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Cdk5 regulates EphA4-mediated dendritic spine retraction through an ephexin1-dependent mechanism

Nature Neuroscience volume 10, pages 6776 (2007) | Download Citation

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Abstract

The development of dendritic spines is thought to be crucial for synaptic plasticity. Dendritic spines are retracted upon Eph receptor A4 (EphA4) activation, but the mechanisms that control this process are not well understood. Here we report an important function of cyclin-dependent kinase 5 (Cdk5) in EphA4-dependent spine retraction in mice. We found that blocking Cdk5 activity inhibits ephrin-A1–triggered spine retraction and reduction of mEPSC frequency at hippocampal synapses. The activation of EphA4 resulted in the recruitment of Cdk5 to EphA4, leading to the tyrosine phosphorylation and activation of Cdk5. EphA4 and Cdk5 then enhanced the activation of ephexin1, a guanine-nucleotide exchange factor that regulates activation of the small Rho GTPase RhoA. The association between EphA4 and ephexin1 was significantly reduced in Cdk5−/− brains and Cdk5-dependent phosphorylation of ephexin1 was required for the ephrin-A1–mediated regulation of spine density. These findings suggest that ephrin-A1 promotes EphA4-dependent spine retraction through the activation of Cdk5 and ephexin1, which in turn modulates actin cytoskeletal dynamics.

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Acknowledgements

We are grateful to A. Kulkarni and T. Curran for Cdk5-null mice, L.H. Tsai for p35-null mice, S. Hisanaga for the recombinant Cdk5-p35 protein, D. Lo for the YFP construct and W. Chau, B. Butt, C. Kwong, K. Hung, K. Ho, W.W.Y. Chien and K. Gong for excellent technical assistance. The expert advice of D. Lo and P. Greer is gratefully acknowledged. We also thank Z. Cheung and M. Zhang for critical reading of the manuscript and members of the Ip laboratory for many helpful discussions. This study was supported in part by the Research Grants Council of Hong Kong (HKUST6131/02M, 6130/03M, 6119/04M, 6421/05M and HKUST 3/03C), the Area of Excellence Scheme of the University Grants Committee (AoE/B-15/01), the Hong Kong Jockey Club, US National Institute of Child Health and Human Development grant K08 HD01384, the William Randolph Hearst Fund (to M.S.), Mental Retardation Research Center grant HD18655, and US National Institutes of Health grant NS045500 (to M.E.G.). N.Y.I. is a Croucher Foundation Senior Research Fellow.

Author information

Author notes

    • Wing-Yu Fu
    •  & Yu Chen

    These authors contributed equally to this paper.

Affiliations

  1. Department of Biochemistry, Biotechnology Research Institute and Molecular Neuroscience Center, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.

    • Wing-Yu Fu
    • , Yu Chen
    • , Xiao-Su Zhao
    • , Lei Shi
    • , Kwok-On Lai
    • , Amy K Y Fu
    • , Michael E Greenberg
    •  & Nancy Y Ip
  2. Neurobiology Program, Children's Hospital and Departments of Neurology and Neurobiology, Harvard Medical School, 300 Longwood Avenue, Boston, Massachusetts 02115, USA.

    • Mustafa Sahin
    •  & Jay B Bikoff
  3. Department of Physiology, Chinese University of Hong Kong Shatin, Hong Kong, China.

    • Wing-Ho Yung

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Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Nancy Y Ip.

Supplementary information

PDF files

  1. 1.

    Supplementary Fig. 1

    EphA4 interacts with Cdk5 and p35.

  2. 2.

    Supplementary Fig. 2

    Cdk5 is directly phosphorylated by EphA4.

  3. 3.

    Supplementary Fig. 3

    Ephrin-A1 stimulates EphA4 clustering in cultured hippocampal neurons.

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    Supplementary Fig. 4

    Presence of EphA4, Cdk5.p35 and ephexin1 in postsynaptic densities.

  5. 5.

    Supplementary Fig. 5

    Ephrin-A1 reduces spine density in cultured hippocampal neurons.

  6. 6.

    Supplementary Fig. 6

    Ephexin1 protein is phosphorylated by recombinant Cdk5.p35 using in vitro kinase assay.

  7. 7.

    Supplementary Fig. 7

    Confocal images showing the expression of overexpressed ephexin1 in hippocampal slices.

  8. 8.

    Supplementary Fig. 8

    Model of regulation of spine morphogenesis by EphA4-Cdk5-ephexin1 signaling.

  9. 9.

    Supplementary Methods

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DOI

https://doi.org/10.1038/nn1811