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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

ABSTRACT

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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    • "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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    • "Collapsin response mediator proteins (CRMPs), consisting of five cytosolic proteins (CRMP1–CRMP5), are a family of proteins that are highly expressed in developing and adult nervous systems [7] [8] [9]. CRMPs function in a variety of cellular processes, including cell migration, differentiation , neurite extension, and axonal regeneration [10] [11]. Unlike microtubule-associated proteins (MAPs), CRMPs likely exist as homo-or heterotetramers in vivo [12], do "
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    ABSTRACT: Cytoskeleton dynamics are critical phenomena that underpin many fundamental cellular processes. Collapsin response mediator proteins (CRMPs) are highly expressed in the developing nervous system, mediating growth cone guidance, neuronal polarity, and axonal elongation. However, whether and how CRMPs associate with microtubules and actin coordinated cytoskeletal dynamics remain unknown. In this study, we demonstrated that CRMP2 and CRMP4 interacted with tubulin and actin in vitro and colocalized with the cytoskeleton in the transition-zone in developing growth cones. CRMP2 and CRMP4 also interacted with one another coordinately to promote growth cone development and axonal elongation. Genetic silencing of CRMP2 enhanced, whereas overexpression of CRMP2 suppressed, the inhibitory effects of CRMP4 knockdown on axonal development. In addition, knockdown of CRMP2 or overexpression of truncated CRMP2 reversed the promoting effect of CRMP4. With the overexpression of truncated CRMP2 or CRMP4 lacking the cytoskeleton interaction domain, the promoting effect of CRMP was suppressed. These data suggest a model in which CRMP2 and CRMP4 form complexes to bridge microtubules and actin and thus work cooperatively to regulate growth cone development and axonal elongation.
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