Identification and validation of a Lewisx glycomimetic peptide

Glycans play important roles in regulating cell recognition and interactions to fine tune development, and synaptic plasticity and regeneration in the adult nervous system. The spatial and temporal expression pattern of Lewisx (a terminal trisaccharide epitope characterized by α1,3-fucosyl-N-acetyl-lactosamine) in the nervous system indicates an important role of this epitope in neurogenesis and brain development. Localization of Lewisx in the proliferative subventricular zone of the developing nervous system and also its expression on stem cells of the adult nervous system suggests a role in neurogenesis and hence regeneration. To provide an alternative tool to elucidate the functional roles of Lewisx, we screened a random peptide phage library against a Lewisx-specific antibody to identify a Lewisx glycomimetic peptide. We identified a peptide that specifically bound to the Lewisx-specific antibody and this binding could be competed by the Lewisx glycan. Different aspects of the Lewisx glycomimetic peptide were investigated by introducing it in in vitro assays measuring neurite outgrowth and in in vivo assays to determine its efficacy in regeneration of peripheral nerve and spinal cord after injury in adult mice. In vitro, neurite outgrowth triggered by the Lewisx-carrying adhesion molecule CD24 was abolished alike by the Lewisx glycan and the glycomimetic peptide, while no influence of the glycomimetic peptide was seen in regeneration. Our results validate the use of Lewisx glycomimetic peptide as a functionally equivalent structure to the Lewisx glycan.