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PKC-dependent ERK phosphorylation is essential for P2X7 receptor-mediated neuronal differentiation of neural progenitor cells.

ABSTRACT: Purinergic receptors have been shown to be involved in neuronal development, but the functions of specific subtypes of P2 receptors during neuronal development remain elusive. In this study we investigate the distribution of P2X7 receptors (P2X7Rs) in the embryonic rat brain using in situ hybridization. At E15.5, P2X7R mRNA was observed in the ventricular zone and subventricular zone, and colocalized with nestin, indicating that P2X7R might be expressed in neural progenitor cells (NPCs). P2X7R mRNA was also detected in the subgranular zone and dentate gyrus of the E18.5 and P4 brain. To investigate the roles of P2X7R and elucidate its mechanism, we established NPC cultures from the E15.5 rat brain. Stimulation of P2X7Rs induced Ca(2+) influx, inhibited proliferation, altered cell cycle progression and enhanced the expression of neuronal markers, such as TUJ1 and MAP2. Similarly, knockdown of P2X7R by shRNA nearly abolished the agonist-stimulated increases in intracellular Ca(2+) concentration and the expression of TUJ1 and NeuN. Furthermore, stimulation of P2X7R induced activation of ERK1/2, which was inhibited by the removal of extracellular Ca(2+) and treatment with blockers for P2X7R and PKC activity. Stimulation of P2X7R also induced translocation of PKC? and PKC?, but not of PKC?, whereas knockdown of either PKC? or PKC? inhibited ERK1/2 activation. Inhibition of PKC or p-ERK1/2 also caused a decrease in the number of TUJ1-positive cells and a concomitant increase in the number of GFAP-positive cells. Taken together, the activation of P2X7R in NPCs induced neuronal differentiation through a PKC-ERK1/2 signaling pathway.

SUBMITTER: Tsao HK

PROVIDER: S-EPMC3763436 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

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PKC-dependent ERK phosphorylation is essential for P2X7 receptor-mediated neuronal differentiation of neural progenitor cells.

Tsao H-K HK Chiu P-H PH Sun S H SH

Cell death & disease 20130801

Purinergic receptors have been shown to be involved in neuronal development, but the functions of specific subtypes of P2 receptors during neuronal development remain elusive. In this study we investigate the distribution of P2X7 receptors (P2X7Rs) in the embryonic rat brain using in situ hybridization. At E15.5, P2X7R mRNA was observed in the ventricular zone and subventricular zone, and colocalized with nestin, indicating that P2X7R might be expressed in neural progenitor cells (NPCs). P2X7R m ...[more]

PMID: 23907465

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Project description:BackgroundActivin A is a protein that participates principally in reproductive functions. In the adult brain, Activin is neuroprotective, but its role in brain development is still elusive.Methodology/principal findingsWe studied if Activin A influences proliferation, differentiation or survival in rat cerebrocortical neural progenitor cells (NPC). After stimulation of NPC with Activin A, phosphorylation and nuclear translocation of Smad 2/3 were induced. In proliferating NPC, Activin produced a significant decrease in cell area and also a discrete increase in the number of neurons in the presence of the mitogen Fibroblast Growth Factor 2. The percentages of cells incorporating BrdU, or positive for the undifferentiated NPC markers Nestin and Sox2, were unchanged after incubation with Activin. In differentiating conditions, continuous treatment with Activin A significantly increased the number of neurons without affecting astroglial differentiation or causing apoptotic death. In cells cultured by extended periods, Activin treatment produced further increases in the proportion of neurons, excluding premature cell cycle exit. In clonal assays, Activin significantly increased neuronal numbers per colony, supporting an instructive role. Activin-induced neurogenesis was dependent on activation of its receptors, since incubation with the type I receptor inhibitor SB431542 or the ligand-trap Follistatin prevented neuronal differentiation. Interestingly, SB431542 or Follistatin by themselves abolished neurogenesis and increased astrogliogenesis, to a similar extent to that induced by Bone Morphogenetic Protein (BMP)4. Co-incubation of these Activin inhibitors with the BMP antagonist Dorsomorphin restored neuronal and astrocytic differentiation to control levels.ConclusionsOur results show an instructive neuronal effect of Activin A in cortical NPC in vitro, pointing out to a relevant role of this cytokine in the specification of NPC towards a neuronal phenotype.

Project description:: Phosphatase and tension homolog (PTEN) is a widely known negative regulator of insulin/phosphatidylinositol 3-kinase (PI3K) signaling. The PI3K/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) and Ras-extracellular signal-regulated kinase (Ras-ERK) signaling pathways are the chief mechanisms controlling the survival, proliferation, and differentiation of neural stem cells (NSCs). However, the roles of PTEN in Akt/mTOR and ERK signaling during proliferation and neuronal differentiation of human NSCs (hNSCs) are poorly understood. Treatment of proliferating hNSCs with a specific inhibitor of PTEN or overexpression of the PTEN inactive mutant G129E resulted in an increase in the expression levels of Ki67, p-S6 kinase (p-S6K), and p-ERK without affecting p-Akt expression during proliferation of hNSCs. Therefore, we focused on the regulatory effect of PTEN in S6K and ERK signaling during dopaminergic neuronal differentiation of hNSCs. Overexpression of PTEN during neuronal differentiation of hNSCs caused an increase in p-S6K expression and a decrease in p-ERK expression. Conversely, inhibition of PTEN increased p-ERK expression and decreased p-S6K expression. Inhibition of ERK by a specific chemical inhibitor, U0126, promoted neuronal generation, especially of tyrosine hydroxylase-positive neurons. p-S6K expression increased in a time-dependent manner during differentiation, and this effect was enhanced by U0126. These results indicated that PTEN promoted neuronal differentiation by inhibition of ERK signaling, which in turn induced activation of S6K. Our data suggest that ERK pathways participate in crosstalk with S6K through PTEN signaling during neuronal differentiation of hNSCs. These results represent a novel pathway by which PTEN may modulate the interplay between ERK and S6K signaling, leading to increased neuronal differentiation in hNSCs.SignificanceThis article adds to the body of knowledge about the mechanism of extracellular signal-regulated kinase (ERK)-mediated differentiation by describing the molecular function of phosphatase and tension homolog (PTEN) during the neuronal differentiation of human neural stem cells (hNSCs). Previous studies showed that S6K signaling promoted neuronal differentiation in hNSCs via the phosphatidylinositol 3-kinase Akt-mammalian target of rapamycin signaling pathway. A further series of studies investigated whether this S6 kinase-induced differentiation in hNSCs involves regulation of ERK signaling by PTEN. The current study identified a novel mechanism by which PTEN regulates neuronal differentiation in hNSCs, suggesting that activating PTEN function promotes dopaminergic neuronal differentiation and providing an important resource for future studies of PTEN function.

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PKC-dependent ERK phosphorylation is essential for P2X7 receptor-mediated neuronal differentiation of neural progenitor cells.

Publications

PKC-dependent ERK phosphorylation is essential for P2X7 receptor-mediated neuronal differentiation of neural progenitor cells.

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