Tyrosine phosphatases Shp1 and Shp2 have unique and opposing roles in oligodendrocyte development

SHP-1 tyrosine phosphatase binding to c-Src kinase phosphor-dependent conformations: A comparative structural framework

SHP-1 is a cytosolic tyrosine phosphatase that is primarily expressed in hematopoietic cells. It acts as a negative regulator of numerous signaling pathways and controls multiple cellular functions involved in cancer pathogenesis. This study describes the binding preferences of SHP-1 (pY536) to c-Srcopen (pY416) and c-Srcclose (pY527) through in silico approaches. Molecular dynamics simulation analysis revealed more conformational changes in c-Srcclose upon binding to SHP-1, as compared to its active/open conformation that is stabilized by the cooperative binding of the C-SH2 domain and C-terminal tail of SHP-1 to c-Src SH2 and KD. In contrast, c-Srcclose and SHP-1 interaction is mediated by PTP domain-specific WPD-loop (WPDXGXP) and Q-loop (QTXXQYXF) binding to c-Srcclose C-terminal tail residues. The dynamic correlation analysis demonstrated a positive correlation for SHP-1 PTP with KD, SH3, and the C-terminal tail of c-Srcclose. In the case of the c-Srcopen-SHP-1 complex, SH3 and SH2 domains of c-Srcopen were correlated to C-SH2 and the C-terminal tail of SHP-1. Our findings reveal that SHP1-dependent c-Src activation through dephosphorylation relies on the conformational shift in the inhibitory C-terminal tail that may ease the recruitment of the N-SH2 domain to phosphotyrosine residue, resulting in the relieving of the PTP domain. Collectively, this study delineates the intermolecular interaction paradigm and underlying conformational readjustments in SHP-1 due to binding with the c-Src active and inactive state. This study will largely help in devising novel therapeutic strategies for targeting cancer development.

Modeling (not so) rare developmental disorders associated with mutations in the protein-tyrosine phosphatase SHP2

Src homology region 2 (SH2)-containing protein tyrosine phosphatase 2 (SHP2) is a highly conserved protein tyrosine phosphatase (PTP), which is encoded by PTPN11 and is indispensable during embryonic development. Mutations in PTPN11 in human patients cause aberrant signaling of SHP2, resulting in multiple rare hereditary diseases, including Noonan Syndrome (NS), Noonan Syndrome with Multiple Lentigines (NSML), Juvenile Myelomonocytic Leukemia (JMML) and Metachondromatosis (MC). Somatic mutations in PTPN11 have been found to cause cancer. Here, we focus on the role of SHP2 variants in rare diseases and advances in the understanding of its pathogenesis using model systems.

Molecular features underlying differential SHP1/SHP2 binding of immune checkpoint receptors

A large number of inhibitory receptors recruit SHP1 and/or SHP2, tandem-SH2-containing phosphatases through phosphotyrosine-based motifs immunoreceptor tyrosine-based inhibitory motif (ITIM) and immunoreceptor tyrosine-based switch motif (ITSM). Despite the similarity, these receptors exhibit differential effector binding specificities, as exemplified by the immune checkpoint receptors PD-1 and BTLA, which preferentially recruit SHP2 and SHP1, respectively. The molecular basis by which structurally similar receptors discriminate SHP1 and SHP2 is unclear. Here, we provide evidence that human PD-1 and BTLA optimally bind to SHP1 and SHP2 via a bivalent, parallel mode that involves both SH2 domains of SHP1 or SHP2. PD-1 mainly uses its ITSM to prefer SHP2 over SHP1 via their C-terminal SH2 domains (cSH2): swapping SHP1-cSH2 with SHP2-cSH2 enabled PD-1:SHP1 association in T cells. In contrast, BTLA primarily utilizes its ITIM to prefer SHP1 over SHP2 via their N-terminal SH2 domains (nSH2). The ITIM of PD-1, however, appeared to be de-emphasized due to a glycine at pY+1 position. Substitution of this glycine with alanine, a residue conserved in BTLA and several SHP1-recruiting receptors, was sufficient to induce PD-1:SHP1 interaction in T cells. Finally, structural simulation and mutagenesis screening showed that SHP1 recruitment activity exhibits a bell-shaped dependence on the molecular volume of the pY+1 residue of ITIM. Collectively, we provide a molecular interpretation of the SHP1/SHP2-binding specificities of PD-1 and BTLA, with implications for the mechanisms of a large family of therapeutically relevant receptors.

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.

Role of EGFR in the Nervous System

Epidermal growth factor receptor (EGFR) is the first discovered member of the receptor tyrosine kinase superfamily and plays a fundamental role during embryogenesis and in adult tissues, being involved in growth, differentiation, maintenance and repair of various tissues and organs. The role of EGFR in the regulation of tissue development and homeostasis has been thoroughly investigated and it has also been demonstrated that EGFR is a driver of tumorigenesis. In the nervous system, other growth factors, and thus other receptors, are important for growth, differentiation and repair of the tissue, namely neurotrophins and neurotrophins receptors. For this reason, for a long time, the role of EGFR in the nervous system has been underestimated and poorly investigated. However, EGFR is expressed both in the central and peripheral nervous systems and it has been demonstrated to have specific important neurotrophic functions, in particular in the central nervous system. This review discusses the role of EGFR in regulating differentiation and functions of neurons and neuroglia. Furthermore, its involvement in regeneration after injury and in the onset of neurodegenerative diseases is examined.

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.

Regulation of peripheral and central immunity: Understanding the role of Src homology 2 domain-containing tyrosine phosphatases, SHP-1 & SHP-2

Protein tyrosine phosphorylation is a potent post-translational regulatory mechanism necessary for maintaining normal physiological functioning of immune cells and it is under the stringent control of antagonizing actions of Protein tyrosine phosphatases and kinases. Two such important Non-Receptor protein tyrosine phosphatases, SHP-1 and SHP-2, have been found to be expressed in immune cells and reported to be key regulators of immune cell development, functions, and differentiation by modulating the duration and amplitude of the downstream cascade transduced via receptors. They also have been conceded as the immune checkpoints & therapeutic targets and hence, it is important to understand their significance intricately. This review compares the roles of these two important cytoplasmic PTPs, SHP1 & SHP-2 in the regulation of peripheral as well as central immunity.

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.

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.

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.

Metformin Attenuates Cognitive Impairments in Hypoxia-Ischemia Neonatal Rats via Improving Remyelination

Perinatal hypoxia-ischemia (H/I) causes brain injury and myelination damage. Finding efficient methods to restore myelination is critical for the recovery of brain impairments. By applying an H/I rat model, we demonstrate that metformin (Met) treatment significantly ameliorates the loss of locomotor activity and cognition of H/I rat in the Morris water maze and open field task tests. After administration of Met to H/I rat, the proliferation of Olig2+ oligodendrocyte progenitor cells and the expression of myelin basic protein are obviously increased in the corpus callosum. Additionally, the myelin sheaths are more compact and the impairments are evidently attenuated. These data indicate that Met is beneficial for the amelioration of H/I-induced myelination and behavior deficits.

EGFR and PDGFRA co-expression and heterodimerization in glioblastoma tumor sphere lines

Concurrent amplifications of EGFR and PDGFRA have been reported in up to 5% of glioblastoma (GBM) and it remains unclear why such independent amplification events, and associated receptor overexpression, would be adaptive during glioma evolution. Here, we document that EGFR and PDGFRA protein co-expression occurs in 37% of GBM. There is wide cell-to-cell variation in the expressions of these receptor tyrosine kinases (RTKs) in stable tumor sphere lines, frequently defining tumor cell subpopulations with distinct sensitivities to growth factors and RTK inhibitors. We also find evidence for functional transactivation of PDGFRA by EGFR and EGF-induced receptor heterodimerization, both of which are abolished by EGFR inhibitors. These results indicate that GBM growth responses to targeted therapies previously tested in clinical trials are strongly influenced by the balance of EGFR and PDGFRA activation in individual cells, which is heterogeneous at baseline.

The control of reactive oxygen species production by SHP-1 in oligodendrocytes

We have previously described reduced myelination and corresponding myelin basic protein (MBP) expression in the central nervous system of Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1) deficient motheaten (me/me) mice compared with normal littermate controls. Deficiency in myelin and MBP expression in both brains and spinal cords of motheaten mice correlated with reduced MBP mRNA expression levels in vivo and in purified oligodendrocytes in vitro. Therefore, SHP-1 activity seems to be a critical regulator of oligodendrocyte gene expression and function. Consistent with this role, this study demonstrates that oligodendrocytes of motheaten mice and SHP-1-depleted N20.1 cells produce higher levels of reactive oxygen species (ROS) and exhibit corresponding markers of increased oxidative stress. In agreement with these findings, we demonstrate that increased production of ROS coincides with ROS-induced signaling pathways known to affect myelin gene expression in oligodendrocytes. Antioxidant treatment of SHP-1-deficient oligodendrocytes reversed the pathological changes in these cells, with increased myelin protein gene expression and decreased expression of nuclear factor (erythroid-2)-related factor 2 (Nrf2) responsive gene, heme oxygenase-1 (HO-1). Furthermore, we demonstrate that SHP-1 is expressed in human white matter oligodendrocytes, and there is a subset of multiple sclerosis subjects that demonstrate a deficiency of SHP-1 in normal-appearing white matter. These studies reveal critical pathways controlled by SHP-1 in oligodendrocytes that relate to susceptibility of SHP-1-deficient mice to both developmental defects in myelination and to inflammatory demyelinating diseases.

NF-κB signaling regulates myelination in the CNS

Besides myelination of neuronal axons by oligodendrocytes to facilitate propagation of action potentials, oligodendrocytes also support axon survival and function. A key transcription factor involved in these processes is nuclear factor-κB (NF-κB), a hetero or homodimer of the Rel family of proteins, including p65, c-Rel, RelB, p50, and p52. Under unstimulated, NF-κB remains inactive in the cytoplasm through interaction with NF-κB inhibitors (IκBs). Upon activation of NF-κB the cytoplasmic IκBs gets degradated, allowing the translocation of NF-κB into the nucleus where the dimer binds to the κB consensus DNA sequence and regulates gene transcription. In this review we describe how oligodendrocytes are, directly or indirectly via neighboring cells, regulated by NF-κB signaling with consequences for innate and adaptive immunity and for regulation of cell apoptosis and survival.

The protein tyrosine phosphatase Shp2 is required for the generation of oligodendrocyte progenitor cells and myelination in the mouse telencephalon

The protein tyrosine phosphatase Shp2 (PTPN11) is crucial for normal brain development and has been implicated in dorsal telencephalic neuronal and astroglia cell fate decisions. However, its roles in the ventral telencephalon and during oligodendrogenesis in the telencephalon remain largely unknown. Shp2 gain-of-function (GOF) mutations are observed in Noonan syndrome, a type of RASopathy associated with multiple phenotypes, including cardiovascular, craniofacial, and neurocognitive abnormalities. To gain insight into requirements for Shp2 (LOF) and the impact of abnormal Shp2 GOF mutations, we used a Shp2 conditional mutant allele (LOF) and a cre inducible Shp2-Q79R GOF transgenic mouse in combination with Olig2(cre/+) mice to target embryonic ventral telencephalic progenitors and the oligodendrocyte lineage. In the absence of Shp2 (LOF), neuronal cell types originating from progenitors in the ventral telencephalon were generated, but oligodendrocyte progenitor cell (OPC) generation was severely impaired. Late embryonic and postnatal Shp2 cKOs showed defects in the generation of OPCs throughout the telencephalon and subsequent reductions in white matter myelination. Conversely, transgenic expression of the Shp2 GOF Noonan syndrome mutation resulted in elevated OPC numbers in the embryo and postnatal brain. Interestingly, expression of this mutation negatively influenced myelination as mice displayed abnormal myelination and fewer myelinated axons in the white matter despite elevated OPC numbers. Increased proliferating OPCs and elevated MAPK activity were also observed during oligodendrogenesis after expression of Shp2 GOF mutation. These results support the notion that appropriate Shp2 activity levels control the number as well as the differentiation of oligodendrocytes during development.

Quercetin improves hypoxia-ischemia induced cognitive deficits via promoting remyelination in neonatal rat

Myelination failure is associated with perinatal cerebral hypoxia-ischemia (PHI) induced brain injury in premature infants. How to efficiently promote remyelination is crucial for improving cognitive deficits caused by brain injury. Here, we demonstrated that quercetin (Que), a kind of flavonoids, significantly improved cognitive deficits and the behavior of PHI-rat in Morris water maze and open field tasks. After administration of Que to PHI-rat, the number of neogenetic Olig2⁺ oligodendrocyte progenitor cells (OPCs) was evidently increased in the subventricular zone. Additionally, in corpus callosum (CC), the expression of MBP (myelin basic protein) was increased, and the myelin sheaths reached normal level at 30 days with more compact while less damaged myelin sheaths and more mature oligodendrocytes (OLs) repopulating the CC compared with PHI groups. In a word, our findings indicated that Que could remarkably improve both cognition performance and myelination in the context of PHI-induced brain injury by promoting the proliferation of OPCs and strengthening survival of OLs in vivo.

Receptor tyrosine kinase (RTK) signalling in the control of neural stem and progenitor cell (NSPC) development

Important developmental responses are elicited in neural stem and progenitor cells (NSPC) by activation of the receptor tyrosine kinases (RTK), including the fibroblast growth factor receptors, epidermal growth factor receptor, platelet-derived growth factor receptors and insulin-like growth factor receptor (IGF1R). Signalling through these RTK is necessary and sufficient for driving a number of developmental processes in the central nervous system. Within each of the four RTK families discussed here, receptors are activated by sets of ligands that do not cross-activate receptors of the other three families, and therefore, their activation can be independently regulated by ligand availability. These RTK pathways converge on a conserved core of signalling molecules, but differences between the receptors in utilisation of signalling molecules and molecular adaptors for intracellular signal propagation become increasingly apparent. Intracellular inhibitors of RTK signalling are widely involved in the regulation of developmental signalling in NSPC and often determine developmental outcomes of RTK activation. In addition, cellular responses of NSPC to the activation of a given RTK may be significantly modulated by signal strength. Cellular propensity to respond also plays a role in developmental outcomes of RTK signalling. In combination, these mechanisms regulate the balance between NSPC maintenance and differentiation during development and in adulthood. Attribution of particular developmental responses of NSPC to specific pathways of RTK signalling becomes increasingly elucidated. Co-activation of several RTK in developing NSPC is common, and analysis of co-operation between their signalling pathways may advance knowledge of RTK role in NSPC development.

Signaling mechanisms regulating myelination in the central nervous system

The precise and coordinated production of myelin is essential for proper development and function of the nervous system. Diseases that disrupt myelin, including multiple sclerosis, cause significant functional disability. Current treatment aims to reduce the inflammatory component of the disease, thereby preventing damage resulting from demyelination. However, therapies are not yet available to improve natural repair processes after damage has already occurred. A thorough understanding of the signaling mechanisms that regulate myelin generation will improve our ability to enhance repair. in this review, we summarize the positive and negative regulators of myelination, focusing primarily on central nervous system myelination. Axon-derived signals, extracellular signals from both diffusible factors and the extracellular matrix, and intracellular signaling pathways within myelinating oligodendrocytes are discussed. Much is known about the positive regulators that drive myelination, while less is known about the negative regulators that shift active myelination to myelin maintenance at the appropriate time. Therefore, we also provide new data on potential negative regulators of CNS myelination.

Slit2 regulates the dispersal of oligodendrocyte precursor cells via Fyn/RhoA signaling

Oligodendrocyte precursor cells (OPCs) are a unique type of glia that are responsible for the myelination of the central nervous system. OPC migration is important for myelin formation during central nervous system development and repair. However, the precise extracellular and intracellular mechanisms that regulate OPC migration remain elusive. Slits were reported to regulate neurodevelopmental processes such as migration, adhesion, axon guidance, and elongation through binding to roundabout receptors (Robos). However, the potential roles of Slits/Robos in oligodendrocytes remain unknown. In this study, Slit2 was found to be involved in regulating the dispersal of OPCs through the association between Robo1 and Fyn. Initially, we examined the expression of Robos in OPCs both in vitro and in vivo. Subsequently, the Boyden chamber assay showed that Slit2 could inhibit OPC migration. RoboN, a specific inhibitor of Robos, could significantly attenuate this effect. The effects were confirmed through the explant migration assay. Furthermore, treating OPCs with Slit2 protein deactivated Fyn and increased the level of activated RhoA-GTP. Finally, Fyn was found to form complexes with Robo1, but this association was decreased after Slit2 stimulation. Thus, we demonstrate for the first time that Slit2 regulates the dispersal of oligodendrocyte precursor cells through Fyn and RhoA signaling.

Crystal structure of human protein tyrosine phosphatase SHP-1 in the open conformation

SHP-1 belongs to the family of non-receptor protein tyrosine phosphatases (PTPs) and generally acts as a negative regulator in a variety of cellular signaling pathways. Previously, the crystal structures of the tail-truncated SHP-1 and SHP-2 revealed an autoinhibitory conformation. To understand the regulatory mechanism of SHP-1, we have determined the crystal structure of the full-length SHP-1 at 3.1 Å. Although the tail was disordered in current structure, the huge conformational rearrangement of the N-SH2 domain and the incorporation of sulfate ions into the ligand-binding site of each domain indicate that the SHP-1 is in the open conformation. The N-SH2 domain in current structure is shifted away from the active site of the PTP domain to the other side of the C-SH2 domain, resulting in exposure of the active site. Meanwhile, the C-SH2 domain is twisted anticlockwise by about 110°. In addition, a set of new interactions between two SH2 domains and between the N-SH2 and the catalytic domains is identified, which could be responsible for the stabilization of SHP-1 in the open conformation. Based on the structural comparison, a model for the activation of SHP-1 is proposed.

SHP-2 promotes the maturation of oligodendrocyte precursor cells through Akt and ERK1/2 signaling in vitro

Background

Oligodendrocyte precursor cells (OPCs) differentiate into oligodendrocytes (OLs), which are responsible for myelination. Myelin is essential for saltatory nerve conduction in the vertebrate nervous system. However, the molecular mechanisms of maturation and myelination by oligodendrocytes remain elusive.

Methods and Findings

In the present study, we showed that maturation of oligodendrocytes was attenuated by sodium orthovanadate (a comprehensive inhibitor of tyrosine phosphatases) and PTPi IV (a specific inhibitor of SHP-2). It is also found that SHP-2 was persistently expressed during maturation process of OPCs. Down-regulation of endogenous SHP-2 led to impairment of oligodendrocytes maturation and this effect was triiodo-L-thyronine (T3) dependent. Furthermore, over-expression of SHP-2 was shown to promote maturation of oligodendrocytes. Finally, it has been identified that SHP-2 was involved in activation of Akt and extracellular-regulated kinases 1 and 2 (ERK1/2) induced by T3 in oligodendrocytes.

Conclusions

SHP-2 promotes oligodendrocytes maturation via Akt and ERK1/2 signaling in vitro.