Limits...
An inactive pool of GSK-3 at the leading edge of growth cones is implicated in Semaphorin 3A signaling.

Eickholt BJ, Walsh FS, Doherty P - J. Cell Biol. (2002)

Bottom Line: Glycogen synthase kinase (GSK)-3 is a serine/threonine kinase that has been implicated in several aspects in embryonic development and several growth factor signaling cascades.We show that three different GSK-3 antagonists (LiCl, SB-216763, and SB-415286) can inhibit the growth cone collapse response induced by Sema 3A.These studies reveal a novel compartmentalization of inactive GSK-3 in cells and demonstrate for the first time a requirement for GSK-3 activity in the Sema 3A signal transduction pathway.

View Article: PubMed Central - PubMed

Affiliation: Molecular Neurobiology Group, Medical Research Council Centre for Developmental Biology, King's College London, London SE1 1UL, United Kingdom. Britta.J.Eickholt@kcl.ac.uk

ABSTRACT
Glycogen synthase kinase (GSK)-3 is a serine/threonine kinase that has been implicated in several aspects in embryonic development and several growth factor signaling cascades. We now report that an inactive phosphorylated pool of the enzyme colocalizes with F-actin in both neuronal and nonneuronal cells. Semaphorin 3A (Sema 3A), a molecule that inhibits axonal growth, activates GSK-3 at the leading edge of neuronal growth cones and in Sema 3A-responsive human breast cancer cells, suggesting that GSK-3 activity might play a role in coupling Sema 3A signaling to changes in cell motility. We show that three different GSK-3 antagonists (LiCl, SB-216763, and SB-415286) can inhibit the growth cone collapse response induced by Sema 3A. These studies reveal a novel compartmentalization of inactive GSK-3 in cells and demonstrate for the first time a requirement for GSK-3 activity in the Sema 3A signal transduction pathway.

Show MeSH

Related in: MedlinePlus

Dephosphosphorylation of GSK-3 by inhibition of PI 3-kinase. (A) In primary DRG neurons, treatment with wortmannin (WM) or LY294002 (LY) at given μM concentrations for 1 h reduces the phosphorylation of PKB/AKT and both GSK-3α and GSK-3β. (B) Treatment of DRG explant with wortmannin at 0.1 μM results in a loss of the P-Ser(9)-GSK-3β signal seen in untreated control cultures (insert). (C) In a parallel-performed phalloidin staining, the growth cone is clearly visible. Bars, 15 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2199247&req=5

fig2: Dephosphosphorylation of GSK-3 by inhibition of PI 3-kinase. (A) In primary DRG neurons, treatment with wortmannin (WM) or LY294002 (LY) at given μM concentrations for 1 h reduces the phosphorylation of PKB/AKT and both GSK-3α and GSK-3β. (B) Treatment of DRG explant with wortmannin at 0.1 μM results in a loss of the P-Ser(9)-GSK-3β signal seen in untreated control cultures (insert). (C) In a parallel-performed phalloidin staining, the growth cone is clearly visible. Bars, 15 μm.

Mentions: The phosphatidylinositol (PI) 3-kinase pathway is one of the major pathways that inactivates GSK-3 by stimulating a PKB/Akt-dependent phosphorylation of Ser21 and/or Ser9 (Cross et al., 1995). In primary DRG neurons, treatment with two selective PI 3-kinase inhibitors (wortmannin and LY294002) induces a dramatic reduction in the phosphorylation of GSK-3α on Ser21 and GSK-3β on Ser9 as determined by Western blotting (Fig. 2 A) and immunocytochemistry (Fig. 2 B). These results demonstrate that under our culture conditions PI 3-kinase activity is required for inactivating GSK-3 in the growth cones of primary neurons. It is also interesting to note that although PI 3-kinase inhibition by wortmannin does not result in a collapse of the growth cone, it reduces its outspread morphology and appears to alter the appearance of the actin filaments (Fig. 2 C).


An inactive pool of GSK-3 at the leading edge of growth cones is implicated in Semaphorin 3A signaling.

Eickholt BJ, Walsh FS, Doherty P - J. Cell Biol. (2002)

Dephosphosphorylation of GSK-3 by inhibition of PI 3-kinase. (A) In primary DRG neurons, treatment with wortmannin (WM) or LY294002 (LY) at given μM concentrations for 1 h reduces the phosphorylation of PKB/AKT and both GSK-3α and GSK-3β. (B) Treatment of DRG explant with wortmannin at 0.1 μM results in a loss of the P-Ser(9)-GSK-3β signal seen in untreated control cultures (insert). (C) In a parallel-performed phalloidin staining, the growth cone is clearly visible. Bars, 15 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2199247&req=5

fig2: Dephosphosphorylation of GSK-3 by inhibition of PI 3-kinase. (A) In primary DRG neurons, treatment with wortmannin (WM) or LY294002 (LY) at given μM concentrations for 1 h reduces the phosphorylation of PKB/AKT and both GSK-3α and GSK-3β. (B) Treatment of DRG explant with wortmannin at 0.1 μM results in a loss of the P-Ser(9)-GSK-3β signal seen in untreated control cultures (insert). (C) In a parallel-performed phalloidin staining, the growth cone is clearly visible. Bars, 15 μm.
Mentions: The phosphatidylinositol (PI) 3-kinase pathway is one of the major pathways that inactivates GSK-3 by stimulating a PKB/Akt-dependent phosphorylation of Ser21 and/or Ser9 (Cross et al., 1995). In primary DRG neurons, treatment with two selective PI 3-kinase inhibitors (wortmannin and LY294002) induces a dramatic reduction in the phosphorylation of GSK-3α on Ser21 and GSK-3β on Ser9 as determined by Western blotting (Fig. 2 A) and immunocytochemistry (Fig. 2 B). These results demonstrate that under our culture conditions PI 3-kinase activity is required for inactivating GSK-3 in the growth cones of primary neurons. It is also interesting to note that although PI 3-kinase inhibition by wortmannin does not result in a collapse of the growth cone, it reduces its outspread morphology and appears to alter the appearance of the actin filaments (Fig. 2 C).

Bottom Line: Glycogen synthase kinase (GSK)-3 is a serine/threonine kinase that has been implicated in several aspects in embryonic development and several growth factor signaling cascades.We show that three different GSK-3 antagonists (LiCl, SB-216763, and SB-415286) can inhibit the growth cone collapse response induced by Sema 3A.These studies reveal a novel compartmentalization of inactive GSK-3 in cells and demonstrate for the first time a requirement for GSK-3 activity in the Sema 3A signal transduction pathway.

View Article: PubMed Central - PubMed

Affiliation: Molecular Neurobiology Group, Medical Research Council Centre for Developmental Biology, King's College London, London SE1 1UL, United Kingdom. Britta.J.Eickholt@kcl.ac.uk

ABSTRACT
Glycogen synthase kinase (GSK)-3 is a serine/threonine kinase that has been implicated in several aspects in embryonic development and several growth factor signaling cascades. We now report that an inactive phosphorylated pool of the enzyme colocalizes with F-actin in both neuronal and nonneuronal cells. Semaphorin 3A (Sema 3A), a molecule that inhibits axonal growth, activates GSK-3 at the leading edge of neuronal growth cones and in Sema 3A-responsive human breast cancer cells, suggesting that GSK-3 activity might play a role in coupling Sema 3A signaling to changes in cell motility. We show that three different GSK-3 antagonists (LiCl, SB-216763, and SB-415286) can inhibit the growth cone collapse response induced by Sema 3A. These studies reveal a novel compartmentalization of inactive GSK-3 in cells and demonstrate for the first time a requirement for GSK-3 activity in the Sema 3A signal transduction pathway.

Show MeSH
Related in: MedlinePlus