Caspases and p53 Modulate FOXO3A/Id1 Signaling During Mouse Neural Stem Cell Differentiation

iMed.UL, University of Lisbon, Portugal.
Journal of Cellular Biochemistry (Impact Factor: 3.26). 07/2009; 107(4):748-58. DOI: 10.1002/jcb.22172
Source: PubMed


Neural stem cells (NSCs) differentiate into neurons and glia, and a large percentage undergoes apoptosis. The engagement and activity of apoptotic pathways may favor either cell death or differentiation. In addition, Akt represses differentiation by up-regulating the inhibitor of differentiation 1 (Id1), through phosphorylation of its repressor FOXO3A. The aim of this study was to investigate the potential cross-talk between apoptosis and proliferation during mouse NSC differentiation. We determined the time of neurogenesis and gliogenesis using neuronal beta-III tubulin and astroglial GFAP to confirm that both processes occurred at approximately 3 and 8 days, respectively. p-Akt, p-FOXO3A, and Id1 were significantly reduced throughout differentiation. Caspase-3 processing, p53 phosphorylation, and p53 transcriptional activation increased at 3 days of differentiation, with no evidence of apoptosis. Importantly, in cells exposed to the pancaspase inhibitor z-VAD.fmk, p-FOXO3A and Id1 were no longer down-regulated, p53 phosphorylation and transcriptional activation were reduced, while neurogenesis and gliogenesis were significantly delayed. The effect of siRNA-mediated silencing of p53 on FOXO3A/Id1 was similar to that of z-VAD.fmk only at 3 days of differentiation. Interestingly, caspase inhibition further increased the effect of p53 knockdown during neurogenesis. In conclusion, apoptosis-associated factors such as caspases and p53 temporally modulate FOXO3A/Id1 signaling and differentiation of mouse NSCs.

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Available from: Cecilia Rodrigues, Dec 23, 2013
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    • "Restrictive activation and careful regulation will assure differentiation efficiency and thus avoid cell loss. In this regard, we have previously demonstrated the involvement of specific apoptosis-related microRNAs and proteins, including p53, caspases and calpains, in mouse neural stem cell (NSC) differentiation, by mechanisms that do not result in cell death [7]–[11]. Several studies have shown that inactivation of p53 sustains the undifferentiated state of neural precursor cells [12]–[14], and that p53 is required for both neurite outgrowth and axonal regeneration in mice primary neurons [15]. "
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    ABSTRACT: p63 is a close relative of the p53 tumor suppressor and transcription factor that modulates cell fate. The full-length isoform of p63, containing a transactivation (TA) domain (TAp63) is an essential proapoptotic protein in neural development. The role of p63 in epithelial development is also well established; however, its precise function during neural differentiation remains largely controversial. Recently, it has been demonstrated that several conserved elements of apoptosis are also integral components of cellular differentiation; p53 directly interacts with key regulators of neurogenesis. The aim of this study was to evaluate the role of p63 during mouse neural stem cell (NSC) differentiation and test whether the histone H3 lysine 27-specific demethylase JMJD3 interacts with p63 to redirect NSCs to neurogenesis. Our results showed that JMJD3 and TAp63γ are coordinately regulated to establish neural-specific gene expression programs in NSCs undergoing differentiation. JMJD3 overexpression increased TAp63γ levels in a demethylase activity-dependent manner. Importantly, overexpression of TAp63γ increased β-III tubulin whereas downregulation of TAp63γ by specific p63 siRNA decreased β-III tubulin. Immunoprecipitation assays demonstrated direct interaction between TAp63γ and JMJD3, and modulation of TAp63γ methylation status by JMJD3-demethylase activity. Importantly, the demethylase activity of JMJD3 influenced TAp63γ protein stabilization and cellular distribution, as well as TAp63γ-regulated neurogenesis. These findings clarify the role of p63 in adult neural progenitor cells and reveal TAp63γ as a direct target for JMJD3-mediated neuronal commitment.
    Full-text · Article · Dec 2012 · PLoS ONE
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    • "We have recently demonstrated the involvement of specific apoptosis-associated molecules in mouse NSC differentiation. In fact, apoptosis-associated miRNAs were involved in neural differentiation [41], and caspase inhibition and p53 silencing synergistically delayed neural differentiation, with no evidence of apoptosis [36]. Here, we investigated the potential role of proteases such as calpains in the regulation of NSC self-renewal and differentiation. "
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    ABSTRACT: Calpains are calcium regulated cysteine proteases that have been described in a wide range of cellular processes, including apoptosis, migration and cell cycle regulation. In addition, calpains have been implicated in differentiation, but their impact on neural differentiation requires further investigation. Here, we addressed the role of calpain 1 and calpain 2 in neural stem cell (NSC) self-renewal and differentiation. We found that calpain inhibition using either the chemical inhibitor calpeptin or the endogenous calpain inhibitor calpastatin favored differentiation of NSCs. This effect was associated with significant changes in cell cycle-related proteins and may be regulated by calcium. Interestingly, calpain 1 and calpain 2 were found to play distinct roles in NSC fate decision. Calpain 1 expression levels were higher in self-renewing NSC and decreased with differentiation, while calpain 2 increased throughout differentiation. In addition, calpain 1 silencing resulted in increased levels of both neuronal and glial markers, β-III Tubulin and glial fibrillary acidic protein (GFAP). Calpain 2 silencing elicited decreased levels of GFAP. These results support a role for calpain 1 in repressing differentiation, thus maintaining a proliferative NSC pool, and suggest that calpain 2 is involved in glial differentiation.
    Full-text · Article · Mar 2012 · PLoS ONE
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    • "We have previously reported that induction of mouse NS cell differentiation results in a mixed cell population composed by both neuronal and glial cells, which in turn differentiate in a time-controlled fashion within 8 days [30]. In addition, we have shown that this differentiation process is associated with the modulation of pro-apoptotic miRNA expression, including miR-16, let-7a and miR-34a [31]. "
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    ABSTRACT: MicroRNAs (miRNAs or miRs) participate in the regulation of several biological processes, including cell differentiation. Recently, miR-34a has been implicated in the differentiation of monocyte-derived dendritic cells, human erythroleukemia cells, and mouse embryonic stem cells. In addition, members of the miR-34 family have been identified as direct p53 targets. However, the function of miR-34a in the control of the differentiation program of specific neural cell types remains largely unknown. Here, we investigated the role of miR-34a in regulating mouse neural stem (NS) cell differentiation. miR-34a overexpression increased postmitotic neurons and neurite elongation of mouse NS cells, whereas anti-miR-34a had the opposite effect. SIRT1 was identified as a target of miR-34a, which may mediate the effect of miR-34a on neurite elongation. In addition, acetylation of p53 (Lys 379) and p53-DNA binding activity were increased and cell death unchanged after miR-34a overexpression, thus reinforcing the role of p53 during neural differentiation. Interestingly, in conditions where SIRT1 was activated by pharmacologic treatment with resveratrol, miR-34a promoted astrocytic differentiation, through a SIRT1-independent mechanism. Our results provide new insight into the molecular mechanisms by which miR-34a modulates neural differentiation, suggesting that miR-34a is required for proper neuronal differentiation, in part, by targeting SIRT1 and modulating p53 activity.
    Full-text · Article · Aug 2011 · PLoS ONE
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