蛋白酪氨酸磷酸酶SHP-1在细胞信号系统中的负调控作用

 Src同源区2蛋白酪氨酸磷酸酶-1(SHP-1)主要表达在造血源性细胞胞质中,是改变胞内磷酸化水平的关键因子。SHP-1在不同的细胞中可产生不尽相同的胞内信号,从而发挥各种功能。     

A negative role of SHP-2 tyrosine phosphatase in growth factor-dependent hematopoietic cell survival

SHP-2 tyrosine phosphatase is highly expressed in hematopoietic cells; however, the function of SHP-2 in hematopoietic cell processes is not fully understood. Recent identification of SHP-2 mutations in childhood leukemia further emphasizes the importance of SHP-2 regulation in hematopoietic cells. We previously reported that SHP-2 played a positive role in IL-3-induced activation of Jak2 kinase in a catalytic-dependent manner. Interestingly, enforced expression of wild-type (WT) SHP-2 in Ba/F3 cells enhanced growth factor deprivation-induced apoptosis. Biochemical analyses revealed that although IL-3 activation of Jak2 kinase was increased, tyrosyl phosphorylation of its downstream substrate STAT5 was disproportionately decreased by the overexpression of SHP-2. Following IL-3 deprivation, the tyrosyl phosphorylation of STAT5 that is required for its antiapoptotic activity was rapidly diminished in SHP-2 overexpressing cells. As a result, reduction of the putative downstream targets of STAT5-Bcl-X(L) and pim-1 was accelerated by overexpression of SHP-2. Further investigation showed that SHP-2 associated with STAT5, and that it was indeed able to dephosphorylate STAT5. Finally, overexpression of SHP-2 in primary bone marrow hematopoietic progenitor cells compromised their differentiative and proliferative potential, and enhanced growth factor withdrawal-induced cell death. And, the effect of SHP-2 overexpression on growth factor-dependent survival was diminished in STAT5-deficient hematopoietic cells. Taken together, these results suggest that SHP-2 tyrosine phosphatase negatively regulates hematopoietic cell survival by dephosphorylation of STAT5.     

Protein tyrosine phosphatase SHP-2: A proto-oncogene product that promotes Ras activation

SHP-2 is a cytoplasmic protein tyrosine phosphatase (PTP) that contains two Src homology 2 (SH2) domains. Although PTPs are generally considered to be negative regulators on the basis of their ability to oppose the effects of protein tyrosine kinases, SHP-2 is unusual in that it promotes the activation of the Ras-MAPK signaling pathway by receptors for various growth factors and cytokines. The molecular basis for the activation of SHP-2 is also unique: In the basal state, the NH₂-terminal SH2 domain of SHP-2 interacts with the PTP domain, resulting in autoinhibition of PTP activity; the binding of SHP-2 via its SH2 domains to tyrosine-phosphorylated growth factor receptors or docking proteins, however, results in disruption of this intramolecular interaction, leading to exposure of the PTP domain and catalytic activation. Indeed, SHP-2 proteins with artificial mutations in the NH₂-terminal SH2 domain have been shown to act as dominant active mutants in vitro . Such activating mutations of PTPN11 (human SHP-2 gene) were subsequently identified in individuals with Noonan syndrome, a human developmental disorder that is sometimes associated with juvenile myelomonocytic leukemia. Furthermore, somatic mutations of PTPN11 were found to be associated with pediatric leukemia. SHP-2 is also thought to participate in the development of other malignant disorders, but in a manner independent of such activating mutations. Biochemical and functional studies of SHP-2 and genetic analysis of PTPN11 in human disorders have thus converged to provide new insight into the pathogenesis of cancer as well as potential new targets for cancer treatment. ( Cancer Sci  2009; 100: 1786–1793)     

The tyrosine phosphatase SHP-2 is required for mediating phosphatidylinositol 3-kinase/Akt activation by growth factors

SHP-2 is a ubiquitously expressed non-transmembrane tyrosine phosphatase with two SH2 domains. Multiple reverse-genetic studies have indicated that SHP-2 is a required component for organ and animal development. SHP-2 wild-type and homozygous mutant mouse fibroblast cells in which the N-terminal SH2 domain was target-deleted were used to examine the function of SHP-2 in regulating Phosphatidylinositol 3-Kinase (PI3K) activation by growth factors. In addition, SHP-2 and various mutants were introduced into human glioblastoma cells as well as SHP-2(-/-) mouse fibroblasts. We found that EGF stimulation and EGFR oncoprotein (DeltaEGFR) expression independently induced the co-immunoprecipitation of the p85 subunit of PI3K with SHP-2. Targeted deletion of the N-terminal SH2 domain of SHP-2 severely impaired PDGF- and IGF-induced Akt phosphorylation. Ectopic expression of SHP-2 in U87MG gliobastoma cells elevated EGF-induced Akt phosphorylation, and the effect was abolished by mutation of its N-terminal SH2 domain. Likewise, the reconstitution of SHP-2 expression in the SHP-2(-/-) cells enhanced Akt phosphorylation induced by EGF while rescuing that induced by PDGF and IGF. Further lipid kinase activity assays confirmed that SHP-2 modulation of Akt phosphorylation correlated with its regulation of PI3K activation. Based on these results, we conclude that SHP-2 is required for mediating PI3K/Akt activation, and the N-terminal SH2 domain is critically important for a "positive" role of SHP-2 in regulating PI3K pathway activation.     

蛋白酪氨酸磷酸酶SHP-2参与白细胞介素-1β促发的细胞移动过程

目的 探讨蛋白酪氨酸磷酸酶SHP-2在白细胞介素-1β(IL-1β)所促发的细胞移动中的作用.方法 构建重组质粒SHP-2-GFP以及SHP-2C＞S-GFP并分别转入MCF-7乳腺癌细胞中,建立SHP-2-GFP-MCF-7和SHP-2C＞S-MCF-7细胞株.采用荧光显微镜技术观察细胞移动情况;反转录-聚合酶链反应(RT-PCR)、免疫印迹法检测钙黏蛋白和金属蛋白酶的变化情况,确定蛋白磷酸酶SHP-2在细胞移动中的作用.结果 E-钙黏蛋白在IL-1β刺激的SHP-2转染的乳腺癌细胞株中的表达量是最低的,而金属蛋白酶MMP-9的表达量最高.结论 SHP-2参与IL-1β促发的细胞移动,并且通过减少E-钙黏蛋白的表达以及增强金属蛋白酶MMP-9的分泌来发挥作用.     

蛋白酪氨酸磷酸酶参与促发的细胞移动过程

 目的　探讨蛋白酪氨酸磷酸酶SHP-2在IL-1β所促发的细胞移动中的作用。方法　构建重组质粒SHP-2-GFP以及SHP-2C>S-GFP 并分别转入MCF-7乳腺癌细胞中，建立SHP-2-GFP- MCF-7和SHP-2C>S-MCF-7细胞株。采用荧光显微镜技术观察细胞移动情况；RT-PCR、免疫印迹法检测钙黏蛋白和金属蛋白酶的变化情况，确定蛋白磷酸酶SHP-2在细胞移动中的作用。结果　E-钙黏蛋白在IL-1β刺激的SHP-2转染的乳腺癌细胞株中的表达量是最低的，而金属蛋白酶MMP-9的表达量最高。结论　SHP-2参与IL-1β促发的细胞移动，并且通过减少E-钙黏蛋白的表达以及增强金属蛋白酶MMP-9的分泌来发挥作用的。     

Role of the tyrosine phosphatase SHP-1 in K562 cell differentiation.

The erythro-megakaryoblastic leukemia cell line K562 undergoes erythroid or myeloid differentiation in response to treatment with various inducing agents. We observed that expression of the SH2-containing protein tyrosine phosphatase SHP-1 was induced upon exposure of K562 cells to differentiating agents. Under the same conditions, expression of SHP-2, a close relative of SHP-1, and the more distantly related PTP-1 B remained unchanged. Induction of SHP-1 expression correlates with dephosphorylation of a specific and limited set of tyrosyl phosphoproteins, suggesting that dephosphorylation of these proteins may be important for the differentiation process. Importantly, expression of exogenous SHP-1 inhibits K562 proliferation and alters the adhesion properties of these cells, indicating a more differentiated phenotype. Moreover, SHP-1 is found in a complex with both p210 Bcr-Abl and p190 Bcr-Abl, suggesting that it may regulate Bcr-Abl or Bcr-Abl-associated phosphotyrosyl proteins. Our results indicate that induction of SHP-1 expression is important for K562 differentiation in response to various inducers and raise the possibility that functional inactivation of SHP-1 may play a role in progression to blast crisis in chronic myelogenous leukemia.     

Up-regulation of the protein tyrosine phosphatase SHP-1 in human breast cancer and correlation with GRB2 expression

The protein tyrosine phosphatase SHP-1 is predominantly expressed in hemopoietic cell lineages, where its function is relatively well defined. However, its expression profile also extends to certain epithelial cell types. Furthermore, the negative regulatory role of this enzyme in hemopoietic cell signaling may not apply to other systems, where positive effects on particular tyrosine kinase signaling pathways have been described. Expression of SHP-1 was therefore investigated in human breast cancer cell lines and primary breast cancers. Differential expression of SHP-1 mRNA was observed among the 19 breast cancer cell lines examined, and in an analysis of 72 primary breast cancers, SHP-1 mRNA expression was increased 2- to 12-fold relative to normal breast epithelial cells in 58% of the samples. Interestingly, a subset of the cancers also over-expressed GRB2 mRNA by 2- to 7-fold, and a significant (p < 0.01) positive correlation was observed between SHP-1 and GRB2 mRNA expression. Since these proteins can bind to each other and regulate MEK/MAP kinase activation, their co-ordinate up-regulation may amplify tyrosine kinase signaling in breast cancer cells.     

The SH2 domain-containing protein tyrosine phosphatase SHP-1 is induced by granulocyte colony-stimulating factor (G-CSF) and modulates signaling from the G-CSF receptor.

The SH2 domain-containing protein tyrosine phosphatase SHP-1 is expressed widely in the hematopoietic system. SHP-1 has been shown to negatively control signal transduction from many cytokine receptors by direct docking to either the receptor itself, or to members of the Jak family of tyrosine kinases which are themselves part of the receptor complex. Motheaten and viable motheaten mice, which are deficient in SHP-1, have increased myelopoiesis and show an accumulation of morphologically and phenotypically immature granulocytes, suggesting a role for SHP-1 in granulocytic differentiation. Here, we report that SHP-1 protein levels are up-regulated during the granulocyte colony-stimulating factor (G-CSF)-mediated granulocytic differentiation of myeloid 32D cells. Enforced expression of SHP-1 in these cells leads to decreased proliferation and enhanced differentiation, while introduction of a catalytically inactive mutant produces increased proliferation and results in a delay of differentiation. In vitro binding revealed that the SH2 domains of SHP-1 are unable to associate directly with tyrosine-phosphorylated G-CSF receptor (G-CSF-R). Furthermore, over-expression of SHP-1 in Ba/F3 cells expressing a G-CSF-R mutant lacking all cytoplasmic tyrosines also inhibited proliferation. Together, these data suggest that SHP-1 directly modulates G-CSF-mediated responses in hematopoietic cells via a mechanism that does not require docking to the activated G-CSF-R.     

Protein tyrosine phosphatase PTPN13 negatively regulates Her2/ErbB2 malignant signaling

Deregulated Her2/ErbB2 receptor tyrosine kinase drives tumorigenesis and tumor progression in a variety of human tissues. Her2 transmits oncogenic signals through phosphorylation of its cytosolic domain. To study innate cellular mechanisms for containing Her2 oncogenic phosphorylation, a siRNA phosphatase library was screened for cellular phosphatase(s) that enhance phosphorylation in the signaling motif of Her2 after knockdown. We found that silencing protein tyrosine phosphatase PTPN13 significantly augmented growth factor-induced phosphorylation of the Her2 signaling domain and promoted the invasiveness of Her2-deregulated cancer cells. In addition, we discovered that growth factor-induced phosphorylation of PTPN13 was essential for the dephosphorylation of Her2 suggesting a negative feedback mechanism induced by growth factor to inhibit cellular Her2 activity through PTPN13. Importantly, we showed that PTPN13 mutations previously reported in human tumors significantly reduced the phosphatase activity of PTPN13, and consequently elevated the oncogenic potential of Her2 and the invasiveness of Her2-overexpressing human cancer cells. Taken together, these results suggest that cellular PTPN13 inhibits Her2 activity by dephosphorylating the signal domain of Her2 and plays a role in attenuating invasiveness and metastasis of Her2 overactive tumors.     

Protein tyrosine phosphatase SHP2 promotes invadopodia formation through suppression of Rho signaling

Invadopodia are actin-enriched membrane protrusions that are important for extracellular matrix degradation and invasive cell motility. Src homolog domain-containing phosphatase 2 (SHP2), a non-receptor protein tyrosine phosphatase, has been shown to play an important role in promoting cancer metastasis, but the underlying mechanism is unclear. In this study, we found that depletion of SHP2 by short-hairpin RNA suppressed invadopodia formation in several cancer cell lines, particularly in the SAS head and neck squamous cell line. In contrast, overexpression of SHP2 promoted invadopodia formation in the CAL27 head and neck squamous cell line, which expresses low levels of endogenous SHP2. The depletion of SHP2 in SAS cells significantly decreased their invasive motility. The suppression of invadopodia formation by SHP2 depletion was restored by the Clostridium botulinum C3 exoenzyme (a Rho GTPase inhibitor) or Y27632 (a specific inhibitor for Rho-associated kinase). Together, our results suggest that SHP2 may promote invadopodia formation through inhibition of Rho signaling in cancer cells.     

蛋白酪氨酸磷酸酶Shp2与肿瘤

Shp2（SH2 domain-containing protein-tyrosine phosphatase-2）分子由 PTPN11 基因编码,是一个在体内广泛存在的非受体型蛋白酪氨酸磷酸酶,既可以通过磷酸酶的催化活性来正向调控下游信号转导通路,也可以作为磷酸酶非依赖性的接头蛋白发挥正向调控作用,在特定的条件下亦可发挥负向调控作用,从而广泛参与细胞的分化、迁移等生物学功能的调控及相关的信号转导过程。 PTPN11 突变被认为是青少年粒单细胞白血病（juvenile myelomonocytic leukemia,JMML）的高危因素,同时,因其在不同类型白血病中均存在着 Shp2 的异常活化和突变而被认为是白血病的原癌基因;在前列腺癌、乳腺癌、胰腺癌、胃癌和神经胶质瘤中,Shp2也被报道呈过度活化状态;在肺癌中 Shp2 作为癌基因通过调控多种机制促进肿瘤的发生、发展。但在肝癌发生过程中, Shp2 却在特定环境的影响下发挥抑癌基因的作用。总之,作为重要的节点分子,Shp2在肿瘤发生、发展的过程中发挥着重要的调控作用,是潜在的治疗靶点。     

Roles for the protein tyrosine phosphatase SHP-2 in cytoskeletal organization, cell adhesion and cell migration revealed by overexpression of a dominant negative mutant

SHP-2, a SRC homology 2 domain-containing protein tyrosine phosphatase, mediates activation of Ras and mitogen-activated protein kinase by various mitogens and cell adhesion. Inhibition of endogenous SHP-2 by overexpression of a catalytically inactive (dominant negative) mutant in Chinese hamster ovary cells or Rat-1 fibroblasts has now been shown to induce a marked change in cell morphology (from elongated to less polarized) that is accompanied by substantial increases in the numbers of actin stress fibers and focal adhesion contacts. Overexpression of the SHP-2 mutant also increased the strength of cell-substratum adhesion and resulted in hyperphosphorylation of SHPS-1, a substrate of SHP-2 that contributes to cell adhesion-induced signaling. Inhibition of SHP-2 also markedly increased the rate of cell attachment to and cell spreading on extracellular matrix proteins such as fibronectin and vitronectin, effects that were accompanied by enhancement of adhesion-induced tyrosine phosphorylation of paxillin and p130Cas. In addition, cell migration mediated by fibronectin or vitronectin, but not that induced by insulin, was impaired by overexpression of the SHP-2 mutant. These results suggest that SHP-2 plays an important role in the control of cell shape by contributing to cytoskeletal organization, and that it is an important regulator of integrin-mediated cell adhesion, spreading, and migration as well as of tyrosine phosphorylation of focal adhesion contact-associated proteins.     

SH2-containing phosphotyrosine phosphatase SHP-1 is involved in BCR-ABL signal transduction pathways

The BCR-ABL fusion protein is strongly implicated in the malignant process of Philadelphia (Ph-1)-positive leukemia. The BCR-ABL fusion protein exhibits a deregulated tyrosine kinase activity capable of phosphorylating different cellular substrates in vivo and in vitro. SHP-1 (SHPTP1, PTP1C, HCP, SHP) is an SH2 domain-containing tyrosine phosphatase expressed predominantly in hematopoietic cells. The association of the murine motheaten phenotype of severe hematopoietic dysregulation with loss of SHP-1 tyrosine phosphatase activity indicates a critical role of SHP-1 in the regulation of hematopoietic cell growth and differentiation. Experiments were performed to determine whether SHP-1 might form specific complexes with BCR-ABL signaling pathway. We found that SHP-1 was highly and constitutively tyrosine phosphorylated in 32DCl3 and TF-1 cells transfected with BCR-ABL expression vector. Furthermore, SHP-1 and BCR-ABL formed stable complexes in BCR-ABL expressing cells. Direct binding between SHP-1 and Grb2 was observed in vitro. Expression of BCR-ABL in TF-1 cells resulted in a two-fold increase in SHP-1 phosphatase activity. BCR-ABL tyrosine kinase was able to phosphorylate recombinant SHP-1 protein in vitro. SHP-1 therefore has the capacity to bind and potentially modulate the signaling effectors involved in activation of Ras, and accordingly, regulation of cellular transformation of BCR-ABL.