Regulation of Embryonic Stem Cell Self-renewal by Phosphoinositide 3-Kinase-dependent Signaling

Department of Pharmacy and Pharmacology, Centre for Regenerative Medicine, University of Bath, Claverton Down, Bath BA2 7AY, United Kingdom.
Journal of Biological Chemistry (Impact Factor: 4.57). 12/2004; 279(46):48063-70. DOI: 10.1074/jbc.M406467200
Source: PubMed


The maintenance of murine embryonic stem (ES) cell self-renewal is regulated by leukemia inhibitory factor (LIF)-dependent activation of signal transducer and activator of transcription 3 (STAT3) and LIF-independent mechanisms including Nanog, BMP2/4, and Wnt signaling. Here we demonstrate a previously undescribed role for phosphoinositide 3-kinases (PI3Ks) in regulation of murine ES cell self-renewal. Treatment with the reversible PI3K inhibitor, LY294002, or more specific inhibition of class I(A) PI3K via regulated expression of dominant negative Deltap85, led to a reduction in the ability of LIF to maintain self-renewal, with cells concomitantly adopting a differentiated morphology. Inhibition of PI3Ks reduced basal and LIF-stimulated phosphorylation of PKB/Akt, GSK3alpha/beta, and S6 proteins. Importantly, LY294002 and Deltap85 expression had no effect on LIF-induced phosphorylation of STAT3 at Tyr(705), but did augment LIF-induced phosphorylation of ERKs in both short and long term incubations. Subsequently, we demonstrate that inhibition of MAP-Erk kinases (MEKs) reverses the effects of PI3K inhibition on self-renewal in a time- and dose-dependent manner, suggesting that the elevated ERK activity observed upon PI3K inhibition contributes to the functional response we observe. Surprisingly, upon long term inhibition of PI3Ks we observed a reduction in phosphorylation of beta-catenin, the target of GSK-3 action in the canonical Wnt pathway, although no consistent alterations in cytosolic levels of beta-catenin were observed, indicating this pathway is not playing a major role downstream of PI3Ks. Our studies support a role for PI3Ks in regulation of self-renewal and increase our understanding of the molecular signaling components involved in regulation of stem cell fate.

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Available from: Helen Wheadon, Aug 03, 2015
    • "ESC pluripotency can be maintained in a feeder layer-free state by treatment with leukemia inhibitory factor (LIF) which signals via Stat-3 (Smith and Crompton, 1998; Williams et al., 1988). Many other signaling pathways (e.g., PI3 kinase/AKT, bone morphogenetic protein [BMP], MAPK-ERK kinases, and Wnt pathways) have also been suggested to be sufficient for the maintenance of ESC pluripotency; conversely, however, the regulation of these pathways has been reported to specify the differentiation of ESC into the three germ layers (Lee et al., 2009; Paling et al., 2004; Qi et al., 2004). "
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    ABSTRACT: Mouse embryonic stem cells (ESCs) are self-renewing, pluripotent, and have the ability to differentiate into the three germ layers required to form all embryonic tissues. These properties are maintained by both intrinsic and extrinsic factors. Many studies have contributed to the understanding of the molecular signal transduction required for pluripotency and controlled differentiation. Such an understanding is important in the potential application of stem cells to cell therapy for disease, and thus there is an interest in understanding the cell cycle regulation, pluripotency, and differentiation of ESCs. The regulator of G protein signaling (RGS) family consists of over 20 members. Rgs19, one such protein, specifically interacts with Gαi to enhance its GTPase activity. Growth factor receptors use Gi proteins for signal transduction, and Rgs19 may thus be involved in the regulation of cell proliferation. In a previous gain-of-function study, Rgs19 overexpression was found to enhance proliferation in various cell types. Our data demonstrate a role for Rgs19 in the regulation of ESC differentiation. Based on the presence of Rgs19 in ESCs, the morphological and molecular properties of wild-type and Rgs19 +/- ESCs during LIF withdrawal, in vitro differentiation, and teratoma formation were compared. Our findings provide insight for the first time into the mechanisms involved in Rgs19 regulation of mouse ESC proliferation and differentiation. Copyright © 2015 International Society of Differentiation. Published by Elsevier B.V. All rights reserved.
    Differentiation 03/2015; 89(1-2). DOI:10.1016/j.diff.2015.01.002 · 3.44 Impact Factor
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    • "Please cite this article in press as: Lindström et al., The PI3K Pathway Balances Self-Renewal and Differentiation of Nephron Progenitor Cells through b-Catenin Signaling, Stem Cell Reports (2015), In embryonic stem cells, PI3K inhibition has been shown to reduce b-catenin phosphorylation (Paling et al., 2004). "
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    ABSTRACT: Nephron progenitor cells differentiate to form nephrons during embryonic kidney development. In contrast, self-renewal maintains progenitor numbers and premature depletion leads to impaired kidney function. Here we analyze the PI3K pathway as a point of convergence for the multiple pathways that are known to control self-renewal in the kidney. We demonstrate that a reduction in PI3K signaling triggers premature differentiation of the progenitors and activates a differentiation program that precedes the mesenchymal-to-epithelial transition through ectopic activation of the β-catenin pathway. Therefore, the combined output of PI3K and other pathways fine-tunes the balance between self-renewal and differentiation in nephron progenitors. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Stem Cell Reports 03/2015; 4(4). DOI:10.1016/j.stemcr.2015.01.021 · 5.37 Impact Factor
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    • "It is known that the PI3K/Akt-1 pathway contributes to the proliferation or self-renewal of embryonic stem cells (Paling et al., 2004) and CXCR4 activation regulates second messenger activity through Gi-Go GTP-binding proteins, since PTX (an inhibitor of G proteins) decreased CXCL12-induced NPC proliferation in vitro (Wu et al., 2004). It has been shown that the CXCR4/G protein/PI3K-Akt pathways are responsible for CXCL12-mediated NPC proliferation (Fig. 5), through the phosphorylation of Akt-1 and FOXO3a (Wu et al., 2009; Yumei et al., 2009). "
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    ABSTRACT: In the adult brain, Neural Progenitor Cells (NPCs) reside in the subventricular zone (SVZ) of the lateral ventricles, the dentate gyrus and the olfactory bulb. Following CNS insult, NPCs from the SVZ can migrate along the rostral migratory stream (RMS), a migration of NPCs that is directed by proinflammatory cytokines. Indeed, cells expressing CXCR4 follow a homing signal that ultimately leads to neuronal integration and CNS repair, although such molecules can also promote NPC quiescence. The ligand, SDF1 alpha (or CXCL12) is one of the chemokines secreted at sites of injury that it is known to attract NSC-derived neuroblasts, cells that express CXCR4. In function of its concentration, CXCL12 can induce different responses, promoting NPC migration at low concentrations while favoring cell adhesion via EGF and the alpha 6 integrin at high CXCL12 concentrations. However, the preclinical effectiveness of chemokines and their relationship with NPC mobilization requires further study, particularly with respect to CNS repair. Indeed, NPC migration may also be affected by the release of cytokines or chemokines induced by local inflammation, through autocrine or paracrine mechanisms, as well as through erythropoietin (EPO) or nitric oxide (NO) release. CXCL12 activity requires G-coupled proteins and the availability of its ligand may be modulated by its binding to CXCR7, for which it shows a stronger affinity than for CXCR4. © 2014 Wiley Periodicals, Inc.
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