Multiple sclerosis (MS) is a progressive neurological disorder associated with myelin destruction and neurodegeneration. Oligodendrocyte precursor cells (OPCs) present in demyelinated lesions ...gradually fail to differentiate properly, so remyelination becomes incomplete. Protein tyrosine phosphatase receptor type Z (PTPRZ), one of the most abundant protein tyrosine phosphatases expressed in OPCs, is known to suppress oligodendrocyte differentiation and maintain their precursor cell stage. In the present study, we examined the in vivo mechanisms for remyelination using a cuprizone-induced demyelination model. Ptprz-deficient and wild-type mice both exhibited severe demyelination and axonal damage in the corpus callosum after cuprizone feeding. The similar accumulation of OPCs was observed in the lesioned area in both mice; however, remyelination was significantly accelerated in Ptprz-deficient mice after the removal of cuprizone. After demyelination, the expression of pleiotrophin (PTN), an inhibitory ligand for PTPRZ, was transiently increased in mouse brains, particularly in the neurons involved, suggesting its role in promoting remyelination by inactivating PTPRZ activity. In support of this view, oligodendrocyte differentiation was augmented in a primary culture of oligodendrocyte-lineage cells from wild-type mice in response to PTN. In contrast, these cells from Ptprz-deficient mice showed higher oligodendrocyte differentiation without PTN and differentiation was not enhanced by its addition. We further demonstrated that PTN treatment increased the tyrosine phosphorylation of p190 RhoGAP, a PTPRZ substrate, using an established line of OPCs. Therefore, PTPRZ inactivation in OPCs by PTN, which is secreted from demyelinated axons, may be the mechanism responsible for oligodendrocyte differentiation during reparative remyelination in the CNS.
Multiple sclerosis (MS) is an inflammatory disease of the CNS that destroys myelin, the insulation that surrounds axons. Associated damages to oligodendrocytes (the cells that produce myelin) and nerve fibers produce neurological disability. Most patients with MS have an initial relapsing-remitting course for 5-15 years. Remyelination during the early stages of the disease process has been documented; however, the molecular mechanism underlying remyelination has not been understood. Protein tyrosine phosphatase receptor type Z (PTPRZ) is a receptor-like protein tyrosine phosphatase preferentially expressed in the CNS. This study shows that pleiotrophin, an inhibitory ligand for PTPRZ, is transiently expressed and released from demyelinated neurons to inactivate PTPRZ in oligodendrocyte precursor cells present in the lesioned part, thereby allowing their differentiation for remyelination.
A growing body of evidence indicates that P2X receptors (P2XRs), a family of ligand-gated cation channels activated by extracellular ATP, play an important role in pain signaling. In contrast to the ...role of the P2X3R subtype that has been extensively studied, the precise roles of others among the seven P2XR subtypes (P2X1R-P2X7R) remain to be determined because of a lack of sufficiently powerful tools to specifically block P2XR signaling in vivo. In the present study, we investigated the behavioral phenotypes of a line of mice in which the p2rx4 gene was disrupted in a series of acute and chronic pain assays. While p2rx4−/− mice showed no major defects in pain responses evoked by acute noxious stimuli and local tissue damage or in motor function as compared with wild-type mice, these mice displayed reduced pain responses in two models of chronic pain (inflammatory and neuropathic pain). In a model of chronic inflammatory pain developed by intraplantar injection of complete Freund's adjuvant (CFA), p2rx4−/− mice exhibited attenuations of pain hypersensitivity to innocuous mechanical stimuli (tactile allodynia) and also of the CFA-induced swelling of the hindpaw. A most striking phenotype was observed in a test of neuropathic pain: tactile allodynia caused by an injury to spinal nerve was markedly blunted in p2rx4−/− mice. By contrast, pain hypersensitivity to a cold stimulus (cold allodynia) after the injury was comparable in wild-type and p2rx4−/− mice. Together, these findings reveal a predominant contribution of P2X4R to nerve injury-induced tactile allodynia and, to the lesser extent, peripheral inflammation. Loss of P2X4R produced no defects in acute physiological pain or tissue damaged-induced pain, highlighting the possibility of a therapeutic benefit of blocking P2X4R in the treatment of chronic pain, especially tactile allodynia after nerve injury.
Chondroitin sulfate proteoglycans (CSPGs), which are enriched in demyelinating plaques in neurodegenerative diseases, such as multiple sclerosis (MS), impair remyelination by inhibiting the migration ...and differentiation of oligodendrocyte precursor cells (OPCs) in the central nervous system (CNS). We herein show that protamine (PRM, also known as a heparin antagonist) effectively neutralizes the inhibitory activities of CSPGs, thereby enhancing OPC differentiation and (re)myelination in mice. Cell-based assays using mouse OPC-like OL1 cells revealed that the PRM treatment exerted masking effects on extracellular CSPGs and improved oligodendrocyte differentiation on inhibitory CSPG-coated substrates. PRM also bound to the extracellular region of protein tyrosine phosphatase receptor type Z (PTPRZ), a membrane-spanning CSPG predominantly expressed in OPCs, and functioned as a ligand mimetic of PTPRZ, thereby suppressing its negative regulatory activity on oligodendrocyte differentiation. In primary cultures, the differentiation of OPCs from wild-type and Ptprz-deficient mice was equally enhanced by PRM. Moreover, the intranasal administration of PRM accelerated myelination in the developing mouse brain, and its intracerebroventricular administration stimulated remyelination after cuprizone-induced demyelination. These results indicate that PRM has CSPG-neutralizing activity which promotes oligodendrocyte differentiation under developmental and morbid conditions.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
New neurons, continuously added in the adult olfactory bulb (OB) and hippocampus, are involved in information processing in neural circuits. Here, we show that synaptic pruning of adult-born neurons ...by microglia depends on phosphatidylserine (PS), whose exposure on dendritic spines is inversely correlated with their input activity. To study the role of PS in spine pruning by microglia in vivo, we developed an inducible transgenic mouse line, in which the exposed PS is masked by a dominant-negative form of milk fat globule-EGF-factor 8 (MFG-E8), MFG-E8D89E. In this transgenic mouse, the spine pruning of adult-born neurons by microglia is impaired in the OB and hippocampus. Furthermore, the electrophysiological properties of these adult-born neurons are altered in MFG-E8D89E mice. These data suggest that PS is involved in the microglial spine pruning and the functional maturation of adult-born neurons. The MFG-E8D89E-based genetic approach shown in this study has broad applications for understanding the biology of PS-mediated phagocytosis in vivo.
Protein tyrosine phosphatase receptor type Z (PTPRZ) maintains oligodendrocyte precursor cells (OPCs) in an undifferentiated state. The inhibition of PTPase by its ligand pleiotrophin (PTN) promotes ...OPC differentiation; however, the substrate molecules of PTPRZ involved in the differentiation have not yet been elucidated in detail. We herein demonstrated that the tyrosine phosphorylation of AFAP1L2, paxillin, ERBB4, GIT1, p190RhoGAP, and NYAP2 was enhanced in OPC‐like OL1 cells by a treatment with PTN. AFAP1L2, an adaptor protein involved in the PI3K‐AKT pathway, exhibited the strongest response to PTN. PTPRZ dephosphorylated AFAP1L2 at tyrosine residues in vitro and in HEK293T cells. In OL1 cells, the knockdown of AFAP1L2 or application of a PI3K inhibitor suppressed cell differentiation as well as the PTN‐induced phosphorylation of AKT and mTOR. We generated a knock‐in mouse harboring a catalytically inactive Cys to Ser (CS) mutation in the PTPase domain. The phosphorylation levels of AFAP1L2, AKT, and mTOR were higher, and the expression of oligodendrocyte markers, including myelin basic protein (MBP) and myelin regulatory factor (MYRF), was stronger in CS knock‐in brains than in wild‐type brains on postnatal day 10; however, these differences mostly disappeared in the adult stage. Adult CS knock‐in mice exhibited earlier remyelination after cuprizone‐induced demyelination through the accelerated differentiation of OPCs. These phenotypes in CS knock‐in mice were similar to those in Ptprz‐deficient mice. Therefore, we conclude that the PTN‐PTPRZ signal stimulates OPC differentiation partly by enhancing the tyrosine phosphorylation of AFAP1L2 in order to activate the PI3K‐AKT pathway.
Main points
The PTN‐induced inactivation of PTPRZ stimulates OPC differentiation by AFAP1L2‐mediated PI3K‐AKT‐mTOR signaling.
PTPRZ phosphatase‐inactive knock‐in mice exhibit the enhanced tyrosine phosphorylation of AFAP1L2 together with the early onset expression of MYRF and MBP in the brain.
Protein-tyrosine phosphatase (PTPase) receptor type Z (PTPRZ) has two receptor isoforms, PTPRZ-A and -B, containing tandem intracellular PTP-D1 and -D2 domains, with only D1 being active. ...Pleiotrophin (PTN) binding to the extracellular PTPRZ region leads to inactivation of its PTPase activity, thereby facilitating oligodendrocyte precursor cell (OPC) differentiation and myelination in the central nervous system. However, the mechanisms responsible for PTN-induced PTPRZ inactivation remain unclear. We herein report that the crystal structure of the intracellular region of PTPRZ (PTPRZ-ICR) shows a “head-to-toe”-type dimer conformation, with D2 masking the catalytic site of D1. MS analyses revealed that PTPRZ-ICR proteins remain in monomer-dimer equilibrium in aqueous solution and that a substrate-derived inhibitory peptide or competitive inhibitor (SCB4380) specifically bind to the monomer form in a 1:1 ratio. A D2 deletion (ΔD2) or dimer interface mutation (DDKK) disrupted dimer formation, but SCB4380 binding was maintained. Similar to WT PTPRZ-B, monomer-biased PTPRZ-B-ΔD2 and PTPRZ-B-DDKK variants efficiently dephosphorylated p190RhoGAP at Tyr-1105 when co-expressed in BHK-21 cells. The catalytic activities of these variants were not suppressed by PTN treatment, but were inhibited by the cell-permeable PTPase inhibitor NAZ2329. Of note, the PTN treatment did not enhance OPC differentiation in primary cultured glial cells from ΔD2 or PTPase-inactive PTPRZ-B (CS) mutant knock-in mice. Our results thus indicate that PTN-induced PTPRZ inactivation results from dimer formation of the intracellular tandem PTP domains in a head-to-toe configuration, which is physiologically relevant to the control of OPC differentiation in vivo.
The R5 subfamily of receptor-type protein tyrosine phosphatases (RPTPs) comprises PTPRZ and PTPRG. A recent study on primary human glioblastomas suggested a close association between PTPRZ1 (human ...PTPRZ) expression and cancer stemness. However, the functional roles of PTPRZ activity in glioma stem cells have remained unclear. In the present study, we found that sphere-forming cells from the rat C6 and human U251 glioblastoma cell lines showed high expression levels of PTPRZ-B, the short receptor isoform of PTPRZ. Stable PTPRZ knockdown altered the expression levels of stem cell transcription factors such as SOX2, OLIG2, and POU3F2 and decreased the sphere-forming abilities of these cells. Suppressive effects on the cancer stem-like properties of the cells were also observed following the knockdown of PTPRG. Here, we identified NAZ2329, a cell-permeable small molecule that allosterically inhibits both PTPRZ and PTPRG. NAZ2329 reduced the expression of SOX2 in C6 and U251 cells and abrogated the sphere-forming abilities of these cells. Tumor growth in the C6 xenograft mouse model was significantly slower with the co-treatment of NAZ2329 with temozolomide, an alkylating agent, than with the individual treatments. These results indicate that pharmacological inhibition of R5 RPTPs is a promising strategy for the treatment of malignant gliomas.
After brain ischemia, significant amounts of adenosine 5'-triphosphate are released or leaked from damaged cells, thus activating purinergic receptors in the central nervous system. A number of ...P2X/P2Y receptors have been implicated in ischemic conditions, but to date the P2Y1 receptor (P2Y 1R) has not been implicated in cerebral ischemia. In this study, we found that the astrocytic P2Y 1R, via phosphorylated-RelA (p-RelA), has a negative effect during cerebral ischemia/reperfusion. Intracerebroventricular administration of the P2Y 1R agonist, MRS 2365, led to an increase in cerebral infarct volume 72 hours after transient middle cerebral artery occlusion (tMCAO). Administration of the P2Y 1R antagonist, MRS 2179, significantly decreased infarct volume and led to recovered motor coordination. The effects of MRS 2179 occurred within 24 hours of tMCAO, and also markedly reduced the expression of p-RelA and interleukin-6, tumor necrosis factor-α, monocyte chemotactic protein-1/chemokine (C-C motif) ligand 2 (CCL2), and interferon-inducible protein-10/chemokine (C-X-C motif) ligand 10 (CXCL10) mRNA. P2Y 1R and p-RelA were colocalized in glial fibrillary acidic protein-positive astrocytes, and an increase in infarct volume after MRS 2365 treatment was inhibited by the nuclear factor (NF)-κB inhibitor ammonium pyrrolidine dithiocarbamate. These results provide evidence that the P2Y 1R expressed in cortical astrocytes may help regulate the cytokine/chemokine response after tMCAO/reperfusion through a p-RelA-mediated NF-κB pathway.
Protein tyrosine phosphatase receptor type Z (PTPRZ) is preferentially expressed in the central nervous system as two transmembrane receptor isoforms PTPRZ-A/B and one secretory isoform PTPRZ-S. ...Ptprz-knockout mice lacking the expression of all three isoforms show behavioral, learning, and neurological abnormalities, including increased exploratory activities to novelty, deficits in spatial and contextual learning, and reduced responses to methamphetamine, relative to wild-type mice. To investigate whether PTPRZ isoforms play distinct physiological roles, we herein performed behavioral studies on two knock-in mouse lines: One expresses the catalytically inactive Cys-1930 to Ser (CS) mutants of PTPRZ-A/B, while the other generated in the present study expresses catalytically active mutants of PTPRZ-A/B lacking the negative regulatory PTP-D2 domain and C-terminal PDZ-binding motif (ΔD2) instead of wild-type PTPRZ-A/-B. In contrast to Ptprz-knockout mice, neither increased responses to novelty in the open field nor memory impairments in the inhibitory-avoidance task were observed in Ptprz-CS or Ptprz-ΔD2 mice. However, the effects of methamphetamine on locomotor activity were significantly weaker in Ptprz-KO mice and CS mutant mice than in wild-type mice, but were normal in ΔD2 mutant mice. Furthermore, microdialysis experiments revealed that methamphetamine-evoked dopamine release in the nucleus accumbens was reduced in Ptprz-KO mice and CS mutant mice. These results suggest that the extracellular region of PTPRZ, including the secretory isoform, is crucial for behavioral responses to novelty and the formation of aversive memories, whereas the PTPase activities of PTPRZ receptor isoforms are involved in regulating the dopaminergic system.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Fyn tyrosine kinase-mediated down-regulation of Rho activity through activation of p190RhoGAP is crucial for oligodendrocyte differentiation and myelination. Therefore, the loss of function of its ...counterpart protein tyrosine phosphatase (PTP) may enhance myelination during development and remyelination in demyelinating diseases. To test this hypothesis, we investigated whether Ptprz, a receptor-like PTP (RPTP) expressed abuntantly in oligodendrocyte lineage cells, is involved in this process, because we recently revealed that p190RhoGAP is a physiological substrate for Ptprz.
We found an early onset of the expression of myelin basic protein (MBP), a major protein of the myelin sheath, and early initiation of myelination in vivo during development of the Ptprz-deficient mouse, as compared with the wild-type. In addition, oligodendrocytes appeared earlier in primary cultures from Ptprz-deficient mice than wild-type mice. Furthermore, adult Ptprz-deficient mice were less susceptible to experimental autoimmune encephalomyelitis (EAE) induced by active immunization with myelin/oligodendrocyte glycoprotein (MOG) peptide than were wild-type mice. After EAE was induced, the tyrosine phosphorylation of p190RhoGAP increased significantly, and the EAE-induced loss of MBP was markedly suppressed in the white matter of the spinal cord in Ptprz-deficient mice. Here, the number of T-cells and macrophages/microglia infiltrating into the spinal cord did not differ between the two genotypes after MOG immunization. All these findings strongly support the validity of our hypothesis.
Ptprz plays a negative role in oligodendrocyte differentiation in early central nervous system (CNS) development and remyelination in demyelinating CNS diseases, through the dephosphorylation of substrates such as p190RhoGAP.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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