Nogo-A polypeptide fragment, variant Nogo receptor 1 polypeptide and uses thereof

摘要

Nogo, MAG, and OMgp are myelin-derived proteins that bind to a neuronal Nogo-66 Receptor (NgR) to limit axonal regeneration after CNS injury. Nogo-A protein may play the most prominent role in vivo, perhaps because its action is mediated both by NgR and by other receptors. Here, we extend our previous analysis of Nogo-A and NgR functional domains. In addition to a NgR-dependent Nogo-66 inhibitory domain and a NgR-independent Amino-Nogo-A specific domain, we identify a third Nogo-A specific domain that binds to NgR with nanomolar affinity. This third domain of 19 amino acids (aa) does not alter cell spreading or axonal outgrowth. Ala-scanning mutagenesis of surface residues in NgR partially distinguishes ligand binding sites for the two Nogo domains and for MAG, OMgp and Lingo-1. Fusion of the two NgR-binding Nogo-A domains creates a ligand with ten-fold enhanced affinity for NgR and converts a NgR antagonist peptide to an agonist. Thus, inhibition of axonal regeneration by NgR occurs after binding a subnanomolar bipartite Nogo-A ligand at a site partly overlapping with that for MAG and OMgp.