scholarly journals The phosphoinositide 3-kinase pathway and glycogen synthase kinase-3 positively regulate the activity of metal-responsive transcription factor-1 in response to zinc ions

2018 ◽  
Vol 96 (6) ◽  
pp. 726-733 ◽  
Author(s):  
Yannick Andéol ◽  
Jessica Bonneau ◽  
Laurence M. Gagné ◽  
Kevin Jacquet ◽  
Véronique Rivest ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Glycogen Synthase ◽  
Transition Metal Ions ◽  
Pi3k Pathway ◽  
Glycogen Synthase Kinase ◽  
Hek293 Cells ◽  
Glycogen Synthase Kinase 3 ◽  
Zinc Ions ◽  
Phosphoinositide 3 Kinase ◽  
Transcription Factor 1

Metal-responsive transcription factor-1 (MTF-1) is a metal-regulatory transcription factor essential for induction of the genes encoding metallothioneins (MTs) in response to transition metal ions. Activation of MTF-1 is dependent on the interaction of zinc with the zinc fingers of the protein. In addition, phosphorylation is essential for MTF-1 transactivation. We previously showed that inhibition of phosphoinositide 3-kinase (PI3K) abrogated Mt expression and metal-induced MTF-1 activation in human hepatocellular carcinoma (HCC) HepG2 and mouse L cells, thus showing that the PI3K signaling pathway positively regulates MTF-1 activity and Mt gene expression. However, it has also been reported that inhibition of PI3K has no significant effects on Mt expression in immortalized epithelial cells and increases Mt expression in HCC cells. To further characterize the role of the PI3K pathway on the activity of MTF-1, transfection experiments were performed in HEK293 and HepG2 cells in presence of glycogen synthase kinase-3 (GSK-3), mTOR–C1, and mTOR–C2 inhibitors, as well as of siRNAs targeting Phosphatase and TENsin homolog (PTEN). We showed that inhibition of the mTOR–C2 complex inhibits the activity of MTF-1 in HepG2 and HEK293 cells, while inhibition of the mTOR–C1 complex or of PTEN stimulates MTF-1 activity in HEK293 cells. These results confirm that the PI3K pathway positively regulates MTF-1 activity. Finally, we showed that GSK-3 is required for MTF-1 activation in response to zinc ions.

scholarly journals Functional Effects of PTPN11 (SHP2) Mutations Causing LEOPARD Syndrome on Epidermal Growth Factor-Induced Phosphoinositide 3-Kinase/AKT/Glycogen Synthase Kinase 3β Signaling

2010 ◽  
Vol 30 (10) ◽  
pp. 2498-2507 ◽  
Author(s):  
Thomas Edouard ◽  
Jean-Philippe Combier ◽  
Audrey Nédélec ◽  
Sophie Bel-Vialar ◽  
Mélanie Métrich ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase ◽  
Hek293 Cells ◽  
Glycogen Synthase Kinase 3Β ◽  
Leopard Syndrome ◽  
Epidermal Growth ◽  
Gsk 3Β ◽  
Phosphoinositide 3 Kinase

ABSTRACT LEOPARD syndrome (LS), a disorder with multiple developmental abnormalities, is mainly due to mutations that impair the activity of the tyrosine phosphatase SHP2 (PTPN11). How these alterations cause the disease remains unknown. We report here that fibroblasts isolated from LS patients displayed stronger epidermal growth factor (EGF)-induced phosphorylation of both AKT and glycogen synthase kinase 3β (GSK-3β) than fibroblasts from control patients. Similar results were obtained in HEK293 cells expressing LS mutants of SHP2. We found that the GAB1/phosphoinositide 3-kinase (PI3K) complex was more abundant in fibroblasts from LS than control subjects and that both AKT and GSK-3β hyperphosphorylation were prevented by reducing GAB1 expression or by overexpressing a GAB1 mutant unable to bind to PI3K. Consistently, purified recombinant LS mutants failed to dephosphorylate GAB1 PI3K-binding sites. These mutants induced PI3K-dependent increase in cell size in a model of chicken embryo cardiac explants and in transcriptional activity of the atrial natriuretic factor (ANF) gene in neonate rat cardiomyocytes. In conclusion, SHP2 mutations causing LS facilitate EGF-induced PI3K/AKT/GSK-3β stimulation through impaired GAB1 dephosphorylation, resulting in deregulation of a novel signaling pathway that could be involved in LS pathology.

scholarly journals Convergence of Multiple Signaling Cascades at Glycogen Synthase Kinase 3: Edg Receptor-Mediated Phosphorylation and Inactivation by Lysophosphatidic Acid through a Protein Kinase C-Dependent Intracellular Pathway

2002 ◽  
Vol 22 (7) ◽  
pp. 2099-2110 ◽  
Author(s):  
Xianjun Fang ◽  
Shuangxing Yu ◽  
Janos L. Tanyi ◽  
Yiling Lu ◽  
James R. Woodgett ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Lysophosphatidic Acid ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase ◽  
Hek293 Cells ◽  
Glycogen Synthase Kinase 3 ◽  
Kinase C ◽  
Pkc Inhibitors

ABSTRACT Lysophosphatidic acid (LPA) is a natural phospholipid with multiple biological functions. We show here that LPA induces phosphorylation and inactivation of glycogen synthase kinase 3 (GSK-3), a multifunctional serine/threonine kinase. The effect of LPA can be reconstituted by expression of Edg-4 or Edg-7 in cells lacking LPA responses. Compared to insulin, LPA stimulates only modest phosphatidylinositol 3-kinase (PI3K)-dependent activation of protein kinase B (PKB/Akt) that does not correlate with the magnitude of GSK-3 phosphorylation induced by LPA. PI3K inhibitors block insulin- but not LPA-induced GSK-3 phosphorylation. In contrast, the effect of LPA, but not that of insulin or platelet-derived growth factor (PDGF), is sensitive to protein kinase C (PKC) inhibitors. Downregulation of endogenous PKC activity selectively reduces LPA-mediated GSK-3 phosphorylation. Furthermore, several PKC isotypes phosphorylate GSK-3 in vitro and in vivo. To confirm a specific role for PKC in regulation of GSK-3, we further studied signaling properties of PDGF receptor β subunit (PDGFRβ) in HEK293 cells lacking endogenous PDGF receptors. In clones expressing a PDGFRβ mutant wherein the residues that couple to PI3K and other signaling functions are mutated with the link to phospholipase Cγ (PLCγ) left intact, PDGF is fully capable of stimulating GSK-3 phosphorylation. The process is sensitive to PKC inhibitors in contrast to the response through the wild-type PDGFRβ. Therefore, growth factors, such as PDGF, which control GSK-3 mainly through the PI3K-PKB/Akt module, possess the ability to regulate GSK-3 through an alternative, redundant PLCγ-PKC pathway. LPA and potentially other natural ligands primarily utilize a PKC-dependent pathway to modulate GSK-3.

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