Focal Adhesion Kinase Acts Downstream of EphB Receptors to Maintain Mature Dendritic Spines by Regulating Cofilin Activity

Division of Biomedical Sciences and Neuroscience Program, University of California, Riverside, Riverside, California 92521-0121, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 07/2009; 29(25):8129-42. DOI: 10.1523/JNEUROSCI.4681-08.2009
Source: PubMed


Dendritic spines are the postsynaptic sites of most excitatory synapses in the brain and are highly enriched in polymerized F-actin, which drives the formation and maintenance of mature dendritic spines and synapses. We propose that suppressing the activity of the actin-severing protein cofilin plays an important role in the stabilization of mature dendritic spines, and is accomplished through an EphB receptor-focal adhesion kinase (FAK) pathway. Our studies revealed that Cre-mediated knock-out of loxP-flanked fak prompted the reversion of mature dendritic spines to an immature filopodial-like phenotype in primary hippocampal cultures. The effects of FAK depletion on dendritic spine number, length, and morphology were rescued by the overexpression of the constitutively active FAK(Y397E), but not FAK(Y397F), indicating the significance of FAK activation by phosphorylation on tyrosine 397. Our studies demonstrate that FAK acts downstream of EphB receptors in hippocampal neurons and EphB2-FAK signaling controls the stability of mature dendritic spines by promoting cofilin phosphorylation, thereby inhibiting cofilin activity. While constitutively active nonphosphorylatable cofilin(S3A) induced an immature spine profile, phosphomimetic cofilin(S3D) restored mature spine morphology in neurons with disrupted EphB activity or lacking FAK. Further, we found that EphB-mediated regulation of cofilin activity at least partially depends on the activation of Rho-associated kinase (ROCK) and LIMK-1. These findings indicate that EphB2-mediated dendritic spine stabilization relies, in part, on the ability of FAK to activate the RhoA-ROCK-LIMK-1 pathway, which functions to suppress cofilin activity and inhibit cofilin-mediated dendritic spine remodeling.

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    • "The formation and stabilisation of dendritic spines is heavily dependent on many signalling events that modify the actin cytoskeleton (Schubert and Dotti, 2007). 14-3-3ζ has previously been shown to modulate actin polymerisation by binding to cofilin (Gohla and Bokoch, 2002), a molecule that has recently been implicated as a central mediator of dendritic spine dynamics (Shi et al., 2009). Consistent with the idea that 14-3-3ζ plays a role in regulating spine dynamics, cell fractionation experiments have shown that it is located in the synapse (Rajan et al., 2002), and biochemical studies have shown that it complexes with proteins required for stability of the postsynaptic density such as SPIN90 (Heverin et al., 2012). "
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    ABSTRACT: Clozapine is an atypical antipsychotic drug used in the treatment of schizophrenia, which has been shown to reverse behavioural and dendritic spine deficits in mice. It has recently been shown that deficiency of 14-3-3ζ has an association with schizophrenia, and that a mouse model lacking this protein displays several schizophrenia-like behavioural deficits. To test the effect of clozapine in this mouse model, 14-3-3ζ KO mice were administered clozapine (5mg/kg) for two weeks prior to being analysed in a test battery of cognition, anxiety, and despair (depression-like) behaviours. Following behavioural testing brain samples were collected for analysis of specific anatomical defects and dendritic spine formation. We found that clozapine reduced despair behaviour of 14-3-3ζ KO mice in the Forced Swim Test (FST) and altered the behaviour of wild types and 14-3-3ζ KO mice in the Y-maze task. In contrast, clozapine had no effects on hippocampal laminar defects or decreased dendritic spine density observed in 14-3-3ζ KO mice. Our results suggest that clozapine may have beneficial effects on clinical behaviours associated with deficiencies in the 14-3-3ζ molecular pathway, despite having no effects on morphological defects. These findings may provide mechanistic insight to the action of this drug.
    Pharmacology Biochemistry and Behavior 09/2015; 138. DOI:10.1016/j.pbb.2015.09.006 · 2.78 Impact Factor
    • "It is becoming more evident that dynamic modulation of proteins involved in actin regulation is required for spine development and plasticity (Hotulainen and Hoogenraad, 2010; Pertz, 2010). For example, knockdown of cofilin-1 by siRNA and overexpression of constitutively active cofilin-1 induces similar phenotype in developing neurons: long filopodia-like structures (Hotulainen et al., 2009; Shi et al., 2009). Similarly, both long-term increase and decrease of Rac1 activity leads to reduced number of normal spines and synapses (Nakayama et al., 2000; Zhang et al., 2003). "
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    ABSTRACT: Chloride extrusion in mature neurons is largely mediated by the neuron-specific potassium-chloride cotransporter KCC2. In addition, independently of its chloride transport function, KCC2 regulates the development and morphology of dendritic spines through structural interactions with the actin cytoskeleton. The mechanism of this effect remains largely unknown. In this paper, we show a novel pathway for KCC2-mediated regulation of the actin cytoskeleton in neurons. We found that KCC2, through interaction with the b isoform of Rac/Cdc42 guanine nucleotide exchange factor β-PIX, regulates the activity of Rac1 GTPase and the phosphorylation of one of the major actin-regulating proteins, cofilin-1. KCC2-deficient neurons had abnormally high levels of phosphorylated cofilin-1. Consistently, dendritic spines of these neurons exhibited a large pool of stable actin, resulting in reduced spine motility and diminished density of functional synapses. In conclusion, we describe a novel signaling pathway that couples KCC2 to the cytoskeleton and regulates the formation of glutamatergic synapses. © 2015 Llano et al.
    The Journal of Cell Biology 06/2015; 209(5):671-686. DOI:10.1083/jcb.201411008 · 9.83 Impact Factor
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    • "A distinct Ig-class adhesion molecule, SynCAM1, has been shown to have an opposing effect in stimulating spine growth and excitatory synapse formation in the hippocampus (Robbins et al., 2010). NrCAM might be a bidirectional regulator of spine development and/or plasticity as it physically associates with EphB2, a tyrosine kinase receptor that stabilizes dendritic spines (Shi et al., 2009) and modulates ankyrin B binding to NrCAM by phosphorylating a critical tyrosine residue in the NrCAM cytoplasmic domain (Dai et al., 2013). The cortical expression pattern and localization of NrCAM on dendritic spines of star pyramidal cells, coupled with the ability of NrCAM to rescue Sema3F-induced spine collapse when reexpressed in NrCAM-minus cortical neurons support a postsynaptic role for NrCAM in spine remodeling/elimination. "
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    ABSTRACT: Neuron-glial related cell adhesion molecule (NrCAM) is a regulator of axon growth and repellent guidance, and has been implicated in autism spectrum disorders. Here a novel postsynaptic role for NrCAM in Semaphorin3F (Sema3F)-induced dendritic spine remodeling was identified in pyramidal neurons of the primary visual cortex (V1). NrCAM localized to dendritic spines of star pyramidal cells in postnatal V1, where it was coexpressed with Sema3F. NrCAM deletion in mice resulted in elevated spine densities on apical dendrites of star pyramidal cells at both postnatal and adult stages, and electron microscopy revealed increased numbers of asymmetric synapses in layer 4 of V1. Whole-cell recordings in cortical slices from NrCAM-null mice revealed increased frequency of mEPSCs in star pyramidal neurons. Recombinant Sema3F-Fc protein induced spine retraction on apical dendrites of wild-type, but not NrCAM-null cortical neurons in culture, while re-expression of NrCAM rescued the spine retraction response. NrCAM formed a complex in brain with Sema3F receptor subunits Neuropilin-2 (Npn-2) and PlexinA3 (PlexA3) through an Npn-2-binding sequence (TARNER) in the extracellular Ig1 domain. A trans heterozygous genetic interaction test demonstrated that Sema3F and NrCAM pathways interacted in vivo to regulate spine density in star pyramidal neurons. These findings reveal NrCAM as a novel postnatal regulator of dendritic spine density in cortical pyramidal neurons, and an integral component of the Sema3F receptor complex. The results implicate NrCAM as a contributor to excitatory/inhibitory balance in neocortical circuits.
    The Journal of Neuroscience : The Official Journal of the Society for Neuroscience 08/2014; 34(34):11274-87. DOI:10.1523/JNEUROSCI.1774-14.2014 · 6.34 Impact Factor
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