GSK-3[beta] Regulates Phosphorylation of CRMP-2 and Neuronal Polarity

Department of Cell Pharmacology, Graduate School of Medicine, Nagoya University, 65 Tsurumai, Showa-ku, Nagoya, Aichi 466-8550, Japan.
Cell (Impact Factor: 32.24). 02/2005; 120(1):137-49. DOI: 10.1016/j.cell.2004.11.012
Source: PubMed


Neurons are highly polarized and comprised of two structurally and functionally distinct parts, an axon and dendrites. We previously showed that collapsin response mediator protein-2 (CRMP-2) is critical for specifying axon/dendrite fate, possibly by promoting neurite elongation via microtubule assembly. Here, we showed that glycogen synthase kinase-3beta (GSK-3beta) phosphorylated CRMP-2 at Thr-514 and inactivated it. The expression of the nonphosphorylated form of CRMP-2 or inhibition of GSK-3beta induced the formation of multiple axon-like neurites in hippocampal neurons. The expression of constitutively active GSK-3beta impaired neuronal polarization, whereas the nonphosphorylated form of CRMP-2 counteracted the inhibitory effects of GSK-3beta, indicating that GSK-3beta regulates neuronal polarity through the phosphorylation of CRMP-2. Treatment of hippocampal neurons with neurotrophin-3 (NT-3) induced inactivation of GSK-3beta and dephosphorylation of CRMP-2. Knockdown of CRMP-2 inhibited NT-3-induced axon outgrowth. These results suggest that NT-3 decreases phosphorylated CRMP-2 and increases nonphosphorylated active CRMP-2, thereby promoting axon outgrowth.

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Available from: Kozo Kaibuchi,
    • "Collapsin response mediator protein 2 (CRMP-2; also known as DPYSL2) is a kinesin-binding protein, which promotes the recognition of cargo proteins and is known to regulate neural polarity (Fukata et al., 2002). It has been shown that GSK3β- mediated phosphorylation of CRMP-2, which is trigged by cyclindependent kinase 5 (CDK5), inhibits its binding to tubulin dimers, whereas dephosphorylation facilitates CRMP-2–tubulin binding and promotes axonal growth by delivering tubulin dimers to microtubule terminals for elongation (Yoshimura et al., 2005). "
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    ABSTRACT: Neuronal excitability is strictly regulated by various mechanisms including modulation of ion channel activity and trafficking. Stimulation of m1 muscarinic acetylcholine receptor increases neural excitability by suppressing the M-current generated by the Kv7/KCNQ channel family. We found that m1 muscarinic acetylcholine receptor stimulation also triggers surface transport of KCNQ subunits. This receptor-induced surface transport was observed with KCNQ2 as well as KCNQ3 homomeric channels, but not with Kv3.1 channels. Deletion analyses identified that a conserved domain in a proximal region of the N-terminal tail of KCNQ protein is critical for this surface transport, TL domain. Binding proteins to this domain were identified as α/β tubulin and collapsin response mediator protein 2 (CRMP-2). CK2 inhibitor reduced tubulin binding to TL domain. Glycogen synthase kinse 3 (GSK3) inhibitor facilitated CRMP-2 binding to TL domain. Consistently, GSK3 inhibitor treatment enhanced receptor-induced KCNQ2 surface transport. M-current recordings from neurons showed that GSK3 inhibitor treatment shortened the duration of muscarinic suppression and lead to over-recovery of the M-current. These results suggest that m1 muscarinic acetylcholine receptor stimulates surface transport of KCNQ channels via a CRMP-2 mediated pathway.
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    • "Phosphorylation of CRMP1 and CRMP2 by Cdk5 and sequential phosphorylation of CRMP2 by GSK-3í µí»½ are crucial for Sema3A-induced growth cone collapse response in dorsal root ganglia (DRG) neurons [10] [11]. "
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    • "It is found mainly in the hippocampus, olfactory bulb and cerebellum of the adult human brain [4]. In neurons, the protein is concentrated in the distal segments of neurites, ingrowth cones and synapses [3] [21]. Multiple isoforms of CRMP2 exist due to alternative splicing of the Nterminus , although two of these are predominantly expressed. "
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