Neuroscience 2005 Abstract
| Presentation Number: | 710.7 |
|---|---|
| Abstract Title: | An essential role for glycogen synthase kinase 3 in axon growth. |
| Authors: |
Kim, W.*1
; Zhou, F.1
; Zhou, J.1
; Wang, Y.1
; Snider, W. D.1
1Neuroscience Center, Univ. of North Carolina at Chapel Hill, Chapel Hill, NC |
| Primary Theme and Topics |
Development - Axonal and Dendritic Development -- Axon growth and guidance: Other |
| Session: |
710. Axon Growth and Guidance V Poster |
| Presentation Time: | Tuesday, November 15, 2005 3:00 PM-4:00 PM |
| Location: | Washington Convention Center - Hall A-C, Board # B30 |
| Keywords: | GSK3, NGF, DRG, neurotrophin |
Glycogen synthase kinase 3 (GSK-3) beta and alpha are serine/threonine kinases involved in growth factor signaling and embryonic development. Recently regulation of GSK-3 has been implicated in establishment of hippocampal neuronal polarity and neurotrophin-induced extension of DRG, SCG, and hippocampal axons. However, whether GSK-3 function is absolutely required for axonal development has not been decisively demonstrated. In fact, previous studies in which different concentrations and classes of pharmacological inhibitors were used showed differing results in relation to hippocampal axonal specification. Here using a highly specific pharmacological inhibitor and siRNA, we sought to determine whether GSK3 is required for axon growth.
Both GSK-3 beta and alpha are expressed throughout the embryonic nervous system. Treatment of neurotrophin-responsive peripheral embryonic neurons (DRG and SCG) neurons with a highly specific pharmacological inhibitor (6-bromoindirubin-3ยกรค-acetoxime) active against both isoforms blocked both NGF- and NT3-induced axonal growth. The growth reduction was associated with thickened axons and enlarged growth cones. Treatment with a peptide inhibitor also blocked axon growth. Interestingly, similar axon growth inhibition was observed in cultured hippocampal neurons.
To address the possibility that pharmacological inhibitors are not specific, we designed an siRNA construct to knock down endogenous GSK-3s. Overexpression of siGSK-3 almost completely eliminated synthesis of GSK-3 beta and alpha proteins in cultured DRG and hippocampal neurons. Scrambled siRNA had no effect. Consistent with the effects of pharmacological inhibition, we found that neurons overexpressing siGSK-3 showed marked reduction in axon extension. The finding was further confirmed by transfection with a second siRNA construct with a different sequence.
Our results demonstrate that GSK-3 isoforms have essential functions for neurotrophin-induced DRG axon growth and hippocampal axon elongation in vitro.
Both GSK-3 beta and alpha are expressed throughout the embryonic nervous system. Treatment of neurotrophin-responsive peripheral embryonic neurons (DRG and SCG) neurons with a highly specific pharmacological inhibitor (6-bromoindirubin-3ยกรค-acetoxime) active against both isoforms blocked both NGF- and NT3-induced axonal growth. The growth reduction was associated with thickened axons and enlarged growth cones. Treatment with a peptide inhibitor also blocked axon growth. Interestingly, similar axon growth inhibition was observed in cultured hippocampal neurons.
To address the possibility that pharmacological inhibitors are not specific, we designed an siRNA construct to knock down endogenous GSK-3s. Overexpression of siGSK-3 almost completely eliminated synthesis of GSK-3 beta and alpha proteins in cultured DRG and hippocampal neurons. Scrambled siRNA had no effect. Consistent with the effects of pharmacological inhibition, we found that neurons overexpressing siGSK-3 showed marked reduction in axon extension. The finding was further confirmed by transfection with a second siRNA construct with a different sequence.
Our results demonstrate that GSK-3 isoforms have essential functions for neurotrophin-induced DRG axon growth and hippocampal axon elongation in vitro.
Supported by NIH grant NS R01 31768 (W.D.S.)
Sample Citation:
[Authors]. [Abstract Title]. Program No. XXX.XX. 2005 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2005. Online.
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