Cathepsin E generates a sumoylated intracellular fragment of the cell adhesion molecule L1 to promote neuronal and Schwann cell migration as well as myelination

Authors

  • David Lutz,

    1. Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
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  • Gerrit Wolters-Eisfeld,

    1. Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
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  • Melitta Schachner,

    Corresponding author
    1. Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
    2. Keck Center for Collaborative Neuroscience and Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
    3. Center for Neuroscience, Shantou University Medical College, Shantou, China
    • Address correspondence and reprint requests to Melitta Schachner, Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Martinistr. 52, D-20246 Hamburg, Germany. E-mail: melitta.schachner@zmnh.uni-hamburg.de

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  • Ralf Kleene

    1. Zentrum für Molekulare Neurobiologie, Universitätsklinikum Hamburg-Eppendorf, Hamburg, Germany
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Abstract

The cell adhesion molecule L1 regulates cellular responses in the developing and adult nervous system. Here, we show that stimulation of cultured mouse cerebellar neurons by a function-triggering L1 antibody leads to cathepsin E-mediated generation of a sumoylated 30 kDa L1 fragment (L1-30) and to import of L1-30 into the nucleus. Mutation of the sumoylation site at K1172 or the cathepsin E cleavage site at E1167 abolishes generation of L1-30, while mutation of the nuclear localization signal at K1147 prevents nuclear import of L1-30. Moreover, the aspartyl protease inhibitor pepstatin impairs the generation of L1-30 and inhibits L1-induced migration of cerebellar neurons and Schwann cells as well as L1-dependent in vitro myelination on axons of dorsal root ganglion neurons by Schwann cells. L1-stimulated migration of HEK293 cells expressing L1 with mutated cathepsin E cleavage site is diminished in comparison to migration of cells expressing non-mutated L1. In addition, L1-stimulated migration of HEK293 cells expressing non-mutated L1 is also abolished upon knock-down of cathepsin E expression and enhanced by over-expression of cathepsin E. The findings of the present study indicate that generation and nuclear import of L1-30 regulate neuronal and Schwann cell migration as well as myelination.

image

Cell adhesion molecule L1 regulates cellular responses in the developing and adult nervous system. L1 stimulation triggers sumoylation and cleavage of L1, thus generating the L1-70 fragment (1) which is cleaved by cathepsin E (2) yielding the L1-30 fragment that is imported to the nucleus (3), may bind to DNA and/or nuclear proteins (4), to regulate diverse cellular functions.

Ancillary