Involvement of SHP2 in focal adhesion, migration and differentiation of neural stem cells

Cx40 Levels Regulate Hypoxia-Induced Changes in the Migration, Proliferation, and Formation of Gap Junction Plaques in an Extravillous Trophoblast Cell Model

BACKGROUND

Extravillous trophoblasts (EVTs) form stratified columns at the placenta-uterus interface. In the closest part to fetal structures, EVTs have a proliferative phenotype, whereas in the closest part to maternal structures, they present a migratory phenotype. During the placentation process, Connexin 40 (Cx40) participates in both the proliferation and migration of EVTs, which occurs under hypoxia. However, a possible interaction between hypoxia and Cx40 has not yet been established.

METHODS

We developed two cellular models, one with "low Cx40" (Jeg-3), which reflected the expression of this protein found in migratory EVTs, and one with "high Cx40" (Jeg-3/hCx40), which reflected the expression of this protein in proliferative cells. We analyzed the migration and proliferation of these cells under normoxic and hypoxic conditions for 24 h. Jeg-3 cells under hypoxia increased their migratory capacity over their proliferative capacity. However, in Jeg-3/hCx40, the opposite effect was induced. On the other hand, hypoxia promoted gap junction (GJ) plaque formation between neighboring Jeg-3 cells. Similarly, the activation of a nitro oxide (NO)/cGMP/PKG-dependent pathway induced an increase in GJ-plaque formation in Jeg-3 cells.

CONCLUSIONS

The expression patterns of Cx40 play a crucial role in shaping the responses of EVTs to hypoxia, thereby influencing their migratory or proliferative phenotype. Simultaneously, hypoxia triggers an increase in Cx40 gap junction (GJ) plaque formation through a pathway dependent on NO.

Paternally Inherited Noonan Syndrome Caused by a PTPN11 Variant May Exhibit Mild Symptoms: A Case Report and Literature Review

BACKGROUND

Noonan syndrome (NS)/Noonan syndrome with multiple lentigines (NSML) is commonly characterized by distinct facial features, a short stature, cardiac problems, and a developmental delay of variable degrees. However, as many as 50% of individuals diagnosed with NS/NSML have a mildly affected parent or relative due to variable expressivity and possibly incomplete penetrance of the disorder, and those who are recognized to have NS only after a diagnosis are established in a more obviously affected index case.

METHODS

In order to collect intergenerational data reported from previous studies, electronic journal databases containing information on the molecular genetics of PTPN11 were searched from 2000 to 2022.

RESULTS

We present a case of a proband with a PTPN11 variant (c.1492C > T/p.Arg498Trp) inherited from an asymptomatic father, displaying only mild intellectual disability without classical symptoms of NS. Among our cases and the reported NS cases caused by the PTPN11 p.Arg498Trp variant, cardiac abnormalities (6/11), facial dysmorphism (7/11), skin pigmentation (4/11), growth problems (4/11), and sensorineural hearing loss (2/11) have been observed. NS/NSML patients with the PTPN11 p.Arg498Trp variant tend to exhibit relatively lower frequencies of skin pigmentation, facial dysmorphism and cardiac abnormalities and mild symptoms compared to those carrying any other mutated PTPN11.

CONCLUSIONS

Paternally inherited NS/NSML caused by a PTPN11 p.Arg498Trp variant, including our cases, may exhibit relatively lower frequencies of abnormal features and mild symptoms. This could be ascribed to potential gene-gene interactions, gene-environment interactions, the gender and phenotype of the transmitting parent, or ethnic differences that influence the clinical phenotype.

Dissecting protein tyrosine phosphatase signaling by engineered chemogenetic control of its activity

Protein tyrosine phosphatases (PTPases) are critical mediators of dynamic cell signaling. A tool capable of identifying transient signaling events downstream of PTPases is essential to understand phosphatase function on a physiological time scale. We report a broadly applicable protein engineering method for allosteric regulation of PTPases. This method enables dissection of transient events and reconstruction of individual signaling pathways. Implementation of this approach for Shp2 phosphatase revealed parallel MAPK and ROCK II dependent pathways downstream of Shp2, mediating transient cell spreading and migration. Furthermore, we show that the N-SH2 domain of Shp2 regulates MAPK-independent, ROCK II-dependent cell migration. Engineered targeting of Shp2 activity to different protein complexes revealed that Shp2-FAK signaling induces cell spreading whereas Shp2-Gab1 or Shp2-Gab2 mediates cell migration. We identified specific transient morphodynamic processes induced by Shp2 and determined the role of individual signaling pathways downstream of Shp2 in regulating these events. Broad application of this approach is demonstrated by regulating PTP1B and PTP-PEST phosphatases.

Acute disseminated encephalomyelitis in a patient with Noonan syndrome: A rare autoinflammatory complication or coincidence?

We describe a 13-years-old girl, previously diagnosed with PTPN11-associated Noonan Syndrome (NS), who presented to the pediatric emergency department for fever and drowsiness, which gradually worsened within 48 h. On admission, brain magnetic resonance imaging (MRI) scan showed diffuse, symmetric, multiple, poorly demarcated, confluent hyperintense lesions on MRI T2w-images, located in the Central Nervous System (CNS). In the absence of a better explanation and according to the current diagnostic criteria, a diagnosis of Acute Disseminated Encephalomyelitis (ADEM) was performed. The patient was first treated with intravenous methylprednisolone, then with intravenous immunoglobulin (IVIG). Owing to the poor clinical response, three sessions of therapeutic plasma exchange (TPE) were finally performed, with a progressive improvement. Follow-up MRI performed after three months from the onset revealed a considerable reduction in brain lesions, while cervical and dorsal ones were substantially unmodified. Neurological examination showed a full recovery of cognitive function and improved strength and tone of the upper limbs, while tetrahyporeflexia and proximal weakness of lower limbs were still appreciable. To date, this is the first described case of ADEM occurring in a patient with NS.

The impact of RASopathy-associated mutations on CNS development in mice and humans

The RAS signaling pathway is involved in the regulation of developmental processes, including cell growth, proliferation, and differentiation, in the central nervous system (CNS). Germline mutations in the RAS signaling pathway genes are associated with a group of neurodevelopmental disorders, collectively called RASopathy, which includes neurofibromatosis type 1, Noonan syndrome, cardio-facio-cutaneous syndrome, and Costello syndrome. Most mutations associated with RASopathies increase the activity of the RAS-ERK signaling pathway, and therefore, most individuals with RASopathies share common phenotypes, such as a short stature, heart defects, facial abnormalities, and cognitive impairments, which are often accompanied by abnormal CNS development. Recent studies using mouse models of RASopathies demonstrated that particular mutations associated with each disorder disrupt CNS development in a mutation-specific manner. Here, we reviewed the recent literatures that investigated the developmental role of RASopathy-associated mutations using mutant mice, which provided insights into the specific contribution of RAS-ERK signaling molecules to CNS development and the subsequent impact on cognitive function in adult mice.

Upregulated SHP-2 expression in the epileptogenic zone of temporal lobe epilepsy and various effects of SHP099 treatment on a pilocarpine model

Temporal lobe epilepsy (TLE) is defined as the sporadic occurrence of spontaneous recurrent seizures, and its pathogenesis is complex. SHP-2 (Src homology 2-containing protein tyrosine phosphatase 2) is a widely expressed cytosolic tyrosine phosphatase protein that participates in the regulation of inflammation, angiogenesis, gliosis, neurogenesis and apoptosis, suggesting a potential role of SHP-2 in TLE. Therefore, we investigated the expression patterns of SHP-2 in the epileptogenic brain tissue of intractable TLE patients and the various effects of treatment with the SHP-2-specific inhibitor SHP099 on a pilocarpine model. Western blotting and immunohistochemistry results confirmed that SHP-2 expression was upregulated in the temporal neocortex of patients with TLE. Double-labeling experiments revealed that SHP-2 was highly expressed in neurons, astrocytes, microglia and vascular endothelial cells in the epileptic foci of TLE patients. In the pilocarpine-induced C57BL/6 mouse model, SHP-2 upregulation in the hippocampus began one day after status epilepticus, reached a peak at 21 days and then maintained a significantly high level until day 60. Similarly, we found a remarkable increase in SHP-2 expression at 1, 7, 21 and 60 days post-SE in the temporal neocortex. In addition, we also showed that SHP099 increased reactive gliosis, the release of IL-1β, neuronal apoptosis and neuronal loss, while reduced neurogenesis and albumin leakage. Taken together, the increased expression of SHP-2 in the epileptic zone may be involved in the process of TLE.

Neurodevelopmental Aspects of RASopathies

RAS gene mutations are frequently found in one third of human cancers. Affecting approximately 1 in 1,000 newborns, germline and somatic gain-of-function mutations in the components of RAS/mitogen-activated protein kinase (RAS/MAPK) pathway has been shown to cause developmental disorders, known as RASopathies. Since RAS-MAPK pathway plays essential roles in proliferation, differentiation and migration involving developmental processes, individuals with RASopathies show abnormalities in various organ systems including central nervous system. The frequently seen neurological defects are developmental delay, macrocephaly, seizures, neurocognitive deficits, and structural malformations. Some of the defects stemmed from dysregulation of molecular and cellular processes affecting early neurodevelopmental processes. In this review, we will discuss the implications of RAS-MAPK pathway components in neurodevelopmental processes and pathogenesis of RASopathies.

SHP2-Mediated Signal Networks in Stem Cell Homeostasis and Dysfunction

Stem cells, including embryonic stem cells (ESCs) and adult stem cells, play a central role in mammal organism development and homeostasis. They have two unique properties: the capacity for self-renewal and the ability to differentiate into many specialized cell types. Src homology region 2- (SH2-) containing protein tyrosine phosphatase 2 (SHP-2), a nonreceptor protein tyrosine phosphatase encoded by protein tyrosine phosphatase nonreceptor type 11 gene (PTPN11), regulates multicellular differentiation, proliferation, and survival through numerous conserved signal pathways. Gain-of-function (GOF) or loss-of-function (LOF) SHP2 in various cells, especially for stem cells, disrupt organism self-balance and lead to a plethora of diseases, such as cancer, maldevelopment, and excessive hyperblastosis. However, the exact mechanisms of SHP2 dysfunction in stem cells remain unclear. In this review, we intended to raise the attention and clarify the framework of SHP2-mediated signal pathways in various stem cells. Establishment of integrated signal architecture, from ESCs to adult stem cells, will help us to understand the changes of dynamic, multilayered pathways in response to SHP2 dysfunction. Overall, better understanding the functions of SHP2 in stem cells provides a new avenue to treat SHP2-associated diseases.

Cytotoxic activity of Shp2 inhibitor fumosorinone in human cancer cells

Fumosorinone (Fumos) isolated from entomogenous fungi Isaria fumosorosea exhibited selective inhibition of Src homology phosphotyrosine phosphatase 2 inhibitor (Shp2) in our previous study. The purpose of the present study was to investigate the effects of Fumos on cell cycle arrest, tumor cell migration and the in vitro antiproliferative activity of Fumos alone or in combination with the commonly used cytotoxic drugs 5-fluoracil (5-FU) and p38 inhibitor SB203580. Fumos exhibited cytotoxicity against selected human cancel lines, including HeLa, MDA-MB-231 and MDA-MB-453 cell lines. Fumos exerted selective cytotoxic effects on the human cell lines. Flow cytometric and DAPI assays showed that Fumos did not induce cell apoptosis, however it induced cell cycle arrest at the G1 phase. Fumos inhibited cell migration though reducing the phosphorylation of focal adhesion kinase (FAK) at tyrosine (Tyr)861 and marginally increasing the phosphorylation of FAK at Tyr397, however, Fumos did not affect the phosphorylation of FAK at Tyr576 or Tyr925. The present study also examined the combination effect of Fumos with other chemical agents, including 5-FU and p38 inhibitor SB203580. Fumos exhibited a marked synergistic effect with these agents, particularly with 5-FU. In conclusion, Fumos showed potential anticancer bioactivity, and the combination effect of Fumos with 5-FU or with p38 inhibitor offers a more effective anticancer strategy for carcinoma treatment.

The Protein Tyrosine Phosphatase Shp2 Regulates Oligodendrocyte Differentiation and Early Myelination and Contributes to Timely Remyelination

Shp2 is a nonreceptor protein tyrosine phosphatase that has been shown to influence neurogenesis, oligodendrogenesis, and oligodendrocyte differentiation. Furthermore, Shp2 is a known regulator of the Akt/mammalian target of rapamycin and ERK signaling pathways in multiple cellular contexts, including oligodendrocytes. Its role during later postnatal CNS development or in response to demyelination injury has not been examined. Based on the current studies, we hypothesize that Shp2 is a negative regulator of CNS myelination. Using transgenic mouse technology, we show that Shp2 is involved in oligodendrocyte differentiation and early myelination, but is not necessary for myelin maintenance. We also show that Shp2 regulates the timely differentiation of oligodendrocytes following lysolecithin-induced demyelination, although apparently normal remyelination occurs at a delayed time point. These data suggest that Shp2 is a relevant therapeutic target in demyelinating diseases such as multiple sclerosis.SIGNIFICANCE STATEMENT In the present study, we show that the protein phosphatase Shp2 is an important mediator of oligodendrocyte differentiation and myelination, both during developmental myelination as well as during myelin regeneration. We provide important insight into the signaling mechanisms regulating myelination and propose that Shp2 acts as a transient brake to the developmental myelination process. Furthermore, we show that Shp2 regulates oligodendrocyte differentiation following demyelination and therefore has important therapeutic implications in diseases such as multiple sclerosis.

Recent advances in understanding the role of protein-tyrosine phosphatases in development and disease

Protein-tyrosine phosphatases (PTPs) remove phosphate groups from tyrosine residues, and thereby propagate or inhibit signal transduction, and hence influence cellular processes such as cell proliferation and differentiation. The importance of tightly controlled PTP activity is reflected by the numerous mechanisms employed by the cell to control PTP activity, including a variety of post-translational modifications, and restricted subcellular localization. This review highlights the strides made in the last decade and discusses the important role of PTPs in key aspects of embryonic development: the regulation of stem cell self-renewal and differentiation, gastrulation and somitogenesis during early embryonic development, osteogenesis, and angiogenesis. The tentative importance of PTPs in these processes is highlighted by the diseases that present upon aberrant activity.

Cell-permeable p38 MAP kinase promotes migration of adult neural stem/progenitor cells

Endogenous neural stem/progenitor cells (NPCs) can migrate toward sites of injury, but the migration activity of NPCs is insufficient to regenerate damaged brain tissue. In this study, we showed that p38 MAP kinase (p38) is expressed in doublecortin-positive adult NPCs. Experiments using the p38 inhibitor SB203580 revealed that endogenous p38 participates in NPC migration. To enhance NPC migration, we generated a cell-permeable wild-type p38 protein (PTD-p38WT) in which the HIV protein transduction domain (PTD) was fused to the N-terminus of p38. Treatment with PTD-p38WT significantly promoted the random migration of adult NPCs without affecting cell survival or differentiation; this effect depended on the cell permeability and kinase activity of the fusion protein. These findings indicate that PTD-p38WT is a novel and useful tool for unraveling the roles of p38, and that this protein provides a reasonable approach for regenerating the injured brain by enhancing NPC migration.

Regeneration in the nervous system with erythropoietin

Globally, greater than 30 million individuals are afflicted with disorders of the nervous system accompanied by tens of thousands of new cases annually with limited, if any, treatment options. Erythropoietin (EPO) offers an exciting and novel therapeutic strategy to address both acute and chronic neurodegenerative disorders. EPO governs a number of critical protective and regenerative mechanisms that can impact apoptotic and autophagic programmed cell death pathways through protein kinase B (Akt), sirtuins, mammalian forkhead transcription factors, and wingless signaling. Translation of the cytoprotective pathways of EPO into clinically effective treatments for some neurodegenerative disorders has been promising, but additional work is necessary. In particular, development of new treatments with erythropoiesis-stimulating agents such as EPO brings several important challenges that involve detrimental vascular outcomes and tumorigenesis. Future work that can effectively and safely harness the complexity of the signaling pathways of EPO will be vital for the fruitful treatment of disorders of the nervous system.

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.

Enhancing neural stem cell response to SDF-1α gradients through hyaluronic acid-laminin hydrogels

Traumatic brain injury (TBI) initiates an expansive biochemical insult that is largely responsible for the long-term dysfunction associated with TBI; however, current clinical treatments fall short of addressing these underlying sequelae. Pre-clinical investigations have used stem cell transplantation with moderate success, but are plagued by staggeringly low survival and engraftment rates (2-4%). As such, providing cell transplants with the means to better dynamically respond to injury-related signals within the transplant microenvironment may afford improved transplantation survival and engraftment rates. The chemokine stromal cell-derived factor-1α (SDF-1α) is a potent chemotactic signal that is readily present after TBI. In this study, we sought to develop a transplantation vehicle to ultimately enhance the responsiveness of neural transplants to injury-induced SDF-1α. Specifically, we hypothesize that a hyaluronic acid (HA) and laminin (Lm) hydrogel would promote 1. upregulated expression of the SDF-1α receptor CXCR4 in neural progenitor/stem cells (NPSCs) and 2. enhanced NPSC migration in response to SDF-1α gradients. We demonstrated successful development of a HA-Lm hydrogel and utilized standard protein and cellular assays to probe NPSC CXCR4 expression and NPSC chemotactic migration. The findings demonstrated that NPSCs significantly increased CXCR4 expression after 48 h of culture on the HA-Lm gel in a manner critically dependent on both HA and laminin. Moreover, the HA-Lm hydrogel significantly increased NPSC chemotactic migration in response to SDF-1α at 48 h, an effect that was critically dependent on HA, laminin and the SDF-1α gradient. Therefore, this hydrogel serves to 1. prime NPSCs for the injury microenvironment and 2. provide the appropriate infrastructure to support migration into the surrounding tissue, equipping cells with the tools to more effectively respond to the injury microenvironment.

The Q510E mutation in Shp2 perturbs heart valve development by increasing cell migration

Tightly regulated cellular signaling is critical for correct heart valve development, but how and why signaling is dysregulated in congenital heart disease is not very well known. We focused on protein tyrosine phosphatase Shp2, because mutations in this signaling modulator frequently cause valve malformations associated with Noonan syndrome or Noonan syndrome with multiple lentigines (NSML). To model NSML-associated valve disease, we targeted overexpression of Q510E-Shp2 to mouse endocardial cushions (ECs) using a Tie2-Cre-based approach. At midgestation, Q510E-Shp2 expression increased the size of atrioventricular ECs by 80%. To dissect the underlying cellular mechanisms, we explanted ECs from chick embryonic hearts and induced Q510E-Shp2 expression using adenoviral vectors. Valve cell outgrowth from cultured EC explants into surrounding matrix was significantly increased by Q510E-Shp2 expression. Because focal adhesion kinase (FAK) is a critical regulator of cell migration, we tested whether FAK inhibition counteracts the Q510E-Shp2-induced effects in explanted ECs. The FAK/src inhibitor PP2 normalized valve cell outgrowth from Q510E-Shp2-expressing ECs. Next, chick ECs were further dissociated to assess cell proliferation and migration. Valve cell proliferation was not increased by Q510E-Shp2 as determined by label incorporation. In contrast, valve cell migration as reflected in a wound-healing assay was increased by Q510E-Shp2 expression, indicating that increased migration is the predominant effect of Q510E-Shp2 expression in ECs. In conclusion, PP2-sensitive signaling mediates the pathogenic effects of Q510E-Shp2 on cell migration in EC explant cultures. This suggests a central role for FAK and provides new mechanistic insight into the molecular basis of valve defects in NSML.

Adiponectin modulates focal adhesion disassembly in activated hepatic stellate cells: implication for reversing hepatic fibrosis

Previous evidence indicates that adiponectin possesses antifibrogenic activity in inhibiting liver fibrosis. Therapeutic strategies, however, are limited by adiponectin quaternary structure and effective concentrations in circulation. Here we postulate a novel molecular mechanism, whereby adiponectin targets focal adhesion kinase (FAK) activity and disrupts key features of the fibrogenic response. Adiponectin-null (Ad(-/-)) mice and wild-type littermates were exposed to either saline or carbon tetrachloride (CCl4) for 6 wk. CCl4-gavaged mice were also injected with attenuated adenoviral adiponectin (Ad-Adn) or Ad-LacZ for 2 wk. Hepatic stellate cells (HSCs) were treated with or without adiponectin to elucidate signal transduction mechanisms. In vivo delivery of Ad-Adn markedly attenuates CCl4-induced expression of key integrin proteins and markers of HSC activation: αv, β3, β1, α2(I) collagen, and α-smooth muscle actin. Confocal experiments of liver tissues demonstrated that adiponectin delivery also suppressed vinculin and p-FAK activity in activated HSCs. In vitro, adiponectin induced dephosphorylation of FAK, mediated by a physical association with activated tyrosine phosphatase, Shp2. Conversely, Shp2 knockdown by siRNA significantly attenuated adiponectin-induced FAK deactivation, and expression of TIMP1 and α2(I) collagen was abolished in the presence of adiponectin and si-FAK. Finally, we documented that either adiponectin or the synthetic peptide with adiponectin properties, ADP355, suppressed p-FAK in synthetic matrices with stiffness measurements of 9 and 15 kPa, assessed by immunofluorescent imaging and quantitation. The in vivo and in vitro data presented indicate that disassembly of focal adhesion complexes in HSCs is pivotal for hepatic fibrosis therapy, now that small adiponectin-like peptides are available.

Upregulation of Src homology phosphotyrosyl phosphatase 2 (Shp2) expression in oral cancer and knockdown of Shp2 expression inhibit tumor cell viability and invasion in vitro

OBJECTIVE

This study investigated the clinical significance of Shp2 protein expression in oral squamous cell carcinoma (OSCC) and elucidated its biologic significance in OSCC cells.

STUDY DESIGN

A total of 88 OSCC cases were used to assess Shp2 expression, out of which 70 were for immunohistochemistry and 18 paired tumors vs normal tissues were for Western blot of Shp2 expression. OSCC cells were used to assess the effects of Shp2 knockdown for cell viability, apoptosis, invasion, and protein expressions.

RESULTS

Expression of Shp2 protein was significantly upregulated in OSCC tissues compared with the normal tissues, and Shp2 overexpression was associated with advanced tumor clinical stages and lymph node metastasis ex vivo. Knockdown of Shp2 expression in vitro inhibited OSCC cell viability and invasion but induced apoptosis by regulating expression of the apoptosis-related proteins.

CONCLUSIONS

The data indicated that Shp2 may play an important role in OSCC progression. Further studies will investigate whether a target of Shp2 expression could be a novel therapeutic strategy for clinical control of OSCC.