoptosis of eosinophils. Furthermore, SHP2 induced eosinophil differentiation via regulation of the extracellular signal-regulated kinase pathway. Myeloid shp2 conditional knockout mice (LysM^creshp2^flox/flox) failed to induce eosinophilia as well as airway hyper-responsiveness. The SHP2 inhibitor PHPS-1 also alleviated eosinophilic airway inflammation and airway hyper-responsiveness, accompanied by significantly reduced levels of systemic eosinophils and eosinophil lineage-committed progenitors in allergic mice. We demonstrate that inhibition of eosinophil development is SHP2-dependent and SHP2 is sufficient to promote eosinophil formation in vivo. Our data reveal SHP2 as a critical regulator of eosinophil differentiation, and inhibition of SHP2 specifically in myeloid cells alleviates allergic airway inflammation.

Shp2 SUMOylation promotes ERK activation and hepatocellular carcinoma development

Shp2, an ubiquitously expressed protein tyrosine phosphatase, is essential for regulation of Ras/ERK signaling pathway and tumorigenesis. Here we report that Shp2 is modified by SUMO1 at lysine residue 590 (K590) in its C-terminus, which is reduced by SUMO1-specific protease SENP1. Analysis of wild-type Shp2 and SUMOylation-defective Shp2(K590R) mutant reveals that SUMOylation of Shp2 promotes EGF-stimulated ERK signaling pathway and increases anchorage-independent cell growth and xenografted tumor growth of hepatocellular carcinoma (HCC) cell lines. Furthermore, we find that mutant Shp2(K590R) reduces its binding with the scaffolding protein Gab1, and consistent with this, knockdown of SENP1 increased the interaction between Shp2 and Gab1. More surprisingly, we show that human Shp2 (hShp2) and mouse Shp2 (mShp2) have differential effects on ERK activation as a result of different SUMOylation level, which is due to the event of K590 at hShp2 substituted by R594 at mShp2. In summary, our data demonstrate that SUMOylation of Shp2 promotes ERK activation via facilitating the formation of Shp2-Gab1 complex and thereby accelerates HCC cell and tumor growth, which presents a novel regulatory mechanism underlying Shp2 in regulation of HCC development.

SHP2 acts both upstream and downstream of multiple receptor tyrosine kinases to promote basal-like and triple-negative breast cancer

INTRODUCTION

Dysregulated receptor tyrosine kinase (RTK) signaling is a common occurrence in basal-like and triple-negative breast cancer (BTBC). As a result, RTK-targeting therapies have been initiated but proved difficult, mainly owing to the multiplicity of dysregulated RTKs. Hence, targeting master regulators of RTK signaling might alleviate this obstacle. Before that, however, defining the mechanism of such molecules is required. In this report, we show that the Src homology phosphotyrosyl phosphatase 2 (SHP2) is a master regulator of RTK expression and signaling in BTBC.

METHODS

Xenograft tumor growth studies were used to determine the effect of SHP2 inhibition on tumorigenesis and/or metastasis. Cell proliferation rate, anchorage-independent growth, mammosphere formation, and ALDEFLUOR assays were used to compare the relative functional importance of SHP2 and the epidermal growth factor receptor (EGFR) in BTBC cells. Immunohistochemistry and immunofluorescence analyses were used to determine the state of SHP2 and EGFR coexpression in BTBC. Analysis of mitogenic and cell survival signaling was performed to show SHP2's role in signaling by multiple RTKs.

RESULTS

Inhibition of SHP2 in BTBC cells suppresses their tumorigenic and metastatic properties. Because EGFR is the most commonly dysregulated RTK in BTBC, we first tested the effect of SHP2 inhibition on EGFR signaling and found that SHP2 is important not only for mediation of the Ras/extracellular signal-regulated kinase and the phosphatidyl inositol 3-kinase/Akt signaling pathways but also for the expression of the receptor itself. The existence of a tight association between SHP2 and EGFR expression in tumors and cell lines further suggested the importance of SHP2 in EGFR expression. Comparison of relative biological significance showed the superiority of SHP2 inhibition over that of EGFR, suggesting the existence of additional RTKs regulated by SHP2. Indeed, we found that the expression as well as the signaling efficiency of c-Met and fibroblast growth factor receptor 1, two other RTKs known to be dysregulated in BTBC, are SHP2-dependent. To our knowledge, this is the first demonstration of SHP2 acting both upstream and downstream of RTKs to promote signaling.

CONCLUSIONS

SHP2 upregulates the expression and signaling of multiple RTKs to promote BTBC. These findings provide a mechanistic explanation for the superiority of SHP2 inhibition in BTBC.

Role of Protein Phosphorylation and Tyrosine Phosphatases in the Adrenal Regulation of Steroid Synthesis and Mitochondrial Function

In adrenocortical cells, adrenocorticotropin (ACTH) promotes the activation of several protein kinases. The action of these kinases is linked to steroid production, mainly through steroidogenic acute regulatory protein (StAR), whose expression and activity are dependent on protein phosphorylation events at genomic and non-genomic levels. Hormone-dependent mitochondrial dynamics and cell proliferation are functions also associated with protein kinases. On the other hand, protein tyrosine dephosphorylation is an additional component of the ACTH signaling pathway, which involves the "classical" protein tyrosine phosphatases (PTPs), such as Src homology domain (SH) 2-containing PTP (SHP2c), and members of the MAP kinase phosphatase (MKP) family, such as MKP-1. PTPs are rapidly activated by posttranslational mechanisms and participate in hormone-stimulated steroid production. In this process, the SHP2 tyrosine phosphatase plays a crucial role in a mechanism that includes an acyl-CoA synthetase-4 (Acsl4), arachidonic acid (AA) release and StAR induction. In contrast, MKPs in steroidogenic cells have a role in the turn-off of the hormonal signal in ERK-dependent processes such as steroid synthesis and, perhaps, cell proliferation. This review analyzes the participation of these tyrosine phosphates in the ACTH signaling pathway and the action of kinases and phosphatases in the regulation of mitochondrial dynamics and steroid production. In addition, the participation of kinases and phosphatases in the signal cascade triggered by different stimuli in other steroidogenic tissues is also compared to adrenocortical cell/ACTH and discussed.

Expression and prognosis value of SHP2 in patients with pancreatic ductal adenocarcinoma

SHP2 is an src homology (SH) 2 domain-containing protein tyrosine phosphatase (PTP). SHP2 implicitly contributes to tumorigenesis, but the role of SHP2 in pancreatic ductal adenocarcinoma is still unknown. The purpose of this study was to evaluate the prognostic significance and associated expression of SHP2 in pancreatic ductal adenocarcinoma (PDAC) patients. We used immunohistochemistry to assess the protein expression levels of SHP2 in 79 PDAC specimens. The correlations between SHP2 expression and various clinicopathological features were evaluated by Pearson's chi-square (χ (2)) test, Fisher's exact test, and Spearman's rank. Univariate and multivariate Cox regression analyses were used to identify correlations between the immunohistochemical data for SHP2 expression and the clinicopathologic characteristics in PDAC. Kaplan-Meier survival analysis was used to demonstrate the relation between overall survival and the expression of SHP2. Immunohistochemistry revealed significantly higher rates of high SHP2 expression in PDAC tissues (55.7 %) versus adjacent non-cancer tissues (10.1 %) (P < 0.05). Expression of SHP2 was only significantly correlated with histological differentiation (P = 0.033) and vital status (P = 0.025). Patients with high SHP2 expression had shorter overall survival times compared to those with low SHP2 expression (P = 0.000). Multivariate Cox regression analysis revealed that SHP2 overexpression was an independent prognostic factor in PDAC (P = 0.012). Our study demonstrated for the first time that higher expression of SHP2 might be involved in the progression of pancreatic ductal adenocarcinoma, suggesting that SHP2 may be a potential prognostic marker and target for therapy.

New and Unexpected Biological Functions for the Src-Homology 2 Domain-Containing Phosphatase SHP-2 in the Gastrointestinal Tract

SHP-2 is a tyrosine phosphatase expressed in most embryonic and adult tissues. SHP-2 regulates many cellular functions including growth, differentiation, migration, and survival. Genetic and biochemical evidence show that SHP-2 is required for rat sarcoma viral oncogene/extracellular signal-regulated kinases mitogen-activated protein kinase pathway activation by most tyrosine kinase receptors, as well as by G-protein-coupled and cytokine receptors. In addition, SHP-2 can regulate the Janus kinase/signal transducers and activators of transcription, nuclear factor-κB, phosphatidyl-inositol 3-kinase/Akt, RhoA, Hippo, and Wnt/β-catenin signaling pathways. Emerging evidence has shown that SHP-2 dysfunction represents a key factor in the pathogenesis of gastrointestinal diseases, in particular in chronic inflammation and cancer. Variations within the gene locus encoding SHP-2 have been associated with increased susceptibility to develop ulcerative colitis and gastric atrophy. Furthermore, mice with conditional deletion of SHP-2 in intestinal epithelial cells rapidly develop severe colitis. Similarly, hepatocyte-specific deletion of SHP-2 induces hepatic inflammation, resulting in regenerative hyperplasia and development of tumors in aged mice. However, the SHP-2 gene initially was suggested to be a proto-oncogene because activating mutations of this gene were found in pediatric leukemias and certain forms of liver and colon cancers. Moreover, SHP-2 expression is up-regulated in gastric and hepatocellular cancers. Notably, SHP-2 functions downstream of cytotoxin-associated antigen A (CagA), the major virulence factor of Helicobacter pylori, and is associated with increased risks of gastric cancer. Further compounding this complexity, most recent findings suggest that SHP-2 also coordinates carbohydrate, lipid, and bile acid synthesis in the liver and pancreas. This review aims to summarize current knowledge and recent data regarding the biological functions of SHP-2 in the gastrointestinal tract.

SHP2 sails from physiology to pathology

Over the two past decades, mutations of the PTPN11 gene, encoding the ubiquitous protein tyrosine phosphatase SHP2 (SH2 domain-containing tyrosine phosphatase 2), have been identified as the causal factor of several developmental diseases (Noonan syndrome (NS), Noonan syndrome with multiple lentigines (NS-ML), and metachondromatosis), and malignancies (juvenile myelomonocytic leukemia). SHP2 plays essential physiological functions in organism development and homeostasis maintenance by regulating fundamental intracellular signaling pathways in response to a wide range of growth factors and hormones, notably the pleiotropic Ras/Mitogen-Activated Protein Kinase (MAPK) and the Phosphoinositide-3 Kinase (PI3K)/AKT cascades. Analysis of the biochemical impacts of PTPN11 mutations first identified both loss-of-function and gain-of-function mutations, as well as more subtle defects, highlighting the major pathophysiological consequences of SHP2 dysregulation. Then, functional genetic studies provided insights into the molecular dysregulations that link SHP2 mutants to the development of specific traits of the diseases, paving the way for the design of specific therapies for affected patients. In this review, we first provide an overview of SHP2's structure and regulation, then describe its molecular roles, notably its functions in modulating the Ras/MAPK and PI3K/AKT signaling pathways, and its physiological roles in organism development and homeostasis. In the second part, we describe the different PTPN11 mutation-associated pathologies and their clinical manifestations, with particular focus on the biochemical and signaling outcomes of NS and NS-ML-associated mutations, and on the recent advances regarding the pathophysiology of these diseases.

PTPN11/Shp2 overexpression enhances liver cancer progression and predicts poor prognosis of patients

BACKGROUND & AIMS

We have previously reported that Shp2, a tyrosine phosphatase previously known as a pro-leukemogenic molecule, suppresses the initiation of hepatocellular carcinoma (HCC). However, the role of Shp2 in HCC progression remains obscure.

METHODS

Shp2 expression was determined in human HCC using real-time PCR, immunoblotting and immunohistochemistry. Clinical significance of Shp2 expression was analyzed in 301 HCC tissues with clinico-pathological characteristics and follow-up information. Short hairpin RNA was utilized to investigate the function of Shp2 in hepatoma cell behavior. Role of Shp2 in HCC progression was monitored through nude mice xenograft assay. Kinase activity assay and co-immunoprecipitation were used for mechanism analysis.

RESULTS

Elevated expression of Shp2 was detected in 65.9% (394/598) of human HCCs, and its levels were even higher in metastasized foci. Overexpression of Shp2 correlated well with the malignant clinico-pathological characteristics of HCC and predicted the poor prognosis of patients. Interference of Shp2 expression suppressed the proliferation of hepatoma cells in vitro and inhibited the growth of HCC xenografts in vivo. Down-regulation of Shp2 attenuated the adhesion and migration of hepatoma cells and diminished metastasized HCC formation in mice. Our data demonstrated that Shp2 promotes HCC growth and metastasis by coordinately activating Ras/Raf/Erk pathway and PI3-K/Akt/mTOR cascade. Moreover, down-regulation of Shp2 enhanced the sensitivity of hepatoma cells upon sorafenib treatment, and patients with low Shp2 expression exhibited superior prognosis to sorafenib.

CONCLUSIONS

Shp2 promotes the progression of HCC and may serve as a prognostic biomarker for patients.

Alterations in the phosphoproteomic profile of cells expressing a non-functional form of the SHP2 phosphatase

The phosphatase SHP-2 plays an essential role in growth factor signaling and mutations in its locus is the cause of congenital and acquired pathologies. Mutations of SHP-2 are known to affect the activation of the RAS pathway. Gain-of-function mutations cause the Noonan syndrome, the most common non-chromosomal congenital disorder. In order to obtain a holistic picture of the intricate regulatory mechanisms underlying SHP-2 physiology and pathology, we set out to characterize perturbations of the cell phosphorylation profile caused by an altered localization of SHP-2. To describe the proteins whose activity may be directly or indirectly modulated by SHP-2 activity, we identified tyrosine peptides that are differentially phosphorylated in wild type SHP-2 cells and isogenic cells expressing a non-functional SHP-2 variant that cannot dephosphorylate the physiological substrates due to a defect in cellular localization upon growth factor stimulation. By an iTRAQ based strategy coupled to mass spectrometry, we have identified 63 phosphorylated tyrosine residues in 53 different proteins whose phosphorylation is affected by SHP-2 activity. Some of these confirm already established regulatory mechanisms while many others suggest new possible signaling routes that may contribute to the modulation of the ERK and p38 pathways by SHP-2. Interestingly many new proteins that we found to be regulated by SHP-2 activity are implicated in the formation and regulation of focal adhesions.

CD99 inhibits CD98-mediated β1 integrin signaling through SHP2-mediated FAK dephosphorylation

The human CD99 protein is a 32-kDa type I transmembrane glycoprotein, while CD98 is a disulfide-linked 125-kDa heterodimeric type II transmembrane glycoprotein. It has been previously shown that CD99 and CD98 oppositely regulate β1 integrin signaling, though the mechanisms by which this regulation occurs are not known. Our results revealed that antibody-mediated crosslinking of CD98 induced FAK phosphorylation at Y397 and facilitated the formation of the protein kinase Cα (PKCα)-syntenin-focal adhesion kinase (FAK), focal adhesions (FAs), and IPP-Akt1-syntenin complex, which mediates β1 integrin signaling. In contrast, crosslinking of CD99 disrupted the formation of the PKCα-syntenin-FAK complex as well as FA via FAK dephosphorylation. The CD99-induced dephosphorylation of FAK was apparently mediated by the recruitment of Src homology region 2 domain-containing phosphatase-2 (SHP2) to the plasma membrane and subsequent activation of its phosphatase activity. Further consequences of the activation of SHP2 included the disruption of FAK-talin and talin-β1 integrin interactions and attenuation in the formation of the IPP-Akt1-syntenin complex at the plasma membrane, which resulted in reduced cell-ECM adhesion. This report uncovers the molecular mechanisms underlying the inverse regulation of β1 integrin signaling by CD99 and CD98 and may provide a novel therapeutic approach to treat inflammation and cancer.

Functions of Shp2 in cancer

Diagnostics and therapies have shown evident advances. Tumour surgery, chemotherapy and radiotherapy are the main techniques in treat cancers. Targeted therapy and drug resistance are the main focus in cancer research, but many molecular intracellular mechanisms remain unknown. Src homology region 2-containing protein tyrosine phosphatase 2 (Shp2) is associated with breast cancer, leukaemia, lung cancer, liver cancer, gastric cancer, laryngeal cancer, oral cancer and other cancer types. Signalling pathways involving Shp2 have also been discovered. Shp2 is related to many diseases. Mutations in the ptpn11 gene cause Noonan syndrome, LEOPARD syndrome and childhood leukaemia. Shp2 is also involved in several cancer-related processes, including cancer cell invasion and metastasis, apoptosis, DNA damage, cell proliferation, cell cycle and drug resistance. Based on the structure and function of Shp2, scientists have investigated specific mechanisms involved in cancer. Shp2 may be a potential therapeutic target because this phosphatase is implicated in many aspects. Furthermore, Shp2 inhibitors have been used in experiments to develop treatment strategies. However, conflicting results related to Shp2 functions have been presented in the literature, and such results should be resolved in future studies.

Tyrosine phosphatase SHP-2 mediates C-type lectin receptor-induced activation of the kinase Syk and anti-fungal TH17 responses

Fungal infection stimulates the canonical C-type lectin receptors (CLRs) signaling pathway via Syk activation. Here we show that SHP-2 plays a crucial role in mediating CLRs-induced Syk activation. Genetic ablation of Shp-2 (Ptpn11) in dendritic cells (DCs) and macrophages impaired Syk-mediated signaling and abrogated pro-inflammatory gene expression following fungal stimulation. Mechanistically, SHP-2 operates as a scaffold facilitating the recruitment of Syk to dectin-1 or FcRγ, through its N-SH2 domain and a previously unrecognized C-terminal ITAM motif. We demonstrate that DC-derived SHP-2 is crucial for the induction of IL-1β, IL-6 and IL-23, and anti-fungal T_H17 cell responses to control Candida albicans infection. Together, these data reveal a mechanism by which SHP-2 mediates Syk activation in response to fungal infections

The tyrosine phosphatase SHP2 associates with CUB domain-containing protein-1 (CDCP1), regulating its expression at the cell surface in a phosphorylation-dependent manner

CUB domain-containing protein-1 (CDCP1) is a transmembrane glycoprotein that is phosphorylated by SRC family kinases (SFK) before recruiting and activating PKCδ. CDCP1 is overproduced in many cancers. It promotes metastasis and resistance to anoïkis. The robust production of CDCP1 would be associated with stemness and has been proposed as a novel prognosis marker. The natural transmembrane location of CDCP1 makes it an ideal therapeutic target and treatments based on the use of appropriate antibodies are currently being evaluated. However, we still know very little about the molecular fate of CDCP1 and its downstream signaling events. Improvements in our understanding of the molecular events occurring downstream of CDCP1 are required to make use of changes of CDCP1 production or functions for therapeutic purposes. By the mean of co-immunoprecipitation and affinity precipitation we show here, for the first time, that CDCP1 interacts directly, with the cytosolic tyrosine phosphatase SHP2. Point mutants of CDCP1 show that residues Y734 and Y743 are responsible for its interaction with SHP2. It may therefore compete with SFK. We also demonstrate that a shRNA-mediated down regulation of SHP2 is associated with a stronger CDCP1 phosphorylation and an impairment of antibody-mediated CDCP1 internalization.

Inhibition of SHP2 in basal-like and triple-negative breast cells induces basal-to-luminal transition, hormone dependency, and sensitivity to anti-hormone treatment

Background

The Src homology phosphotyrosyl phosphatase 2 (SHP2) is a positive effector of cell growth and survival signaling as well transformation induced by multiple tyrosine kinase oncogenes. Since the basal-like and triple-negative breast cancer (BTBC) is characterized by dysregulation of multiple tyrosine kinase oncogenes, we wanted to determine the importance of SHP2 in BTBC cell lines.

Methods

Short hairpin RNA-based and dominant-negative expression-based SHP2 inhibition techniques were used to interrogate the functional importance of SHP2 in BTBC cell biology. In addition, cell viability and proliferation assays were used to determine hormone dependency for growth and sensitivity to anti-estrogen treatment.

Results

We show that inhibition of SHP2 in BTBC cells induces luminal-like epithelial morphology while suppressing the mesenchymal and invasive property. We have termed this process as basal-to-luminal transition (BLT). The occurrence of BLT was confirmed by the loss of the basal marker alpha smooth muscle actin and the acquisition of the luminal marker cytokeratin 18 (CK18) expression. Furthermore, the occurrence of BLT led to estrogen receptor alpha (ERα) expression, hormone dependency, and sensitivity to tamoxifen treatment.

Conclusions

Our data show that inhibition of SHP2 induces BLT, ERα expression, dependency on estrogen for growth, and sensitivity to anti-hormone therapy. Therefore, inhibition of SHP2 may provide a therapeutic benefit in basal-like and triple-negative breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1131-2) contains supplementary material, which is available to authorized users.

MKP-3 regulates PDGF-BB effects and MAPK activation in meningioma cells

Autocrine platelet derived growth factor-BB (PDGF-BB) and cerebrospinal fluid, which also contains PDGF, stimulate proliferation of leptomeningeal and meningioma cells, in part, by activation of the Raf-1-MEK-1-MAPK pathway. The negative regulators of this activation are not known. However, PDGF receptors and p44/42 MAPK are regulated, in part, by mitogen activated kinase phosphatase 3 (MKP-3) and Src homology carboxyl terminus protein (SHP-2). Six fetal and one adult human leptomeninges specimens and 22 meningiomas were evaluated for MKP-3, SHP-2, and phospho-SHP-2 as well as activation/phosphorylation of MEK1/2, p44/42 MAPK, Akt and signal transducer and activator of transcription 3 (STAT3) by western blot and MKP3 expression by polymerase chain reaction. PDGF-BB and cerebrospinal fluid effects on these phosphatases and signaling were also studied in vitro. MKP-3 and phospho-p44/42 MAPK were detected in all or six of seven leptomeninges, respectively. MKP-3 was detected in six of eight World Health Organization grade I and II meningiomas. Three of four grade I and five of five grade II with no or low MKP-3 had high levels of phospho-p44/42MAPK. MKP3 was not detected in four of six grade III meningiomas. These had high levels of phospho-p44/42MAPK. SHP2 was found in all leptomeninges and meningiomas while phospho-SHP-2 was found in 11 to 33% of grade I-III meningiomas. Reduced MKP-3 may facilitate PDGF-BB autocrine and paracrine mitogenic effects in a subpopulation of higher grade meningiomas by increasing phospho-p44/42 MAPK.

Myeloid-specific disruption of tyrosine phosphatase Shp2 promotes alternative activation of macrophages and predisposes mice to pulmonary fibrosis

The alternative activation of M2 macrophages in the lungs has been implicated as a causative agent in pulmonary fibrosis; however, the mechanisms underlying M2 polarization are poorly characterized. In this study, we investigated the role of the ubiquitously expressed Src homology domain-containing tyrosine phosphatase Shp2 in this process. Shp2 inactivation augmented IL-4-mediated M2 polarization in vitro, suggesting that Shp2 regulates macrophage skewing and prevents a bias toward the M2 phenotype. Conditional removal of Shp2 in monocytes/macrophages with lysozyme M promoter-driven Cre recombinase caused an IL-4-mediated shift toward M2 polarization. Additionally, an increase in arginase activity was detected in Shp2(∆/∆) mice after i.p. injection of chitin, whereas Shp2-deficient macrophages showed enhanced M2 polarization and protection against schistosome egg-induced schistosomiasis. Furthermore, mutants were more sensitive than control mice to bleomycin-induced inflammation and pulmonary fibrosis. Shp2 was associated with IL-4Rα and inhibited JAK1/STAT6 signaling through its phosphatase activity; loss of Shp2 promoted the association of JAK1 with IL-4Rα, which enhanced IL-4-mediated JAK1/STAT6 activation that resulted in M2 skewing. Taken together, these findings define a role for Shp2 in alveolar macrophages and reveal that Shp2 is required to inhibit the progression of M2-associated pulmonary fibrosis.

Molecular basis of gain-of-function LEOPARD syndrome-associated SHP2 mutations

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.

Noonan and LEOPARD syndrome Shp2 variants induce heart displacement defects in zebrafish

Germline mutations in PTPN11, encoding Shp2, cause Noonan syndrome (NS) and LEOPARD syndrome (LS), two developmental disorders that are characterized by multiple overlapping symptoms. Interestingly, Shp2 catalytic activity is enhanced by NS mutations and reduced by LS mutations. Defective cardiac development is a prominent symptom of both NS and LS, but how the Shp2 variants affect cardiac development is unclear. Here, we have expressed the most common NS and LS Shp2-variants in zebrafish embryos to investigate their role in cardiac development in vivo. Heart function was impaired in embryos expressing NS and LS variants of Shp2. The cardiac anomalies first occurred during elongation of the heart tube and consisted of reduced cardiomyocyte migration, coupled with impaired leftward heart displacement. Expression of specific laterality markers was randomized in embryos expressing NS and LS variants of Shp2. Ciliogenesis and cilia function in Kupffer's vesicle was impaired, likely accounting for the left/right asymmetry defects. Mitogen-activated protein kinase (MAPK) signaling was activated to a similar extent in embryos expressing NS and LS Shp2 variants. Interestingly, inhibition of MAPK signaling prior to gastrulation rescued cilia length and heart laterality defects. These results suggest that NS and LS Shp2 variant-mediated hyperactivation of MAPK signaling leads to impaired cilia function in Kupffer's vesicle, causing left-right asymmetry defects and defective early cardiac development.

Methylation and decreased expression of SHP-1 are related to disease progression in chronic myelogenous leukemia

Despite the unprecedented success of tyrosine kinase inhibitors (TKIs) in treating chronic myelogenous leukemia (CML), some patients nevertheless progress to advanced stages of the disease. Thus far, the biological basis leading to CML progression remains poorly understood. SH2-containing tyrosine phosphatase 1 (SHP-1) is reported to bind to p210BCR‑ABL1 and to function as a tumor suppressor. Furthermore, its substrates have been found to be essential for p210BCR-ABL1 leukemogenesis or CML progression. In the present study, we found that SHP-1 mRNA and protein levels were markedly decreased in patients in the accelerated and blastic phases of CML (AP-CML and BP-CML) compared to those in the chronic phase (CP-CML). In vitro, we demonstrated that overexpression of SHP-1 reduced p210BCR-ABL1 protein expression and activity in the K562 CML cell line and negatively regulated the AKT, MAPK, MYC and JAK2/STAT5 signaling pathways. Moreover, using a methylation-specific polymerase chain reaction (MSP) assay, abnormal methylation of the SHP-1 gene promoter region was found both in K562 cells and bone marrow (BM) or peripheral blood (PB) cells from AP-CML and BP-CML patients. In conclusion, our findings suggest that decreased expression levels of SHP-1 caused by aberrant promoter hypermethylation may play a key role in the progression of CML by dysregulating BCR-ABL1, AKT, MAPK, MYC and JAK2/STAT5 signaling.

Role of SH2-containing tyrosine phosphatase Shp2 in mouse corneal epithelial stratification

PURPOSE

Shp2 protein tyrosine phosphatase mediates a wide variety of receptor tyrosine kinases (RTK) cell signaling. Herein, we investigate the role of Shp2 in corneal morphogenesis and homeostasis.

METHODS

Shp2 was conditionally knocked out (Shp2(cko)) in Krt14-rtTA;tet-O-Cre;Shp2(f/f) triple transgenic mice administrated with doxycycline (Dox) from postnatal day 1 (P1) to P10, P15, and P25, respectively. In addition, corneal epithelial debridement was performed in adult (P42) mice treated with or without Dox for 8 days (from P42-P50). Mouse eyes were then subjected to histology and immunohistochemistry.

RESULTS

Shp2(cko) revealed impaired stratification of conjunctival and corneal epithelia during morphogenesis. Likewise, Shp2(cko) failed to restore epithelial stratification after a corneal epithelial wound in adult Shp2(cko). At the cellular level, the ratio of proliferating cell nuclear antigen (PCNA-positive)/total basal cells remained unchanged, but cells in G2/M (survivin-positive) phase was significantly increased in Shp2(cko) as compared with those in the control littermate. Interestingly, deltaN-p63 (ΔNp63) expression and the asymmetric division of the basal cells were coincidentally dampened in Shp2(cko). Transmission electron microscopic study showed that desmosome and hemidesmosome densities were reduced in the corneal epithelium of Shp2(cko). Immunohistochemistry also demonstrated that expression of E-cadherin/β-catenin junction and laminin-β1 was extensively downregulated in Shp2(cko). On the other hand, corneal epithelium lacking Shp2 remained positive for K14, Pax-6, and keratin 12 (K12), suggesting that Shp2 was dispensable for the corneal epithelial-type differentiation.

CONCLUSIONS

These data argued that Shp2 deficiency predominantly impacted p63-dependent cell division and cell adhesive ability, which resulted in the impairment of stratification during corneal epithelial development and wound healing.

Phospho-Ser/Thr-binding domains: navigating the cell cycle and DNA damage response

Coordinated progression through the cell cycle is a complex challenge for eukaryotic cells. Following genotoxic stress, diverse molecular signals must be integrated to establish checkpoints specific for each cell cycle stage, allowing time for various types of DNA repair. Phospho-Ser/Thr-binding domains have emerged as crucial regulators of cell cycle progression and DNA damage signalling. Such domains include 14-3-3 proteins, WW domains, Polo-box domains (in PLK1), WD40 repeats (including those in the E3 ligase SCF(βTrCP)), BRCT domains (including those in BRCA1) and FHA domains (such as in CHK2 and MDC1). Progress has been made in our understanding of the motif (or motifs) that these phospho-Ser/Thr-binding domains connect with on their targets and how these interactions influence the cell cycle and DNA damage response.

A quantitative assessment of costimulation and phosphatase activity on microclusters in early T cell signaling

T cell signaling is triggered through stimulation of the T cell receptor and costimulatory receptors. Receptor activation leads to the formation of membrane-proximal protein microclusters. These clusters undergo tyrosine phosphorylation and organize multiprotein complexes thereby acting as molecular signaling platforms. Little is known about how the quantity and phosphorylation levels of microclusters are affected by costimulatory signals and the activity of specific signaling proteins. We combined micrometer-sized, microcontact printed, striped patterns of different stimuli and simultaneous analysis of different cell strains with image processing protocols to address this problem. First, we validated the stimulation protocol by showing that high expression levels CD28 result in increased cell spreading. Subsequently, we addressed the role of costimulation and a specific phosphotyrosine phosphatase in cluster formation by including a SHP2 knock-down strain in our system. Distinguishing cell strains using carboxyfluorescein succinimidyl ester enabled a comparison within single samples. SHP2 exerted its effect by lowering phosphorylation levels of individual clusters while CD28 costimulation mainly increased the number of signaling clusters and cell spreading. These effects were observed for general tyrosine phosphorylation of clusters and for phosphorylated PLCγ1. Our analysis enables a clear distinction between factors determining the number of microclusters and those that act on these signaling platforms.

Association between CagA/ERK signaling pathway and gastric cancer

Cytotoxin-associated gene A (CagA) of Helicobacter pylori is the first identified bacterial oncoprotein that plays a critical role in gastric carcinogenesis. Upon delivery into gastric epithelial cells via type IV secretion, CagA can interfere with a number of host signaling pathways. Extracellular signal-regulated kinase (ERK) signaling pathway is a hub in cellular signal transduction, through which CagA elicits a series of cellular events including cell proliferation, apoptosis, scatter and metastasis, all of which are associated with gastric carcinogenesis. Here we perform a review of the association between CagA/ERK signaling pathway and gastric cancer.

Induction of a tumor-associated activating mutation in protein tyrosine phosphatase Ptpn11 (Shp2) enhances mitochondrial metabolism, leading to oxidative stress and senescence

Activating mutations in Ptpn11 (Shp2), a protein tyrosine phosphatase involved in diverse cell signaling pathways, are associated with pediatric leukemias and solid tumors. However, the pathogenic effects of these mutations have not been fully characterized. Here, we report that induction of the Ptpn11(E76K/+) mutation, the most common and active Ptpn11 mutation found in leukemias and solid tumors, in primary mouse embryonic fibroblasts resulted in proliferative arrest and premature senescence. As a result, apoptosis was markedly increased. These cellular responses were accompanied and mediated by up-regulation of p53 and p21. Moreover, intracellular levels of reactive oxygen species (ROS), byproducts of mitochondrial oxidative phosphorylation, were elevated in Ptpn11(E76K/+) cells. Since Shp2 is also distributed to the mitochondria (in addition to the cytosol), the impact of the Ptpn11(E76K/+) mutation on mitochondrial function was analyzed. These analyses revealed that oxygen consumption of Ptpn11(E76K/+) cells and the respiratory function of Ptpn11(E76K/+) mitochondria were significantly increased. Furthermore, we found that phosphorylation of mitochondrial Stat3, one of the substrates of Shp2 phosphatase, was greatly decreased in the mutant cells with the activating mutation Ptpn11(E76K/+). This study provides novel insights into the initial effects of tumor-associated Ptpn11 mutations.